阅读说明：本技术 昔格达地层段浅埋下穿地表大型构筑物施工方法 (Construction method of large structure with Xigeda stratum section shallow-buried underground ground surface ) 是由 张强 刘延龙 吴胜红 奚成 张义君 邹永木 颛孙晓康 邓杰 张彪 尹智勇 陈文萍 于 2021-07-30 设计创作，主要内容包括：本发明涉及隧道施工技术领域,具体涉及一种昔格达地层段浅埋下穿地表大型构筑物施工方法,包括以下步骤,步骤1,超前地质预报；步骤2,洞身开挖；步骤3,初期支护；采用拱架全环支护,相邻拱架之间通过连接筋连接；在各台阶拱脚处,每榀拱架两侧均安设若干第一锁脚锚管；在各台阶拱脚处,相邻的两榀拱架之间搭接纵向拱架,所述纵向拱架上预留锚管孔；喷混凝土后,在所述锚管孔处安设第二锁脚锚管,管内注浆封闭；步骤4,进行二衬衬砌；安设第二锁脚锚管后,能够有效控制隧道沉降。在调整时,并不影响原有的第一锁脚锚管的施工参数,利于加快施工进度。配合三台阶临时仰拱法,在有效控制隧道沉降的同时,缩短了工序循环时间进而缩短了工期。(The invention relates to the technical field of tunnel construction, in particular to a construction method of a large structure with Xigeda stratum section shallow buried and passing through the ground surface, which comprises the following steps of 1, advanced geological forecast; step 2, excavating a hole body; step 3, primary support; adopting full-ring support of the arch centering, and connecting adjacent arch centering through connecting ribs; a plurality of first leg locking anchor pipes are arranged on two sides of each arch truss at the arch leg of each step; at each step arch foot, a longitudinal arch is lapped between two adjacent arches, and an anchor pipe hole is reserved in each longitudinal arch; after concrete is sprayed, a second locking anchor pipe is arranged at the anchor pipe hole, and grouting is carried out in the second locking anchor pipe to seal the second locking anchor pipe; step 4, carrying out secondary lining; after installing second lock foot anchor pipe, can effectively control the tunnel and subside. When the adjusting is carried out, the construction parameters of the original first lock pin anchor pipe are not influenced, and the construction progress is accelerated. And by matching with a three-step temporary inverted arch method, the settlement of the tunnel is effectively controlled, and meanwhile, the process cycle time is shortened, so that the construction period is shortened.)

1. A construction method of a large structure with Xigeda stratum section shallow-buried underground ground surface is characterized by comprising the following steps,

step 1, advance geological forecast;

step 2, excavating a hole body;

step 3, primary support; adopting full-ring support of the arch centering, and connecting adjacent arch centering through connecting ribs; a plurality of first leg locking anchor pipes are arranged on two sides of each arch truss at the arch leg of each step;

at each step arch foot, a longitudinal arch is lapped between two adjacent arches, and an anchor pipe hole is reserved in each longitudinal arch; after concrete is sprayed, a second locking anchor pipe is arranged at the anchor pipe hole, and grouting is carried out in the second locking anchor pipe to seal the second locking anchor pipe;

and 4, carrying out secondary lining.

2. The construction method of a large structure with Xigeda stratum section shallow-buried underground surface as claimed in claim 1, wherein in step 2, a three-step temporary inverted arch method is adopted; the excavation step distance of the upper step, the middle step and the lower step is 5-10m, mechanical excavation is adopted, and the support close following construction is carried out in a mode of excavating one roof truss and supporting one roof truss.

3. The construction method of a large structure with Xigeda stratum section shallow-buried underground surface as claimed in claim 1, wherein during construction, the measurement of surrounding rocks is carried out to obtain the daily cumulative settlement; when the daily accumulated settlement is more than 5mm, the second lock pin anchor pipe is immediately lengthened by 1-2 meters.

4. The method of claim 3, wherein the surrounding rock measurements include settlement and convergence of the dome in the tunnel, the area to be monitored is determined, and then the reference point is set at a non-settlement position. 7 cement pile monitoring points are arranged on a single section, and the distance is 2.5-5 m. And (5) starting to measure when the distance between the tunnel construction tunnel face and the front 30m of the monitoring point is less than 20m, and stopping monitoring after the data display is stable.

5. The method of constructing a Xigeda formation interval shallow-buried underground elephant structure as claimed in claim 1,

under the anhydrous condition, the number of the first lock leg anchor pipes at each arch foot of the upper step, the middle step and the lower step is 2-3;

under the condition of water, at each arch foot of the upper step and the lower step, the number of the first lock foot anchor pipes is 2-3; at the middle step arch springing, the number of the first lock leg anchor pipes is 4-5.

6. The method of constructing a Xigeda formation interval shallow-buried underground elephant structure as claimed in claim 1,

the included angle between the second pin anchor pipe and the horizontal ground is smaller than the maximum included angle between the first pin anchor pipe and the horizontal ground and larger than the minimum included angle between the first pin anchor pipe and the horizontal ground.

7. The method of constructing a Xigeda formation interval shallow-buried underground elephant structure as claimed in claim 1,

the first pin anchor pipe is a phi 42 pin locking anchor pipe, and the length of the first pin anchor pipe is 4-5 m; the second pin anchor pipe is a phi 76 pin locking anchor pipe, and the length of the second pin anchor pipe is 4-10 m.

8. The method for constructing a large structure with shallow buried earth surface in Xigeda stratum according to any one of claims 1 to 7, wherein a small pipe is adopted to match with a pipe shed for advance support before the step 2;

under the anhydrous condition, a double-layer phi 42 small conduit is matched with a phi 76-pipe shed to construct an advance support;

under the water condition, when the upper part of the tunnel 1/2 is Xigeda geology, a single-layer phi 42 small conduit is matched with a phi 108 large pipe shed to carry out advance support, and when the full section of the tunnel is the Xigeda geology, the single-layer phi 42 small conduit and a phi 159 large pipe shed are used to carry out advance support.

9. The construction method of the Xigeda formation section shallow-buried underground ground surface elephant structure as claimed in any one of claims 1 to 7, wherein the arch frame is an I22b steel frame, and the connecting ribs are phi 22 connecting ribs.

10. A supporting structure suitable for a Xigeda ground-level shallow-buried tunnel penetrating through a large earth surface structure is characterized by comprising a pipe shed and a plurality of arch trusses, wherein the pipe shed is supported in advance, the pipe shed is positioned in a top arch area of the tunnel, the arch trusses are arranged along the extending direction of the tunnel, and connecting ribs are connected between every two adjacent arch trusses; two sides of each arch center are provided with first lock leg anchor pipes; a longitudinal arch is connected between the adjacent arches, and a second locking anchor pipe is arranged on the longitudinal framework; the diameter of the second lock pin anchor pipe is larger than that of the first lock pin anchor pipe.

Technical Field

The invention relates to the technical field of tunnel construction, in particular to a construction method of a large structure with Xigeda stratum section shallow buried and penetrating through the ground surface.

Background

The Geda geology is in a semi-diagenetic shape, has the characteristics of soil and rock, but has extremely poor stability, water is extremely easy to soften, the Geda geology is peeled, decomposed and pulverized layer by layer after being dehydrated, the atomization speed is high when the Geda geology is exposed in the air, the Geda geology is joint-developed, the Geda geology is often subjected to the conditions of collapse and the like in construction, and even the tunnel roof fall and the like are caused. Along with main part tunnel excavation, broken the balance of rock mass, the stratum will receive the disturbance on every side certainly, then warp, and the deformation of rock mass leads to the building of earth's surface and earth's surface to take place the unstability, can lead to existing building to lose stability and destroy when serious, influences existing earth's surface building's safety in utilization.

In order to ensure that the construction period can be completed on time, how to accelerate the construction footage when the Xigeda tunnel is shallowly buried in a large-scale earth surface structure without influencing the safe use of the large-scale earth surface structure and how to shorten the time for passing through the building are problems to be solved urgently. The safe and rapid tunnel construction technology is a comprehensive technology, relates to each link of design and construction, and has the advantages that dynamic tunnel construction needs to be realized to realize safe and rapid tunneling and a reasonable supporting system for safe and rapid tunnel construction is established. Besides advanced geological forecast, informatization monitoring and the like, safe and rapid support is an important ring for realizing safe and rapid tunneling.

It is particularly important to monitor the settlement parameters and to adjust the support mode in time. However, in the current construction process, a plurality of locking anchor pipes are arranged at each arch truss, and the number of the locking anchor pipes is large, so that the supporting structure is difficult to adjust rapidly according to settlement parameters.

Disclosure of Invention

The invention aims to: aiming at the problems that when the Xigeda stratum extra-long tunnel safe and rapid underground construction of a shallow buried section is constructed by penetrating through an earth surface building under the condition of not influencing the safe use of the earth surface large structure in the prior art, the settlement is obviously increased, and the support structure is difficult to rapidly adjust by the conventional construction and support mode, the construction method of the Xigeda stratum shallow buried underground earth surface large structure is provided. According to the method, through a large locking leg construction technology, under the condition that an original designed locking leg anchor pipe is kept unchanged, the large locking leg is arranged between adjacent arch frames, the Xigeda stratum tunnel settlement is effectively controlled, the supporting mode of the existing building penetrating through the Xigeda stratum section under the tunnel is optimized, and the safe and rapid tunneling of the tunnel is facilitated.

In order to achieve the purpose, the invention adopts the technical scheme that:

a construction method of a large structure with Xigeda stratum section shallow-buried underground surface comprises the following steps,

step 1, advance geological forecast;

step 2, excavating a hole body;

step 3, primary support; adopting full-ring support of the arch centering, and connecting adjacent arch centering through connecting ribs; a plurality of first leg locking anchor pipes are arranged on two sides of each arch truss at the arch leg of each step;

at each step arch foot, a longitudinal arch is lapped between two adjacent arches, and an anchor pipe hole is reserved in each longitudinal arch; after concrete is sprayed, a second locking anchor pipe is arranged at the anchor pipe hole, and grouting is carried out in the second locking anchor pipe to seal the second locking anchor pipe;

step 4, carrying out secondary lining;

and when the hole body is excavated, a step type temporary inverted arch method or a CRD method is adopted. In the implementation process, a settlement control mode is usually adopted, wherein a plurality of first lock pin anchor pipes are arranged on two sides of each arch truss. The arrangement mode is easy to cause the problem that the sedimentation rate exceeds the standard when the arch centering is lengthened with the upper step after the middle step is excavated, particularly when a three-step temporary inverted arch method is adopted. The main reason is that the anchor pipe with the locking feet has limited functions, so that when the tunnel steel frame of the small anchor pipe in Xigeda soft slurry is settled, the soft rock is easily cut, and the steel frame is difficult to lock. The longitudinal arch is arranged between two adjacent palace arches, and the settlement of the tunnel can be effectively controlled after the second locking anchor pipe is arranged.

As a preferred scheme of the invention, in the step 2, a three-step temporary inverted arch method is adopted; the excavation step distance of the upper step, the middle step and the lower step is 5-10m, mechanical excavation is adopted, and the support close following construction is carried out in a mode of excavating one roof truss and supporting one roof truss.

The three-step temporary inverted arch method is adopted, and the footage is about 50m per month. Whereas the dual sidewall pit-guide approach only extends about 20m per month and the CRD approach only extends about 25m per month. The three-step temporary inverted arch method is combined with the mode of adding the second foot locking anchor pipe, so that the settlement of the tunnel is effectively controlled, and meanwhile, the process cycle time is shortened, and the construction period is shortened.

As a preferred scheme of the invention, during the construction process, the surrounding rock measurement is carried out to obtain the daily accumulated settlement; when the daily accumulated settlement is more than 5mm, the second lock pin anchor pipe is immediately lengthened by 1-2 meters.

And increasing the length of the second lock pin anchor pipe in the subsequent construction in real time according to the measurement result. The original first lock pin anchor pipe is constructed under the condition of keeping the same conditions, construction parameters are consistent, and the construction progress is kept favorably.

As a preferable scheme of the invention, the surrounding rock measurement comprises the settlement and convergence of the arch crown in the tunnel, a monitoring area is determined, and then a datum point is set at a non-settlement position. 7 cement pile monitoring points are arranged on a single section, and the distance is 2.5-5 m. And (5) starting to measure when the distance between the tunnel construction tunnel face and the front 30m of the monitoring point is less than 20m, and stopping monitoring after the data display is stable.

The monitoring and measuring method comprises the following steps: the monitoring measurement adopts the settlement and convergence of the arch crown in the tunnel, and the settlement and displacement monitoring of the road surface and the ground surface of the building is adopted above the tunnel. The method is used for testing the influence on the ground settlement during tunnel excavation and the influence range of the influence on the ground settlement, and mainly comprises a ground surface settlement point, a building settlement observation point and a road surface settlement observation point. When the ground surface settlement point sinks, the total station is used for measuring the displacement of the measuring point, so that whether the measuring point sinks vertically or transversely is judged, and whether the measuring point sinks in direct relation with the tunnel or not is analyzed. And (3) implementing informatization management, combining advanced geological forecast, and timely adjusting construction procedures and support parameters to ensure that the construction is in a safe and controllable state.

As a preferred scheme of the invention, under the anhydrous condition, at each arch foot of the upper step, the middle step and the lower step, the number of the first lock foot anchor pipes is 2-3; under the condition of water, at each arch foot of the upper step and the lower step, the number of the first lock foot anchor pipes is 2-3; at the middle step arch springing, the number of the first lock leg anchor pipes is 4-5.

Under the waterless condition, when the number of the first lock leg anchor pipes at each position of the upper, middle and lower step arch springs is 2-3, the included angle between the first lock leg anchor pipe and the horizontal ground is 20-30 degrees, the second lock leg anchor pipe is positioned below the first lock leg anchor pipe, and the included angle between the two first lock leg anchor pipes is 20-30 degrees; the number of the second lock pin anchor pipes is 1, and the included angle between the second lock pin anchor pipes and the horizontal bottom surface is 20-60 degrees;

under the condition of water, on the basis of the above condition, the number of the first lock leg anchor pipes at the middle step arch springing position is increased. At the middle step arch foot, the number of the first lock foot anchor pipes at each position is 4-5, each first lock foot anchor pipe is 4-5 meters long, the included angle between the first lock foot anchor pipe and the horizontal ground is 15 degrees, the second first lock foot anchor pipe is positioned below the first lock foot anchor pipe, the third first lock foot anchor pipe is positioned below the second first lock foot anchor pipe, the fourth first lock foot anchor pipe is positioned below the third first lock foot anchor pipe, and the included angle between every two adjacent first lock foot anchor pipes is 10 degrees; the number of the second lock pin anchor pipes is 1, and the included angle between the second lock pin anchor pipes and the horizontal ground is 15-45 degrees

As a preferred embodiment of the present invention, an included angle between the second pin anchor tube and the horizontal ground is smaller than a maximum included angle between the first pin anchor tube and the horizontal ground, and is larger than a minimum included angle between the first pin anchor tube and the horizontal ground.

As the preferred scheme of the invention, the first pin anchor pipe is a phi 42 pin locking anchor pipe, and the length is 4-5 m; the second pin anchor pipe is a phi 76 pin locking anchor pipe, and the length of the second pin anchor pipe is 4-10 m.

As the preferred scheme of the invention, before step 2, adopt the small conduit to cooperate with the way of the pipe shed to construct the advance support; under the anhydrous condition, a double-layer phi 42 small conduit is matched with a phi 76-pipe shed to construct an advance support; under the water condition, when the upper part of the tunnel 1/2 is Xigeda geology, a single-layer phi 42 small conduit is matched with a phi 108 large pipe shed to carry out advance support, and when the full section of the tunnel is the Xigeda geology, the single-layer phi 42 small conduit and a phi 159 large pipe shed are used to carry out advance support.

As the preferable scheme of the invention, the arch center is an I22b steel frame, and the connecting ribs are phi 22 connecting ribs.

As a preferred scheme of the invention, under the condition of water, when large strand water appears, the construction is carried out for water prevention and drainage, and water plugging measures are taken for basic treatment.

The invention also provides a supporting structure suitable for a Xigeda ground-section shallow-buried underpass ground surface large-scale structure tunnel, which comprises a pipe shed for advanced supporting and a plurality of arch trusses, wherein the pipe shed is positioned in a top arch area of the tunnel, the plurality of arch trusses are arranged along the extending direction of the tunnel, and connecting ribs are connected between adjacent arch trusses; two sides of each arch center are provided with first lock leg anchor pipes; a longitudinal arch is connected between the adjacent arches, and a second locking anchor pipe is arranged on the longitudinal framework; the diameter of the second lock pin anchor pipe is larger than that of the first lock pin anchor pipe.

Through the structure, the first lock pin anchor pipe meets the basic settlement requirement, the length of the second lock pin anchor pipe can be flexibly adjusted to control the settlement of the tunnel, and the construction progress can be accelerated.

In summary, due to the adoption of the technical scheme, the invention has the beneficial effects that:

1. the construction method of the large structure with Xigeda ground layer for shallow burying and underground ground surface penetration can effectively control the settlement of the tunnel by arranging the longitudinal arch frame between two adjacent arch frames and arranging the second locking anchor pipe on the basis of arranging a plurality of first locking anchor pipes on two sides of each arch frame which is usually adopted. Through real-time supervision in the work progress, when daily settlement is greater than 5mm, adjust the length of second lock foot anchor pipe immediately, when the adjustment, do not influence the construction parameter of original first lock foot anchor pipe, do benefit to and accelerate the construction progress. And by matching with a three-step temporary inverted arch method, the settlement of the tunnel is effectively controlled, and meanwhile, the process cycle time is shortened, so that the construction period is shortened.

2. According to the construction method of the large structure with the Xigeda stratum shallowly buried and underneath-penetrating ground surface, different advanced support methods are adopted according to different tunnel settlement under different geological conditions under different working conditions such as no water and water, and further the control of the tunnel settlement can be realized by adjusting the length of the second lock pin anchor pipe. Under different working conditions, different advanced support modes are combined with the length of the second lock pin anchor pipe to form a set of complete support scheme, so that the tunnel construction is efficiently and safely completed, and the structural safety and normal use of the surface building are ensured. The construction method meets the design, meets the standard, ensures the construction safety, improves the construction efficiency and ensures the construction quality. Especially, the construction period is shortened, and the cost is reduced.

Drawings

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

FIG. 2 is a schematic diagram of a three-step temporary inverted arch construction process under anhydrous conditions according to the construction method of the present invention;

FIG. 3 is a schematic diagram of a CRD construction process under anhydrous condition according to the construction method of the present invention;

FIG. 4 is a schematic diagram of a three-step temporary inverted arch construction process under water conditions according to the construction method of the present invention;

FIG. 5 is a schematic view of a CRD construction process under water condition according to the construction method of the present invention;

FIG. 6 is a schematic view showing the installation position of the anchor pipe of the second locking leg according to the construction method of the present invention;

fig. 7 is a schematic view of the construction method of the present invention, showing a surface subsidence monitoring arrangement.

Icon: 1-an arch frame; 2-longitudinal arch frame; 3-anchor pipe hole; 4-welding part.

Detailed Description

The present invention will be described in detail below with reference to the accompanying drawings.

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Example 1

The exit of a certain tunnel passes through three lines under D6K584+ 681-D6K 584+850(169m) to build a museum, the exit section is a weak surrounding rock Xigeda stratum, and the distance between the top of the tunnel and the pile bottom of the three lines of museums is 31 m.

A construction method of a large structure with Xigeda stratum section shallow-buried underground surface comprises the following steps,

step 1, advance geological forecast;

step 2, excavating a hole body;

step 3, primary support; adopting full-ring support of the arch centering, and connecting adjacent arch centering through connecting ribs; a plurality of first leg locking anchor pipes are arranged on two sides of each arch truss at the arch leg of each step; at each step arch foot, a longitudinal arch is lapped between two adjacent arches, and an anchor pipe hole is reserved in each longitudinal arch; after concrete is sprayed, a second locking anchor pipe is arranged at the anchor pipe hole, and grouting is carried out in the second locking anchor pipe to seal the second locking anchor pipe;

step 4, carrying out secondary lining;

the formed supporting structure comprises a pipe shed for advanced supporting and a plurality of arch trusses, wherein the pipe shed is positioned in a tunnel top arch area, the arch trusses are arranged along the extending direction of a tunnel, and connecting ribs are connected between every two adjacent arch trusses; two sides of each arch center are provided with first lock leg anchor pipes; a longitudinal arch is connected between the adjacent arches, and a second locking anchor pipe is arranged on the longitudinal framework; the diameter of the second lock pin anchor pipe is larger than that of the first lock pin anchor pipe.

The specific construction process also comprises the steps of laying a waterproof layer and performing inverted arch advanced construction after primary support. The detailed construction process flow chart is shown in the attached figure 1. Wherein the surrounding rock measurement 1 and the surrounding rock measurement 2 are respectively settlement measurement and convergence measurement.

The monitoring and measuring method comprises the following steps:

the monitoring measurement adopts the settlement and convergence of the arch crown in the tunnel, the surface settlement and displacement monitoring is adopted in the upper propylene road of the tunnel, and the settlement and displacement monitoring is adopted in the surface of a three-line building museum. The influence and the influence range of the ground settlement of the polypropylene road and the museum during tunnel excavation are tested, and a ground surface settlement point, a building settlement observation point and a polypropylene road surface settlement observation point are mainly arranged. When the ground surface settlement point sinks, the total station is used for measuring the displacement of the measuring point, so that whether the measuring point sinks vertically or transversely is judged, and whether the measuring point sinks in direct relation with the tunnel or not is analyzed.

Ground monitoring points are arranged on the left side and the right side of the tunnel axis and the tunnel axis, the longitudinal burying of monitoring measuring points takes the tunnel axis as the direction, and the specific buried point section is shown in table 1.

TABLE 1 vertical space table for earth surface settlement observation points

Tunnel buried depth and excavation width	Longitudinal measuring point spacing (m)
		2B＜H0＜2.5B	20～50
B＜H0≤2B	10～20
		H0≤B	5～10

H0 represents the clear distance between the tunnel and the ground, and B represents the tunnel excavation width.

The transverse section spacing is determined according to topographic conditions, the spacing is controlled according to 2.5-4.5 m, the spacing is controlled according to 1.5-3 m near the center line of the tunnel, and the width of the buried points on the left side and the right side of the center line of the tunnel cannot be smaller than the sum of the tunnel buried depth and the tunnel excavation width. After the monitoring area is determined, a reference point is first set at a position where the monitoring area does not settle. 7 cement pile monitoring points are arranged on a single section, and the distance is 2.5-5 m. The tunnel construction face starts to be measured 30m before the monitoring point, the monitoring is stopped after the face exceeds the measuring point by 20m and the data display is stable, as shown in fig. 7. Monitoring according to specified frequency, sorting the data by an internal group, analyzing the data and making a time-displacement curve, carrying out regression analysis by analyzing curve change, analyzing the rock mass peristalsis rule, forming a feedback mechanism, and further adjusting the site dynamic tunnel construction.

The Xigeda stratum construction guiding idea is as follows: advancing pipe, no blasting, short footage, strong support, measurement, early sealing and fast lining. The excavation step distances of the upper step, the middle step and the lower step are controlled within the range of 5-10m, mechanical excavation is adopted, disturbance to surrounding rocks is reduced, and support following construction is carried out in a mode of excavating one roof truss and supporting one roof truss. The construction method and the support parameters are explained below for different construction conditions.

1. Under the condition of no water

1) Geological time of Xigeda above tunnel 1/2

The construction method adopts a three-step temporary inverted arch method.

Advance support and reinforced support parameters: adopting a double-layer phi 42 small conduit to cooperate with a phi 76-pipe shed for constructing advanced support; wherein the circumferential distance of the phi 42 small guide pipes is 0.4m, 2.4 m/ring, 51/ring and 3.5 m/ring; the annular spacing of the phi 76 pipe sheds is 0.4m, 51 pipes are arranged in each ring, the length of each pipe is 10m, and the pipes are lapped by 3 m; i22b steel frame full-ring support is adopted, and the distance is 0.5 m/pin; the connecting ribs are phi 22 connecting ribs, and the spacing is 0.5 m. The first lock pin anchor pipe is a phi 42 lock pin anchor pipe, the number of the upper step, the middle step and the lower step is two, and the length is 4.5 m;

and phi 76 leg locking anchor pipes are arranged between adjacent arch centering at arch legs of each step, each leg is 4.5m long, and each leg is arranged between every two adjacent arch centering. As shown in figure 2 of the drawings, in which,

2) geological time of tunnel full section Xigeda

Firstly, according to the settlement observation result, when the cumulative settlement amount is more than 5mm, the phi 76 locking anchor pipe with the length of 4.5m is adjusted to be 6 m.

Secondly, the clear distance between the tunnel and the ground is less than 50m, and the tunnel construction can adopt a CRD construction method; the clear distance between the tunnel and the ground is more than 50m, and a three-step temporary inverted arch method is preferably selected in tunnel construction. As shown in figure 3 of the drawings,

2. under the condition of water (without larger strand water)

1) When the tunnel 1/2 is above the third series Xigeda geology

Firstly, a three-step temporary inverted arch method is adopted in the construction method, and a single-layer phi 42 small conduit is matched with a phi 108 large pipe shed for advance support; wherein the annular spacing of the small guide pipes is 0.4m, 51 pipes/ring, 2.4 m/ring and 3.5 m/pipe; the annular spacing of the phi 108 large pipe shed is 0.4m, 54 pipes/ring and 45 m/pipe; i25b steel frame full-ring support is adopted, the spacing is 0.4 m/pin, and the longitudinal phi 22 connecting rib spacing is adjusted from 1.0m to 0.5 m. The first lock pin anchor pipe is a phi 42 lock pin anchor pipe with the length of 4.5 m.

And phi 76 leg locking anchor pipes are arranged between adjacent arch centering at arch legs of each step, each leg is 4.5m long, and each leg is arranged between every two adjacent arch centering. As shown in figure 4 of the drawings,

secondly, according to the settlement observation result, when the cumulative settlement amount is more than 5mm, the phi 76 pin-locking anchor pipe with the length of 4.5m is adjusted to be 6-8 m.

And thirdly, in order to ensure the safety and the stability of the structure, in the water section of the Xigeda stratum tunnel, construction is carried out by adopting a mode of increasing the lining thickness to 55cm and the type of the lining reinforcing steel bar main reinforcing steel bar to phi 25 reinforcing steel bar.

2) When the whole section of the hole is Xigeda geology

Firstly, the clear distance between the tunnel and the top surface is less than 50m, and a CRD method can be adopted as a construction method; the clear distance between the tunnel and the top surface is more than 50m, the construction method can adopt a three-step temporary inverted arch method, and a single-layer phi 42 small conduit and a phi 159 large pipe shed are adopted to construct an advance support; wherein the annular spacing of phi 42 small catheters is 0.4m, 3.5 m/ring, 2.4 m/ring and 51/ring; phi 159 large pipe shed annular spacing is 0.4m, 45 m/root, 54/ring; i25b steel double-layer steel frames are adopted for staggered full-ring support, the relative spacing is 0.4 m/pin, and the longitudinal phi 22 connecting rib spacing is adjusted to 0.5 m. The first lock pin anchor pipe is a phi 42 lock pin anchor pipe, and the length is 4.5 m;

and a phi 76 large locking anchor pipe is added to each step arch springing, and each locking anchor pipe is 6m long. As shown in figure 5 of the drawings,

secondly, according to the settlement observation result, when the cumulative settlement amount is more than 5mm, the phi 76 pin-locking anchor pipe with the length of 6-8 m is adjusted to be 10 m.

And thirdly, in order to ensure the safety and the stability of the structure, in the water section of the Xigeda stratum tunnel, construction is carried out by adopting a mode of increasing the lining thickness to 55cm and the type of the lining reinforcing steel bar main reinforcing steel bar to phi 25 reinforcing steel bar.

The specific implementation method comprises the following steps: the phi 76 large lock pin is adopted, and the length is selected to be different according to different working conditions. And (3) overlapping a longitudinal arch frame 2 between two arch frames 1, reserving an anchor pipe hole 3 with the diameter of phi 76 on the longitudinal arch frame 2, drilling a hole at the anchor pipe hole 3 after the arch frames 1 are erected and concrete is sprayed, installing a second locking anchor pipe, and grouting and sealing in the pipe. The angle is normally set according to the angle of the foot-locking anchor rod in the original design. The setting position of the phi 76 large lock pin (second lock pin anchor tube) is shown in figure 6. In the figure, 4 is a weld site.

Test example Tunnel construction method selection

1. When the construction method adopts a double-side-wall pit guiding method.

Advanced support and reinforced support parameters: the arch part is reinforced and supported by a single layer of phi 42 small guide pipes and a phi 159 large pipe shed, wherein the annular distance between the phi 42 small guide pipes is 0.4m, 2.4 m/ring, 51 pipes/ring and 3.5 m/ring; the circumferential spacing of the large pipe shed is 0.4m, 51 pipes are arranged per ring, the length of the large pipe shed is 60m per pipe, and the large pipe shed is lapped by 5 m; the method adopts double-layer steel frame full-ring support (HW 175 steel on the outer layer of an arch wall, I18 steel on the inner layer and I20b steel frame on the single layer of an inverted arch) with the spacing of 0.8 m/beam, and is provided with phi 42 locking feet with the length of 4.5m for each beam. The longitudinal phi 22 connecting rib spacing is 1 m. Each excavation is not more than 1, and the monthly footage is about 20 m.

2. When the construction method adopts a three-step temporary inverted arch method.

The advanced support adopts a single-layer phi 42 small conduit to match with a phi 108 large pipe shed, the annular spacing of the small conduits is 0.4m, 51/ring, 2.4 m/ring and 3.5 m/ring, the annular spacing of the pipe shed is 0.4m, 54/ring and 45 m/ring, I25b steel frame full-ring support is adopted, the spacing is 0.6 m/pin, and the longitudinal phi 22 connecting rib spacing is adjusted to 0.5m from 1.0 m. Each excavation is not more than 1, and the monthly footage is about 50 m.

a. According to the settlement observation result, when the daily accumulated settlement is more than 5mm, the phi 76 foot-locking anchor pipe with the length of 4.5m is adjusted to be 6-8 m.

b. In order to ensure the safety and stability of the structure, the construction is carried out in a water section of the Xigeda stratum tunnel by increasing the lining thickness to 55cm and the type of the main reinforcement of the lining reinforcement to phi 25 reinforcement.

3. When the construction method adopts a CRD method;

the advanced support is implemented by adopting a single-layer phi 42 small conduit and a phi 159 large pipe shed, the annular distance between the small conduits is 0.4m, 3.5 m/ring, 2.4 m/ring and 51/ring, the annular distance between the pipe sheds is 0.4m, 45 m/ring and 54/ring, I25b steel double-layer steel frame staggered full-ring support is adopted, the relative distance is 0.4 m/truss, and the longitudinal phi 22 connecting rib distance is 1 m. Each excavation is not more than 1, and the monthly footage is about 25 m.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.