CN115788518A - Underground large vertical tank body excavation method - Google Patents

Abstract

The invention belongs to the technical field of excavation supporting of underground caverns, and relates to an excavation method of a large-diameter cylindrical tank body. The excavation method of the underground large vertical tank body comprises the following steps: excavating an upper channel pilot tunnel, excavating a lower channel pilot tunnel, excavating a slag chute, and excavating a dome cavern by adopting an annular excavation reserved rock pillar method; and (3) dome coating construction: the ring beam and the dome concrete are separately poured, and a construction joint is reserved at the boundary of the ring beam and the shell and is 500mm close to one side of the shell; excavating the tank body: after the dome covering construction is finished and the strength of the concrete reaches 28 days, the tank body excavation is started; adopting an excavation method combining vertical layering, horizontal looping and depth; coating construction of the can body: and (5) preparing the construction of coating the tank body after the tank body is excavated and the initial support is finished. The invention provides an excavation method for an underground large vertical tank, which has the characteristics of economy, safety, rapidness and simplicity and has important significance for improving the construction efficiency and reducing the construction risk and the engineering investment.

Description

Underground large vertical tank body excavation method

Technical Field

The invention belongs to the technical field of excavation supporting of underground caverns, and particularly relates to an excavation method of a large-diameter cylindrical tank body.

Background

With the continuous development of underground space development and utilization, the underground structure is built more and more, the construction task is heavier and heavier, and the technical requirement is higher and higher. As an important component of an underground cavern, the tank body is cylindrical, has the characteristics of large section, small section of an access passage, low degree of mechanization, easy deformation and instability of surrounding rocks, difficult forming and the like, is limited by the section of the passage, is difficult to adopt large-scale excavation and supporting equipment, influences the construction progress and increases the construction cost.

An underground cave depot excavation method of a cylindrical tank body and a dome with an oversized section is proposed in the patent number CN112065470A, but the method has the following defects:

1) The slag sliding well is arranged on the opposite side of a lower channel opening of the tank body, the second part of excavation is performed by obliquely upwards excavating to the opposite side of the tank body from the bottom of the tank body to serve as a slag discharging channel for subsequent excavation, and along with the fact that a covering layer on the top of a lower channel guide hole is thinner and thinner, the probability of collapse and block falling is higher, and the safety of construction operators and equipment in the lower channel guide hole cannot be guaranteed.

2) And (3) excavating each natural layer by taking the vertical shaft excavated by the third part as an inscribed circle to outwards expand a plurality of rings, and gradually performing cylindrical expanding excavation from inside to outside until the contour line on the other side of the tank body. However, the thickness of the surrounding rock between the rings is different, the requirement on the drilling depth is higher, the control difficulty of the explosive loading of the blast hole is high, the operability is poor, and the forming quality is difficult to control.

3) Excavation and supporting are carried out simultaneously, the working procedures are changed alternately frequently, the construction period is long, and the investment is large.

4) In the tank body blasting, no effective measures are taken to protect the finished dome coating.

Therefore, a method for excavating large underground vertical tanks is needed to overcome the defects of the existing construction process.

Disclosure of Invention

The invention provides an excavation method of an underground large vertical tank body, which aims to solve the problems of low mechanization degree, difficult forming, frequent process alternation, poor stability of surrounding rocks, low construction efficiency, high construction cost and the like in the excavation process of a large-diameter vertical shaft at present.

Aiming at the defects of the prior construction technology, the invention adopts the following technical scheme:

an excavation method for an underground large vertical tank body comprises the following steps:

step one, excavating an upper channel pilot tunnel: in order to reduce the amount of temporary support engineering, the upper channel pilot tunnel adopts a direct top-raising excavation method: after the upper channel enters the dome cavern, carrying out forward flip excavation along the contour line of the top of the dome, carrying out excavation while supporting until the contour line of the inner ring is excavated, and carrying out excavation longitudinal gradient and the tangent inclination angle of the dome contour line;

step two, excavating a lower channel pilot tunnel: adopting a direct top-lifting excavation method which is the same as the excavation method of the upper channel pilot tunnel;

step three, excavating the slag chute: in order to reduce the workload of hoisting slag, improve the construction efficiency of tank body excavation slag and reduce the safety risk of hoisting slag, a slag chute connecting an upper channel and a lower channel is blasted and excavated from top to bottom right above a guide hole of the lower channel, and the diameter of the slag chute is 3.0m;

step four, excavating a dome cavern:

the dome cavern adopts an annular excavation reserved rock pillar method, namely a rock pillar reserved in the middle is used as a key support, a radial middle pilot tunnel is excavated firstly, then annular blasting excavation is carried out in sequence, after each cycle of footage excavation, preliminary bracing is carried out in time, a ring is closed as soon as possible, and finally a central rock pillar is excavated;

step five, dome covering construction: the ring beam and the dome concrete are separately poured, and a construction joint is reserved at the boundary of the ring beam and the shell and is 500mm close to one side of the shell;

step six, tank body excavation: after the dome covering construction is finished and the strength of the concrete reaches 28 days, the tank body excavation is started; the method comprises the steps of adopting an excavation method combining vertical layering, horizontal looping and depth, controlling the height of layering steps to be about 3.0m, before each layer of excavation, firstly expanding and excavating a slag chute, then expanding and excavating the slag chute from inside to outside to a reserved protective layer in a looping manner by taking the slag chute after expansion and excavation as a free surface, reserving the protective layer with the thickness of 1.0-3.0 m around a tank body for temporarily not excavating, after the excavation of a main explosion area of the layer is finished, removing the protective layer by smooth blasting in a segmenting manner, and timely following up primary support;

step seven, construction of tank body coating: after the tank body is excavated and the initial support is finished, preparing tank body coating construction; the waterproof board is laid according to the requirement before secondary lining; in order to accelerate the pouring speed, reduce the labor intensity, ensure the safety and improve the quality, the slip form is adopted to implement the tank body coating construction; assembling the slip form at the bottom of the well, and pouring concrete after the assembly is finished; the construction procedure is as follows: construction preparation → waterproof and drainage construction → reinforcement binding → slip form assembly → concrete pouring → slip form sliding up (pouring while sliding) → slip form dismantling; the tank body foundation belongs to an enlarged foundation, the section width of the tank body foundation is inconsistent with the wall thickness, and the tank body foundation is independently finished before slip form construction.

In the first step, the excavation of the tank body is limited by the section of the access passage, large-scale excavation equipment cannot be applied, and in order to overcome the limitation of small-section passage construction, the width of the passage is 4.0m, and the excavation height is 4.5m.

And in the second step, excavation and supporting are carried out according to design requirements until the position of the slag sliding well, forward tunneling is stopped, and a lower channel opening is sealed to prepare for excavating the slag sliding well from top to bottom.

And in the third step, a down-the-hole drill is adopted to vertically drill, the hole diameter of the drilled hole is about 90mm, the drilling is stopped when the hole reaches 50cm of the top surface of the lower channel, then the phi 32 emulsion explosive is filled, the detonation is carried out from inside to outside in a circle by circle, and the slag chute is communicated and then can be used as a slag discharging channel for the excavation of the dome cavern and the tank body.

In the fourth step, in the process of excavating the inner ring and the core column, a 3m high platform is reserved in the center of the cavern and is not excavated; after the fifth construction step is finished, a 3m high platform reserved in the center of the grotto can be excavated;

the construction sequence in the fifth step is as follows: primary support detection → measurement lofting → ring beam construction → temporary operation platform erection → waterproof layer construction → dome outer layer and inner layer steel bar installation → bearing support assembly → dome template and wood plate installation → support reinforcement → concrete pouring and maintenance → template and support dismantling; and (3) removing the template and the bracket: beginning at the center of the dome, the rings are removed outward.

Step five, pouring and molding the dome shell covered with concrete at one time; the concrete is distributed in layers from the arch springing to the arch crown during the pouring of the concrete, so as to ensure that the load applied to the arch crown at any time is uniform and avoid bias. And (4) treating the unfilled part in a grouting manner.

Step six, excavating a first layer and a second layer: firstly, expanding and digging a slag chute, then expanding and digging the slag chute circle by circle from inside to outside by taking the expanded and dug slag chute as a free face to reserve a protective layer on a tank body, reserving the protective layer with the thickness of 1.0-3.0 m around the tank body, temporarily not excavating, after the main explosion area of the layer is completely excavated, removing the protective layer by section through smooth blasting, and timely following up initial support; when the thickness of the reserved protective layer is larger than 0.5m, a row of auxiliary blasting holes are additionally arranged on the outer side of the optical blasting hole, and the optical blasting hole is blasted after the auxiliary blasting holes, namely the optical blasting hole is blasted at last. Before detonation, a gun is covered to protect a dome cover and an embedded part; in the sixth step, after the second-layer excavation supporting is finished, firstly, a second-layer temporary construction ramp is excavated, and a protective railing and a safety net are additionally arranged at an upper passage port, so that the safety of construction personnel is ensured; the slag chute is enlarged and dug circle by circle from inside to outside to a reserved protective layer, and the digging and supporting method is the same as that of the first layer and the second layer; after the third layer of excavation supporting is finished, continuing to expand and dig the slag chute to the position flush with the ground of the lower channel, and reserving a temporary construction ramp, so that construction mechanical equipment can conveniently enter and exit from the lower channel; slag discharging of the channel above the first layer and the second layer is mainly performed, and slag discharging of the slag chute is assisted; and the third layer to the fifth layer are discharged from the lower channel.

Step six, net hanging and guniting: taking un-excavated bedrock as an operation platform, and excavating the protective layer around the tank body in sections; according to the principle of 'excavating layer by layer, supporting layer by layer, excavating one section and supporting one section', after the segmental excavation of the tank body protective layer is finished, a net should be hung and the slurry should be sprayed in time, so that the overlong exposure time of the surrounding rock is avoided. If the surrounding rock is broken and seriously weathered, the segmental excavation length is strictly controlled, and the disturbance to the surrounding rock is reduced by weak blasting.

The invention provides an underground large vertical tank body excavation method which has the following beneficial effects:

in the whole excavation process, the pit slag does not need to be lifted, so that the safety risk of hoisting slag is avoided, the construction efficiency of excavation and slag discharging of the tank body is improved, and the construction progress of excavation of the large-section tank body is greatly improved.

The invention takes the slag sliding well as the free surface to carry out expanding excavation from top to bottom, can obviously improve the utilization rate of blast holes, reduce the explosive consumption and improve the economic benefit.

The invention takes the slag sliding well as the free surface to carry out expanding excavation from top to bottom, has high working efficiency, is economic and reasonable, and is safe and reliable.

The construction equipment of the invention has simple requirements, can continuously use the existing mechanical equipment of the project, does not need to purchase new equipment, and can not cause idle waste of equipment resources.

And after the tank body is excavated to the design contour line, primary support is immediately carried out, and coating construction is carried out after the tank body is completely excavated, so that the construction process is simplified, the construction speed is improved, and the engineering cost is reduced.

Drawings

FIG. 1 is a schematic view of a vertical section of a vertical tank compartment;

FIG. 2 is a schematic view of a dome cavern annular excavation plane partition;

FIG. 3 isbase:Sub>A cross-sectional view A-A of an annular excavation ofbase:Sub>A dome cavern;

FIG. 4 is a schematic diagram of a first layer excavation of the can body;

FIG. 5 is a schematic diagram of a second layer excavation of the tank body;

FIG. 6 is a schematic view of a second layer of the tank body being excavated circle by circle;

FIG. 7 is a schematic view of a third layer of the tank body excavation;

FIG. 8 is a schematic diagram of the fourth and fifth excavation of the tank body;

FIG. 9 is a front view of arrangement of blast holes in a main explosion area of a tank body;

FIG. 10 is a side view of arrangement of blast holes in a main explosion area of a tank body;

FIG. 11 is a schematic view of the first and second layers of slag tapping of the vessel body;

FIG. 12 is a schematic view of the third to fifth slag tapping of the vessel body;

in the figure, 1, an upper channel; 2. a lower channel; 3. excavating a contour line; 4. a slag sliding well; 5. a protective layer of a tank body excavation area; 6. a dome cavern excavation area; 7. a first-layer excavation area of the tank body; 8. a second-layer excavation area of the tank body; 9. a third-layer excavation area of the tank body; 10. a fourth layer of excavation area of the tank body; 11. and a fifth excavation area of the tank body.

Detailed Description

The invention is further illustrated by the following figures and examples. It is to be understood that the described embodiments are merely illustrative of some, but not all, of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention shall fall within the protection scope of the claims of the present invention.

As shown in fig. 1 to 12, there is provided a method for excavating an underground large vertical tank, comprising the steps of:

step one, excavating a guide tunnel of an upper channel 1: in order to reduce the temporary support engineering quantity, the pilot tunnel of the upper channel 1 adopts a direct top-lifting excavation method: namely, after the upper channel 1 enters the dome cavern, the top-raising excavation is carried out along the dome top contour line 3, the excavation and the supporting are carried out simultaneously until the excavation is carried out to the inner ring contour line, and the longitudinal slope of the excavation is the same as the tangential inclination angle of the dome contour line 3. The excavation of the tank body is limited by the section of the access passage, large-scale excavation equipment cannot be applied, and in order to overcome the limitation of small-section passage construction, the width of the passage is expanded to 4.0m, and the excavation height is 4.5m;

step two, excavating guide tunnels of the lower channel 2: excavating and supporting according to design requirements until the position of the slag sliding well 4, stopping advancing, and sealing the opening of the lower channel 2 to prepare for excavating the slag sliding well 4 from top to bottom; step three, excavating the slag chute 4: in order to reduce the workload of hoisting slag, improve the construction efficiency of tank body excavation slag and reduce the safety risk of hoisting slag, a slag chute 4 connecting an upper channel and a lower channel is blasted and excavated from top to bottom right above a pilot tunnel of the lower channel 2, and the diameter of the slag chute is about 3.0m;

1) The conventional slag tapping method for excavating the slag chute 4 from top to bottom comprises the following steps: the method comprises the following steps of firstly, manually lowering the shaft to load slag, then lifting the slag to the outside of a slag chute 4 by using a small lifting device, and finally conveying the slag to a specified slag abandoning field by using a slag car, so that the slag discharging efficiency is low, the construction progress is slow, the cost is high, and the safety risk is high; firstly, vertically drilling by using a down-the-hole drilling machine, wherein the hole diameter of a drilled hole is about 90mm, stopping drilling until the drilled hole reaches 50cm from the top surface of a lower channel 2, then loading a phi 32 emulsion explosive, detonating from inside to outside in circles, and penetrating a slag chute 4 to be used as a slag discharging channel for dome cavern excavation and tank body excavation;

2) As the surrounding rock stress of the boundary area of the pilot tunnel of the lower channel 2 and the chute 4 is concentrated, collapse and block falling are easy to occur during dome construction, the longitudinal distance of the arch centering corresponding to the area is encrypted to 75 cm/truss, the distance of the anchor rods is adjusted accordingly, and the encryption range is not less than 3m;

step four, excavating a dome cavern: as shown in fig. 2 and 3, the dome cavern adopts an annular excavation reserved rock pillar method, namely, a middle reserved rock pillar v is used as a key support, a radial middle pilot tunnel i is excavated first, then, sequential annular blasting excavation ii, iii and iv are performed, each circulation of footage excavation is performed, then, initial support is performed timely and closed to form a ring as soon as possible, and finally, a central rock pillar v is excavated: the construction technical key points are as follows:

1) Step I (upper pilot tunnel excavation): in order to shorten the construction period, the existing working face is fully utilized, after the upper pilot tunnel is excavated to the inner ring contour line, the upper pilot tunnel begins to be expanded and excavated to two sides, a certain safety distance is staggered when the opposite side is excavated, the construction safety is ensured, and a supporting reinforcing measure must be taken when the hole is excavated to ensure the safety of the excavation. The opening is a stress concentration area, and 3 trusses of temporary arch frames are densely arranged in a range of 3m;

2) Step II (outer ring excavation): after the reinforcing support construction at the hole opening position is completed, construction is performed step by step along the outer ring until the outer ring construction is completed; constructing arch frames and hollow grouting anchor rods one by one in the construction process; when the opposite heading distance is short, one working face is stopped, the single heading is changed into the opposite heading, and the sealing work of the working face is well done;

3) Step III: after the outer ring anchor cable construction is finished (tensioning is finished), continuously forming holes in the outer wall of the inner ring, and extending the upper pilot hole to the inner wall of the inner ring;

4) Step iv (inner ring excavation): step II;

5) Step V (central rock pillar excavation): after the inner ring anchor cable construction is finished (tensioning is finished), excavating a central rock pillar from top to bottom, and completing supporting of the center part of the dome in the excavating process;

6) Supporting in time after the dome is expanded and dug; roughly leveling the hole slag to be used as a temporary construction platform, using the temporary platform by constructors to lay a prestressed anchor cable (rod), hanging a reinforcing mesh sheet, and spraying early-strength and high-strength steel fiber concrete;

7) In order to reduce the setting height of the full-space support in the step five, improve the overall stability of the support, reduce safety risks and reduce the using amount of turnover materials and labor employment; in the excavation processes of the step IV and the step V, a 3m high platform is reserved in the center of the cavern and is not excavated (figure 3); after the fifth construction step is finished, a 3m high platform reserved in the center of the grotto can be excavated;

8) Stress concentration exists at the joint of the dome and the side wall, the joint is a weak stress area, surrounding rock collapse, breaking and block falling frequently occur in the excavation process, monitoring measurement should be enhanced in the construction process, temporary support is timely increased according to monitoring measurement results, supporting parameters are adjusted, and the excavation sequence and the distance are timely increased; step five, dome covering construction:

1) The dome coating and the tank body coating in the sixth step belong to two independent stress structures, the dome coating transmits the self load to the bedrock through a ring beam, and the tank body coating transmits the self load to the bedrock through a strip foundation; therefore, after the step four-excavation supporting is finished, the dome covering construction can be started;

2) The dome is large in size, large in one-time pouring forming difficulty and long in duration, and construction quality cannot be guaranteed, so that the ring beam and the dome concrete are poured separately, and a construction joint is reserved at the boundary of the ring beam and the shell and is close to one side of the shell by 500 mm;

3) Because the dome is covered by a wall-attached reinforced concrete structure, a constructor can only stand below the dome structure to operate, the installation of the reinforcing steel bars must be completed before the erection of the bearing support and the installation of the template, and the corresponding construction sequence is as follows: primary support detection → measurement lofting → ring beam construction → temporary operation platform erection → waterproof layer construction → dome outer layer and inner layer steel bar installation → bearing support assembly → dome template and wood plate installation → support reinforcement → concrete pouring and maintenance → template and support dismantling;

4) In the construction of large-span dome steel bars, the dome steel bars often sink to a large extent or even collapse due to large span and small rise, and temporary supports are added below the dome steel bars according to the construction condition;

5) The dome template adopts phi 108 common steel pipes as bearing upright columns, I16I-shaped steel as a radial main beam and phi 25 round steel as lateral connecting ribs between the I-shaped steel, the template is formed by splicing bamboo plywood and a 50mm thick wood board, and the 50mm thick wood board is processed into an isosceles trapezoid;

6) The dome bottom template is prefabricated on site and assembled in sections in an amplification sample mode; the edge joints are laid from the periphery to the center in a ring-by-ring manner, and the joint joints are sealed by adopting adhesive tapes, so that slurry leakage in the concrete pouring process is prevented, and the joint joints and the later-stage top surface repair work are reduced;

7) The dome shell is formed by one-time pouring of the covering concrete. The concrete is distributed in layers from the arch springing to the arch crown during the pouring of the concrete, so as to ensure that the load applied to the arch crown at any time is uniform and avoid bias. The unfilled part is treated in a grouting way;

8) And (3) removing the template and the bracket: beginning at the center of the dome, the rings are removed outward.

And step six, excavating the tank body.

And in the fifth step, after the template and the support are removed, the tank body is excavated. A top-down layering and partition excavation method is adopted, and the layering thickness is controlled to be about 3.0 m.

1) Excavating a first layer and a second layer (figures 4-6); firstly, expanding and digging a slag chute 4, then expanding and digging the slag chute (4) after expanding and digging to a tank body reserved with a protective layer 5 from inside to outside in circles by taking the slag chute (4) as a free face, reserving the protective layer 5 with the thickness of 1.0-3.0 m around the tank body for temporarily not excavating, after the main explosion area 7 (or 8) of the layer is completely excavated, removing the protective layer 5 by smooth blasting in sections, and timely following up the initial support; when the thickness of the reserved protective layer 5 is larger (larger than 0.5 m), a row of auxiliary blastholes can be added on the outer side of the optical blastholes, and the optical blastholes are detonated after the auxiliary blastholes, namely the optical blastholes are detonated at last. Before detonation, a gun is covered to protect a dome cover and an embedded part;

because of there is the discrepancy in elevation in excavation working face and the upper channel 1 ground, adopt the hole sediment to pave a temporary construction ramp, make things convenient for construction machinery equipment from upper channel 1 business turn over.

The blast hole adopts a continuous charging structure, the hole opening is blocked by stemming, and the hole blocking depth is not less than 20cm. In order to control the influence of blasting vibration on a dome supporting structure, the maximum single-section loading capacity is controlled to be 25kg, and the one-time total loading capacity is controlled to be within 100 kg; as shown in fig. 9 and fig. 10, the main explosion area adopts YT-28 air drill to construct horizontal holes, 4 rows of holes are distributed on each layer of step, the minimum resistance line is 100cm, the aperture is 40mm, the hole depth is 300cm, the hole spacing is 100mm, and the row spacing is 70 cm and 60cm. Each row of blast holes is a section of detonating hole, and four sections of detonating blast holes are provided.

2) Third layer excavation (fig. 7): after the second-layer excavation supporting is finished, firstly excavating a second-layer temporary construction ramp, and additionally arranging a protective railing and a safety net at the opening 1 of the upper channel to ensure the safety of construction personnel; then enlarging and digging the slag chute 4 to a reserved protective layer 5 from inside to outside circle by circle, wherein the digging and supporting method is the same as that of the first layer and the second layer;

3) Fourth and fifth excavations (fig. 8): after the third layer excavation supporting is finished, the expanding excavation slag sliding well 4 is continued to be parallel and level to the ground of the lower channel 2, a temporary construction ramp is reserved, and construction mechanical equipment can conveniently enter and exit from the lower channel 2.

4) And (4) discharging slag (fig. 11 and 12). The first and second layers of slag are mainly discharged from the channel 1 and the slag from the slag chute 4 is used as an auxiliary; the third layer to the fifth layer are discharged from the lower channel 2; 2, adopting a 60-type excavator to cooperate with 1 30-type loader to load slag, stopping slag discharge vehicles at a passage port to load the slag, and conveying the slag to a specified slag disposal site;

5) Hanging a net and spraying: taking un-excavated bedrock as an operation platform, and excavating the protective layer 5 around the tank body in sections; according to the principle of 'excavating layer by layer, supporting layer by layer, excavating one section and supporting one section', after the segmental excavation of the tank body protection layer 5 is finished, a net should be hung and guniting should be carried out in time, and the surrounding rock exposure time is prevented from being overlong. If the surrounding rock is broken and seriously weathered, strictly controlling the segmental excavation length and reducing the disturbance on the surrounding rock by adopting weak blasting;

the primary support of the tank body adopts the protection forms of anchoring, spraying and netting, namely phi 10 reinforcing mesh is hung, and the grid interval is 15 multiplied by 15cm; spraying CF25 steel fiber concrete with the thickness of 20 cm;

25 (or

22 ) cement mortar anchor rods.

6) Anchor rod construction: after the spraying is finished, 3 425S-shaped down-the-hole drills (or 6 suspension drills) are adopted to construct a horizontal anchor rod hole, and an anchor rod is timely fed and grouted. Considering the stress concentration condition of the bedrock at the bottom of the dome ring beam, the strengthening treatment is required to be carried out: the range from the bottom of the ring beam to the lower part of 1.5m is an anchor rod strengthening area, and 3 layers of anchor rods with the length of 12m are arranged

25, arranging cement mortar anchor rods in a quincunx manner, wherein the circumferential direction is multiplied by the vertical distance of 100 multiplied by 50 cm; the normal zone is 8m long

22 cement mortar anchor rods are annularly multiplied by the vertical distance of 150 multiplied by 100cm and arranged in a quincunx manner.

7) In the construction process, monitoring measurement must be enhanced, the deformation of the surrounding rock is monitored, supporting reinforcement is performed if necessary, and the situation that the stability of the tunnel body is endangered due to the overlarge deformation of the surrounding rock is prevented through monitoring.

Step seven, construction of tank body coating:

1) After the tank body is excavated and the initial support is finished, preparing tank body coating construction; the waterproof board is laid as required before secondary lining. In order to accelerate the pouring speed, reduce the labor intensity, ensure the safety and improve the quality, the slip form is adopted to implement the tank body coating construction; and assembling the slip form at the bottom of the well, and pouring concrete after the assembly is finished. The construction procedure is as follows: construction preparation → waterproof and drainage construction → reinforcement binding → slip form assembly → concrete pouring → slip form sliding up (pouring while sliding) → slip form dismantling;

2) The tank body foundation belongs to an enlarged foundation, the section width of the tank body foundation is inconsistent with the wall thickness, and the tank body foundation is independently finished before slip form construction;

3) The concrete pouring adopts layered symmetrical pouring, and the layered thickness is not more than 30cm; the first sliding of the sliding mould is slowly carried out, in the process, the hydraulic device, the template structure and related facilities are comprehensively checked under the load condition, the problems are timely treated, and the sliding mould can be normally lifted after all the sliding mould is normal;

4) During normal sliding, observing the surface quality of the demolded concrete by a person to determine proper sliding time and sliding speed; the pouring process needs to be continuous, so that a 'cold joint' caused by stop is avoided, the pause time is not more than the setting time of the concrete (which is equivalent to the time when the penetration resistance value of the concrete is 0.35 kN/cm), and when the interval time is over the specification, the stubbles are processed according to the requirements of the construction joints;

5) And after the concrete is demoulded, the concrete is required to be checked and trimmed in time and maintained in time, so that the concrete wall surface is always kept in a wet state, and the maintenance time at the normal temperature state is not less than 7 days.

Claims (9)

1. The excavation method of the underground large vertical tank body is characterized in that: the excavation method comprises the following steps:

step one, excavating an upper channel pilot tunnel: in order to reduce the amount of temporary support engineering, the upper channel pilot tunnel adopts a direct top-raising excavation method: after the upper channel enters the dome cavern, carrying out forward top-raising excavation along the contour line of the top of the dome continuously, and supporting while excavating until the inner ring contour line is excavated, wherein the longitudinal excavation slope is the same as the tangential dip angle of the dome contour line;

step two, excavating a lower channel pilot tunnel: adopting a direct top-lifting excavation method which is the same as the excavation method of the upper channel pilot tunnel;

step three, excavating the slag chute: in order to reduce the workload of hoisting slag, improve the construction efficiency of tank body excavation slag and reduce the safety risk of hoisting slag, a slag chute connecting an upper channel and a lower channel is blasted and excavated from top to bottom right above a guide hole of the lower channel, and the diameter of the slag chute is 3.0m;

step four, excavating a dome cavern:

the dome cavern adopts an annular excavation reserved rock pillar method, namely a rock pillar reserved in the middle is used as a key support, a radial middle pilot tunnel is excavated firstly, then annular blasting excavation is carried out in sequence, after each cycle of footage excavation, preliminary bracing is carried out in time, a ring is closed as soon as possible, and finally a central rock pillar is excavated;

step five, dome covering construction: the ring beam and the dome concrete are separately poured, and a construction joint is reserved at the boundary of the ring beam and the shell and is 500mm close to one side of the shell;

step six, tank body excavation: after the dome covering construction is finished and the strength of the concrete reaches 28 days, the tank body excavation is started; the method comprises the steps of adopting an excavation method combining vertical layering, horizontal looping and depth, controlling the height of a layering step to be about 3.0m, before each layer of excavation, firstly expanding and excavating a slag chute, then expanding and excavating from inside to outside to reserve a protective layer by loops by taking the slag chute after expanding and excavating as an empty surface, reserving the protective layer with the thickness of 1.0-3.0 m around a tank body for the time of excavation, after the excavation of a main explosion area of the layer is finished, adopting smooth blasting to excavate the protective layer in a segmenting way, and timely following up primary support;

step seven, construction of tank body coating: after the tank body is excavated and the initial support is finished, preparing tank body coating construction; the waterproof board is laid according to the requirement before secondary lining; in order to accelerate the pouring speed, reduce the labor intensity, ensure the safety and improve the quality, the slip form is adopted to implement the can body covering construction; assembling the slip form at the bottom of the well, and pouring concrete after the assembly is finished; the construction procedure is as follows: construction preparation → waterproof and drainage construction → reinforcement binding → slip form assembly → concrete pouring → slip form sliding and lifting → slip form dismantling; the tank body foundation belongs to an enlarged foundation, the section width of the tank body foundation is inconsistent with the wall thickness, and the tank body foundation is independently finished before slip form construction.

2. The excavation method for the large-scale underground vertical tank body according to claim 1, wherein: in the first step, the tank body excavation is limited by the section of the access passage, large-scale excavation equipment cannot be applied, and in order to overcome the limitation of small-section passage construction, the width of the passage is 4.0m, and the excavation height is 4.5m.

3. The excavation method of the underground large vertical tank body according to claim 1, wherein: and in the second step, excavation supporting is carried out according to design requirements until the position of the slag sliding well is reached, forward excavation is stopped, and a lower channel opening is sealed to prepare for excavating the slag sliding well from top to bottom.

4. The excavation method of the underground large vertical tank body according to claim 1, wherein: and in the third step, a down-the-hole drill is adopted to vertically drill, the hole diameter of the drilled hole is about 90mm, the drilling is stopped until the position of 50cm away from the top surface of the lower channel, then the phi 32 emulsion explosive is loaded later, the detonation is carried out circle by circle from inside to outside, and the slag chute is communicated and can be used as a slag discharging channel for dome cavern excavation and tank body excavation.

5. The excavation method for the large-scale underground vertical tank body according to claim 1, wherein: in the fourth step, in the excavation process of the inner ring and the core column, a 3m high platform is reserved in the center of the cavern and is not excavated; and after the fifth construction step is finished, excavating a 3m high platform reserved in the center of the cavern.

6. The excavation method of the underground large vertical tank body according to claim 1, wherein: the construction sequence in the fifth step is as follows: primary support detection → measurement lofting → ring beam construction → temporary operation platform erection → waterproof layer construction → dome outer layer and inner layer steel bar installation → bearing support assembly → dome template and wood plate installation → support reinforcement → concrete pouring and maintenance → template and support dismantling; and (3) dismantling the template and the bracket: beginning at the center of the dome, the rings are removed outward.

7. The excavation method of the underground large vertical tank body according to claim 1, wherein: step five, pouring and molding the dome shell covered with concrete at one time; during concrete pouring, the materials are distributed from the arch springing to the arch crown in a layered mode to ensure that the load applied to the arch crown at any time is uniform, bias voltage is avoided, and the unfilled part is treated in a grouting mode.

8. The excavation method for the large-scale underground vertical tank body according to claim 1, wherein: step six, excavating a first layer and a second layer: firstly, expanding and digging a slag chute, then expanding and digging the slag chute circle by circle from inside to outside by taking the expanded and dug slag chute as a free face to reserve a protective layer on a tank body, reserving the protective layer with the thickness of 1.0-3.0 m around the tank body, temporarily not excavating, after the main explosion area of the layer is completely excavated, removing the protective layer by section through smooth blasting, and timely following up initial support; when the thickness of the reserved protective layer is larger than 0.5m, a row of auxiliary blasting holes are additionally arranged on the outer side of the optical blasting holes, the optical blasting holes are blasted after the auxiliary blasting holes, namely the optical blasting holes are blasted at last, and a gun is used for covering before blasting to protect the dome cover and the embedded part; in the sixth step, after the second-layer excavation supporting is finished, firstly, a second-layer temporary construction ramp is excavated, and a protective railing and a safety net are additionally arranged at the upper passage opening, so that the safety of construction personnel is ensured; the slag chute is enlarged and dug circle by circle from inside to outside to a reserved protective layer, and the digging and supporting method is the same as that of the first layer and the second layer; after the third layer of excavation support is finished, continuing to expand and excavate the slag sliding shaft to the position flush with the ground of the lower channel, and reserving a temporary construction ramp, so that construction mechanical equipment can conveniently enter and exit from the lower channel; slag discharging of the channel above the first layer and the second layer is mainly performed, and slag discharging of the slag chute is assisted; and deslagging from the third layer to the fifth layer from the lower channel.

9. The excavation method of the underground large vertical tank body according to claim 1, wherein: step six, net hanging and guniting: taking un-excavated bedrock as an operation platform, and excavating the protective layer around the tank body in sections; according to the principle of 'excavating layer by layer, supporting layer by layer, excavating one section and supporting one section', after the segmental excavation of the tank body protective layer is finished, a net is hung and guniting is carried out in time, the situation that the surrounding rock is exposed for too long time is avoided, if the surrounding rock is broken and severely weathers, the segmental excavation length is strictly controlled, and the disturbance to the surrounding rock is reduced by weak blasting.

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