CN117966638A - High-position high-steep falling stone protection structure suitable for 8000KJ falling stone impact energy level - Google Patents
High-position high-steep falling stone protection structure suitable for 8000KJ falling stone impact energy level Download PDFInfo
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Abstract
The invention discloses a high-position high-steep falling stone protection structure suitable for 8000KJ falling stone impact energy level, which belongs to the falling stone protection field, and comprises a protection net arranged at one side of an entrance and an exit of a mountain tunnel or at the side of a mountain slope, wherein the protection net is fixed on the ground through a plurality of support columns; the protection net is a grid structure formed by criss-cross multiple transverse NPR steel strands and multiple longitudinal NPR steel strands, two ends of each transverse NPR steel strand penetrate through a support column at the outermost end and then extend continuously, and the extending part is anchored on a mountain slope or the ground after prestress is applied. The invention adopts the high-position high-steep falling stone protection structure with the structure and suitable for 8000KJ falling stone impact energy level, adopts the NPR steel strands which are crisscrossed vertically and horizontally to form the protection net, and can effectively break through the falling stone impact protection energy level of the traditional passive protection net by utilizing the yield elongation and the fracture elongation of the NPR steel strands, thereby having remarkable collapse falling stone impact effect on high-position high-steep high dangerous rock bodies.
Description
Technical Field
The invention relates to the technical field of falling stone protection, in particular to a high-position high-steep falling stone protection structure suitable for 8000KJ falling stone impact energy level.
Background
When the railway and highway is built in mountain areas, the road is limited by the topography, and the road can inevitably pass through the mountains and the steep hills in the form of bridges and tunnels. The geological conditions between mountain bodies are severe, and bridge tunnels are usually required to traverse dangerous rock body influence areas. Dangerous rock mass has become one of the main geological disasters threatening the driving safety of mountain railway highways. Once the dangerous rock collapses, the impact energy is enough to destroy the common protective measures, the light person causes the interruption of railway driving, and the heavy person causes the overturning of the train or serious personnel injury.
At present, the method and means for remedying the geological disaster of the dangerous rock body are limited, mainly comprising blasting clearing, reinforcing, intercepting, blocking and bypassing, and the measures are often complex in construction, high in manufacturing cost and even damage to the surrounding ecological environment. On the basis, the active protective net and the passive protective net are applied. Further in 1995, flexible protection nets were introduced domestically and applied first to hydropower engineering, and then gradually applied to railway and highways.
The patent CN218880898U discloses a low-loss safe side slope passive protection net, which mainly comprises a protection net body, a mounting column, a reinforcing rod and a first mounting seat. Both sides of protection network body and the inboard fixed connection of erection column, the spout has all been seted up to the bottom of erection column front and back, and the equal fixedly connected with installation slider in the right side of first mount pad inner wall front side and rear side, the surface and the inner wall sliding connection of spout of installation slider. Through setting up first mount pad, user accessible unscrews the screw rod and takes out the screw rod, and then the user is rotatory with the erection column right side to dismantle the protection network body and take off, solved protection network and slope and be through welded fastening, lead to the protection network when appearing damaging, it is not enough convenient to change and maintenance with the protection network, thereby reduced the problem of change efficiency by a wide margin, reached the effect of being convenient for change the protection network. However, the falling rocks of the protection net have lower impact protection energy level, and cannot meet the protection requirement of the high-level high-steep high-dangerous rock body collapse falling rocks in the mountain area.
Meanwhile, researchers also research and develop a passive protection system, and as patent CN109681228A discloses a three-dimensional protection design method for a falling stone disaster at a tunnel portal. The construction steps are as follows: (1) The energy dissipation proportion principle of each structure of the curtain type protective net above the tunnel portal, the branch guide net and the curtain type protective net at the two sides of the tunnel portal is defined; (2) Determining the width, length and longitudinal initial position of a curtain type protective net above a tunnel portal; (3) Determining the width, length, relation with the hole, horizontal slope, longitudinal slope position and angle of the branch guide net; (4) Determining the width and the span of curtain type protective nets at two sides of a tunnel portal; (5) Determining the primary selection of each part of the curtain type protective net above the tunnel portal, the branch guide net and the curtain type protective nets on the two sides of the tunnel portal; (6) And determining the length and the height of the flexible shed tunnel at the tunnel portal. The technology adopts the design principle of energy matching, so that the design of each structure is more scientific and reasonable, the detailed design of each structure is considered, and the three-dimensional protection of falling rocks at the tunnel portal is realized. However, the protection system has a complex structure and a long construction period, and can be realized only by a better construction platform.
Under the action of natural disasters such as rainwater, earthquake and the like, the high-level high-steep high-dangerous rock body is easy to form collapse rock, and the collapse rock is large in volume, high in speed and high in impact energy, so that the passive protective net with limited energy level range for the traditional collapse rock impact is not suitable any more. However, currently, researches on a falling stone impact protection system for high-efficiency construction above 8000kJ are carried out.
Disclosure of Invention
In order to solve the problems, the invention provides a high-position high-steep falling stone protection structure suitable for 8000KJ falling stone impact energy level, which adopts the NPR steel strands which are criss-cross to form a protection net, and can effectively break through the falling stone impact protection energy level of the traditional passive protection net by utilizing the yield elongation and the fracture elongation of the NPR steel strands, and has remarkable collapse falling stone impact effect on high-position high-steep high dangerous rock bodies.
In order to achieve the aim, the invention provides a high-position high-steep falling stone protection structure suitable for 8000KJ falling stone impact energy level, which comprises a protection net arranged at one side of an entrance and an exit of a mountain tunnel or at the side of a mountain slope, wherein the protection net is fixed on the ground through a plurality of support columns;
The protection net is a grid structure formed by criss-cross multiple transverse NPR steel strands and multiple longitudinal NPR steel strands, two ends of each transverse NPR steel strand penetrate through a support column at the outermost end and then extend continuously, the extending part is anchored on a mountain slope or the ground after prestress is applied, and the extending part of each transverse NPR steel strand and the protection net are located on the same plane.
Preferably, the heights of the support columns and the protective screening are more than or equal to 12m;
the yield elongation of the transverse NPR steel strand and the longitudinal NPR steel strand are both more than or equal to 0.2 percent, and the fracture elongation of the transverse NPR steel strand and the longitudinal NPR steel strand are both more than or equal to 20 percent.
Preferably, the distance between two adjacent transverse NPR steel strands is less than or equal to 0.3m;
and the spacing between two adjacent transverse NPR steel strands meets the following relation:
H N is the interval between two adjacent transverse NPR steel strands; n is the number of the transverse NPR steel strands; v ls is the equivalent volume of the falling stone;
Wherein, the number n of the transverse NPR steel strands satisfies the following relation:
MgH≤n(W1+W2) (2)
W1＝F2Lδ1-F1Lδ0 (3)
W2＝F2L(δ2-δ1) (4)
Wherein M is the mass of falling rocks; g is gravity acceleration; h is the vertical height equivalent value of the slope surface of the mountain; w 1 is the elastic stage work of a single transverse NPR steel strand; w 2 is the plastic stage work of a single-beam transverse NPR steel strand; f 1 is the pretightening force applied to the single transverse NPR steel strand; f 2 is the yield critical force of the single-beam transverse NPR steel strand; l is the length of a single transverse NPR steel strand; delta 0 is the pretightening stretching rate of a single-beam transverse NPR steel strand; delta 1 is the yield elongation of a single-beam transverse NPR steel strand; delta 2 is the plastic deformation elongation of a single bundle of transverse NPR steel strands.
Preferably, the transverse NPR steel strand and the longitudinal NPR steel strand are connected through a fastener;
the fasteners comprise T-shaped fasteners and cross-shaped fasteners, and the T-shaped fasteners and the cross-shaped fasteners are made of NPR alloy steel;
The T-shaped fastener is used for connecting a set beam of transverse NPR steel strands at the top with a crossed single Shu Shuxiang NPR steel strand and connecting a set beam of transverse NPR steel strands at the bottom with a crossed single Shu Shuxiang NPR steel strand;
the cross-shaped fastener is used for connecting a single transverse NPR steel strand positioned between a set transverse NPR steel strand at the top of the connection and a set transverse NPR steel strand positioned at the bottom of the connection with a crossed single Shu Shuxiang NPR steel strand;
the beam is set to be at least two beams.
Preferably, the T-shaped fastener comprises a cutting sleeve for penetrating through a set bundle of transverse NPR steel strands at the top or a set bundle of transverse NPR steel strands at the bottom, a U-shaped connecting fork lug with one end connected with the cutting sleeve and a wedge-shaped assembly connected with the other end of the U-shaped connecting fork lug, wherein the wedge-shaped assembly comprises a wedge-shaped cutting sleeve with one end connected with the outer wall of the U-shaped connecting fork lug through a locking nut, a wedge-shaped hole cavity is formed in the wedge-shaped cutting sleeve far away from the inner part of one end of the U-shaped connecting fork lug, a wedge-shaped clamping ring is axially arranged in the wedge-shaped hole cavity in a sliding manner, and a vertical NPR steel strand is clamped in the wedge-shaped clamping ring; the U-shaped connecting fork lug stretches into the wedge-shaped clamping sleeve and is in pressure connection with the wedge-shaped clamping ring through a compression nut, and the compression nut is fixedly connected with the outer circumferential side of the vertical NPR steel strand passing through the wedge-shaped clamping ring;
The cross fastener comprises a base body and cover plates arranged at the upper end and the lower end of the base body through bolts, wherein a transverse groove and a longitudinal groove are respectively formed between the top end of the base body and the corresponding cover plate and between the bottom end of the base body and the corresponding cover plate, and transverse NPR steel strands and longitudinal NPR steel strands are respectively clamped in the transverse groove and the longitudinal groove.
Preferably, the support column is divided into j equal parts according to the length h 1 from top to bottom, and the bending moment calculation formula of the support column is as follows:
Wherein E is the elastic modulus of the support column; i is the section inertia distance of the support column; x k is the horizontal deflection of the k support column, x k+1 is the horizontal deflection of the k+1st support column, and x k-1 is the horizontal deflection of the k-1 st support column; and k.epsilon.2, j-1.
Preferably, a plurality of pre-stressed anchor cables are uniformly fixed on the support column from top to bottom, and the plane formed by the pre-stressed anchor cables is vertical to the plane where the protective net is positioned;
the prestressed anchor cable is anchored to the ground.
Preferably, the support column comprises a plurality of vertical reinforcing bars which are arranged at equal intervals, and a concrete protection layer poured on the vertical reinforcing bars;
the support column is divided into an upper section, a middle section and a bottom section from top to bottom, and the height ratio of the upper section, the middle section and the bottom section is (0.8-1.2): (4.8-5.2): (2.8-3.2);
The ratio of the intervals of the prestressed anchor cable to the upper section, the middle section and the bottom section is (0.9-1.1): (1.4-1.6): (2.9-3.1).
Preferably, the number of vertical reinforcements satisfies the following formula:
Wherein m is the number of vertical reinforcing bars; m τ is the bending moment of a single support column; f y is the yield strength of the vertical reinforcement; a s is the sectional area of a single vertical reinforcement; h 0 is the cross-sectional height of the single support column; a' s is the thickness of the concrete protective layer on the individual support columns.
The invention has the following beneficial effects:
1. The yield elongation and the breaking elongation of the NPR steel strands can effectively break through the falling rock impact protection energy level of the traditional passive protection net, and meanwhile, the method has the advantages of high efficiency in construction, easiness in maintenance and the like, and has remarkable impact effect on falling rock collapse of high-level high-steep dangerous rock bodies in tunnel entrance and exit and shed tunnel protection between two mountain slopes;
2. The height of the protective net can be set to be at least 12m, so that the protective height of the passive protective net is 6-10 times of that of the traditional passive protective net;
3. Because the support column lateral NPR steel strand is directly anchored on the slope surface of a mountain or the ground, the high-efficiency construction of the passive protection system can be realized;
4. By calculating the spacing and the number of the transverse NPR steel strands, the protection system can realize the protection of high-level high-steep high-crisscross rock high-level falling rock impact under the conditions that the height of the protection net is more than or equal to 12m, the yield elongation of the NPR steel strands is more than or equal to 0.2 percent, and the breaking elongation is more than or equal to 20 percent;
5. Based on analysis of the impact characteristics of falling rocks, the prestressed anchor cables distributed at different intervals are arranged, and the number of the prestressed anchor cables is designed in advance, so that the stability of the whole support column is ensured.
The technical scheme of the invention is further described in detail through the drawings and the embodiments.
Drawings
FIG. 1 is a schematic installation diagram of a high-level high-steep falling stone protection structure suitable for 8000KJ falling stone impact energy level;
FIG. 2 is a schematic structural view of a cross fastener of the present invention for a high-level high-steep falling-stone protection structure with an impact energy level of 8000KJ falling-stone;
FIG. 3 is a schematic structural view of a T-shaped fastener of the present invention for a high-level high-steep falling-stone protection structure with an impact energy level of 8000KJ falling-stone;
fig. 4 is a schematic diagram of a support column structure of a high-level high-steep falling stone protection structure suitable for 8000KJ falling stone impact energy level according to the present invention.
Wherein: 1. a protective net; 11. transverse NPR steel strands; 12. longitudinal NPR steel strands; 2. a support column; 3. cross-shaped fasteners; 4. a T-shaped fastener; 41. a cutting sleeve; 42. u-shaped connecting fork lugs; 43. a lock nut; 44. a compression nut; 45. a wedge-shaped snap ring; 46. wedge-shaped cutting ferrule.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application more apparent, the embodiments of the present application will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the detailed description and specific examples, while indicating the embodiment of the application, are intended for purposes of illustration only and are not intended to limit the scope of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application. Examples of the embodiments are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements throughout or elements having like or similar functionality.
It should be noted that the terms "comprises" and "comprising," along with any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or server that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed or inherent to such process, method, article, or apparatus, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
Like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further definition or explanation thereof is necessary in the following figures.
In the description of the present invention, it should be noted that, directions or positional relationships indicated by terms such as "upper", "lower", "inner", "outer", etc., are directions or positional relationships based on those shown in the drawings, or those that are conventionally put in use, are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the apparatus or elements to be referred to must have a specific direction, be constructed and operated in a specific direction, and thus should not be construed as limiting the present invention.
In the description of the present invention, it should also be noted that, unless explicitly specified and limited otherwise, the terms "disposed," "mounted," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.
Aiming at the high-level high-steep high-risk collapse rock-fall dangerous rock mass, the invention is designed: as shown in figure 1, the high-position high-steep falling stone protection structure suitable for 8000KJ falling stone impact energy level comprises a protection net 1 arranged at one side of an entrance and an exit of a mountain tunnel or at one side of a slope surface of a mountain, wherein the protection net 1 is fixed on the ground (the support columns 2 are embedded in a hard rock stratum below the ground) through a plurality of support columns 2, and the space between the support columns 2 is determined according to the width of a canyon between two mountains; the protection net 1 is a grid structure formed by a plurality of transverse NPR steel strands 11 and a plurality of longitudinal NPR steel strands 12 which are crisscrossed, two ends of the transverse NPR steel strands 11 pass through a support column 2 positioned at the outermost end and then continue to extend, the extension part is anchored on a slope surface of a mountain or the ground after prestressing force is applied (the transverse NPR steel strands 11 apply pretightening force before anchoring so as to realize tensioning of the protection net 1), and the extension part of the transverse NPR steel strands 11 and the protection net 1 are positioned on the same plane.
The heights of the support columns 2 and the protective net 1 are more than or equal to 12m; the yield elongation of the transverse NPR steel stranded wire 11 and the longitudinal NPR steel stranded wire 12 is more than or equal to 0.2%, and the fracture elongation of the transverse NPR steel stranded wire 11 and the longitudinal NPR steel stranded wire 12 is more than or equal to 20%.
In order to avoid the situation that mountain collapse rock passes through the gaps among the stranded wires due to larger spacing, the spacing between two adjacent transverse NPR steel stranded wires 11 is designed as follows: the distance between two adjacent transverse NPR steel strands 11 is less than or equal to 0.3m; and the spacing between two adjacent transverse NPR steel strands 11 satisfies the following relationship:
H N is the interval between two adjacent transverse NPR steel strands 11; n is the number of the transverse NPR steel strands 11; v ls is the equivalent volume of the falling stone;
Namely, through fully considering the conditions of falling rocks and mountain bodies at the setting positions of the protection system, according to the characteristics of the transverse NPR steel strands 11, different parameters of an elastic stage and a plastic stage of the transverse NPR steel strands are considered, the number of the transverse NPR steel strands 11 to be set is finally obtained, and according to the number of the transverse NPR steel strands 11 to be set and the conditions of falling rocks, the spacing between the adjacent transverse NPR steel strands 11 is finally obtained. According to the protection net 1 arranged at intervals between the corresponding transverse NPR steel strands 11, high-energy protection of preset falling rocks, mountain tunnel inlets and outlets and shed holes can be achieved.
And the number of the longitudinal NPR steel strands 12 and the spacing between the adjacent longitudinal NPR steel strands 12 can be correspondingly set according to the spacing of the transverse NPR steel strands 11 and the historical data size of the falling rocks in the application scene. In the present embodiment, the pitch of the longitudinal NPR strands 12 is not greater than the pitch of the transverse NPR strands 11, and is not greater than the minimum value of the falling rock size in the history.
After the distance between the adjacent lateral NPR strands 11 is determined, the lateral NPR strands 11 are then threaded through the support columns 2 and are embedded on the mountain or the ground, and the embodiment anchors the lateral NPR strands 11 while embedding the lateral NPR strands 11 on the mountain. After the transverse NPR steel strand 11 is embedded and fixed on the mountain, the longitudinal NPR steel strand 12 is fixed on the transverse NPR steel strand 11 through a fastener.
When the energy of falling rocks falling from the slope of the mountain (including rolling, sliding, bouncing and the like) is researched, the energy is converted into the energy under the condition of free falling of the falling rocks according to the pre-calculated and practical scene test experience values, namely the vertical height equivalent value of the slope of the mountain is converted, so that the numerical value of the height of the slope of the mountain is replaced.
The transverse NPR steel strand 11 and the longitudinal NPR steel strand 12 have high yield strength and high uniform elongation, and the stress deformation process mainly comprises the following three stages: an elastic phase, a plastic phase and a breaking phase. When the transverse NPR steel strand 11 initially applies a pretightening force F 1, the transverse NPR steel strand 11 of the protection network is in an elastic stage; when the transverse NPR steel strand 11 of the protection network is impacted by collapse stones, the transverse NPR steel strand 11 of the protection network starts to transition from an elastic stage to a plastic stage, namely, from a pre-tightening force F 1 which is applied at the beginning to a critical force F 2 which is yielded; when the transverse NPR steel strand 11 of the protection network reaches the yield critical force F 2 after being impacted by collapse rock, the transverse NPR steel strand 11 of the protection network is plastically deformed, and the impact of the rock falling can only reach the plastic deformation stage of the transverse NPR steel strand 11 of the protection network to the maximum through the analysis and the arrangement of the protection network.
The main energy conversion in the whole process that the falling rocks impact on the protective net main body and stop is as follows: the gravitational potential energy of the collapse rock is converted into kinetic energy and is impacted to the protective net main body, the protective net main body has good extensibility, and the protective net main body is stopped by extending to do work to absorb impact energy.
The situation of falling rocks and mountain bodies at the setting position of the blocking protection structure is fully considered, different parameters of an elastic stage and a plastic stage of the transverse NPR steel strand 11 are considered according to the characteristics of the transverse NPR steel strand 11, the number of the transverse NPR steel strands 11 to be set is finally obtained, and the distance between the adjacent transverse NPR steel strands 11 is finally obtained according to the number of the transverse NPR steel strands 11 to be set and the situation of falling rocks. According to the protection net arranged at intervals between the corresponding transverse NPR steel strands 11, high-energy protection under the conditions of preset falling rocks and mountain bodies can be completed.
Wherein the number n of transverse NPR steel strands 11 satisfies the following relationship:
MgH≤n(W1+W2) (2)
W1＝F2Lδ1-F1Lδ0 (3)
W2＝F2L(δ2-δ1) (4)
Wherein M is the mass of falling rocks; g is gravity acceleration; h is the vertical height equivalent value of the slope surface of the mountain; w 1 is the elastic phase work of the single-beam transverse NPR steel strand 11; w 2 is the plastic phase work of the single-beam transverse NPR steel strand 11; f 1 is the pretightening force applied to the single transverse NPR steel strand 11; f 2 is the yield critical force of the single-beam transverse NPR steel strand 11; l is the length of a single transverse NPR steel strand 11; delta 0 is the pretightening stretching rate of the single-bundle transverse NPR steel strand 11; delta 1 is the yield elongation of the single-bundle transverse NPR steel strand 11; delta 2 is the plastic deformation elongation of the single bundle of transverse NPR steel strands 11.
The transverse NPR steel strand 11 and the longitudinal NPR steel strand 12 are connected through a fastener; the fastener comprises a T-shaped fastener 4 and a cross-shaped fastener 3, wherein the T-shaped fastener 4 and the cross-shaped fastener 3 are made of NPR alloy steel; as shown in fig. 3, the T-shaped fastener 4 is used for connecting a set bundle of transverse NPR steel strands 11 at the top with a crossed single Shu Shuxiang NPR steel strand and connecting a set bundle of transverse NPR steel strands 11 at the bottom with a crossed single Shu Shuxiang NPR steel strand; as shown in fig. 2, the cross fastener 3 is used for connecting a single transverse NPR steel strand 11 and a crossed single Shu Shuxiang NPR steel strand between a set transverse NPR steel strand 11 positioned at the top of the connection and a set transverse NPR steel strand 11 positioned at the bottom; the beam is set to be at least two beams.
The T-shaped fastener 4 comprises a clamping sleeve 41 for penetrating through a set bundle of transverse NPR steel strands 11 at the top or a set bundle of transverse NPR steel strands 11 at the bottom, a U-shaped connecting fork lug 42 with one end connected with the clamping sleeve 41 and a wedge-shaped assembly connected with the other end of the U-shaped connecting fork lug 42, wherein the wedge-shaped assembly comprises a wedge-shaped clamping sleeve 46 with one end connected with the outer wall of the U-shaped connecting fork lug 42 through a locking nut 43, a wedge-shaped cavity is formed in the inner part of one end, far away from the U-shaped connecting fork lug 42, of the wedge-shaped clamping sleeve 46, a wedge-shaped clamping ring 45 is axially arranged in the wedge-shaped cavity in a sliding manner, and a vertical NPR steel strand is clamped in the wedge-shaped clamping ring 45; the U-shaped connecting fork lug 42 stretches into the wedge-shaped clamping sleeve 46 and is in pressure connection with the wedge-shaped clamping ring 45 through the compression nut 44, and the compression nut 44 is fixedly connected with the outer circumference side of the vertical NPR steel strand passing through the wedge-shaped clamping ring 45; when the wedge assembly is used for fixing the longitudinal NPR steel strand 12, one end of the longitudinal NPR steel strand 12 is fixed through the compression nut 44, and then the wedge-shaped clamping ring 45 is extruded through the cooperation of the locking nut 43 and the wedge-shaped clamping sleeve 46, so that the wedge-shaped clamping ring 45 and the longitudinal NPR steel strand 12 are clamped and fixed.
The cross fastener 3 comprises a base body and cover plates arranged at the upper end and the lower end of the base body through bolts, wherein transverse grooves and longitudinal grooves are respectively formed between the top end of the base body and the corresponding cover plate, and between the bottom end of the base body and the corresponding cover plate, and transverse NPR steel strands 11 and longitudinal NPR steel strands 12 are respectively clamped in the transverse grooves and the longitudinal grooves. When the transverse NPR steel stranded wires 11 and the longitudinal NPR steel stranded wires 12 are fixed through the cross-shaped fastener 3, the transverse NPR steel stranded wires 11 and the longitudinal NPR steel stranded wires 12 are respectively placed in the transverse grooves and the longitudinal grooves on two sides of the base body, then the two cover plates are covered on two sides of the base body, and the cover plates and the base body are fixed through bolts, so that the fixing of the transverse NPR steel stranded wires 11 and the longitudinal NPR steel stranded wires 12 is completed.
In this embodiment, the cross-shaped fastener 3 and the T-shaped fastener 4 are made of materials with high yield strength and high uniform elongation, and take top and bottom impacts into consideration, and the transverse NPR steel strands 11 and the longitudinal NPR steel strands 12 are fixed by the fasteners, so that the whole protection net 1 system can resist high-energy level falling stone impacts.
Dividing the support column 2 into j equal parts according to the length h 1 of each section from top to bottom, and calculating the bending moment of the support column 2 according to the following formula:
Wherein E is the elastic modulus of the support column 2; i is the section inertia distance of the support column 2; x k is the horizontal deflection of the k-th support column 2, x k+1 is the horizontal deflection of the k+1th support column 2, and x k-1 is the horizontal deflection of the k-1 th support column 2; and k.epsilon.2, j-1.
The bending moment of the pile in this embodiment can also be simulated by finite elements.
Meanwhile, the section size of the support column 2 is determined by trial calculation according to the impact force transmitted to the support column 2 by the transverse NPR steel strand 11, if in a certain case, the support column 2 is 43m long, the extension length is 28m, the embedding length is 15m, the section of the support column 2 is 2.0x3.0m, 16 rows of prestressed anchor cables are arranged on the support column 2 in a propping mode, and the design load of the prestressed anchor cables is 100kN. And (3) trial calculation: the maximum bending moment of the support column 2 is 76734.40kN.m, the maximum shearing force is 5898.7064kN, the top displacement of the support column 2 is 0.041m, 108 vertical phi 32mm main ribs are arranged in a range of a single side long side of the single-side pile of the support column 2, 12 vertical phi 32mm main ribs are arranged on a short side of the single-side pile, and the transverse allowable bearing capacity of the support column 2 is 9000kPa, so that the requirements are met.
A plurality of prestressed anchor cables are uniformly fixed on the support column 2 from top to bottom, and the plane formed by the plurality of prestressed anchor cables is vertical to the plane where the protective net 1 is positioned; the prestressed anchor cable is anchored to the ground.
When the pre-stressed anchor cable is arranged in the embodiment, firstly, dangerous rock falling Dan Guiji is analyzed according to the on-site investigation condition to obtain the impact speed and the impact energy of falling rocks and the falling point range; then, giving a preliminary interval and number of pre-stressed anchor cables; and finally, carrying out numerical simulation checking calculation on the distance and the quantity of the preliminary prestressed anchor cables, if the allowable stress of the prestressed anchor cables and the bearing capacity of the support column 2 are met, checking calculation is passed, and if the checking calculation is not passed, continuing to change the distance and the quantity to carry out checking calculation until the requirements are met.
As shown in fig. 4, the support column 2 includes a plurality of equally spaced vertical reinforcement bars and a concrete protection layer poured on the vertical reinforcement bars, and the vertical reinforcement bars are configured to ensure that the support column 2 has sufficient stability against deformation caused by stretch bending; because the stress effects of the support columns 2 at different heights are different, the support columns 2 are divided into an upper section, a middle section and a bottom section from top to bottom, and the height ratio of the upper section, the middle section and the bottom section is (0.8-1.2): (4.8-5.2): (2.8-3.2); the ratio of the intervals of the prestressed anchor cable to the upper section, the middle section and the bottom section is (0.9-1.1): (1.4-1.6): (2.9-3.1).
Through carrying out corresponding design to the adjacent prestressing anchor cable interval on upper segment, middle segment, the bottom segment, can make support column 2 of this embodiment have better bearing effect to make protection system have better protection effect. Considering that the upper section is the position with the least adverse impact load, the space between the pre-stressed anchor cables is minimum, the space between the pre-stressed anchor cables in the middle section is inferior, and the space between the pre-stressed anchor cables in the bottom section is maximum. In a specific embodiment, the total length of the support column 2 is 35m, the cantilever height is 20m, the cross section size is 2m×3m, the anchoring depth is 15m, and 28 pre-stressed anchor cables are arranged.
The number of the vertical reinforcing bars meets the following formula:
Wherein m is the number of vertical reinforcing bars; m τ is the bending moment of the single support column 2; f y is the yield strength of the vertical reinforcement; a s is the sectional area of a single vertical reinforcement; h 0 is the cross-sectional height of a single support column 2; a' s is the thickness of the concrete protective layer on the single support column 2.
The construction method comprises the following steps:
S1, mounting a support column 2:
s11, pouring a bottom reinforced concrete column:
Based on the arrangement of the arrays of the support columns 2, a pile well is excavated below the mountain, vertical reinforcing bars are buried in the pile well, and then a concrete protection layer is poured;
s21, drilling holes on a mountain slope or on the ground, placing reverse pre-stress anchor cables and connecting the support columns 2:
s3, the transverse NPR steel stranded wires 11 penetrate through the support columns 2 and then extend and anchor on hillsides or the ground;
s4, arranging longitudinal NPR steel strands 12 along the transverse NPR steel strands 11, and connecting the intersected transverse NPR steel strands 11 and the longitudinal NPR steel strands 12 by using fasteners.
Examples
The entrance mileage of a certain railway tunnel is K93+583.766, the exit mileage is K96+174.792, and the total length of the tunnel is 2591.026m. The tunnel address area belongs to the erosion peak cluster Gu Demao, the mountain shape is steep, the topography is big, the depression and valley are wide. Through on-site investigation, the slope bedrock mainly takes dolomite limestone and dolomite limestone-clamped limestone as main materials, the joint and corrosion crack are relatively developed, the rock mass is continuously cut and separated by the corrosion structural surface and the joint crack surface, and the rock mass integrity is poor, so that dangerous stones are formed. Under the action of long-term gravity, the jeopardy mass gradually expands on the perpetrator surface, when the tensile stress exceeds the tensile strength of the rock at the joint, the tensile crack rapidly develops downwards, and finally the protruding rock mass is burst to form falling rocks.
The slope surface of the tunnel outlet develops 20 dangerous rocks (groups), and the high-position high-steep rocks are required to be protected against the dangerous rocks at the upper part of the tunnel upward slope besides the necessary measures such as cleaning, active protection net and the like. Through analysis of the movement track of the collapse rock of the dangerous rock body, the maximum impact energy formed by the dangerous rock body is 7999.21kJ, the bouncing height is 6.98m, and the maximum bouncing height of the slope surface is 26.88m.
At the moment, a protective net (which is formed by meshes woven by NPR steel strands, wherein the mesh spacing is 0.25mX0.25m) is arranged on the side, far away from a line, of the existing stone blocking wall, and the bouncing height is 12.63m; the energy level of the protective net for blocking dangerous rock is designed according to 8000kJ, and the blocking spring height is designed to be 20m. The longitudinal length of the protective net is 59m, and the height of each side is 20m. NPR steel lines are fixed on two support columns 2 with the cross section of 2m multiplied by 3m, the height of the support columns 2 extending out of the ground is 20m, the depth of the support columns extending into the ground is 15m, C40 reinforced concrete is adopted for coagulation, 28 NP prestressed anchor cables with the diameter of 5 phi of 25.8mm are adopted for reinforcing each support column 2, and the energy of a high-level rock mass at a protective net can be blocked by testing to be 7288.35kJ, and the impact speed is 23.67m/s.
Therefore, the high-position high-steep falling rock protection structure with the structure and suitable for 8000KJ falling rock impact energy level is adopted, the protection net is formed by adopting the NPR steel strands which are crisscrossed vertically and horizontally, the yield elongation and the fracture elongation of the NPR steel strands are utilized, the falling rock impact protection energy level of the traditional passive protection net can be effectively broken through, and the collapse falling rock impact effect on high-position high-steep high dangerous rock body is obvious.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention and not for limiting it, and although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that: the technical scheme of the invention can be modified or replaced by the same, and the modified technical scheme cannot deviate from the spirit and scope of the technical scheme of the invention.
Claims (9)
1. Be suitable for high-order high steep falling stone protective structure of 8000KJ falling stone impact energy level, its characterized in that: the protection net is fixed on the ground through a plurality of support columns;
The protection net is a grid structure formed by criss-cross multiple transverse NPR steel strands and multiple longitudinal NPR steel strands, two ends of each transverse NPR steel strand penetrate through a support column at the outermost end and then extend continuously, the extending part is anchored on a mountain slope or the ground after prestress is applied, and the extending part of each transverse NPR steel strand and the protection net are located on the same plane.
2. The high-order high-steep falling stone protection structure suitable for 8000KJ falling stone impact energy level according to claim 1, wherein: the heights of the support columns and the protective net are more than or equal to 12m;
the yield elongation of the transverse NPR steel strand and the longitudinal NPR steel strand are both more than or equal to 0.2 percent, and the fracture elongation of the transverse NPR steel strand and the longitudinal NPR steel strand are both more than or equal to 20 percent.
3. The high-order high-steep falling stone protection structure suitable for 8000KJ falling stone impact energy level according to claim 1, wherein: the distance between two adjacent transverse NPR steel strands is less than or equal to 0.3m;
and the spacing between two adjacent transverse NPR steel strands meets the following relation:
H N is the interval between two adjacent transverse NPR steel strands; n is the number of the transverse NPR steel strands; v ls is the equivalent volume of the falling stone;
Wherein, the number n of the transverse NPR steel strands satisfies the following relation:
MgH≤n(W1+W2) (2)
W1＝F2Lδ1-F1Lδ0 (3)
W2＝F2L(δ2-δ1) (4)
Wherein M is the mass of falling rocks; g is gravity acceleration; h is the vertical height equivalent value of the slope surface of the mountain; w 1 is the elastic stage work of a single transverse NPR steel strand; w 2 is the plastic stage work of a single-beam transverse NPR steel strand; f 1 is the pretightening force applied to the single transverse NPR steel strand; f 2 is the yield critical force of the single-beam transverse NPR steel strand; l is the length of a single transverse NPR steel strand; delta 0 is the pretightening stretching rate of a single-beam transverse NPR steel strand; delta 1 is the yield elongation of a single-beam transverse NPR steel strand; delta 2 is the plastic deformation elongation of a single bundle of transverse NPR steel strands.
4. The high-order high-steep falling stone protection structure suitable for 8000KJ falling stone impact energy level according to claim 1, wherein: the transverse NPR steel strand and the longitudinal NPR steel strand are connected through a fastener;
the fasteners comprise T-shaped fasteners and cross-shaped fasteners, and the T-shaped fasteners and the cross-shaped fasteners are made of NPR alloy steel;
The T-shaped fastener is used for connecting a set beam of transverse NPR steel strands at the top with a crossed single Shu Shuxiang NPR steel strand and connecting a set beam of transverse NPR steel strands at the bottom with a crossed single Shu Shuxiang NPR steel strand;
the cross-shaped fastener is used for connecting a single transverse NPR steel strand positioned between a set transverse NPR steel strand at the top of the connection and a set transverse NPR steel strand positioned at the bottom of the connection with a crossed single Shu Shuxiang NPR steel strand;
the beam is set to be at least two beams.
5. The high-order high-steep falling stone protection structure suitable for 8000KJ falling stone impact energy level according to claim 4, wherein: the T-shaped fastener comprises a cutting sleeve for penetrating through a set bundle of transverse NPR steel strands at the top or a set bundle of transverse NPR steel strands at the bottom, a U-shaped connecting fork lug with one end connected with the cutting sleeve and a wedge-shaped assembly connected with the other end of the U-shaped connecting fork lug, wherein the wedge-shaped assembly comprises a wedge-shaped cutting sleeve with one end connected with the outer wall of the U-shaped connecting fork lug through a locking nut, a wedge-shaped cavity is formed in the wedge-shaped cutting sleeve far away from the inner part of one end of the U-shaped connecting fork lug, a wedge-shaped clamping ring is axially arranged in the wedge-shaped cavity in a sliding manner, and a vertical NPR steel strand is clamped in the wedge-shaped clamping ring; the U-shaped connecting fork lug stretches into the wedge-shaped clamping sleeve and is in pressure connection with the wedge-shaped clamping ring through a compression nut, and the compression nut is fixedly connected with the outer circumferential side of the vertical NPR steel strand passing through the wedge-shaped clamping ring;
The cross fastener comprises a base body and cover plates arranged at the upper end and the lower end of the base body through bolts, wherein a transverse groove and a longitudinal groove are respectively formed between the top end of the base body and the corresponding cover plate and between the bottom end of the base body and the corresponding cover plate, and transverse NPR steel strands and longitudinal NPR steel strands are respectively clamped in the transverse groove and the longitudinal groove.
6. The high-order high-steep falling stone protection structure suitable for 8000KJ falling stone impact energy level according to claim 1, wherein: dividing the support column into j equal parts according to the length h 1 of each section from the top to the bottom, wherein the bending moment calculation formula of the support column is as follows:
Wherein E is the elastic modulus of the support column; i is the section inertia distance of the support column; x k is the horizontal deflection of the k support column, x k+1 is the horizontal deflection of the k+1st support column, and x k-1 is the horizontal deflection of the k-1 st support column; and k.epsilon.2, j-1.
7. The high-order high-steep falling stone protection structure suitable for 8000KJ falling stone impact energy level according to claim 1, wherein: a plurality of prestressed anchor cables are uniformly fixed on the support column from top to bottom, and the plane formed by the plurality of prestressed anchor cables is vertical to the plane where the protective net is positioned;
the prestressed anchor cable is anchored to the ground.
8. The high-order high-steep falling stone protection structure applicable to 8000KJ falling stone impact energy level according to claim 7, wherein: the support column comprises a plurality of vertical reinforcing bars which are arranged at equal intervals and a concrete protection layer poured on the vertical reinforcing bars;
the support column is divided into an upper section, a middle section and a bottom section from top to bottom, and the height ratio of the upper section, the middle section and the bottom section is (0.8-1.2): (4.8-5.2): (2.8-3.2);
The ratio of the intervals of the prestressed anchor cable to the upper section, the middle section and the bottom section is (0.9-1.1): (1.4-1.6): (2.9-3.1).
9. The high-order high-steep falling stone protection structure applicable to 8000KJ falling stone impact energy level according to claim 8, wherein: the number of the vertical reinforcing bars meets the following formula:
Wherein m is the number of vertical reinforcing bars; m τ is the bending moment of a single support column; f y is the yield strength of the vertical reinforcement; a s is the sectional area of a single vertical reinforcement; h 0 is the cross-sectional height of the single support column; a s' is the thickness of the concrete protective layer on the individual support columns.
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