CN118187935A - Surrounding rock deformation control method for soft rock tunnel yielding composite support system construction by step method - Google Patents

Abstract

The invention discloses a surrounding rock deformation control method for soft rock tunnel yielding composite support system construction by a step method. The method comprises the following steps: before the first cycle excavation supporting, adopting self-advancing advance pipe shed pre-grouting to advance and reinforce the arch crown of the soft rock tunnel; dividing the cross section of the soft rock tunnel into an upper step, a middle step, a lower step and a bottom arch from top to bottom in sequence, and arranging a double-layer primary supporting structure for each step and each bottom arch; repeating the steps to carry out second and third cycle excavation supporting; a slow release energy dissipation layer is arranged on the outer side of the double-layer primary supporting structure; and the outer side of the slow-release energy dissipation layer is clung to the cast-in-situ reinforced concrete lining layer. The construction method has the capacity of jointly deforming with surrounding rock while providing stable supporting force, can effectively control the large deformation of the surrounding rock of the soft-rock tunnel, and solves the problems of limit invasion and instability of a supporting structure; meanwhile, the stress characteristic of the reinforced concrete lining layer is effectively improved, and the long-term stability of the reinforced concrete lining layer is ensured.

Description

Surrounding rock deformation control method for soft rock tunnel yielding composite support system construction by step method

Technical Field

The invention relates to the technical field of hydraulic and hydroelectric engineering design, in particular to a surrounding rock deformation control method for soft rock tunnel yielding composite support system construction by a step method.

Background

In the west and southwest mountain and drastic mountain areas with concentrated water resources in China, water diversion projects are built, tunnel water delivery modes are mostly adopted, and long-distance water delivery tunnels are key control projects for water diversion project construction. Because the tunnel line is long, most of tunnel lines need to pass through mountain areas with complex geological structure background, adverse factors such as severe natural environment, high earthquake intensity, complex topography geological conditions and the like are faced, and the tunnel or the tunnel is long in single hole and large in burial depth. Numerous engineering practices have shown that for deeply buried soft rock tunnels, surrounding rock large deformation instability is one of the most common and difficult to control catastrophe modes in tunnel construction. The large deformation of surrounding rock in the construction period of the deeply buried soft rock tunnel often causes the phenomena of supporting structure damage, primary supporting intrusion limit and the like, and if the surrounding rock of the tunnel is collapsed and even completely blocked due to improper treatment, the surrounding rock is extremely easy to cause constructor casualties, destroy construction equipment, delay construction period and increase engineering cost.

In response to large deformation of surrounding rocks of the soft-rock tunnel, the traditional method is to enhance the primary support strength, such as increasing the spraying thickness, reducing the arrangement interval of steel arches or adopting high-specification steel arches. However, engineering practice shows that surrounding rock deformation often has obvious timeliness characteristics after the soft rock tunnel is excavated, and continuous timeliness deformation of the surrounding rock can finally lead to continuous increase of stress of the supporting system, so that the tunnel instability risk is caused.

In order to overcome the defects of the countermeasures, more and more projects attempt to adopt yielding supporting measures, such as yielding anchor rods, telescopic steel arches, compressible buffer layers, compressible linings and the like, wherein the telescopic steel arches represented by U-shaped steel arches are widely applied to large-deformation roadways of coal mines. However, the coal mine tunnel is obviously different from the hydraulic tunnel or the traffic tunnel in the aspects of excavation mode, section form and the like, and a unified and effective yielding support system and a construction method are not formed in the field of tunnel or tunnel engineering at present.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides the surrounding rock deformation control method for the construction of the soft rock tunnel yielding composite support system by the step method, which not only ensures safe construction and limits initial deformation, but also limits further deformation in the later stage, and effectively controls the large deformation of the surrounding rock of the soft rock tunnel.

In order to achieve the purpose, the invention provides a method for controlling deformation of surrounding rock during construction of a soft rock tunnel yielding composite support system by a step method, which is characterized by comprising the following steps:

S1) before the first cycle excavation supporting, adopting self-advancing advance pipe shed pre-grouting to carry out advanced reinforcement on the vault of the soft rock tunnel;

s2) dividing the cross section of the soft rock tunnel into an upper step, a middle step, a lower step and a bottom arch from top to bottom in sequence, and arranging a double-layer primary supporting structure for each step and the bottom arch, wherein the concrete steps are as follows,

S21) excavating an arc pilot pit of an upper step of a soft rock tunnel in a circumferential direction, reserving core soil, erecting outer H-shaped steel arches at intervals along the longitudinal direction of the tunnel, and punching foot locking anchor pipes at the positions of the H-shaped steel arches which are clung to the edges of the two sides of the upper step, wherein the foot locking anchor pipes are fixedly connected with the corresponding H-shaped steel arches, and spraying concrete to the designed thickness between the H-shaped steel arches longitudinally arranged on the upper step;

s22) excavating middle steps on the left side and the right side of a soft rock tunnel, reserving core soil, butting all outer H-shaped steel arches in the step S21), and tightly attaching all H-shaped steel arches on the left side and the right side edges of the middle steps to form foot locking anchor pipes, wherein the foot locking anchor pipes are fixedly connected with the corresponding H-shaped steel arches, and concrete is sprayed between all H-shaped steel arches longitudinally arranged on the middle steps to the designed thickness;

S23) clinging to the outer sides of concrete at the positions of the upper step and the middle step, and erecting inner-layer U-shaped steel arches at intervals along the longitudinal direction of the tunnel;

s24) excavating left and right lower steps of a soft rock tunnel, reserving core soil, butting all outer H-shaped steel arches in the step S22), and tightly abutting all H-shaped steel arches at the left and right side edges of the lower steps to form foot locking anchor pipes, wherein the foot locking anchor pipes are fixedly connected with the corresponding H-shaped steel arches, and concrete is sprayed between all H-shaped steel arches longitudinally arranged on the lower steps to the designed thickness;

s25) excavating a soft-rock tunnel bottom arch, butting all outer-layer H-shaped steel arches in the step S24), sealing each outer-layer H-shaped steel arch into a ring, and arranging a foot locking anchor pipe at each H-shaped steel arch position close to the edges of two sides of the bottom arch, wherein the foot locking anchor pipe is fixedly connected with the corresponding H-shaped steel arch, and injecting concrete between all H-shaped steel arches longitudinally arranged on the bottom arch to the designed thickness;

s26) clinging to the outer sides of concrete at the positions of the lower step and the bottom arch, butting all inner layer U-shaped steel arches in the step S23), sealing each inner layer U-shaped steel arch into a ring, and filling polyethylene between the outer layer H-shaped steel arches and supporting gaps of the inner layer U-shaped steel arches and among all inner layer U-shaped steel arches longitudinally arranged;

S3) repeating the steps S1) and S2), and carrying out second and third cycle excavation supporting;

s4) clinging to the outer side of the double-layer primary supporting structure, and arranging a slow-release energy dissipation layer;

s5) clinging to the outer side of the slow-release energy dissipation layer, and casting the reinforced concrete lining layer in situ.

Further, in S1), a plurality of self-advancing type leading pipe sheds are arranged at intervals in the range of 150-170 degrees for the arch crown of the soft rock tunnel, each leading pipe shed is longitudinally inclined towards the tunnel, and the camber angle is 5-10 degrees.

Furthermore, in S1), the leading pipe sheds are drilled and installed according to the holes with odd numbers firstly and holes with even numbers secondly, and staggered installation is adopted between the leading pipe sheds in the adjacent cyclic excavation support.

Further, in S1), the grouting sequence is from bottom to top, the slurry is concentrated and then diluted, the grouting amount is firstly big and then small, and the grouting pressure is from small to big.

Further, in S21), after the upper step arc pilot pit of the soft rock tunnel is excavated in the circumferential direction, immediately and initially spraying 2-3 cm of concrete on the top wall of the upper step arc pilot pit, paving a reinforcing steel mesh, erecting an outer layer H-shaped steel arch, and tightly attaching to the positions 20-40 cm above the arch feet of each H-shaped steel arch on the two side edges of the upper step, and punching a foot locking anchor pipe;

s22), after the left middle step and the right middle step of the soft rock tunnel are excavated, immediately and primarily spraying 2-3 cm concrete on the side walls of the left middle step and the right middle step, paving a reinforcing steel mesh, erecting an outer layer H-shaped steel arch, and tightly attaching the positions 20-40 cm above the arch feet of the H-shaped steel arch at the left side edge and the right side edge of the middle step, and punching a foot locking anchor pipe;

s24), after the left lower step and the right lower step of the soft rock tunnel are excavated, immediately and initially spraying 2-3 cm of concrete on the side walls of the left lower step and the right lower step, paving a reinforcing steel mesh, erecting an outer layer H-shaped steel arch, and tightly attaching the positions 20-40 cm above the arch feet of each H-shaped steel arch on the left side edge and the right side edge of the lower step, and punching a foot locking anchor pipe;

S25), after the bottom arch of the soft-rock tunnel is excavated, immediately and initially spraying 2-3 cm of concrete on the bottom wall of the bottom arch, paving a reinforcing steel mesh, erecting an outer layer H-shaped steel arch, and tightly attaching to the positions 20-40 cm below the arch feet of each H-shaped steel arch at the edges of the two sides of the bottom arch, and punching foot locking anchor pipes.

Further, in S21), the length of each excavation rule is 3-3.6 m, and the truss distance between the outer H-shaped steel arches longitudinally adjacent to the tunnel is 0.3-0.5 m; s23), the truss distance between the longitudinally adjacent inner U-shaped steel arches of the tunnel is 1.0-1.4 m.

In S2), connecting plates are adopted to connect the H-shaped steel arches corresponding to the upper step, the middle step, the lower step and the bottom arch, the connecting plates are closely attached to the corresponding rock wall, and the connecting plates are connected with the rock wall through bolts;

Further, in S2), the foot locking anchor pipes corresponding to the upper step, the middle step, the lower step and the bottom arch are splayed foot locking anchor pipes, and the tail parts of the splayed foot locking anchor pipes are fixedly connected with the outer sides of the corresponding H-shaped steel arches in pairs by adopting L-shaped connecting ribs.

Further, in S4), the slow-release energy dissipation layer is composed of polyethylene precast blocks, and the polyethylene precast blocks are adhered to the outer side of the double-layer primary supporting structure during construction.

Further, in S1), prior to pre-grouting of the advanced pipe shed, advanced geological prediction is adopted for detecting and collecting engineering geology and hydrogeology conditions within a set distance in front of the tunnel face.

The invention has the advantages that:

1. the pre-grouting of the forepoling shed can effectively control the collapse of the vault and ensure the safety of site construction;

2. The double-layer primary supporting structure comprises supporting measures such as an H-shaped steel arch, a U-shaped steel arch, an outer splayed foot locking anchor pipe, sprayed concrete, a reinforcing steel mesh and the like, and is characterized in that the core of the double-layer primary supporting structure is a yielding supporting structure consisting of the H-shaped steel arch, the U-shaped steel arch and the outer splayed foot locking anchor pipe, and the double-layer primary supporting structure has the capacity of jointly deforming with surrounding rocks while providing stable supporting force, can effectively control the large deformation of the surrounding rocks of a soft rock tunnel, and solves the problems of limit invasion and instability of the supporting structure;

3. The invention adopts the step-by-step (reserved core soil) excavation construction, and the outer H-shaped steel arch frame is closely attached to the tunnel excavation step-by-step installation; the inner layer U-shaped steel arch frame is installed in two steps, after the upper step and the middle step of the H-shaped steel arch frame are installed, the U-shaped steel arch frame above the arching line is installed, after the lower step of the H-shaped steel arch frame and the bottom arch are installed, the lower half part of the U-shaped steel arch frame is installed and sealed to form a ring, and the U-shaped steel arch frame must be immediately sealed to form a ring after the H-shaped steel arch frame is sealed to form a ring;

4. According to the invention, the slow-release energy dissipation layer is paved between the double-layer primary supporting structure and the reinforced concrete lining layer, so that the deformation pressure born by the reinforced concrete lining layer of the soft rock tunnel due to the rheological effect of surrounding rock is reduced, the stress characteristic of the reinforced concrete lining layer is effectively improved, the reinforced concrete lining layer is prevented from cracking, and the long-term stability of the reinforced concrete lining layer is ensured;

the method for controlling the deformation of the surrounding rock in the construction of the soft-rock tunnel yielding composite supporting system by the step method has the capacity of jointly deforming with the surrounding rock while providing stable supporting force, can effectively control the large deformation of the surrounding rock of the soft-rock tunnel, and solves the problems of limit invasion and instability of a supporting structure; meanwhile, the stress characteristic of the reinforced concrete lining layer is effectively improved, the reinforced concrete lining layer is prevented from cracking, and the long-term stability of the reinforced concrete lining layer is ensured.

Drawings

FIG. 1 is a flow chart of a method for controlling deformation of surrounding rock during construction of a soft rock tunnel yielding composite support system by a step method;

FIG. 2 is a schematic cross-sectional view of a yielding composite support system in accordance with the present invention;

FIG. 3 is a schematic view of a steel arch and foreleg canopy pre-grouting longitudinal section of the yielding composite support system of the present invention;

FIG. 4 is a schematic diagram of an advanced borehole layout for advanced geological forecast in accordance with the present invention;

FIG. 5 is a flow chart of the construction process of the forepoling shed in the invention;

FIG. 6 is a flow chart of a double-layer primary support construction process in the invention;

FIG. 7 is a flow chart of the construction process of the H-shaped steel arch centering in the invention;

FIG. 8 is a schematic view of a U-shaped steel arch in the present invention in cross-section;

FIG. 9 is a flow chart of the construction process of the foot locking anchor pipe in the invention;

FIG. 10 is a flow chart of the construction process of the shotcrete according to the present invention;

FIG. 11 is a flow chart of a reinforced concrete lining course construction process in the invention;

In the figure: the device comprises an advance pipe shed 1, a double-layer primary supporting structure 2, a slow-release energy dissipation layer 3 and a reinforced concrete lining layer 4;

the double-layer primary support structure 2 includes: the steel bar reinforced concrete arch comprises an H-shaped steel arch 2-1, a foot locking anchor pipe 2-2, concrete 2-3, a U-shaped steel arch 2-4, polyethylene 2-5 and a steel bar mesh 2-6.

Detailed Description

The invention is described in further detail below with reference to the drawings and specific examples.

In the description of the present invention, it should be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like indicate orientations or positional relationships based on the orientation or positional relationships shown in the drawings, merely to facilitate describing the present invention and simplify the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore should not be construed as limiting the invention.

As shown in FIG. 1, the method for controlling the deformation of surrounding rock in the construction of the soft rock tunnel yielding composite support system by the step method is suitable for the excavation construction of a tunnel (channel) which is easy to generate large deformation of the surrounding rock in soft rock strata such as mudstones, sandy mudstones and claystone, and comprises the following steps:

S1) pre-grouting by adopting a self-advancing type advance pipe shed 1 before the first cyclic excavation supporting, and carrying out advanced reinforcement on the vault of the soft rock tunnel.

Advanced support is carried out before excavation, so that vault collapse can be effectively controlled, and site construction safety is ensured. Specifically, a plurality of self-advancing type leading pipe sheds 1 are arranged at intervals in the range of 150-170 degrees for the arch crown of the soft rock tunnel, each leading pipe shed 1 is longitudinally inclined towards the tunnel, and the camber angle is 5-10 degrees.

In the embodiment, a self-feeding middle pipe shed with phi of 63mm is arranged in a range of 160 degrees of the tunnel arch part, the middle pipe shed adopts hot-rolled seamless steel pipes with the wall thickness of 6mm, and quincuncial slurry overflow holes with the diameter of 8mm are arranged around every 20cm of the pipe body. The arch part is in a range of 100 degrees, the center distance of the pipe shed is 25cm, the range of 60 degrees is 30cm, the row distance is 1.6m, the lap joint length is 2.9m, and the rod body L=4.5 m.

Preferably, the leading pipe sheds 1 are drilled and installed according to odd holes and even holes, and staggered installation is adopted among the leading pipe sheds 1 in adjacent cyclic excavation supporting.

Preferably, the grouting sequence is from bottom to top, the slurry is concentrated and then diluted, the grouting amount is firstly large and then small, and the grouting pressure is from small to large. In this example, the grouting material: cement paste water cement ratio is 0.5:1-1:1 (weight ratio); grouting pressure is 0.8-1.0 MPa; and filling the steel pipe with M30 cement mortar after grouting.

In addition, preferably, before the advance pipe shed 1 is pre-grouting, advanced geological forecast is adopted for detecting and collecting engineering geology and hydrogeology conditions in a set distance in front of the tunnel face, and a basis is provided for correctly selecting a tunneling mode and corresponding technical parameters. By comprehensively analyzing the geological forecast information, the geological condition of the corresponding construction area can be accurately determined, so that the construction is scientifically guided.

In this embodiment, advanced drilling is adopted as an advanced geological prediction method, advanced drilling is used to judge the front geological, water-rich condition and water pressure, the possibility of water gushing, mud gushing and collapse is prejudged, corresponding and feasible technical measures and construction schemes are formulated, the construction is strictly carried out according to the schemes, tunnel construction is carried out after advanced treatment measures are implemented, a geological professional engineer carries out detailed geological investigation and geological sketch, and the surrounding rock condition and the advanced treatment measures of the front non-excavated area are accurately judged through the combination of the advanced geological survey and the geological sketch.

As shown in fig. 4, 4 advanced geological detection holes are drilled in each step of the tunnel, the hole depth is 30-100 m, the drilling position and angle are adjusted according to the surrounding rock disclosure, and the lap joint length is kept to be more than 15 m; the orifice sealing device is well arranged and fixed in the drilling process, so that the water burst caused by mud is prevented. FIG. 5 shows a flow chart of the construction process of the forepoling shed in the invention.

S2) dividing the cross section of the soft rock tunnel into an upper step, a middle step, a lower step and a bottom arch from top to bottom in sequence, and arranging a double-layer primary supporting structure 2 on each step and each bottom arch, wherein the concrete steps are as follows:

S21) excavating a soft rock tunnel upper step arc pilot pit in a circumferential direction, reserving core soil, erecting outer H-shaped steel arches 2-1 at intervals along the longitudinal direction of the tunnel, and arranging a foot locking anchor pipe 2-2 at the position of each H-shaped steel arch 2-1 close to the edges of the two sides of the upper step, wherein the foot locking anchor pipe 2-2 is fixedly connected with the corresponding H-shaped steel arch 2-1, and spraying concrete 2-3 to the designed thickness between each H-shaped steel arch longitudinally arranged on the upper step.

In this embodiment, the length of the core soil is preferably 3-4 m, the excavation height is 2.08m, and the width is preferably 1/3-1/2 of the tunnel excavation width. The excavation circulation footage is determined according to the distance between the primary support steel frames, and the maximum footage is not more than 0.8 meter.

Specifically, after a step arc pilot pit on a soft rock tunnel is excavated in a circumferential direction, immediately and initially spraying 2-3 cm of concrete on the top wall of the step arc pilot pit, paving a reinforcing steel net 2-6, erecting an outer layer H-shaped steel arch 2-1, tightly attaching the positions 20-40 cm above the arch feet of each H-shaped steel arch 2-1 on the edges of the two sides of the step, and punching a foot locking anchor pipe 2-2, wherein the foot locking anchor pipe 2-2 is welded with the corresponding H-shaped steel arch 2-1.

Specifically, the length of each excavation rule is 3-3.6 m, and the truss distance between the outer H-shaped steel arches 2-1 longitudinally adjacent to the tunnel is 0.3-0.5 m.

S22) excavating middle steps on the left side and the right side of a soft rock tunnel, reserving core soil, butting the outer H-shaped steel arches 2-1 in the step S21), and punching a foot locking anchor pipe 2-2 at the position of each H-shaped steel arch 2-1 close to the left side edge and the right side edge of the middle step, wherein the foot locking anchor pipe 2-2 is fixedly connected with the corresponding H-shaped steel arch 2-1, and concrete 2-3 is sprayed between the H-shaped steel arches 2-2 longitudinally arranged in the middle step to the designed thickness.

The excavation footage is determined according to the distance between the primary support steel frames, and in the embodiment, the maximum excavation height is not more than 1.6m, the excavation height is 2.08m, and the steps on the left side and the right side are staggered by 2m.

Specifically, after the left middle step and the right middle step of a soft rock tunnel are excavated, immediately and initially spraying concrete of 2-3 cm on the side walls of the left middle step and the right middle step, paving a reinforcing steel mesh 2-6, erecting an outer layer H-shaped steel arch 2-1, tightly attaching the positions 20-40 cm above the arch feet of each H-shaped steel arch 2-1 on the edges of the left side and the right side of the middle step, and punching a foot locking anchor pipe 2-2, wherein the foot locking anchor pipe 2-2 is welded with the corresponding H-shaped steel arch 2-1.

S23) clinging to the outer sides of the concrete 2-3 at the positions of the upper step and the middle step, and erecting inner-layer U-shaped steel arches 2-4 at intervals along the longitudinal direction of the tunnel.

Specifically, the truss distance between the longitudinally adjacent inner U-shaped steel arches 2-4 of the tunnel is 1.0-1.4 m.

S24) excavating left and right lower steps of a soft rock tunnel, reserving core soil, butting the outer H-shaped steel arches 2-1 in the step S22), and tightly arranging a foot locking anchor pipe 2-2 at the position of each H-shaped steel arch 2-1 on the left and right side edges of the lower steps, wherein the foot locking anchor pipe 2-2 is fixedly connected with the corresponding H-shaped steel arch 2-1, and spraying concrete 2-3 to the designed thickness between the H-shaped steel arches 2-1 longitudinally arranged on the lower steps.

The excavation footage is determined according to the distance between the primary support steel frames, in the embodiment, the maximum excavation height is not more than 1.6m, the excavation height is generally 2.5-3 m, and the steps on the left side and the right side are staggered by 2m.

Specifically, after the left and right lower steps of a soft rock tunnel are excavated, immediately and initially spraying concrete of 2-3 cm on the side walls of the left and right lower steps, paving a reinforcing steel net 2-6, erecting an outer layer H-shaped steel arch 2-1, tightly attaching the positions 20-40 cm above the arch feet of each H-shaped steel arch 2-1 on the left and right side edges of the lower steps, and punching a foot locking anchor pipe 2-2, wherein the foot locking anchor pipe 2-2 is welded with the corresponding H-shaped steel arch 2-1.

S25) excavating a soft-rock tunnel bottom arch, butting the outer H-shaped steel arches 2-1 in the step S24), sealing each outer H-shaped steel arch 2-1 into a ring, and tightly attaching the positions of the H-shaped steel arches 2-1 on the edges of the two sides of the bottom arch to form a foot locking anchor pipe 2-2, wherein the foot locking anchor pipe 2-2 is fixedly connected with the corresponding H-shaped steel arch 2-1, and concrete 2-3 is sprayed between the H-shaped steel arches 2-1 longitudinally arranged on the bottom arch to the design thickness.

Specifically, after a soft rock tunnel bottom arch is excavated, immediately and initially spraying 2-3 cm of concrete on the bottom wall of the bottom arch, paving a reinforcing steel mesh 2-6, erecting an outer layer H-shaped steel arch frame 2-1, tightly attaching to the positions 20-40 cm below the arch feet of each H-shaped steel arch frame 2-1 on the edges of the two sides of the bottom arch, and punching a foot locking anchor pipe 2-2, wherein the foot locking anchor pipe 2-2 is welded with the corresponding H-shaped steel arch frame 2-1.

S26) clinging to the outer side of the concrete 2-3 at the lower step and the bottom arch position, butting the inner U-shaped steel arches 2-4 in the step S23), sealing each inner U-shaped steel arch 2-4 into a ring, and filling polyethylene 2-5 between the supporting gaps of the outer H-shaped steel arches 2-1 and the inner U-shaped steel arches 2-4 and between the inner U-shaped steel arches 2-4 longitudinally arranged.

FIG. 2 is a schematic cross-sectional view of the yielding composite support system of the present invention; FIG. 3 is a schematic view of a steel arch and foreline canopy pre-grouting longitudinal section of the yielding composite support system of the present invention.

Specifically, the H-shaped steel arches 2-1 corresponding to the upper step, the middle step, the lower step and the bottom arch are connected by adopting connecting plates, the connecting plates are closely attached to the corresponding rock walls, and the connecting plates are connected with the rock walls by adopting bolts.

Preferably, the foot locking anchor pipes 2-2 corresponding to the upper step, the middle step, the lower step and the bottom arch are splayed foot locking anchor pipes, and the tail parts of the splayed foot locking anchor pipes are fixedly connected with the outer sides of the corresponding H-shaped steel arches 2-1 in pairs by adopting L-shaped connecting ribs.

FIG. 6 shows a flow chart of a double-layer primary support construction process in the invention; as shown in fig. 7, a process flow chart of H-beam arch construction in the present invention is shown. In the embodiment, the H-shaped steel arch 2-1 is formed by bending H125-shaped steel, is designed to be a full-section support, and has a truss distance of 40cm. After each part of the tunnel is excavated and primary spraying concrete is finished, steel frames are installed in time in steps, steel bars with phi 20 are longitudinally adopted for connection, steel bar meshes are paved and hung between the steel frames, an outer splayed foot locking anchor pipe is arranged, and then the concrete is sprayed again to the design thickness. The steel arch bending and tunnel excavation combined method adopts a section steel bending machine to bend according to the section curvature of the tunnel, and after the bending is finished, trial assembly is carried out on a trial assembly die frame. In the assembling process of each section of steel frame, the required dimension is accurate, the arc shape is round and smooth, and the contour error along the periphery of the tunnel is required to be not more than 3cm; when the steel arch is horizontally placed, the plane warping is smaller than 2cm.

The H-shaped steel arch centering 2-1 is installed immediately after the primary spraying of the face excavation is finished, and whether the primary spraying is needed or not can be determined according to the actual surrounding rock exposure condition. According to the position of the test, each section of H-shaped steel arch frame 2-1 is connected with the face by bolts, and the connecting plates are closely attached. In order to ensure that each section of H-shaped steel arch frame 2-1 is placed on a stable foundation before full ring closure, the broken residues and sundries under the bottom foot of each section of H-shaped steel arch frame 2-1 should be removed before installation.

After the H-shaped steel arch 2-1 is excavated and installed at the arch part, as the self stability of surrounding rock is poor and the excavation of each part is pulled away for a certain distance, the H-shaped steel arch 2-1 cannot be closed in a full section in a short time, and the vault H-shaped steel arch 2-1 possibly sinks, so that the surrounding rock is unstable or invades a lining limit, the monitoring and measurement of the H-shaped steel arch 2-1 after being installed are required to be enhanced in the construction process, and effective measures are taken to strengthen if necessary, so that the vault H-shaped steel arch 2-1 is prevented from sinking. The specific measures are as follows: after the H-shaped steel arch 2-1 is installed, spraying concrete to seal in time so as to finish stress; collision and damage during construction are prevented.

In this embodiment, the U-shaped steel arch 2-4 adopts U29-shaped steel, each truss is divided into 5 sections, the upper half section 3 and the lower half section 2, as shown in fig. 8, which is a schematic drawing of a processing section of the U-shaped steel arch in the present invention. The U-shaped steel arch centering 2-4 is installed by adopting a two-step method, after the upper and middle steps of each bin of H125-shaped steel are supported, the upper 3 sections of the U29-shaped steel are fixed between each H125-shaped steel by adopting a hanging embedded part and a foot locking anchor pipe 2-2 in time, and after the H125-shaped steel is closed into a ring, the U-shaped steel must be immediately closed into a ring.

The arch crown is suspended and fixed by adopting phi 25 steel bars to manufacture U-shaped steel arch frames 2-4, 1 pair of L=4.5m and phi 63 pin locking anchor pipes 2-2+phi 25 and double U-shaped steel bars are respectively used for manufacturing locking members at the position 60cm upwards of left and right arch legs of the arch wire, the U-shaped steel arch frames 2-4 are locked on the locking members, and the U-shaped steel arch frames 2-4 are welded with the phi 25 and the double U-shaped steel bars.

The arch foot of each step of the tunnel adopts a phi 63 multiplied by 6 outer splayed locking anchor pipe 2-2, the phi 63 multiplied by 6 outer splayed locking anchor pipe 2-2 has a length of 6m, the camber angle is 15 degrees, the downward inclination angle is 30 degrees to 45 degrees, and the L-shaped connecting ribs are welded with the outer sides of the arches pairwise.

Spraying operation procedure of concrete 2-3: opening wind, slowly opening a main wind valve, starting an accelerator metering pump, a main motor and a vibrator, and adding concrete into a hopper.

The concrete 2-3 spraying operation should be performed in sequence of sectioning, slicing and layering, and the spraying sequence should be from bottom to top. When spraying, the depression is sprayed approximately flat, and then is sprayed in a layered and reciprocating manner from bottom to top. The spraying speed is appropriate to facilitate the compaction of the concrete. The wind pressure is too high, the injection speed is increased, and the rebound is increased; the air pressure is too small, the spraying speed is too small, the compaction force is small, and the strength of sprayed concrete is affected. Therefore, after the machine is started, the wind pressure needs to be observed, the operation can be started after the initial wind pressure reaches 0.5MPa, and the operation can be adjusted according to the discharging condition of the nozzle. The wind pressure of the common work is 0.4MPa to 0.45MPa. The spray is performed with a suitable distance between the nozzle and the sprayed surface, and the spray angle is perpendicular to the sprayed surface, so that maximum compaction and minimum rebound are obtained. The distance between the nozzle and the sprayed surface is preferably 0.6-1 m; the nozzle should continuously and slowly make transverse circular movement, one circle is pressed for half a circle, and the circular ring drawn by the hand is sprayed; the spraying operation should change the distance between the spraying angle of the spraying nozzle and the sprayed surface, the back of the steel frame and the steel bar net should be sprayed and filled tightly, and if necessary, grouting and filling should be carried out after the steel frame and the primary support.

FIG. 9 shows a construction process flow chart of the foot locking anchor pipe in the invention; as shown in fig. 10, a flow chart of the construction process of the shotcrete according to the present invention is shown.

S3) repeating the steps S1) and S2), and carrying out second and third cycle excavation supporting. The length of the excavation rule is 3-3.6 m in each cycle, and after three tunnel bottom excavation and supporting cycles are completed, the bottom arch primary support is timely applied after excavation.

S4) clinging to the outer side of the double-layer primary supporting structure 2, and arranging a slow-release energy dissipation layer 3.

Specifically, the slow-release energy dissipation layer 3 is composed of polyethylene prefabricated blocks, and the polyethylene prefabricated blocks are adhered to the outer side of the double-layer primary supporting structure 2 during construction. After the primary support construction procedure, the size and specification of the polyethylene precast block are processed on site according to construction requirements, and the polyethylene material should avoid high temperature and open flame environment as much as possible, if flame retardant measures should not be taken to prevent combustion damage.

S5) clinging to the outer side of the slow-release energy dissipation layer 3, and casting the reinforced concrete lining layer 4.

The construction flow of the reinforced concrete lining layer 4 is as follows: measuring and paying out, positioning steel bars, binding outer layer distributing steel bars, binding inner layer steel bars and binding inner layer distributing steel bars.

The casting of concrete should be carried out continuously in sections and layers, and the height of the casting layer should be determined according to the concrete supply capacity, the primary casting amount, the initial setting time of the concrete, the air temperature, the structural characteristics and the steel bar density, and can be 30 cm-40 cm.

When the concrete is poured, whether the template, the reinforcing steel bars, the reserved holes, the embedded parts, the dowel bars and the like move, deform or block is frequently observed, the problem is found to be immediately processed, and the concrete is allowed to stay intact before the poured concrete is initially set.

The first layer window and the second layer window are respectively provided with 1 inserted vibrator for compaction, and 8 attached vibrators are used outside the bin for vibration. The plug-in vibrator is required to be plugged in and pulled out quickly, plug-in points are required to be arranged uniformly, the plug-in points are moved point by point and are sequentially carried out, omission is avoided, and uniform compaction is achieved. The distance between movements is not more than 1.5 times the radius of vibration (typically 30 cm). When the upper layer is vibrated, the lower layer is inserted by 5cm so as to firmly combine the two layers of concrete. When vibrating, the vibrating rod cannot touch the steel bars and the templates. The vibration time is determined by a site vibration test, the vibration time is 30s per time without test data according to the standard requirement, and the concrete coarse aggregate is not obviously sunk and starts to flood, so that the leakage vibration, the lack of vibration and the excessive vibration are avoided. The side arch concrete should be evenly and symmetrically fed according to a certain thickness, the concrete surface should be evenly and horizontally symmetrically lifted, the height difference at two sides should not be more than 30cm, and unnecessary construction joints are not allowed to be generated. When the blocking head template is blocked, a template is reserved in the center of the vault, the template is temporarily not blocked, and when concrete is poured to the vault, the reserved template is gradually blocked along with the rising of the height of the concrete, so that the full-warehouse pouring of the vault concrete is ensured.

When concrete is poured under the working window for 50cm, before the working window is closed, concrete slurry residues and other dirt near the window are cleaned, a release agent is coated, the concrete is tightly closed, and uneven patches and even slurry leakage on the concrete surface at the window position are prevented.

And after the concrete is poured, the water spraying and curing are started after the concrete is initially set, and the curing is performed for a minimum of 28 days. And after the concrete is finally set, the blocking head template can be dismantled, the mold can be dismantled after the strength of the top arch concrete reaches 5MPa and the strength of the bottom arch concrete reaches more than 2.5MPa, the concrete surface is subjected to sprinkling and moisturizing maintenance after the mold is dismantled, the concrete surface is guaranteed to be moist, the maintenance period is 28 days, and the concrete maintenance is provided with special personnel for charge, and a maintenance record is made. As shown in fig. 11, a process flow chart of the reinforced concrete lining course construction in the invention is shown.

The method for controlling the deformation of the surrounding rock in the construction of the soft-rock tunnel yielding composite supporting system by the step method has the capacity of jointly deforming with the surrounding rock while providing stable supporting force, can effectively control the large deformation of the surrounding rock of the soft-rock tunnel, and solves the problems of limit invasion and instability of a supporting structure; meanwhile, the stress characteristic of the reinforced concrete lining layer is effectively improved, the reinforced concrete lining layer is prevented from cracking, and the long-term stability of the reinforced concrete lining layer is ensured.

The above examples are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above examples, and any other changes, modifications, substitutions, combinations, and simplifications that do not depart from the spirit and principle of the present invention should be made in the equivalent manner, and the embodiments are included in the protection scope of the present invention.

Claims (10)

1. The method for controlling deformation of surrounding rock in step-method construction of soft-rock tunnel yielding composite support system is characterized by comprising the following steps:

S1) pre-grouting by adopting a self-advancing type advance pipe shed (1) before first cyclic excavation supporting, and carrying out advanced reinforcement on the vault of the soft-rock tunnel;

s2) dividing the cross section of the soft rock tunnel into an upper step, a middle step, a lower step and a bottom arch from top to bottom in sequence, and arranging a double-layer primary supporting structure (2) on each step and the bottom arch, wherein the concrete steps are as follows,

S21), firstly excavating a step arc-shaped pilot pit on a soft rock tunnel in a circumferential direction, reserving core soil, erecting outer H-shaped steel arches (2-1) at intervals along the longitudinal direction of the tunnel, and arranging a foot locking anchor pipe (2-2) at the position of each H-shaped steel arch (2-1) close to the edges of the two sides of the upper step, wherein the foot locking anchor pipe (2-2) is fixedly connected with the corresponding H-shaped steel arch (2-1), and spraying concrete (2-3) between the H-shaped steel arches longitudinally arranged on the upper step to the designed thickness;

s22) excavating middle steps on the left side and the right side of a soft rock tunnel, reserving core soil, butting all outer H-shaped steel arches (2-1) in the step S21), and tightly attaching all H-shaped steel arches (2-1) on the left side and the right side edges of the middle steps to form foot locking anchor pipes (2-2), wherein the foot locking anchor pipes (2-2) are fixedly connected with the corresponding H-shaped steel arches (2-1), and concrete (2-3) is sprayed between all H-shaped steel arches (2-2) longitudinally arranged on the middle steps to reach the designed thickness;

S23) clinging to the outer sides of the concrete (2-3) at the positions of the upper step and the middle step, and erecting inner-layer U-shaped steel arches (2-4) at intervals along the longitudinal direction of the tunnel;

S24) excavating left and right lower steps of a soft rock tunnel, reserving core soil, butting all outer H-shaped steel arches (2-1) in the step S22), and tightly arranging foot locking anchor pipes (2-2) at the positions of all H-shaped steel arches (2-1) on the left and right side edges of the lower steps, wherein the foot locking anchor pipes (2-2) are fixedly connected with the corresponding H-shaped steel arches (2-1), and spraying concrete (2-3) between all H-shaped steel arches (2-1) longitudinally arranged on the lower steps to the designed thickness;

S25) excavating a soft-rock tunnel bottom arch, butting all outer-layer H-shaped steel arches (2-1) in the step S24), sealing each outer-layer H-shaped steel arch (2-1) into a ring, and tightly attaching the positions of all the H-shaped steel arches (2-1) on the edges of the two sides of the bottom arch to form a foot locking anchor pipe (2-2), wherein the foot locking anchor pipe (2-2) is fixedly connected with the corresponding H-shaped steel arch (2-1), and spraying concrete (2-3) between all the H-shaped steel arches (2-1) longitudinally arranged on the bottom arch to the designed thickness;

S26) clinging to the outer side of the concrete (2-3) at the lower step and the bottom arch position, butting the inner U-shaped steel arches (2-4) in the step S23), sealing each inner U-shaped steel arch (2-4) into a ring, and filling polyethylene (2-5) between the outer H-shaped steel arch (2-1) and the supporting gap of the inner U-shaped steel arch (2-4) and between the inner U-shaped steel arches (2-4) longitudinally arranged;

S3) repeating the steps S1) and S2), and carrying out second and third cycle excavation supporting;

S4) clinging to the outer side of the double-layer primary supporting structure (2), and arranging a slow-release energy dissipation layer (3);

s5) clinging to the outer side of the slow-release energy dissipation layer (3), and casting a reinforced concrete lining layer (4) in situ.

2. The soft rock tunnel yielding composite support system step method construction surrounding rock deformation control method according to claim 1, which is characterized by comprising the following steps: in S1), a plurality of self-advancing pipe sheds (1) are arranged at intervals in a range of 160 degrees for the arch crown of the soft-rock tunnel, each pipe shed (1) longitudinally inclines towards the tunnel, and the camber angle is 5-10 degrees.

3. The soft-rock tunnel yielding composite support system step method construction surrounding rock deformation control method according to claim 2, which is characterized by comprising the following steps: in the S1), the pipe sheds (1) are drilled and installed according to the first odd holes and the second even holes, and the pipe sheds (1) in the adjacent cyclic excavation support are installed in a staggered mode.

4. The soft-rock tunnel yielding composite support system step method construction surrounding rock deformation control method according to claim 3, wherein the method is characterized by comprising the following steps: in S1), the grouting sequence is from bottom to top, the slurry is concentrated and then diluted, the grouting amount is larger and then smaller, and the grouting pressure is from small to large.

5. The soft rock tunnel yielding composite support system step method construction surrounding rock deformation control method according to claim 1, which is characterized by comprising the following steps:

S21), after a step arc pilot pit on a soft rock tunnel is excavated in a circumferential direction, immediately and initially spraying 2-3 cm of concrete on the top wall of the step arc pilot pit, paving a reinforcing steel mesh (2-6), erecting an outer layer H-shaped steel arch (2-1), and tightly attaching the positions 20-40 cm above the arch feet of each H-shaped steel arch (2-1) on the edges of the two sides of the step, and punching a foot locking anchor pipe (2-2);

s22), after the left middle step and the right middle step of the soft rock tunnel are excavated, immediately and primarily spraying 2-3 cm concrete on the side walls of the left middle step and the right middle step, paving a reinforcing mesh (2-6), erecting an outer layer H-shaped steel arch (2-1), and tightly attaching the positions 20-40 cm above the arch feet of each H-shaped steel arch (2-1) at the edges of the left side and the right side of the middle step, and punching a foot locking anchor pipe (2-2);

S24), after the left and right lower steps of the soft rock tunnel are excavated, immediately and primarily spraying 2-3 cm of concrete on the side walls of the left and right lower steps, paving a reinforcing mesh (2-6), erecting an outer layer H-shaped steel arch (2-1), and tightly attaching the positions 20-40 cm above the arch feet of each H-shaped steel arch (2-1) on the left and right side edges of the lower steps, and punching a foot locking anchor pipe (2-2);

S25), after a soft rock tunnel bottom arch is excavated, immediately and initially spraying 2-3 cm of concrete on the bottom wall of the bottom arch, paving a reinforcing mesh (2-6), erecting an outer layer H-shaped steel arch (2-1), and tightly attaching to the positions 20-40 cm below the arch feet of each H-shaped steel arch (2-1) at the edges of the two sides of the bottom arch, and punching a foot locking anchor pipe (2-2).

6. The method for controlling deformation of surrounding rock during construction of soft-rock tunnel yielding composite support system by a step method is characterized by comprising the following steps of: s21), excavating the length of the entering ruler for each cycle to be 3-3.6 m, wherein the truss distance between the outer H-shaped steel arches (2-1) longitudinally adjacent to the tunnel is 0.3-0.5 m; s23), the truss distance between the longitudinally adjacent inner U-shaped steel arches (2-4) of the tunnel is 1.0-1.4 m.

7. The soft rock tunnel yielding composite support system step method construction surrounding rock deformation control method according to claim 6, which is characterized in that: s2), connecting plates are adopted to connect the H-shaped steel arches (2-1) corresponding to the upper step, the middle step, the lower step and the bottom arch, the connecting plates are closely attached to the corresponding rock wall, and the connecting plates are connected with the rock wall through bolts.

8. The soft rock tunnel yielding composite support system step method construction surrounding rock deformation control method according to claim 7, wherein the method is characterized in that: in S2), the foot locking anchor pipes (2-2) corresponding to the upper step, the middle step, the lower step and the bottom arch are splayed foot locking anchor pipes, and the tail parts of the splayed foot locking anchor pipes are fixedly connected with the outer sides of the corresponding H-shaped steel arches (2-1) in pairs by adopting L-shaped connecting ribs.

9. The soft rock tunnel yielding composite support system step method construction surrounding rock deformation control method according to claim 1, which is characterized by comprising the following steps: s4), the slow-release energy dissipation layer (3) is formed by polyethylene precast blocks, and the polyethylene precast blocks are adhered to the outer side of the double-layer primary supporting structure (2) during construction.

10. The soft rock tunnel yielding composite support system step method construction surrounding rock deformation control method according to claim 1, which is characterized by comprising the following steps: in the S1), before pre-grouting of the advance pipe shed (1), advanced geological forecast is adopted for detecting and collecting engineering geology and hydrogeology conditions in a set distance in front of the tunnel face.