A method for demolishing an existing tunnel structure and excavating in situ for expansion

Abstract

The present invention relates to a method for demolishing an existing tunnel structure and excavating in-situ expansion. By pre-grouting the original separated lining and the loose rock strata outside the excavation contour line, the present invention does not use mechanical means to demolish the existing tunnel. Instead, it uses drilling and blasting to achieve the effect of "uncaging" the existing tunnel lining. At the same time, it cooperates with a mechanical hydraulic clamp to cut and break the steel bars in the lining structure, designs blasting parameters using the existing free face, and conducts smooth blasting on the surrounding rock within the excavation contour line to optimize the blasting effect. Meanwhile, it utilizes the available parts of the existing tunnel to reduce construction costs. The present invention is applicable to the reconstruction and expansion of tunnels in various surrounding rock geological conditions. At the same time, it can solve various problems faced in construction, such as poor construction geological conditions and high construction safety risks. The present invention can reduce transportation costs, simplify cumbersome processes, and accelerate the construction speed.

Description

Technical Field

[0001] The present invention relates to a method for demolishing and in-situ excavation of an existing tunnel structure. Background Art

[0002] With the continuous improvement of road and railway networks, etc., sometimes it is necessary to in-situ reconstruct, expand or demolish existing tunnels on the reconstructed line. This is because existing tunnels have mostly existed for decades and have the characteristics of being old, small, narrow and low, making it difficult to meet the increasing traffic flow requirements of the region. The traditional method for expanding or demolishing existing tunnels on the reconstructed line is to first use machinery to demolish the existing tunnel, and then carry out in-situ excavation and blasting operations, that is, use a mechanical breaker to demolish the existing tunnel structure section by section. Generally, after demolishing 1 - 2 m, then use manual torque to cut the lining steel bars, that is, demolish the first cycle of lining structure. Repeat the construction with the same principle, demolish the remaining lining structures section by section, and then use tunnel blasting construction technology to drill holes and wire the blasting to excavate the surrounding rock to provide enough space for the construction of the new tunnel.

[0003] The following are the deficiencies of this traditional method:

[0004] (1) After using machinery to demolish the lining structure of the existing tunnel, the working rock layer loses the support or partial force of the existing tunnel lining structure, resulting in the collapse of the rock layer on the working surface, which not only increases the construction difficulty and workload, but also makes it difficult to ensure the safety of construction personnel.

[0005] (2) Using machinery to demolish the lining structure of the existing tunnel, the working surface is narrow, the demolition speed is too slow, laborious and time-consuming, the work efficiency is low, the construction period is long, and the process is cumbersome.

[0006] (3) Using machinery to demolish the lining structure of the existing tunnel, the existing tunnel lining structure cannot be effectively utilized, resulting in a large amount of materials used and high construction costs.

[0007] (4) Using tunnel blasting construction technology, the blasting distance cannot meet the requirements, resulting in the collapse of the rock layer on the working surface, seriously restricting the subsequent excavation of the surrounding rock. Summary of the Invention

[0008] The purpose of the present invention is to provide a method for demolishing and in-situ excavation of an existing tunnel structure to solve the above problems, which can reduce construction costs, simplify the cumbersome process and speed up the construction speed.

[0009] To achieve the above purpose, a method for demolishing and in-situ excavation of an existing tunnel structure is provided, including the following steps:

[0010] (1) Preparation of muck truck: Prepare a muck truck according to the width of the existing tunnel, which is used to receive and transport the muck formed during the demolition of the existing tunnel to the muck yard. The carriage of the muck truck is a flatbed truck body. There is an iron plate layer on the upper end surface of the flatbed truck body. Axles are provided on both sides of the lower end of the truck body. Wheels are provided on both sides of the axles. Side baffles are pivotally connected to both sides of the truck body. Tightening hooks are provided at both ends of the upper part of the inner side of the side baffle. Towing hooks are provided in the middle of the other two sides of the truck body;

[0011] (2) Advanced geological exploration and determination plan:

[0012] (a) Before construction, conduct longitudinal and transverse advanced geological exploration holes on the original lining section and the enlarged excavation section of the existing tunnel to be reconstructed and expanded. Use geological drilling or radar scanning for advanced geological forecasting operations;

[0013] (b) Determine the thickness of the original lining section. According to the forecast of the original lining section from the advanced geological exploration holes, judge the thickness of the existing tunnel to be demolished, the surrounding rock behind the existing tunnel, and the relevant situation of the separation distance;

[0014] (c) Whether advanced support is required. By judging the surrounding rock and the separation distance behind the lining of the original lining section, combined with the specification standards and the characteristics of the surrounding rock, determine the surrounding rock level. According to the self-stabilizing ability of the surrounding rock and the vibration of the surrounding rock caused by blasting, judge whether advanced support is required for the next step of construction;

[0015] If: The outer enlarged excavation section of the original lining section of the reconstructed and expanded tunnel is detected as a loose and easily caving geological layer or there is a curtain cavity behind the original lining, then proceed to step (3) for advanced pre-support; otherwise, proceed to step (4);

[0016] (3) Advanced pre-support: The advanced pre-support uses the drilling and grouting method to grout and fill the curtain cavity behind the original lining and reinforce the loose rock layer;

[0017] (4) Demolition design of the original lining section: The demolition design of the original lining section is divided into partial demolition and complete demolition of the original lining section; Partial demolition means that one side of the designed excavation contour line is located inside the existing tunnel, and complete demolition means that the designed excavation contour line is located outside the existing tunnel;

[0018] (a) Partial demolition. When one side of the designed excavation contour line is located inside the existing tunnel, the space between the designed excavation contour line located inside the existing tunnel and the inner wall of the existing tunnel forms a backfill area, and the backfill area is backfilled; The existing tunnel in the backfill area is retained, and the remaining part of the existing tunnel within the designed excavation contour line is demolished; The retained part of the existing tunnel can be used as a component of the newly built corresponding tunnel wall or the outer support part of the newly built corresponding tunnel wall according to its quality.

[0019] (b) Complete demolition. Demolish the existing tunnel;

[0020] (5) Demolition of the existing tunnel to be demolished: The demolition is carried out by combining blasting and mechanical shearing of steel bars;

[0021] Drilling and blasting demolition of the existing tunnel:

[0022] (a) According to the geological forecast and the condition of the original lining structure, design the blasting parameters of reinforced concrete to ensure the "cage removal" effect of blasting;

[0023] (b) According to the designed drilling and blasting parameters, carry out on-site actual engineering operations. Operate to drill blast holes longitudinally along the original lining structure and make dynamic parameter adjustments according to the actual on-site situation;

[0024] The diameter d of the blast hole is 38 - 44 mm; the depth L of the blast hole, L = 1.8 m;

[0025] (c) Hole layout: To ensure the smooth progress of the blasting of the existing tunnel and the tunnel excavation, take the minimum resistance line as W = 0.25 - 0.3 m, the hole spacing a = 0.5 - 0.8 m; take the layer spacing b = 0.6 m;

[0026] (d) The explosive consumption per cubic meter q: Select q = 2.0 kg / m 3 , and it can also be adjusted according to the actual on-site situation and the first trial blasting during the construction process;

[0027] (e) The charge amount per single hole Q.

[0028] Q = q·a·b·L = 2.0×0.6×0.6×1.8 = 1.29 kg, take Q = 1.2 Kg, and divide it into 6 rolls of explosives;

[0029] The plugging length at the hole mouth is 0.4 m. The explosive used is 2# rock emulsion explosive, select the φ32 specification, the density of the explosive cartridge is 0.95 - 1.25 g / cm 3 , the length is 200 mm, and each section is 200 g;

[0030] The charging structure is to use segmented charging in the blast hole. The ends of adjacent explosive cartridges in each hole are 4 cm apart, and the plugging length at the hole mouth is 0.4 m;

[0031] For the blasting demolition of the existing tunnel, the blasting length is 1.8 - 2.2 m. After 2 cyclic blasting operations can be carried out;

[0032] (6) Ventilation and danger removal: When the tunneling length of the tunnel construction exceeds 150 m, mechanical ventilation is set up. After the blasting demolition of the existing tunnel, mechanical ventilation is carried out for more than 30 minutes, and then mechanical equipment is used to remove dangerous rocks to ensure the safety of subsequent construction operations;

[0033] (7) Temporary support and cross-section measurement: Based on the comparison between the advanced prediction of the surrounding rock grade and the situation after removal, determine whether to carry out temporary support. The main form of support is to use I16 steel I-beams as temporary supports and carry out shotcrete and bolt support to ensure the force safety of the structure;

[0034] Cross-section measurement is carried out after the removal of the original lining structure to conduct cross-section review, verify whether the thickness of the original lining judged by the advanced exploration holes is correct, and provide guidance for subsequent operations;

[0035] (8) Mechanically hydraulic cutting of steel bars: When blasting to remove the cage, it is difficult to damage the steel bars inside the original lining structure, and mechanical hydraulic pliers need to be used for cutting. No manual assistance is required. The cutting machine is an excavator equipped with an H.S-250 type hydraulic pliers; Use large mechanical hydraulic pliers or eagle beak pliers to cut the steel bars of the removed cage, complete the rapid removal of the original lining structure, and repeat the cyclic construction to gradually remove the remaining existing tunnel lining structure;

[0036] (9) After the blasting and mechanical cutting removal of the existing tunnel lining, it is an important basis for verifying whether the removal operation method of the original lining structure is feasible by judging the effect after the removal of the lining structure;

[0037] (10) Design of excavation blasting: According to the determination of the surrounding rock grade after the removal of the original lining structure, design the blasting parameters for surrounding rock excavation. Utilize the free face after the removal of the lining structure to optimize the blasting parameter design to achieve the best smooth blasting effect;

[0038] (11) Drilling and blasting operation of the excavated surrounding rock: Use the working surface after the removal of the lining structure as the free face for the blasting excavation of the excavated surrounding rock. When designing the blasting parameters, only the perimeter holes and auxiliary holes need to be designed, and the cut holes are not involved. According to the designed drilling and blasting parameters, carry out on-site actual engineering operations, drill holes longitudinally along the tunnel, and adjust the dynamic parameters according to the actual situation on site. The specific construction parameters are as follows:

[0039] Hole diameter, take d = 40mm; Hole depth, take L = 1.8m; Hole layout, take a = 0.4m, b = 0.6m; Specific charge q, the specific charge of the auxiliary hole explosive is q = 2.0kg / m 3 , the specific charge of the smooth blasting hole explosive qsmooth = 0.25 - 0.30kg / m 3 ; It can also be adjusted according to the actual situation on site and the situation of the first trial blast during the construction process;

[0040] Charge per single hole Q:

[0041] (a) Charge per single hole of the auxiliary hole: Q = q·a·b·L = 2×0.4×0.6×1.8 = 0.86kg, take Q = 800g;

[0042] (b) The charge amount of a single light blasting hole is Qlight = qlight × L = 250 × 1.8 = 450g, and 400g is taken; for the convenience of operation and guidance during construction, the line charge density is controlled, and the line charge density qlight = 250g / m, and the blast hole is fully filled with charge;

[0043] (c) The length of the blast hole plugging is 0.4m;

[0044] (12) Ventilation, danger elimination and cross-section measurement after excavation of surrounding rock:

[0045] According to the specification, mechanical ventilation is required for tunnel construction when the excavation length exceeds 150m. After the expansion blasting, mechanical ventilation is required for more than 30 minutes, and then the machinery is used to remove dangerous rocks to ensure the safety of subsequent construction operations.

[0046] Cross-section measurement is to check whether there is over-excavation or under-excavation after the surrounding rock is expanded, and whether the outline dimensions required by the design drawings are met, so as to provide basic guidance for subsequent operations;

[0047] (13) Initial support after excavation of surrounding rock:

[0048] After the surrounding rock is expanded, the initial support is mainly frame anchor spraying support. The support parameters are I16 I-beam as steel arch frame, 22 diameter mortar anchor and lock anchor, 8 diameter single-layer steel mesh with a spacing of 20cm, and C25 wet spraying process sprayed concrete;

[0049] (14) Monitoring and measurement after excavation of surrounding rock:

[0050] The surrounding rock perimeter convergence and settlement observation results during the whole process should ensure that the perimeter convergence value is within 2.5mm, the overall settlement is about 2-3mm, and the maximum value is less than 5mm;

[0051] (15) Drainage and lining construction after excavation of surrounding rock

[0052] Waterproofing and drainage are divided into waterproofing and drainage construction. Waterproofing is mainly based on geotextiles and waterproof boards, supplemented by transverse semicircular pipes and longitudinal drainage pipes; drainage is a comprehensive waterproofing and drainage system with central ditches and inspection wells as the main components and road drainage ditches as the auxiliary components.

[0053] The new expansion lining construction adopts form-cast concrete, and the construction formwork is a mechanical trolley and manual formwork. During the concrete pouring process, attention should be paid to symmetrical pouring, and the pouring speed should not be too fast. Various tests of concrete should be carried out on site to ensure the concrete pouring effect and meet the requirements of tunnel construction specifications.

[0054] As a further solution of the present invention: the advanced pre-support adopts the drilling and grouting method to grout the curtain cavity behind the original lining and reinforce the loose rock layer, including the following steps:

[0055] (a) Drill grouting holes through the original lining into the loose rock stratum 1 - 1.2 m outside the designed excavation contour line. If there is a curtain cavity behind the original lining, the grouting holes shall communicate with the curtain cavity, and the adjacent grouting holes shall be 1 - 1.2 m apart;

[0056] (b) Use lightweight perlite concrete slurry to grout and reinforce the loose rock stratum outside the original lining through the drilled grouting holes, grout and fill the cavity area, and the filling thickness shall not be less than 1.5 m;

[0057] The weight ratio of the lightweight perlite concrete slurry is: water: cement: perlite: sand = 65:100:600:300;

[0058] (c)Use grouting equipment to grout into the grouting holes, the grouting pressure is 0.5 - 1.0 MPa, and the final pressure is less than 1.5 MPa; when the grout intake is less than 20 - 25 L / min, the grouting pressure gradually increases, reaches the final pressure and holds the pressure for more than 10 minutes, then the grouting can be stopped, and the grouting port shall be blocked in time to prevent air from entering the pipe;

[0059] (d)The grouting filling starts from the two side arch feet first, and the arch feet are filled in 2 - 3 times up to the arch crown;

[0060] As a further solution of the present invention: when grouting and filling the cavity area, the cavity grouting is carried out in 3 times. The first time is to fill the lightweight perlite concrete slurry, and the second and third times are to fill the perlite mortar. The grouting thickness each time is 50 cm, and the filling height is confirmed through the overflow observation pipes at different heights; after each grouting is completed, it is left standing for more than 4 hours before starting the next grouting.

[0061] As a further solution of the present invention: the filled perlite mortar contains 168 Kg of cement, 1.16 m 3 of perlite and 0.4 m 3 of water per cubic meter of mortar.

[0062] As a further solution of the present invention: the construction of removing and in-situ excavating the generated muck is carried out when the muck truck is in the state below the muck generation construction, and the upper ends of the side baffles at both ends of the muck truck are supported on the corresponding tunnel walls to be demolished.

[0063] As a further solution of the present invention: when one side of the newly built tunnel wall is located inside the existing tunnel, the space between the designed excavation contour line inside the existing tunnel and the inner wall of the existing tunnel forms a backfill space, and the backfill space is backfilled, and the backfill materials are sand, bricks and cast concrete.

[0064] As a further solution of the present invention: the wheels are rail wheels located on the track or wheels on the ground.

[0065] As a further solution of the present invention: the limiting blocks between adjacent cartridge ends in each hole are foam plastic blocks or air bags.

[0066] The beneficial effects of the present invention are as follows:

[0067] 1. Compared with the prior art, the present invention does not require mechanical demolition of existing tunnels. By pre-grouting the original separated lining and the loose rock stratum outside the excavation contour line, and using drilling and blasting to achieve the effect of "uncaging" the existing tunnel lining. At the same time, cooperate with a mechanical hydraulic clamp to cut and break the steel bars in the lining structure, use the existing free face to design blasting parameters, and perform smooth blasting on the surrounding rock within the excavation contour line to optimize the blasting effect. At the same time, utilize the available part of the existing tunnel to reduce construction costs. The present invention is suitable for the reconstruction and expansion of tunnels in various surrounding rock geological conditions. At the same time, it can solve various problems faced in construction, such as poor construction geological conditions and high construction safety risks. The present invention can reduce transportation costs, simplify cumbersome processes, and speed up construction.

[0068] 2. Compared with the prior art, the present invention can reduce transportation costs, simplify cumbersome processes, speed up construction, has a wide working surface, fast demolition speed, saves labor, has high work efficiency, and a short construction period.

[0069] 3. It is measured that compared with the prior art, the demolition speed of the present invention is 1 time faster, the number of construction personnel is halved, the construction cost is reduced by 50%, the construction period is shortened by 50%, and the construction work efficiency is increased by 40 - 41%. And the construction of the present invention will not cause the collapse of the working rock stratum, the construction is safe, and the overall economic and social benefits are remarkable.

[0070] The following further describes the present invention with reference to the accompanying drawings. Description of the Drawings

[0071] Figure 1 It is a schematic structural diagram of the cross-section of the reconstruction and expansion of the existing tunnel of the present invention;

[0072] Figure 2 It is a schematic structural diagram of the available existing tunnel and the reconstruction and expansion location of the present invention;

[0073] Figure 3 It is a schematic structural diagram of the available existing tunnel and the excavation and expansion location of the present invention;

[0074] Figure 4 It is a schematic structural diagram of the blast hole layout for demolishing the existing tunnel of the present invention;

[0075] Figure 5 It is a schematic diagram of the blast hole layout distribution of the excavation rock stratum part of the present invention;

[0076] Figure 6 It is a schematic structural diagram of the muck truck of the present invention;

[0077] Figure 7 Schematic diagram of the charge structure in the blast hole of the present invention;

[0078] Figure 8 Schematic diagram of the steps for demolishing and expanding the original tunnel lining structure of the present invention. Specific implementation manners

[0079] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. In order to make the technical means, creative features, achieved purposes and effects of the present invention easy to understand, the present invention will be further described below with specific embodiments. However, the following embodiments are only the preferred embodiments of the present invention and not all of them. Based on the embodiments in the implementation manners, other embodiments obtained by those skilled in the art without creative efforts all belong to the protection scope of the present invention. The methods in the following embodiments are all conventional methods unless otherwise specified. The materials, devices, equipment, etc. used in the following embodiments can all be obtained from commercial channels unless otherwise specified.

[0080] Embodiment 1: As Figure 1 shown, the structure of the cross-section of the reconstruction and expansion of the existing tunnel of the present invention is as follows: The section between the original lining contour line 1 and the original surrounding rock contour line 2 is the original lining section 7, which can also be called the existing tunnel or the part to be demolished; the section between the original surrounding rock contour line 2 and the designed excavation contour line 4 is the excavation section 6 outside the reconstructed and expanded original lining section, and there is often a curtain cavity 5 behind the original lining therein; and the actual excavation contour line 3 is often larger than the designed excavation contour line 4.

[0081] Please refer to Figures 1 to 8 , a method for demolishing and in-situ excavating the existing tunnel structure, comprising the following steps:

[0082] (1) Prepare a muck truck: Prepare a muck truck according to the width of the existing tunnel for receiving and transporting the muck formed during the demolition of the existing tunnel to the muck yard. The carriage of the muck truck is a flatbed truck body 16, and an iron plate layer 14 is provided on the upper end surface of the flatbed truck body. The iron plate layer is made of a steel plate with a thickness of 5-7 mm to facilitate receiving the collapsed rock muck. Axles 17 are provided on both sides of the lower end of the truck body, and wheels 13 are provided on both sides of the axles. For example, it can be modified from an old railway carriage or a traction steering carriage to reduce costs; when the existing tunnel has a track, the wheels are rail wheels located on the track, otherwise they are wheels on the ground.

[0083] On both sides of the car body, side baffles 11 are pivotally connected by shaft 12. An iron plate layer is also provided on the inner end surface of the side baffle to expand the area for receiving the collapsed rock and soil. The optimal width of the side baffle is such that the upper end of the side baffle can support on the corresponding tunnel wall to be demolished. At both ends of the upper part inside the side baffle, tension hooks 18 are provided. A zipper with a tensioner is provided between the tension hooks 18 on the corresponding two sides. By operating the tensioner to contract or extend the length of the zipper, the outward expansion angle and closing of the side baffle can be controlled. In the middle of the other two sides of the car body, towing hooks 15 are provided to facilitate towing by a towing vehicle.

[0084] (2) Advanced geological exploration and determination plan:

[0085] (a) Before construction, longitudinal and transverse advanced geological exploration holes are drilled for the existing tunnel to be reconstructed and expanded, and the excavation section. Advanced geological forecasting operations are carried out by means of geological drilling or radar scanning.

[0086] (b) Determine the thickness of the original lining section. According to the forecast of the original lining section from the advanced geological exploration holes, judge the thickness of the existing tunnel to be demolished, the surrounding rock behind the existing tunnel, and the relevant situation of the separation distance.

[0087] (c) Whether advanced support is required. By judging the surrounding rock behind the lining of the original lining section and the separation distance, combined with the specification standards and the characteristics of the surrounding rock, determine the surrounding rock grade. According to the self-stabilizing ability of the surrounding rock and the vibration of the surrounding rock caused by blasting, judge whether advanced support is required for the next step of construction.

[0088] If: the outer excavation section 6 of the original lining section 7 of the reconstructed and expanded tunnel is a loose and easily collapsible geological layer detected by geological exploration or there is a curtain cavity 5 behind the original lining, then advanced pre-support is required.

[0089] The advanced pre-support uses the drilling and grouting method to grout and fill the curtain cavity behind the original lining and reinforce the loose rock layer; it includes the following steps:

[0090] (a) Drill grouting holes through the original lining 7 into the loose rock layer 1 - 1.2 m outside the designed excavation contour line 4. If there is a curtain cavity behind the original lining, the grouting holes communicate with the curtain cavity, and the adjacent grouting holes are 1 - 1.2 m apart.

[0091] (b) Use lightweight perlite concrete slurry to grout and reinforce the loose rock layer outside the original lining through the drilled grouting holes, and grout and fill the cavity area, with the filling thickness not less than 1.5 m.

[0092] The weight ratio of the lightweight perlite concrete slurry is: water: cement: perlite: sand = 65:100:600:300;

[0093] (c) Use a grouting equipment to grout the grouting holes. The grouting pressure is 0.5 - 1.0 MPa, and the final pressure is less than 1.5 MPa. When the grout intake is less than 20 - 25 L / min, the grouting pressure gradually increases. When the final pressure is reached and maintained for more than 10 minutes, the grouting can be stopped, and the grouting port should be blocked in time to prevent air from entering the pipe.

[0094] (d) The grouting filling starts from the two side arch feet first, and the arch feet are filled to the arch top in 2 - 3 times.

[0095] If grouting and filling the cavity area, the cavity grouting is carried out in 3 times. The first time fills the lightweight material perlite concrete slurry, and the second and third times fill the perlite mortar. The perlite mortar contains 168 Kg of cement, 1.16 m 3 of perlite and 0.4 m 3 of water per cubic meter of mortar. The thickness of each grouting is 50 cm, and the filling height is confirmed through the overflow observation pipes at different heights. After each grouting is completed, it is left standing for more than 4 hours before starting the next grouting.

[0096] If: the extended excavation section outside the original lining section is detected as a hard and non - collapsible geological layer through geological exploration, and other geological conditions and after advanced pre - support, then the demolition design of the original lining section is carried out.

[0097] Such as Figure 2 and as Figure 3 shown, (4) Demolition design of the original lining section: The demolition design of the original lining section 7 is divided into partial demolition and total demolition of the original lining section. The partial demolition means that one side of the designed excavation contour line 4 is located inside the existing tunnel or the original lining section 7.

[0098] Such as Figure 1 shown, the total demolition means that the designed excavation contour line is located outside the existing tunnel;

[0099] (a) Partial demolition: When one side of the designed excavation contour line 4 is located inside the existing tunnel, the space between the designed excavation contour line located inside the existing tunnel and the inner wall of the existing tunnel forms a backfill void 8, and the backfill void 8 is backfilled. The backfill materials are sand, gravel, bricks and cast - in - place concrete. The existing tunnel of the backfill void is retained, and the remaining part of the existing tunnel inside the designed excavation contour line 4 is demolished; In actual operation, the actual demolition separation area 9 is often larger than the designed excavation contour line to leave enough construction space.

[0100] (b) Total demolition: Demolish the existing tunnel;

[0101] (5) Demolition of the existing tunnel corresponding to the demolition: The demolition adopts a combination of blasting and mechanical shearing of steel bars for demolition;

[0102] Drilling and blasting demolition of the existing tunnel:

[0103] (a) According to the geological forecast and the condition of the original lining structure, design the blasting parameters of reinforced concrete to ensure the "cage removal" effect; "cage removal" means the separation of the original lining structure from the geological layer.

[0104] (b) According to the designed drilling and blasting parameters, carry out the actual on-site engineering operations. Operate to drill blast holes longitudinally along the original lining structure and adjust the dynamic parameters according to the actual on-site situation.

[0105] The diameter d of blast hole 10 is 38 - 44 mm; the depth L of the blast hole, L = 1.8 m.

[0106] (c) Hole layout: To ensure the smooth progress of the blasting of the existing tunnel and the tunnel excavation, take the minimum resistance line as W = 0.25 - 0.3 m, the hole spacing a = 0.5 - 0.8 m; take the layer spacing b = 0.6 m.

[0107] (d) The explosive consumption per cubic meter q: Select q = 2.0 kg / m 3 , and it can also be adjusted according to the actual on-site situation and the first trial blasting during the construction process.

[0108] (e) The charge amount per single hole Q.

[0109] Q = q·a·b·L = 2.0×0.6×0.6×1.8 = 1.29 kg, take Q = 1.2 Kg, and divide it into 6 rolls of explosives.

[0110] The length of the hole mouth plugging is 0.4 m. The explosive used is 2# rock emulsion explosive, and the φ32 specification is selected. The density of the explosive cartridge is 0.95 - 1.25 g / cm 3 , the length is 200 mm, and each section is 200 g.

[0111] As Figure 7 shown, the charging structure is segmented charging in blast hole 10. The ends of adjacent explosive cartridges in each hole are 4 cm apart. The length of the hole mouth plugging is 0.4 m; the limiting blocks between the ends of adjacent explosive cartridges in each hole are foam plastic blocks or air bags, and each limiting block controls the ends of adjacent explosive cartridges in each hole to be 4 cm apart.

[0112] For the blasting demolition of the existing tunnel, the blasting length is 1.8 - 2.2 m. After 2 cycles of blasting operations can be carried out;

[0113] (6) Ventilation and danger removal: When the tunneling length of the tunnel construction exceeds 150 m, mechanical ventilation is set up. After the blasting demolition of the existing tunnel, the mechanical ventilation lasts for more than 30 minutes, and then mechanical equipment is used to remove the dangerous rocks to ensure the safety of subsequent construction operations.

[0114] (7) Temporary support and cross-section measurement: Based on the comparison between the advanced prediction of the surrounding rock grade and the situation after removal, determine whether to carry out temporary support. If there is a risk of surrounding rock collapse, carry out temporary support. The support form mainly uses I16 steel beams for temporary support and shotcrete support to ensure the structural stress safety. This is a traditional support method, so it will not be elaborated here.

[0115] Cross-section measurement is carried out after the original lining structure is removed to conduct cross-section review, verify whether the thickness of the original lining judged by the advanced exploration holes is correct, and make guiding adjustments for subsequent operations.

[0116] (8) Mechanical hydraulic cutting of steel bars: When blasting to remove the cage, it is difficult to damage the steel bars inside the original lining structure, and mechanical hydraulic pliers need to be used for cutting. No manual assistance is required. The cutting machine is an excavator equipped with an H.S-250 type hydraulic pliers; use large mechanical hydraulic pliers or eagle beak pliers to cut the steel bars of the removed cage, complete the rapid removal of the original lining structure, and repeat the cyclic construction to gradually remove the remaining existing tunnel lining structure.

[0117] (9) After the blasting and mechanical cutting removal of the existing tunnel lining, it is an important basis for verifying whether the removal operation method of the original lining structure is feasible by judging the effect after the lining structure is removed. The drilling and blasting parameters can be adjusted according to the obtained basis, such as adjusting the hole spacing, charge amount, etc.

[0118] (10) Blasting design for excavation: According to the determination of the surrounding rock grade after the removal of the original lining structure, design the blasting parameters for surrounding rock excavation. Utilize the free face after the removal of the lining structure to optimize the blasting parameter design to achieve the best smooth blasting effect;

[0119] (11) Drilling and blasting operation for excavated surrounding rock: Use the working surface after the removal of the lining structure as the free face for blasting excavation of the surrounding rock. When designing the blasting parameters, only the perimeter holes and auxiliary holes need to be designed, and the cut holes do not need to be involved. According to the designed drilling and blasting parameters, carry out on-site actual engineering operations, drill holes longitudinally along the tunnel, and make dynamic parameter adjustments according to the actual situation on site. The specific construction parameters are as follows:

[0120] Hole diameter, take d = 40mm; hole depth, take L = 1.8m; hole layout, take a = 0.4m, b = 0.6m; specific charge q, specific charge of auxiliary holes q = 2.0 kg / m 3 , specific charge of smooth blasting holes qsmooth = 0.25 - 0.30 kg / m 3 ; It can also be adjusted according to the actual situation on site and the first trial blasting situation during the construction process;

[0121] Charge amount per single hole Q:

[0122] (a) Charge amount per single hole of auxiliary holes: Q = q · a · b · L = 2 × 0.4 × 0.6 × 1.8 = 0.86 kg, take Q = 800 g;

[0123] (b) The single-hole charge of the smooth blasting holes, \(Q_{light}=q_{light}\times L = 250\times1.8 = 450g\), take \(400g\); for easy operation and construction guidance during construction, the linear charge density control is adopted, take the linear charge density \(q_{light}=250g / m\), and full filling charge is adopted within the blast holes 10.

[0124] The smooth blasting holes are the smooth blasting holes (blast holes) located in the outermost circle of the blasting surface. The innermost circle of the blasting surface is the cut holes, and the auxiliary holes are located between the two.

[0125] (c)The plugging length at the orifice of the blast hole is \(0.4m\);

[0126] (12) Ventilation, danger removal, and cross-section measurement after the surrounding rock is excavated and enlarged:

[0127] According to the specification requirements, mechanical ventilation is set when the tunneling length exceeds 150m during tunnel construction. After the excavation and enlargement blasting, mechanical ventilation lasts for more than 30 minutes, and then mechanical equipment is used to remove dangerous rocks to ensure the safety of subsequent construction operations;

[0128] Cross-section measurement is carried out after the surrounding rock is excavated and enlarged to check the cross-section again, whether there is overbreak or underbreak, and whether the contour dimensions meet the requirements of the design drawings, providing a basic guidance for subsequent operations.

[0129] (13) Initial support after the surrounding rock is excavated and enlarged:

[0130] The initial support after the surrounding rock is excavated and enlarged is mainly the support of setting up steel arches, spraying concrete with bolts. The support parameters are I16 steel I-beams as steel arches, 22mm diameter mortar bolts and locking bolts, 8mm diameter single-layer steel mesh with a spacing of 20cm, and wet spraying process of C25 concrete.

[0131] (14) Monitoring and measurement after the surrounding rock is excavated and enlarged:

[0132] The results of the whole-process observation of the convergence and settlement of the surrounding rock should ensure that the convergence value is within 2.5mm, the overall settlement is about 2 - 3mm, and the maximum value is less than 5mm.

[0133] (15) Waterproofing, drainage, and lining construction after the surrounding rock is excavated and enlarged:

[0134] The waterproofing and drainage are divided into waterproofing and drainage construction. The waterproofing is mainly based on geotextiles and waterproof boards, supplemented by horizontal semi-circular pipes and longitudinal drain pipes; the drainage is mainly based on the central drainage ditch and inspection wells, supplemented by the road surface drainage ditch, forming a comprehensive waterproofing and drainage system, which is a traditional construction method.

[0135] For the newly expanded lining construction, cast-in-place concrete is used. The construction formwork is mechanical trolley and manual formwork support. During the concrete pouring process, attention should be paid to symmetric pouring, and the pouring speed should not be too fast. Conduct various tests on the concrete on-site to ensure the concrete pouring effect and meet the requirements of the tunnel construction specifications. Since it is a traditional method, it will not be elaborated here.

[0136] It should be noted that the construction of removing and in-situ excavating the muck is carried out when the muck truck is in the state below the muck-producing construction, and the upper ends of the side baffles at both ends of the muck truck are supported on the corresponding tunnel wall to be demolished. Thus, it is ensured that the muck produced by the removal and in-situ excavation can directly fall onto the muck truck. After the muck truck compartment is full, the zipper with a tensioner between the tension hooks 18 corresponding to both sides at the upper end of the side baffle can be tightened to control the inward inclination angle and closing of the side baffle, and then the muck truck is towed out of the tunnel by a tractor for unloading the muck.

[0137] Table 1 is a comparison table of the advantages and disadvantages of the present invention and the prior art: Table 1:

[0138]

[0139] Table 1 shows that compared with the prior art, the removal speed of the present invention is twice as fast, the number of construction workers is halved, the construction cost is reduced by 50%, the construction period is shortened by 50%, and the construction efficiency is increased by 40 - 41%. Moreover, the construction of the present invention will not cause the collapse of the working rock stratum, the construction is safe, and the overall economic and social benefits are remarkable.

[0140] The above-mentioned is only the preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, making equivalent substitutions or changes, should be covered within the protection scope of the present invention.

Claims

1. A method for demolishing and in-situ excavation of an existing tunnel structure, characterized in that, it includes the following steps: (1) Prepare a muck truck: Prepare a muck truck according to the width of the existing tunnel, which is used to receive and transport the muck formed during the demolition of the existing tunnel to the muck yard. The carriage of the muck truck is a flatbed truck body. There is an iron plate layer on the upper end surface of the flatbed truck body. Axles are provided on both sides of the lower end of the truck body. Wheels are provided on both sides of the axles. Side baffles are pivotally connected to both sides of the truck body. Tightening hooks are provided at both ends of the upper part of the inner side of the side baffle. Traction hooks are provided in the middle of the other two sides of the truck body; (2) Advanced geological exploration and determination plan: (a) Before construction, conduct longitudinal and transverse advanced geological exploration holes on the original lining section and the excavation section of the existing tunnel to be renovated and expanded. Use geological drilling or radar scanning for advanced geological forecasting operations; (b) Determine the thickness of the original lining section. According to the forecast of the original lining section by the advanced geological exploration holes, judge the thickness of the existing tunnel to be demolished, the surrounding rock behind the existing tunnel, and the relevant situation of the separated part; (c) Whether advanced support is required. By judging the surrounding rock and the separation distance behind the lining of the original lining section, combined with the specification standards and the characteristics of the surrounding rock, determine the surrounding rock level. According to the self-stabilizing ability of the surrounding rock and the vibration of the surrounding rock caused by blasting, judge whether advanced support is required for the next step of construction; If: The outer excavation section of the original lining section of the renovated and expanded tunnel is a loose and easily collapsible geological layer or there is a curtain cavity behind the original lining after geological exploration, then step (3) of advanced pre-support is required; otherwise, step (4) is carried out; (3) Advanced pre-support: The advanced pre-support uses the method of drilling and grouting to grout and fill the curtain cavity behind the original lining and reinforce the loose rock layer; (4) Demolition design of the original lining section: The demolition design of the original lining section is divided into partial demolition and full demolition of the original lining section; Partial demolition means that one side of the designed excavation contour line is located inside the existing tunnel, and full demolition means that the designed excavation contour line is located outside the existing tunnel; (a) Partial demolition. When one side of the designed excavation contour line is located inside the existing tunnel, the space between the designed excavation contour line located inside the existing tunnel and the inner wall of the existing tunnel forms a backfill area, and the backfill area is backfilled; The existing tunnel in the backfill area is retained, and the remaining part of the existing tunnel within the designed excavation contour line is demolished; (b) Full demolition. Demolish the existing tunnel; (5) Demolition of the existing tunnel to be demolished: The demolition is carried out by a combination of blasting and mechanical shearing of steel bars; Drilling and blasting demolition of the existing tunnel: (a) According to the geological forecast and the situation of the original lining structure, design the blasting parameters of reinforced concrete to ensure the "cage removal" effect of blasting; (b) According to the designed drilling and blasting parameters, carry out on-site actual engineering operations. Operate to drill blast holes longitudinally along the original lining structure and make dynamic parameter adjustments according to the actual situation on site; The diameter d of the blast hole is 38 - 44 mm; The depth L of the blast hole, L = 1.8 m; (c) Hole layout: In order to ensure the smooth progress of the blasting of the existing tunnel and the tunnel excavation and expansion, take the minimum resistance line as W = 0.25 - 0.3 m, the hole spacing a = 0.5 - 0.8 m; Take the layer spacing b = 0.6 m; (d)Explosive consumption per cubic meter q: Select q = 2.0 kg / m 3 , or it can be adjusted according to the actual site conditions and the first trial blasting situation during the construction process; (e) Single-hole charge amount Q; Q = q·a·b·L = 2.0×0.6×0.6×1.8 = 1.29 kg. Take Q = 1.2 Kg and divide it into 6 rolls of explosives; The length of the orifice blockage is 0.4 m. The explosive used is No. 2 rock emulsion explosive, with a selected φ32 specification and a cartridge density of 0.95 - 1.25 g / cm 3 , a length of 200 mm, and 200 g per section; The charging structure is segmented charging in the blast hole. The ends of adjacent explosive rolls in each hole are 4 cm apart, and the stemming length at the hole mouth is 0.4 m; For the blasting demolition of the existing tunnel, the blasting length is 1.8 - 2.2 m. After 2 cycles of blasting operations can be carried out; (6) Ventilation and danger removal: When the tunneling length of the tunnel construction exceeds 150 m, mechanical ventilation is set up. After the blasting demolition of the existing tunnel, mechanical ventilation lasts for more than 30 minutes, and then mechanical equipment is used to remove dangerous rocks to ensure the safety of subsequent construction operations; (7) Temporary support and cross-section measurement: According to the comparison between the advanced prediction of the surrounding rock grade and the situation after demolition, it is judged whether temporary support is needed. The support form mainly uses I16 steel I-beams for temporary support and shotcrete support to ensure the structural force safety; Cross-section measurement is carried out after the removal of the original lining structure to recheck the cross-section and verify whether the thickness of the original lining judged by the advanced exploration holes is correct, so as to provide guidance for subsequent operations; (8) Mechanical hydraulic cutting of steel bars: When blasting to remove the cage, it is very difficult to damage the steel bars inside the original lining structure. Mechanical hydraulic pliers need to be used for cutting, and no manual assistance is required. The cutting machine is an excavator equipped with an H.S-250 type hydraulic pliers; Use large mechanical hydraulic pliers or eagle beak pliers to cut the steel bars of the removed cage to complete the rapid removal of the original lining structure, and repeat the cyclic construction to gradually remove the remaining lining structure of the existing tunnel; (9) After the blasting and mechanical cutting demolition of the existing tunnel lining, it is an important basis for verifying whether the demolition operation method of the original lining structure is feasible by judging the effect after the demolition of the lining structure; (10) Design of the excavation blasting: According to the determination of the surrounding rock grade after the removal of the original lining structure, design the blasting parameters for the excavation of the surrounding rock. Utilize the free face after the removal of the lining structure to optimize the blasting parameter design to achieve the best smooth blasting effect; (11) Drilling and blasting operations for the excavation of the surrounding rock: Use the working surface after the removal of the lining structure as the free face for the blasting excavation of the surrounding rock. When designing the blasting parameters, only the perimeter holes and the auxiliary blast holes need to be designed, and the cut holes are not involved. According to the designed drilling and blasting parameters, carry out the actual engineering operations on site. Operate to drill holes longitudinally along the tunnel and adjust the dynamic parameters according to the actual situation on site. The specific construction parameters are as follows: Aperture, take d = 40 mm; hole depth, take L = 1.8 m; hole layout, take a = 0.4 m, b = 0.6 m; specific charge q, specific charge of auxiliary holes q = 2.0 kg / m 3 , specific charge of smooth blasting holes qsmooth = 0.25 - 0.30 kg / m 3 ; it can also be adjusted according to the actual site conditions and the situation of the first trial blasting during the construction process; Single-hole charge amount Q: (a) Single-hole charge for the auxiliary blast hole: Q = q·a·b·L = 2×0.4×0.6×1.8 = 0.86 kg. Take Q = 800 g; (b) Single-hole charge for the smooth blasting hole, Qsmooth = qsmooth×L = 250×1.8 = 450 g. Take 400 g; For easy operation and construction guidance during construction, the linear charge density control is adopted. Take the linear charge density qsmooth = 250 g / m, and the blast hole is filled with explosives; (c) The stemming length at the blast hole mouth is 0.4 m; (12) Ventilation, danger removal, and cross-section measurement after the excavation of the surrounding rock: According to the specification requirements, mechanical ventilation is set up when the tunneling length of the tunnel construction exceeds 150 m. After the excavation blasting, mechanical ventilation lasts for more than 30 minutes, and then mechanical equipment is used to remove dangerous rocks to ensure the safety of subsequent construction operations; Cross-section measurement is carried out after the surrounding rock is excavated to a larger extent to review the cross-section, check for over-excavation and under-excavation, and determine whether the contour dimensions meet the requirements of the design drawings, providing a basic guidance for subsequent operations; (13) Initial support after excavating the surrounding rock to a larger extent: After excavating the surrounding rock to a larger extent, the initial support mainly consists of setting up steel arches and shotcreting. The support parameters are I16 steel I-beams as steel arches, 22-diameter mortar bolts and locking bolts, 8-diameter single-layer steel mesh with a spacing of 20 cm, and C25 wet shotcrete technology for spraying concrete; (14) Monitoring and measurement after excavating the surrounding rock to a larger extent: The results of the whole-process convergence and settlement observations of the surrounding rock should ensure that the convergence value of the surrounding rock is within 2.5 mm, the overall settlement is about 2 - 3 mm, and the maximum value is less than 5 mm; (15) Waterproofing, drainage and lining construction after excavating the surrounding rock to a larger extent The waterproofing and drainage are divided into waterproofing construction and drainage construction. The waterproofing mainly uses geotextiles and waterproof membranes, supplemented by horizontal semi-circular pipes and longitudinal drain pipes; the drainage mainly uses a comprehensive waterproofing and drainage system with a central drainage ditch and inspection wells as the main components and the road surface drainage ditch as the auxiliary component; For the newly expanded lining construction, cast-in-place concrete is used. The construction formwork is mechanical trolley and manual formwork support. During the concrete pouring process, attention should be paid to symmetric pouring, and the pouring speed should not be too fast. Various tests of the concrete should be done on-site to ensure the concrete pouring effect and meet the requirements of the tunnel construction specifications.

2. According to the method described in claim 1, it is characterized in that: The advanced pre-support uses the drilling and grouting method to grout and fill the curtain cavity behind the original lining and reinforce the loose rock stratum, including the following steps: (a) Drill grouting holes through the original lining into the loose rock stratum 1 - 1.2 m outside the designed excavation contour line. If there is a curtain cavity behind the original lining, the grouting holes should communicate with the curtain cavity, and the adjacent grouting holes are 1 - 1.2 m apart; (b) Use lightweight perlite concrete slurry to grout and reinforce the loose rock stratum outside the original lining through the drilled grouting holes, and grout and fill the cavity area, with the filling thickness not less than 1.5 m; The weight ratio of the lightweight perlite concrete slurry is: water: cement: perlite: sand = 65:100:600:300; (c) Use a grouting device to grout into the grouting holes, with the grouting pressure being 0.5 - 1.0 MPa and the final pressure being less than 1.5 MPa; when the grout intake is less than 20 - 25 L / min, the grouting pressure gradually increases. When the final pressure is reached and maintained for more than 10 minutes, the grouting can be stopped, and the grouting port should be blocked in time to prevent air from entering the pipe; (d) The grouting and filling start from the two side arch feet first, and the arch feet are filled in 2 - 3 times up to the arch crown.

3. According to the method described in claim 2, it is characterized in that: If grouting and filling the cavity area, the cavity grouting is carried out in 3 times. The first time fills lightweight perlite concrete slurry, and the second and third times fill perlite mortar. The grouting thickness each time is 50 cm, and the filling height is confirmed through overflow observation pipes at different heights; after each grouting is completed, it should be left standing for more than 4 hours before starting the next grouting.

4. According to the method described in claim 3, it is characterized in that: The perlite-filled mortar contains 168 Kg of cement, 1.16 m³ of perlite, and 0.4 m³ of water per cubic meter of mortar. 3 and 0.4 m³ of water 3 .

5. According to the method described in claim 1, it is characterized in that: The construction of removing and in-situ excavating the muck is carried out when the muck truck is in the state below the muck-producing construction, and the upper ends of the side baffles at both ends of the muck truck are supported on the corresponding tunnel wall to be demolished.

6. According to the method described in claim 1, it is characterized in that: When one side of the newly built tunnel wall is located inside the existing tunnel, the space between the designed excavation contour line inside the existing tunnel and the inner wall of the existing tunnel forms a backfill space, and the backfill space is backfilled. The backfill materials are sand, bricks and cast concrete.

7. According to the method described in claim 1, it is characterized in that: The wheels are track wheels located on the track or wheels on the ground.

8. According to the method described in claim 1, it is characterized in that: The limiting blocks between the adjacent cartridge ends in each hole are foam plastic blocks or air bags.

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