阅读说明：本技术 空间上下分布的隧道锚与分岔隧道近接工程同步施工方法 (Tunnel anchor and bifurcation tunnel proximity engineering synchronous construction method distributed up and down in space ) 是由 龙立敦 张学民 李少方 韩宵 龙勍 王朝国 廖万辉 陈元忠 吴扬 于 2021-09-10 设计创作，主要内容包括：本发明公开了一种空间上下分布的隧道锚与分岔隧道近接工程同步施工方法,分岔隧道施工进入小净距段施工后,隧道锚搭设出渣系统,开始进行锚室开挖与支护工作,后续隧道锚与隧道开挖支护工作交叉独立进行,直至隧道锚与分岔隧道开挖完成。和现有施工方案相比,避免了新建洞室施工对已建好洞室的影响。同时,较之常规的先施工下方分岔隧道,后施工上方隧道锚的施工组织方式,该工法通过分岔隧道与隧道锚协同同步施工,使开州湖特大桥隧道锚提前15个月开工,极大缩短了工期,使项目总工期缩减15个月。经测算,项目单月管理人员工资、行政办公费达80万元,则节省15个月工期可为项目节省成本1200万元。(The invention discloses a synchronous construction method for tunnel anchor and bifurcation tunnel proximity projects which are distributed up and down in space. Compared with the existing construction scheme, the method avoids the influence of the construction of the newly-built cavern on the well-built cavern. Meanwhile, compared with the conventional construction organization mode of firstly constructing the lower forked tunnel and then constructing the upper tunnel anchor, the construction method has the advantages that the forked tunnel and the tunnel anchor are cooperatively and synchronously constructed, so that the tunnel anchor of the Kaizhou lake grand bridge is started 15 months in advance, the construction period is greatly shortened, and the total construction period of a project is shortened by 15 months. Through measurement and calculation, the wage and administrative handling fee of project monthly managers reaches 80 ten thousand yuan, so that the project cost can be saved by 1200 ten thousand yuan for 15-month construction period.)

1. A tunnel anchor and bifurcation tunnel approach engineering synchronous construction method distributed up and down in space is characterized in that: the bifurcation tunnel enters a hole from a split tunnel end hole or a transverse hole positioned at the side of the split tunnel section, the bifurcation tunnel is firstly constructed by the split tunnel section or the transverse hole, meanwhile, a tunnel anchor carries out the work of hole side and upward slope excavation, protection and arch sleeving construction, after the bifurcation tunnel construction enters a small clear distance section construction, a slag discharging system is built by the tunnel anchor, the anchor room excavation and supporting work are started, and the subsequent tunnel anchor and the tunnel excavation supporting work are alternately and independently carried out until the tunnel anchor and the bifurcation tunnel excavation are finished.

2. The synchronous construction method of the tunnel anchor and branch tunnel approach engineering distributed up and down in space according to claim 1, characterized in that: the construction flow of the bifurcation tunnel comprises the following steps: when the small clear distance section pilot tunnel is excavated to the starting point of the transition section, gradually enlarging the excavation section by adopting the normal linear gradient of the step, and timely constructing an enlarged section support, when the start point of the multi-arch section is reached, enlarging the width of the tunnel face of the transition section to the side wall of the middle pilot tunnel; when the rear row of the small clear distance section is excavated to the position 2 times of the excavation width of the single tunnel of the tunnel from the starting point of the transition section, the construction is suspended, and the tunnel face is closed; closing the tunnel face after the construction of the transition section is finished, then excavating a middle pilot tunnel, excavating the middle pilot tunnel together with the middle partition wall foundation during the excavation of the middle pilot tunnel, and simultaneously preparing reinforcing steel bars and templates required by the construction of the middle partition wall according to the design of the middle partition wall; after the middle pilot tunnel is communicated, constructing a middle partition wall from the interior of the tunnel to the opening, improving the strength of the middle partition wall foundation and the first and second model concretes of the wall body by one label, recovering the tunneling of the first tunnel of the main tunnel after the strength of the first and second model concretes of the wall body of the middle partition wall meets the design requirement, and always keeping the distance of the mileage of the middle partition wall behind the tunnel face of the first tunnel to be not less than 2 times of the tunneling width of a single tunnel; when the front hole excavation of the multi-arch section main hole is finished by not less than 2 times of the distance of the single hole excavation width of the tunnel, backfilling the expanding excavation transition section by adopting an artificial rock pillar combined layered concrete spraying process, restoring to a designed excavation section, and then restoring the excavation construction of the rear hole of the main hole; and (3) recovering secondary lining construction along with the excavation progress of the main hole, finally forming an intermediate wall foundation and pouring an intermediate wall body of the bifurcated tunnel, excavating and supporting the advanced hole and the backward hole of the main hole, and performing secondary lining construction on the advanced hole and the backward hole of the main hole in a line production manner on 6 working surfaces to finish construction of the bifurcated tunnel.

3. The synchronous construction method of the tunnel anchor and branch tunnel approach engineering distributed up and down in space according to claim 1, characterized in that: and after the tunnel anchor is excavated, construction is carried out according to the construction sequence of the second back anchor chamber liner → the synchronous pouring of the anchor plug body → the second front anchor chamber liner, and the construction of the second back anchor chamber liner concrete of the bifurcated tunnel at the lower cross section such as the pouring of the anchor plug body is started after the strength of the second back anchor chamber liner concrete reaches the design requirement.

4. The synchronous construction method of the tunnel anchor and branch tunnel approach engineering distributed up and down in space according to claim 1, characterized in that: the construction of the small clear distance section is specifically as follows: determining the initial mileage and the ending mileage of a transitional expanding excavation section connected between the small clear distance section and the multi-arch tunnel section, when the first tunnel is reversely tunneled to the initial mileage of the transitional expanding excavation section, gradually expanding the excavation section from the expanding excavation initial mileage by adopting a step method linear gradual change mode, tunneling to the starting point of the multi-arch tunnel section, and suspending construction when the tunnel face of the later tunnel is tunneled to a preset position away from the starting mileage of the multi-arch tunnel section; then, starting middle pilot tunnel construction preparation and tunneling; after the middle pilot tunnel is communicated, constructing an intermediate wall from the starting point mileage of the intra-tunnel arch tunnel section, synchronously starting the tunneling of the multi-arch tunnel section of the front tunnel after the middle partition wall meets the strength requirement, and simultaneously constructing an artificial rock pillar on the expanded excavation transition expanded excavation section; after the artificial rock pillar is constructed and meets the strength requirement, the top of the expanded excavation section of the transitional expanded excavation section is backfilled by adopting a layered concrete spraying process, and grouting reinforcement is carried out; and when the first hole of the transitional expanding excavation section is restored to the standard section, organizing the construction of the backward hole, and normally constructing the first hole and the backward hole of the tunnel.

5. The synchronous construction method of the tunnel anchor and branch tunnel approach engineering distributed up and down in space according to claim 4, characterized in that: the backward holes of the small clear distance section adopt mechanical crushing excavation aiming at rock masses within 1m of the adjacent middle rock pillar, the artificial rock pillar of the small clear distance section, grouting and reinforcing surrounding rock at the upper part of the middle wall rock pillar, adopting common cement grout as grout, adopting horizontal low-prestress counter-pulling anchor rods penetrating through two holes at the middle lower part of the middle wall rock pillar, wherein the distance between the anchor rods is 60-100cm, adopting a secondary tensioning process for the low-prestress counter-pulling anchor rods, namely, after the anchor rod is excavated and constructed in the first hole, the anchor rod is primarily tensioned by a torque wrench when the strength of slurry in the anchor rod drilling hole reaches the designed strength, and after the end part of the anchor rod is exposed by excavation in the second hole, the thread protection package which is pre-installed is removed, applying a pretension force to a design value through a torque wrench, wherein the prestress requirement of low prestress on the tension anchor rod is not less than 100kN, the tensile load of the anchor rod body is not less than 180kN, and the elongation is not less than 6%; the grouting pressure is 1 MPa-2 MPa.

6. The synchronous construction method of the tunnel anchor and branch tunnel approach engineering distributed up and down in space according to claim 1, characterized in that: in the work progress, through warping to the country rock, supporting construction internal force to and the blasting vibration speed carries out continuous monitoring, and according to monitoring result dynamic optimization adjustment support parameter and blasting scheme, all be in regulation and design requirement within range with each item monitoring index of guaranteeing structure deformation and internal force, blasting vibration speed, specifically including strengthening tunnel country rock and tunnel anchor well included rock mass advance geology forecast, to unfavorable geology: reinforcing the karst, the corrosion crushing zone and the joint dense zone, and reinforcing by grouting and filling.

7. The synchronous construction method of the tunnel anchor and branch tunnel approach engineering distributed up and down in space according to claim 6, characterized in that: still include tunnel anchor and tunnel support quality detection and reinforcement, after tunnel and tunnel anchor are under the construction completion of just propping up, adopt the radar to survey just propping up the degree of hugging closely with the country rock, there is the cavity when just propping up and country rock, or when pressing from both sides the poor or enhancement tunnel wall post-grouting when the country rock deformation of rock mass in the tunnel top, process flow is as follows: construction preparation → hole distribution → hole forming → grouting pipe insertion → grouting → hole sealing → on-site cleaning.

Technical Field

The invention relates to a tunnel construction method, in particular to a synchronous construction method for tunnel anchor and bifurcation tunnel proximity engineering which are distributed up and down in space.

Background

The demand for constructing highways in mountainous areas is continuously increased, the proportion of bridges and tunnels occupying the whole line is increased, and the landscapes connected with bridges and tunnels are increased in the highways in mountainous areas. The west mountain area canyon features are numerous, the number of high-pier large-span suspension bridges is in the rising trend in recent years, and the anchor is an important bearing structure in a stress system of the suspension bridge. Compared with a gravity type anchorage, the tunnel type anchorage structure gives full play to the axial rigidity of the prestressed rock anchor, and meanwhile, rock masses in a large range participate in structural stress, so that the excavation amount is small, and the disturbance to the rock masses is small. The tunnel anchor is one of important forms of a large-span suspension bridge anchor in western large development construction in China, meanwhile, in order to meet the linear standard of a route, a tunnel structure form of a bridge-tunnel connecting section mostly adopts a bifurcation tunnel, the bifurcation tunnel is a tunnel construction form provided in the process of constructing a mountain expressway under the condition of complex terrain and geology, and the bifurcation tunnel is usually gradually transited to an up-down separated double-tunnel from an arch-connected tunnel. The bifurcation tunnel of the bridge-tunnel connection section has the characteristics of multiple types of tunnels such as a separation tunnel with a standard interval, a small clear distance tunnel, a multi-arch tunnel and the like.

Due to the restriction of space and field and the linear influence of routes, the tunnel anchors of the connected suspension bridge are often distributed in the near range of the bifurcation tunnel, and the excavation of the tunnel anchors and the bifurcation tunnel inevitably causes multiple disturbances on surrounding rocks. Meanwhile, in order to meet the requirement of the construction period, the tunnel anchor is usually excavated within a short time after the tunnel is just excavated, and even the tunnel and the tunnel anchor are excavated simultaneously. Because of suspension bridge tunnel anchor and bifurcation tunnel are upper and lower distribution in the space, the construction technology degree of difficulty is big, the safe risk is high, and tunnel anchor and the synchronous construction of bifurcation tunnel have more engineering difficult and difficult point problem: the tunnel anchor axis is overlapped with the bifurcation tunnel axis or is intersected with the bifurcation tunnel axis at a small angle, and the intersection range is large; the tunnel anchor has a large excavation section; the two are constructed synchronously, and the mutual influence is large in the excavation process; the bifurcated tunnel has complex forms such as a multi-arch tunnel and a small clear distance tunnel, and the engineering safety problems such as collapse of surrounding rocks and cracking of a tunnel structure can be caused by carelessness. Therefore, at present, for the tunnel anchor and bifurcation tunnel proximity engineering distributed up and down in space, the design requirement and the conventional construction sequence are that the lower tunnel is constructed firstly, and after the lining structure of the lower tunnel is stable, the tunnel anchor above the lower tunnel can be constructed, especially when the tunnel anchor is positioned right above the tunnel and the clear distance between the tunnel anchor and the upper tunnel is small.

However, a grand bridge such as a suspension bridge to which a tunnel anchor belongs is generally used as a control project of a whole highway project line, the construction time of the grand bridge determines the total construction period of the project, and the grand bridge has a great influence on the traffic time and the social and economic benefits of investment of the project. The conventional construction sequence can cause the construction starting time of the tunnel anchor to be greatly delayed backwards, so that the total project period is greatly delayed backwards, and even the target project period of the whole investment project is broken through; in addition, the bridge-tunnel connected suspension bridge is usually used for crossing a V-shaped mountain valley, a bifurcation tunnel arch end opening is usually located on a steep bank slope, the entrance condition is poor, and if the arch end opening enters the tunnel, the tunnel construction and the suspension bridge pier tower construction generate large cross interference, which is not beneficial to the construction safety control. Therefore, the construction of the bifurcation tunnel is carried out from the side of the end opening or the transverse hole of the separated tunnel under the condition that the entrance of the arch-connected end opening is not provided, and the construction from the small-clearance tunnel to the arch-connected tunnel is carried out in the reverse direction, so that the construction time of the bifurcation tunnel below is further increased, the completion time of the anchor of the tunnel above is further delayed, the total construction period of the highway project is finally greatly delayed, and the investment benefit and the economic and social benefits are reduced.

Disclosure of Invention

The invention aims to provide a synchronous construction method for tunnel anchor and bifurcation tunnel proximity engineering which are distributed vertically in space. The problem of long construction period caused by conventional excavation construction sequence in group tunnel engineering is effectively solved, potential safety hazards and potential quality hazards in the synchronous construction process are effectively avoided, and the requirements of design and specification are well met.

The technical scheme of the invention is as follows: a tunnel anchor and bifurcation tunnel approach project synchronous construction method distributed up and down in space is characterized in that a bifurcation tunnel enters a hole from an end hole of a separate tunnel or a transverse hole positioned on the side of a separate tunnel section, the bifurcation tunnel is firstly constructed on the separate tunnel section or the transverse hole, meanwhile, the tunnel anchor carries out the work of hole side and upward slope excavation, protection and arch sleeving construction, after the bifurcation tunnel construction enters a small clear distance section, a slag discharging system is built on the tunnel anchor to start anchor room excavation and support work, and the follow-up tunnel anchor and tunnel excavation support work are carried out alternately and independently until the tunnel anchor and the bifurcation tunnel excavation are finished.

The tunnel anchor and bifurcation tunnel approach engineering synchronous construction method distributed vertically in space comprises the following construction processes: when the small clear distance section pilot tunnel is excavated to the starting point of the transition section, gradually enlarging the excavation section by adopting the normal linear gradient of the step, and timely constructing an enlarged section support, when the start point of the multi-arch section is reached, enlarging the width of the tunnel face of the transition section to the side wall of the middle pilot tunnel; when the rear row of the small clear distance section is excavated to the position 2 times of the excavation width of the single tunnel of the tunnel from the starting point of the transition section, the construction is suspended, and the tunnel face is closed; closing the tunnel face after the construction of the transition section is finished, then excavating a middle pilot tunnel, excavating the middle pilot tunnel together with the middle partition wall foundation during the excavation of the middle pilot tunnel, and simultaneously preparing reinforcing steel bars and templates required by the construction of the middle partition wall according to the design of the middle partition wall; after the middle pilot tunnel is communicated, constructing a middle partition wall from the interior of the tunnel to the opening, improving the strength of the middle partition wall foundation and the first and second model concretes of the wall body by one label, recovering the tunneling of the first tunnel of the main tunnel after the strength of the first and second model concretes of the wall body of the middle partition wall meets the design requirement, and always keeping the distance of the mileage of the middle partition wall behind the tunnel face of the first tunnel to be not less than 2 times of the tunneling width of a single tunnel; when the front hole excavation of the multi-arch section main hole is finished by not less than 2 times of the distance of the single hole excavation width of the tunnel, backfilling the expanding excavation transition section by adopting an artificial rock pillar combined layered concrete spraying process, restoring to a designed excavation section, and then restoring the excavation construction of the rear hole of the main hole; and (3) recovering secondary lining construction along with the excavation progress of the main hole, finally forming an intermediate wall foundation and pouring an intermediate wall body of the bifurcated tunnel, excavating and supporting the advanced hole and the backward hole of the main hole, and performing secondary lining construction on the advanced hole and the backward hole of the main hole in a line production manner on 6 working surfaces to finish construction of the bifurcated tunnel.

According to the tunnel anchor and bifurcation tunnel approach engineering synchronous construction method distributed vertically in space, after the tunnel anchor is excavated, construction is carried out according to the construction sequence of the second liner of the rear anchor chamber → the synchronous casting of the anchor plug body → the second liner of the front anchor chamber, and the casting of the anchor plug body and the like is started after the strength of the second liner concrete of the bifurcation tunnel at the lower cross section meets the design requirement.

The synchronous construction method for the tunnel anchor and bifurcation tunnel approach engineering distributed vertically in space comprises the following specific steps: determining the initial mileage and the ending mileage of a transitional expanding excavation section connected between the small clear distance section and the multi-arch tunnel section, when the first tunnel is reversely tunneled to the initial mileage of the transitional expanding excavation section, gradually expanding the excavation section from the expanding excavation initial mileage by adopting a step method linear gradual change mode, tunneling to the starting point of the multi-arch tunnel section, and suspending construction when the tunnel face of the later tunnel is tunneled to a preset position away from the starting mileage of the multi-arch tunnel section; then, starting middle pilot tunnel construction preparation and tunneling; after the middle pilot tunnel is communicated, constructing an intermediate wall from the starting point mileage of the intra-tunnel arch tunnel section, synchronously starting the tunneling of the multi-arch tunnel section of the front tunnel after the middle partition wall meets the strength requirement, and simultaneously constructing an artificial rock pillar on the expanded excavation transition expanded excavation section; after the artificial rock pillar is constructed and meets the strength requirement, the top of the expanded excavation section of the transitional expanded excavation section is backfilled by adopting a layered concrete spraying process, and grouting reinforcement is carried out; and when the first hole of the transitional expanding excavation section is restored to the standard section, organizing the construction of the backward hole, and normally constructing the first hole and the backward hole of the tunnel.

The synchronous construction method of the tunnel anchor and the bifurcation tunnel proximity engineering which are distributed up and down in space is characterized in that mechanical crushing excavation is adopted for rock bodies within 1m range adjacent to the middle rock pillar, the small-clear-distance section artificial rock pillar is used for grouting and reinforcing surrounding rock at the upper part of the middle wall rock pillar, common cement grout is adopted as grout, horizontal low-prestress counter-pulling anchor rods penetrating through two holes are adopted for the middle lower part of the middle wall rock pillar, the distance between the anchor rods is 60-100cm, a secondary tensioning process is adopted for the low-prestress counter-pulling anchor rods, namely after the anchor rods are dug and applied in the front hole, the strength of the grout in anchor rod drilling holes reaches the designed strength, the anchor rods are subjected to primary tensioning through a torque wrench, after the rear hole is dug and the end parts of the anchor rods are exposed, a pre-installed screw thread protection package is removed, a pre-tensioning force is applied to the designed value through the torque wrench, and the pre-tensioning force of the low-prestress counter-pulling anchor rods is not less than 100kN, the breaking load of the anchor rod body is not less than 180kN, and the elongation is not less than 6%; the grouting pressure is 1 MPa-2 MPa.

The tunnel anchor and bifurcation tunnel approach engineering synchronous construction method distributed up and down in the space is characterized in that in the construction process, deformation of surrounding rocks, internal force of a supporting structure and blasting vibration speed are continuously monitored, supporting parameters and blasting schemes are dynamically optimized and adjusted according to monitoring results, all monitoring indexes of structural deformation and internal force and blasting vibration speed are guaranteed to be in the range of specifications and design requirements, advance geological forecast of rock masses in the surrounding rocks of the reinforced tunnel, the tunnel and the tunnel anchor is realized, and unfavorable geology is realized: reinforcing the karst, the corrosion crushing zone and the joint dense zone, and reinforcing by grouting and filling.

The tunnel anchor and bifurcation tunnel approach engineering synchronous construction method distributed up and down in space further comprises the steps of detecting and reinforcing the support quality of the tunnel anchor and the tunnel, detecting the close contact degree of the primary support and the surrounding rock by adopting a radar after the primary support construction of the tunnel and the tunnel anchor is completed, and strengthening the grouting behind the wall of the tunnel when the primary support and the surrounding rock have a cavity or the surrounding rock deforms or the rock is clamped in the upper part of the tunnel, wherein the process flow is as follows: construction preparation → hole distribution → hole forming → grouting pipe insertion → grouting → hole sealing → on-site cleaning.

The invention has the beneficial effects that: the invention has the following characteristics:

1. compared with the construction scheme of the conventional bifurcation tunnel and tunnel anchor approach engineering, the method avoids the influence of newly-built cavern construction on the built cavern. Meanwhile, compared with the conventional construction organization mode of firstly constructing the lower forked tunnel and then constructing the upper tunnel anchor, the construction method has the advantages that the forked tunnel and the tunnel anchor are cooperatively and synchronously constructed, so that the tunnel anchor of the Kaizhou lake grand bridge is started 15 months in advance, the construction period is greatly shortened, and the total construction period of a project is shortened by 15 months. Through measurement and calculation, the wage and administrative handling fee of project monthly managers reaches 80 ten thousand yuan, so that the project cost can be saved by 1200 ten thousand yuan for 15-month construction period.

2. Social benefits

The construction method is used for synchronous construction of the bifurcated tunnel and the tunnel anchor, the total construction period of a project is shortened, disturbance and damage of newly-built cavern construction to an established cavern structure are effectively avoided, and through measures such as advanced geological forecast, blasting control and monitoring, wall post-grouting and the like of a cross section, stability and construction safety of a middle-sandwiched rock mass are guaranteed, construction progress is accelerated, energy consumption and atmospheric pollution are reduced, meanwhile, the newly-built expressway is served for social and economic development along the line in advance, poverty removal and hardness attack are assisted, and good social benefits are obtained.

The construction method for transition from a small clear distance section to a multi-arch section is disclosed in a bridge-tunnel connection bifurcation tunnel construction method in Chinese patent CN111810165A previously applied by the applicant in the related technology, and has the advantages of small expanding and excavating engineering quantity, short construction period, high construction efficiency, high safety and the like. The construction method of the transition section between the bifurcated tunnel and the multi-arch section only can shorten the construction period of the bifurcated tunnel and cannot realize synchronous construction of the bifurcated tunnel and the tunnel anchor. This patent technique is emphasized: the construction method is characterized in that the bearing capacity of the middle wall rock pillar and the tunnel supporting structure of the lower bifurcated tunnel is enhanced through the application of technical means such as split anchor rod reinforcement technology of the middle rock pillar in the small clear distance section of the bifurcated tunnel, mechanical crushing of rock pillars near the middle rock pillar in the backward tunnel of the small clear distance tunnel, layered anchor spraying or combined spraying and concrete pouring construction of the transition section of the small clear distance tunnel and the multiple arch tunnel, and self-compacting concrete integrated backfilling of gaps between the middle wall top and the arch crown of the middle guide tunnel in the multiple arch tunnel; and secondly, because the multi-arch tunnel is positioned under the tunnel anchor, the construction progress and quality directly restrict the construction progress and safety of the upper tunnel anchor. The research of the technology provides construction optimization methods such as excavation of a pilot tunnel in the multi-arch tunnel together with an intermediate wall foundation, self-compacting concrete pouring of the intermediate wall, integrated backfilling of the top space of the intermediate wall and the like, greatly improves the construction speed and quality of the multi-arch tunnel, and can form stable and effective support below a tunnel anchor as early as possible to ensure the construction safety of the tunnel anchor above the tunnel anchor; thirdly, a tunnel anchor and tunnel proximity engineering dynamic construction method based on real-time monitoring is adopted, tunnel and tunnel anchor excavation support parameters are dynamically adjusted and a blasting scheme is dynamically optimized through continuous surrounding rock deformation monitoring, support structure internal force monitoring and blasting vibration monitoring in the construction process, dynamic construction is implemented, all control indexes of the tunnel anchor and the tunnel are in the range of specifications and design requirements, and the safety of a cavern structure during synchronous construction of group holes in the tunnel anchor and tunnel proximity engineering is guaranteed; and fourthly, for construction of the intersection section of the bifurcation tunnel and the tunnel anchor, the technology adopts multiple means to jointly carry out advanced geological forecast on surrounding rocks, the tunnel anchor and the sandwiched rock mass between the tunnels, and finds unfavorable geology and processes in time. In addition, the construction quality of the tunnel and the tunnel anchor support is detected, and grouting filling is carried out in time when a cavity exists, so that the support is ensured to be closely attached to the surrounding rock, the branched tunnel support structure and the surrounding rock can form a stable whole, the stress generated by the surrounding rock is ensured to be transmitted according to the design direction, the occurrence of unfavorable working conditions such as stress concentration is avoided, meanwhile, the integral stability of stress of the surrounding rock and the support structure can be effectively improved, and stable support is provided for safe construction of the tunnel anchor; fifthly, construction organization is carried out aiming at the procedure of casting the anchor plug body of the tunnel anchor with high risk, and after the secondary lining strength of the lower bifurcated tunnel reaches the design strength value, casting of the anchor plug body can be carried out, so that the anchor plug body can be stably and effectively supported, and the overall safety of the project is ensured. In conclusion, the key point of the method is that effective and timely support is provided through the lower bifurcation tunnel, the safety of synchronous construction of the upper large-span tunnel anchor is guaranteed, the tunnel anchor does not need to be constructed according to the conventional process requirements, construction can be started after the construction of the lower bifurcation tunnel is completed, the time for starting construction of the suspension bridge tunnel anchor is effectively advanced, and the total construction period of the suspension bridge serving as the full-line control engineering is guaranteed.

Drawings

FIG. 1 is a construction flow chart of the present invention;

FIG. 2 is a schematic view of the tunnel anchor and bifurcated tunnel structure of the present invention;

FIG. 3 is a top plan view of the bifurcated tunnel and tunnel anchor of the present invention;

fig. 4 is a schematic diagram of the construction method of the subsection division and the transition section of the bifurcated tunnel of the invention.

Detailed Description

The invention is further illustrated by the following figures and examples, which are not to be construed as limiting the invention.

Example 1 of the invention:

a tunnel anchor and bifurcation tunnel approach project synchronous construction method distributed up and down in space is disclosed, as shown in figures 1 and 2, a bifurcation tunnel enters a hole from an end hole of a separate tunnel or a transverse hole positioned at the side of a separate tunnel section, the bifurcation tunnel is firstly subjected to separate tunnel section or transverse hole construction, meanwhile, the tunnel anchor is subjected to work of hole side and inverted slope excavation, protection and arch sleeving construction, after the bifurcation tunnel construction enters a small clear distance section construction, a slag discharging system is erected on the tunnel anchor to start anchor room excavation and support work, and subsequent tunnel anchor and tunnel excavation support work are performed alternately and independently until the tunnel anchor and bifurcation tunnel excavation are completed.

The construction safety technical key points

In the tunnel anchor and bifurcation tunnel space up-and-down distribution approach engineering, the tunnel anchor axis is overlapped with the bifurcation tunnel routing or intersected at a small angle, and the crossing range is large; the tunnel anchor has a large excavation section; the two are constructed synchronously, and the mutual influence is large in the excavation process; the bifurcated tunnel has complex forms such as a multi-arch tunnel and a small clear distance tunnel, and the engineering safety problems such as collapse of surrounding rocks and cracking of a tunnel structure can be caused by carelessness. Therefore, the construction method aims at the problem of construction safety control of the cross section, controls the cross section from the aspects of technology and management measures, and realizes synchronous construction of the proximity engineering on the premise of ensuring safety.

The construction flow of the bifurcation tunnel comprises the following steps: when the small clear distance section pilot tunnel is excavated to the starting point of the transition section, gradually enlarging the excavation section by adopting the normal linear gradient of the step, and timely constructing an enlarged section support, when the start point of the multi-arch section is reached, enlarging the width of the tunnel face of the transition section to the side wall of the middle pilot tunnel; when the rear row of the small clear distance section is excavated to the position 2 times of the excavation width of the single tunnel of the tunnel from the starting point of the transition section, the construction is suspended, and the tunnel face is closed; closing the tunnel face after the construction of the transition section is finished, then excavating a middle pilot tunnel, excavating the middle pilot tunnel together with the middle partition wall foundation during the excavation of the middle pilot tunnel, and simultaneously preparing reinforcing steel bars and templates required by the construction of the middle partition wall according to the design of the middle partition wall; after the middle pilot tunnel is communicated, constructing a middle partition wall from the interior of the tunnel to the opening, improving the strength of the middle partition wall foundation and the first and second model concretes of the wall body by one label, recovering the tunneling of the first tunnel of the main tunnel after the strength of the first and second model concretes of the wall body of the middle partition wall meets the design requirement, and always keeping the distance of the mileage of the middle partition wall behind the tunnel face of the first tunnel to be not less than 2 times of the tunneling width of a single tunnel; when the front hole excavation of the multi-arch section main hole is finished by not less than 2 times of the distance of the single hole excavation width of the tunnel, backfilling the expanding excavation transition section by adopting an artificial rock pillar combined layered concrete spraying process, restoring to a designed excavation section, and then restoring the excavation construction of the rear hole of the main hole; and (3) recovering secondary lining construction along with the excavation progress of the main hole, finally forming an intermediate wall foundation and pouring an intermediate wall body of the bifurcated tunnel, excavating and supporting the advanced hole and the backward hole of the main hole, and performing secondary lining construction on the advanced hole and the backward hole of the main hole in a line production manner on 6 working surfaces to finish construction of the bifurcated tunnel.

The bifurcation tunnel has the characteristics of various tunnels such as a separation tunnel with a standard interval, a small clear distance tunnel, a multi-arch tunnel or a four-lane single-span large-arch tunnel. Aiming at the reverse construction working condition of the bifurcation tunnel from the small clear distance section to the multi-arch section, the construction safety risk is higher and the construction efficiency is lower than that of the conventional working condition of forward construction from the multi-arch section to the small clear distance section. Therefore, organization and construction are strictly carried out according to the new Austrian method, and relevant construction measures are taken to ensure construction safety, and the construction is subject to the following steps: less disturbance, pipe advance, tight slip casting, short excavation, strong support, fast closure, tight lining, measurement of duty, fast feedback principle in addition, still need improve the bearing capacity of bifurcation tunnel country rock, accelerate bifurcation tunnel construction speed from the following aspect to make it earlier stable and can resist the adverse effect of upper portion tunnel anchor construction.

And after the tunnel anchor is excavated, construction is carried out according to the construction sequence of the second back anchor chamber liner → the synchronous pouring of the anchor plug body → the second front anchor chamber liner, and the construction of the second back anchor chamber liner concrete of the bifurcated tunnel at the lower cross section such as the pouring of the anchor plug body is started after the strength of the second back anchor chamber liner concrete reaches the design requirement.

The construction of the small clear distance section is specifically as follows: determining the initial mileage and the ending mileage of a transitional expanding excavation section connected between the small clear distance section and the multi-arch tunnel section, when the first tunnel is reversely tunneled to the initial mileage of the transitional expanding excavation section, gradually expanding the excavation section from the expanding excavation initial mileage by adopting a step method linear gradual change mode, tunneling to the starting point of the multi-arch tunnel section, and suspending construction when the tunnel face of the later tunnel is tunneled to a preset position away from the starting mileage of the multi-arch tunnel section; then, starting middle pilot tunnel construction preparation and tunneling; after the middle pilot tunnel is communicated, constructing an intermediate wall from the starting point mileage of the intra-tunnel arch tunnel section, synchronously starting the tunneling of the multi-arch tunnel section of the front tunnel after the middle partition wall meets the strength requirement, and simultaneously constructing an artificial rock pillar on the expanded excavation transition expanded excavation section; after the artificial rock pillar is constructed and meets the strength requirement, the top of the expanded excavation section of the transitional expanded excavation section is backfilled by adopting a layered concrete spraying process, and grouting reinforcement is carried out; and when the first hole of the transitional expanding excavation section is restored to the standard section, organizing the construction of the backward hole, and normally constructing the first hole and the backward hole of the tunnel.

The backward holes of the small clear distance section adopt mechanical crushing excavation aiming at rock masses within 1m of the adjacent middle rock pillar, the artificial rock pillar of the small clear distance section, grouting and reinforcing surrounding rock at the upper part of the middle wall rock pillar, adopting common cement grout as grout, adopting horizontal low-prestress counter-pulling anchor rods penetrating through two holes at the middle lower part of the middle wall rock pillar, wherein the distance between the anchor rods is 60-100cm, adopting a secondary tensioning process for the low-prestress counter-pulling anchor rods, namely, after the anchor rod is excavated and constructed in the first hole, the anchor rod is primarily tensioned by a torque wrench when the strength of slurry in the anchor rod drilling hole reaches the designed strength, and after the end part of the anchor rod is exposed by excavation in the second hole, the thread protection package which is pre-installed is removed, applying a pretension force to a design value through a torque wrench, wherein the prestress requirement of low prestress on the tension anchor rod is not less than 100kN, the tensile load of the anchor rod body is not less than 180kN, and the elongation is not less than 6%; the grouting pressure is 1 MPa-2 MPa.

In the work progress, through warping to the country rock, supporting construction internal force to and the blasting vibration speed carries out continuous monitoring, and according to monitoring result dynamic optimization adjustment support parameter and blasting scheme, all be in regulation and design requirement within range with each item monitoring index of guaranteeing structure deformation and internal force, blasting vibration speed, specifically including strengthening tunnel country rock and tunnel anchor well included rock mass advance geology forecast, to unfavorable geology: reinforcing the karst, the corrosion crushing zone and the joint dense zone, and reinforcing by grouting and filling.

The construction method also comprises the steps of detecting and reinforcing the support quality of the tunnel anchor and the tunnel, after the primary support construction of the tunnel and the tunnel anchor is completed, detecting the close contact degree of the primary support and the surrounding rock by using a radar, and reinforcing the tunnel wall post-grouting when a cavity exists between the primary support and the surrounding rock or when the surrounding rock is deformed or the included rock mass is poor above the tunnel, wherein the process flow is as follows: construction preparation → hole distribution → hole forming → grouting pipe insertion → grouting → hole sealing → on-site cleaning.

When the tunnel anchor and the intersection section of the bifurcation tunnel are constructed, besides the construction safety is guaranteed through the technical measures, the safety management and control are carried out through the following two measures in the aspect of management:

(1) and (5) making process coordination. In the construction process, tunnel anchors and various procedures of tunnel construction are gradually optimized, so that the tunnel anchors and the tunnel blasting operation time gradually tend to be consistent, blasting operation is finally independently carried out in the same time period, the tunnel anchors and the tunnel are operated in a crossed and independent mode, and the condition that one party breaks the operation due to blasting construction is reduced.

(2) And enhancing information communication and establishing a blasting early warning system. The blasting construction of the tunnel anchor and the main tunnel is to strengthen information communication, implement a blasting early warning system, and strictly forbid all operation activities when one party carries out blasting operation and the other party carries out blasting operation; after blasting, the two parties enter a working face for checking and communicating information, and can enter the next construction procedure or resume construction under the condition of no abnormal condition.