CN102678134B - Collapse and sink intrusion limit construction method for treating wind accumulated sand loess tunnel through stride shed pipe - Google Patents

Abstract

The invention relates to a construction method for loess tunnels, in particular to a construction method for treating the subsidence and subsidence of eolian sandy loess tunnels with a mai-type pipe shed, which solves the problems of relatively large construction space and high cost in the construction of existing large pipe sheds. 1) Treatment of surface cracks; 2) Backfilling in the cave; 3) Determining the range of arch replacement; 4) The excavation method adopts the three-step method, and radial anchors are installed before the arch replacement, and the After reinforcement, replace the steel arch frame one by one, method: a. Use the excavator vibrating hammer to cooperate with the artificial wind pick to remove the initial support of the subsidence encroachment section one by one. Shed structure; c. Erection of steel arches, and the upper, middle and lower guide arch feet are set with Mai-style locking foot anchors; d. Follow the steps above to remove them one by one and support them in time. The construction speed is fast, the required space is small, the operation is simple, the machinery investment is small, the construction quality and safety are guaranteed, and the application range is wide.

Description

Construction method of Mai-style pipe shed to deal with subsidence and encroachment of wind-accumulated sandy loess tunnel

technical field

The invention relates to a construction method of an aeolian sandy loess tunnel, in particular to a construction method for treating the subsidence and encroachment of an aeolian sandy loess tunnel with a step-type pipe shed.

Background technique

Aeolian sandy loess is mainly sandy soil. For loess, it is sandy loess, which is prone to collapse during construction. Due to the verticality of the structure, its characteristics determine that the mechanical properties of the loess are anisotropic, which is directly related to the stability of the face after construction. If the stress of the surrounding rock after construction is greater than the strength of the loess in the vertical direction, it will be Cause the instability of the excavation working face. In case of collapsibility, the water content exceeds a certain value or after encountering water, there will be a large "subsidence" deformation and loss of bearing capacity. Engineering practice has proved that the stress concentration at the side wall and foot of the tunnel is too large, requiring a large foundation bearing capacity, while the insufficient bearing capacity of the side wall and foot of the loess tunnel is one of the important reasons for the collapse of the tunnel. Because the earth pressure distribution of the loess tunnel is extremely unbalanced, generally speaking, it is distributed in a saddle shape. In the case of shallow burial, since the arching effect cannot be exerted, in this case, there will be either a large relaxation pressure or an overall sinking phenomenon. In short, at present, during the construction of wind-accumulated sandy loess tunnels, it is very easy for the vault to sink, the side walls to collapse, converge, encroach, the shotcrete peels off, the supporting steel arches are twisted and deformed, the anchor pipes of the locking feet are cut off, and the surface appears Multiple horizontal and vertical cracks and other construction phenomena.

At present, most of the above-mentioned construction phenomena are constructed by using the traditional large pipe shed structure. First, the large pipe shed is built radially and vertically to form a whole protective shell in the subsidence area, and then the whole is excavated and the arches are replaced one by one. The shortcomings of this method The advantage is that the length of each large pipe shed is 15m, which is relatively long, requires a large construction space, huge equipment, high rental costs, high construction costs, and the use of machinery in the cave has a lot of sewage and noise, which is harmful to the operators. More importantly, the construction period is long, which is not conducive to the rapid treatment of mud outbursts, and there are potential safety hazards. In addition, in order to promptly and quickly meet the construction requirements for ring formation of support after tunnel excavation and prevent tunnel collapse, it is necessary to seize the best time to complete the support ring formation of weak surrounding rock after excavation. Arches are an important means of support ring formation , the lock-foot anchor rod and the steel arch frame are connected to form an integral reinforcement technology. The lock-foot anchor rod is driven through the steel plate hole, so that the driven anchor pipe can fully play a supporting role and provide greater support resistance to the surrounding surrounding rock. , to prevent excessive deformation of the surrounding rock, the main function is to limit the rigid body displacement of the steel arch frame as much as possible, so that it can bear the pressure caused by the deformation of the surrounding rock as soon as possible, and ensure the initial stability of the tunnel. The traditional installation method of locking foot bolts is as follows: after the vertical arch frame, the locking foot bolts are close to the arch frame and driven in left and right, and the left and right anchor bolts are welded with steel bars. The defect of this reinforcement method is that when the surrounding rock pressure is high At that time, the anchor bolt and the arch frame had broken before reaching the limit of bearing capacity, the anchor rod and the steel arch frame did not form a whole, and lost their function prematurely. Only by limiting the displacement of the steel arch frame to resist the deformation of the surrounding rock, The overall stability is poor, which reduces the construction safety.

Contents of the invention

In order to solve the problem of subsidence and subsidence of existing aeolian sandy loess tunnels, the present invention adopts traditional large pipe sheds for construction, which requires relatively large construction space, high construction costs, long periods, and reinforced connections between steel arch frames and locking foot bolts. In order to solve the problems of poor overall structural stability and poor construction safety, a construction method for the subsidence and encroachment limit of the aeolian sandy loess tunnel is provided by a Mai-style pipe shed.

The present invention is realized by adopting the following technical scheme: a construction method for treating wind-accumulated sandy loess tunnel collapse subsidence and encroachment limit construction method with Mai-style pipe shed, including the following steps: 1) Surface crack treatment, first excavating trenches along the cracks, and then Cement grout is directly poured into the cracks at a distance of about 30cm. After grouting, the cracked ground is plastered with cement mortar to make a circular arc shape; 2) Backfill the hole, and the initial support sinks and invades the limited section to backfill the hole slag, and the arch part is 1.5m The high range is backfilled with shotcrete; 3) According to the subsidence of the tunnel and combined with the clearance measurement data, the range of arch replacement is determined; 4) The excavation method adopts the three-step method, and radial anchors are installed before the arch replacement. Type bolts, the circumferential × longitudinal spacing is 100×40cm, arranged in a quincunx shape, the anchors are filled with grout, and after the grouting is strengthened, the subsidence-invasion-limited steel arches are removed one by one. The specific methods are as follows: a. Use the excavator vibrating hammer to cooperate with the artificial wind pick to remove the initial support of the subsidence and invasion section one by one. Lay out within 180°, the circumferential spacing of each layer is 15-25cm, the longitudinal overlap is not less than 2.5m, the elevation angle is controlled at 10°-15°, and grout is injected into the anchor rod to form a Mai-style pipe shed structure; c. The steel arch frame of the subsidence and invasion limit section, the spacing of the steel arch frame of the subsidence and invasion limit section is the same as that of the original construction steel arch frame. , The steel arches of the adjacent subsidence and invasion limit sections are connected by channel steel, the circumferential distance is 50-70cm, and the sprayed concrete is closed in time; d. Follow the steps above to dismantle the arches one by one and support them in time. For each arch replacement, repeat the process from step a to step d until the arch replacement is completed. The three-step excavation method is a well-known technology in the art, and is a commonly used method for tunnel excavation.

In order to limit the rigid body displacement of the steel arch to the greatest extent, make it bear the pressure caused by the deformation of the surrounding rock as soon as possible, and ensure the initial stability of the tunnel, the steel arch of the subsidence encroachment section erected in the above step c, and close to the surrounding Positioning steel plates are fixed at intervals on one side of the rock, and the two ends of each positioning plate are respectively opened with positioning holes on both sides of the steel arch frame of the subsidence invasion limit section. The exposed ends of the Mai-style lock foot anchor rods located on both sides of the steel arch are connected by ring connectors and fixed with the steel arch of the steel subsidence limit section. The quantity and spacing distance of the positioning steel plates can be determined according to the requirements of the construction site.

In order to further optimize the reinforcement structure of the steel arch frame and the lock-foot bolt and improve its design, the driving end of the Mai-style lock-foot bolt is horseshoe-shaped, which is more conducive to driving the Mai-style lock-foot bolt into the surrounding rock, reducing resistance; the angle between the Mai-style lock-foot anchor rod and the horizontal direction is 15-20°, and the positioning hole on the positioning steel plate is a longitudinal oval hole. In the surrounding rock, the positioning hole is a longitudinal elliptical hole; the ring-shaped connector is a ring-shaped structure formed by movably connecting two straight-hooked steel bars, and the distance can be adjusted to facilitate construction operations. the

Using the construction method described in the present invention, before the step-type pipe shed is reinforced, the collapsed body is first pre-grouted, the cracks are filled with cement grout, and then the subsidence support is removed by using the vibrating hammer of the excavator and the manual jack chisel For the anchor body, use oxygen welding to cut the sinking steel arch, anchor pipe, and mesh, and cannot use blasting to remove it, so as to reduce the disturbance of vibration to the deformed soil. One arch frame is replaced each time, the steel arch frame is erected after the excavation contour is formed, and the Mai-type advanced anchor pipe shed is laid section by section. The length and spacing are arranged according to the design, and the anchors are grouted in time to form a pipe shed Reinforcement, every time a arch is replaced, the above process is repeated until the arch replacement is completed. The Mai-style pipe shed is used as the longitudinal support, and the steel arch is used as the horizontal circular support. Grout is injected into the shed pipe. After the grout is hardened, the surrounding rock mass is pre-reinforced to form a Mai-style pipe shed reinforcement, which can withstand the subsidence and limit soil erosion. Body pressure and constrained deformation. In addition, a new reinforcement technology of steel arch frame and lock foot anchor rod is adopted, and the steel arch frame and lock foot anchor pipe are fixed more firmly through positioning holes, positioning steel plates and ring connectors to form a whole, and the ultimate bearing capacity is further improved, so that after driving The locking foot anchor pipe fully exerts the supporting function, provides greater support resistance to the surrounding rock, prevents excessive deformation of the surrounding rock, limits the rigid body displacement of the steel arch frame as much as possible, and makes it bear the pressure caused by the deformation of the surrounding rock as soon as possible To ensure the initial stability of the tunnel, it is especially suitable for the reinforcement connection of steel arch lock foot anchor pipes in tunnels with weak railways and roads and loess surrounding rocks.

Compared with the prior art, the construction method of the present invention has the advantages of fast construction speed, small required space, strong practicability, simple operation of the construction process, less mechanical investment, wide application range, and guaranteed construction quality and safety. The use of machinery in the construction tunnel of the large pipe shed has less sewage discharge and less noise, which can reduce the exhaust emission of the machinery, has little harm to the operators, and has created good environmental protection benefits for the construction. This method is suitable for the collapse, subsidence, erosion It is suitable for narrow space operations and emergency construction, effectively controls tunnel collapse, and can also be used for road and hydraulic tunnel construction.

Description of drawings

Fig. 1 is the top treatment figure of the surface crack of the present invention;

Fig. 2 is backfill longitudinal sectional view in the hole described in the present invention;

Fig. 3 is a structural schematic diagram of the step-type pipe shed of the present invention;

Fig. 4 is a schematic diagram of the vertical connection of the steel arch according to the present invention;

Fig. 5 is a schematic diagram of radial bolt support of the present invention;

Fig. 6 is a schematic diagram of the front structure of the connection between the steel arch frame and the Mai-style lock-foot anchor rod according to the present invention;

Fig. 7 is a schematic diagram of the side structure of the connection between the steel arch frame and the Mai-style lock-foot anchor rod according to the present invention;

Fig. 8 is a schematic structural view of the annular connector of the present invention;

In the figure: 1-steel arch; 2-Mai-style lock foot anchor; 3-positioning steel plate; 4-positioning hole; 5-ring connector; 6-surface crack; 7-radial anchor; 8-double layer Mai-style anchor; 9-steel arch frame for subsidence and invasion limit section; 10-channel steel; 11-initial support; 12-backfill hole slag; 13-shotcrete; Down the steps; 17 - Ground line.

Detailed ways

The Mai-style pipe shed construction method for dealing with wind-accumulated sandy loess tunnel collapse subsidence encroachment limit construction method includes the following steps:

1) Surface crack 6 treatment, in order to prevent surface water seepage and soften the soil, it is necessary to grout the surface cracks: first excavate trenches along the cracks, and then use the funnel weight method to directly grout the cracks at a distance of about 30cm 1: 1 cement slurry, after the cement slurry is filled and solidified, it is then shifted for refilling. When the amount of pouring is large, the pouring should be stopped, and the grouting should be carried out after the poured cement slurry has solidified. After grouting, the cracked ground is plastered with cement mortar and made into an arc shape to prevent rainwater from infiltrating, as shown in Figure 1.

2) Backfill in the cave, backfill the cave slag 12 in the subsidence and invasion limit section of the initial support 11, and use C25 shotcrete 13 to backfill and compact the 1.5m high range of the arch, as shown in Figure 2;

3) According to the tunnel subsidence and encroachment conditions, combined with the clearance measurement data, determine the range of arch replacement;

4) The excavation method adopts the three-step method. First, the front of the backfill body is reinforced, using φ42×3.5mm steel pipes with a spacing of 1.0×1.0m, arranged in a quincunx shape, 4m long, and drilled every 3m, injecting cement slurry Reinforcement, install radial anchors 7 before changing the arch, adopt Mai-style anchors, the circumferential × longitudinal distance is 100×40cm, and the plum blossom shape is arranged, as shown in Figure 5, the anchors are filled with grout, and after the grouting is strengthened Then dismantle the subsidence and encroachment limiting section steel arches one by one, the specific method is as follows:

a. Use the excavator vibratory hammer to cooperate with the artificial pneumatic pick to remove the initial support of the subsidence and invasion limit section one by one, and carry out the initial spraying to seal the surrounding rock in time after the removal;

b. For advance support, double-layer stepping bolts 8 are used, and they are arranged along the 180° range of the tunnel section. 15°, grout is injected into the anchor rod to form a Mai-style pipe shed structure, as shown in Figure 3;

c. Erect the steel arch frame 9 of the subsidence and invasion limit section, the spacing of the steel arch frame of the subsidence and invasion limit section is the same as that of the original construction steel arch frame, and the upper guide, middle guide and lower guide arch feet are set with Mai-type locking foot anchors, Grout is injected into the anchor rod, and channel steel 10 is used to connect the steel arch frames of the adjacent subsidence-invaded sections, with a circumferential distance of 50-70 cm, as shown in Figure 4, and the shotcrete is sealed in time;

d. Follow the steps above to dismantle the arches one by one and support them in time. For each arch replacement, repeat the process from step a to step d until the arch replacement is completed.

In addition, during the construction, the steel arch frame and the lock foot bolt are reinforced and connected by the following method, as shown in Figures 6 and 7, the steel arch frame 9 of the subsidence encroachment limit section erected in step c is on the side of the surrounding rock Positioning steel plates 3 are fixed at intervals, and the two ends of each positioning plate are respectively provided with positioning holes 4 located on both sides of the steel arch frame of the subsidence encroachment section. The exposed ends of the lock-foot anchor pipes on both sides of the steel arch frame are connected by ring connectors 5 and fixed with the steel arch frame of the sinking section. As shown in Figure 8, the ring connector 5 is formed by connecting two straight steel bars. It is formed in a ring shape, and the spacing can be adjusted for the convenience of construction work. The locking foot anchor pipe 2 is driven into a horseshoe shape, the angle between the locking foot anchor pipe 2 and the horizontal direction is 15-20°, and the positioning hole 4 on the positioning steel plate 3 is a longitudinal oval hole. During the specific production, after the steel arch 1 is erected, the positioning steel plate is welded to the end of the steel arch close to the surrounding rock, the length of the locking foot anchor pipe is not less than 3.5-4m, and it is processed with a Φ42mm small conduit, and the entry end is driven by a cutting machine Cut into a horseshoe shape, and use a YT-28 air gun to drive the lock-foot anchor pipe into the reinforcement connection. The exposed end of the lock-foot anchor pipe is connected with a ring piece for overlay welding, and the connecting ring piece is bent from a Φ22mm steel bar. The positioning steel plate is composed of two upper and lower pieces with a distance of 15cm. Each piece is 45cm long, 25cm wide and 16mm thick. 20°, a total of 4 holes are drilled; the diameter of the positioning hole is 50mm, cut into an oval shape with oxygen (or drilled with a drill press), the length is controlled within the range of 13cm, and the connecting end of the lower end of the steel arch is connected with the middle guide or lower guide arch Plate, reserve the connecting bolt holes.

The method of the present invention will be further described in conjunction with the following engineering examples:

Project Overview

The construction period of the new Dazhun-Shuohuang railway connection line undertaken by the applicant is only 574 days. The construction period is tight and the safety risk is high. The entrance section has 579m of sandy loess surrounding rock, Dk128+832～Dk128 +856 shallow buried partial pressure eolian sandy loess section, covered above the vault with a thickness of 28-30m, as shown in Figure 2, 24 hours after the completion of the initial support of the Dk128+856 upper guide, on March 13, 2012 Collapse and subsidence occurred; the sprayed concrete of the middle guide Dk128+832~Dk128+849 spalled, deformed, collapsed, and invaded; the lower guide Dk128+832~Dk128+841.6 cracked, deformed and sank. There are many horizontal and vertical cracks on the surface, the scope is advanced, and the maximum crack width is 12cm. According to the measurement records of the surrounding rock, the maximum sinking of the vault is 89cm (Dk128+848) 13/3, and the minimum sinking is 62cm (Dk128+828); side), the right Dk128+848 side wall sinks 80cm, converges, and invades to a limit of 1.2cm. The supporting steel arches were distorted and deformed, and the anchor pipes at the lock feet were cut off, indicating a sign of roof collapse.

Construction method:

1) Surface crack 6 treatment, in order to prevent surface water seepage and soften the soil, it is necessary to grout the surface cracks: first excavate trenches along the cracks, and then use the funnel weight method to directly grout the cracks at a distance of about 30cm 1: 1 cement slurry, after the cement slurry is filled and solidified, it is then shifted for refilling. When the amount of pouring is large, the pouring should be stopped, and the grouting should be carried out after the poured cement slurry has solidified. After grouting, the cracked ground is plastered with cement mortar and made into an arc shape to prevent rainwater from infiltrating, as shown in Figure 1.

2) Backfilling in the hole

DK128+828～DK128+856 primary support cracking and deformation limit section, backfill the hole slag, and the 1.5m high range of the arch part is backfilled with C25 shotcrete, as shown in Figure 2;

3) Processing steps

Firstly, the front of the backfill body is reinforced, using φ42×3.5mm steel pipes with a spacing of 1.0×1.0m, arranged in a quincunx shape, 4m in length, drilled every 3m, and reinforced with grout. The radial anchor 7 is installed, using the Mai-style anchor, the circumferential × longitudinal spacing is 100 × 40cm, arranged in a quincunx shape, and the arch can only be replaced after grouting for reinforcement. The specific treatment method is as follows:

⑴ The inverted arch section of DK128+830～DK128+832 has been constructed

In view of the fact that the inverted arch has been completed in this section, combined with the clearance measurement data, the upper and middle guides are limited, and the range of arch replacement is the upper and middle guides, and the lower guides do not need to be replaced.

①Remove the initial support of the upper and middle guide in the section DK128+830～DK128+830.4 by using artificial picks, and seal the surrounding rock with initial spraying in time after the removal;

②Advance support: use double-layer R5L1 self-advancement bolts, 7.5m long, 180° range layout, 20cm circumferential distance between each layer, no less than 2.5m longitudinal overlap, and control the elevation angle at 10°～15° , grout injection;

③Establish the first and second I25a steel arches, the distance between the steel arches is 40cm (same as the distance between the original construction steel arches), the middle guide arch foot is set on the unremoved initial support, and welded firmly with the unremoved steel arch , A total of 20 R51L self-advancing locking foot bolts are installed at the upper and middle guide arch feet, with a length of 6m, including 12 upper guides and 8 middle guides, grouted; φ8 steel mesh, grid size 20×20cm; steel arch Frames are connected by [12.6 channel steel, with a circumferential spacing of 60cm; the middle guide part is equipped with radial anchor rods, using R51L self-advancing anchor rods, with a length of 7.5m and a spacing of 100×40cm (circumferential direction×longitudinal), plum blossom shape Arrangement, the tail end is firmly connected with the steel arch frame, and grout is injected; the thickness of C25 shotcrete is 35cm.

⑵ Section DK128+832～DK128+841.6

According to the construction situation of this section, combined with the clearance measurement data, the upper and middle guides are limited, but the lower guide steel arch has been distorted and deformed, and the range of arch replacement is upper, middle and lower guides. The excavation method adopts the three-step method. Firstly, the steel arch frame of the upper step is replaced, and radial anchors are installed at the middle and lower guides. The length of the anchor rod at the part is 7.5m, and the length of the anchor rod at the lower guide part is 6m, arranged in a quincunx shape and injected with grout. After grouting and reinforcement, the middle and lower guide steel arches shall be removed and replaced one by one.

① Construction of advance support: use double-layer R51L self-advancing anchor rods, 7.5m long, 180° range layout, 20cm circumferential distance between each layer, no less than 2.5m longitudinal overlap, and control the elevation angle at 10°～15° , inject grout.

②Use excavator vibratory hammer and manual pneumatic pick to remove the upper, middle and lower initial support of the DK128+832～DK128+841.6 section one by one, and perform initial spraying to seal the surrounding rock in time after the removal.

③Establish I25a-type steel and steel arches with a spacing of 40cm (same as the original construction steel arch spacing). A total of 28 R51L self-advancing locking foot anchors are installed at the upper, middle, and lower guide arch feet, with a length of 6m. 12 wires, 8 middle guides, 8 lower guides, grouted; φ8 steel mesh, grid size 20×20cm; [12.6 channel steel connection between steel arch frames, circumferential spacing 60cm; C25 shotcrete thickness 35cm.

④The same steps as above, and support in time after dismantling one by one.

⑶ DK128+841.6～DK128+849 section

According to the construction situation of this section, combined with the clearance measurement data, the scope of arch replacement is the upper and middle guides, and the lower guides are not excavated. The excavation method adopts the three-step method. For the anchor bolts, R51L self-advancement bolts are used, with a spacing of 100×40cm (circumferential direction×longitudinal), the length of the anchor bolts at the middle guide part is 7.5m, and the length of the anchor bolts at the down guide part is 6m. After the grouting is reinforced, the middle and lower guide steel arches are replaced one by one.

① Remove the initial support of the upper and middle guides of the section DK128+841.6 ~ DK128+849 one by one by using artificial picks, and seal the surrounding rock with initial spraying in time after the removal;

②Advance support: use double-layer R51L self-propelled bolts with a length of 7.5m and a range of 180°. The circumferential spacing of each layer is 20cm, the longitudinal overlap is not less than 2.5m, and the elevation angle is controlled at 10°～15° , grout injection;

③Establish I25a-type steel and steel arches with a spacing of 40cm (same as the original construction steel arch spacing). A total of 28 R51L self-advancing locking foot anchors are installed at the upper, middle, and lower guide arch feet, with a length of 6m. 12 wires, 8 middle guides, 8 lower guides, grouted; φ8 steel mesh, grid size 20×20cm; [12.6 channel steel connection between steel arch frames, circumferential spacing 60cm; C25 shotcrete thickness 35cm.

④The same steps as above, and support in time after dismantling one by one.

⑷DK128+849～DK128+856 section

According to the construction situation of this section, combined with the clearance measurement data, the range of arch change is the upper guide, the middle and lower guides are not excavated, and the excavation method adopts the three-step method. Firstly, radial anchor rods are drilled at the arch foot of the upper step, using R51L Self-advancing bolts, with a spacing of 100×40cm (circumferential×longitudinal), 7.5m long, arranged in a plum blossom shape, and grouted. After grouting and reinforcement, the upper guide steel arches are replaced one by one.

①Use excavator vibratory hammer and manual pneumatic pick to remove the initial support of the upper guide of the DK128+849~DK128+856 section one by one, and perform initial spraying to seal the surrounding rock in time after the removal. The middle and lower guide supports are followed up in time;

②Advance support: use double-layer R51L self-propelled bolts with a length of 7.5m and a range of 180°. The circumferential spacing of each layer is 20cm, the longitudinal overlap is not less than 2.5m, and the elevation angle is controlled at 10°～15° , grout injection;

③Establish I25a-type steel and steel arches with a spacing of 40cm (same as the original construction steel arch spacing). A total of 28 R51L self-advancing locking foot anchors are installed at the upper, middle, and lower guide arch feet, with a length of 6m. 12 bolts, 8 middle guides, 8 lower guides, and grouting; radial anchors are installed at the middle and lower steps, using R51L self-advancing anchors, with a spacing of 100×40cm (circumferential × longitudinal), and the middle guides The length of the bolt is 7.5m, and the length of the bolt at the lower guide part is 6m. It is arranged in a quincunx shape and injected with grout. φ8 steel mesh, grid size 20×20cm; steel arch frames are connected by [12.6 channel steel, with a circumferential spacing of 60cm; C25 shotcrete thickness 35cm.

④The same steps as above, and support in time after dismantling one by one.

Beneficial effect:

1) Social benefits

This method is suitable for the treatment of collapse, subsidence, encroachment and arch replacement of railway aeolian sandy loess tunnels, and can effectively control tunnel collapse. It can also be used for highways and hydraulic tunnels. Wide range, reliable technology, great advantages, easy to popularize and use;

The construction quality and safety of this method are guaranteed, it has little environmental pollution, is non-toxic, has a high degree of civilized construction, and has good results. Construction experience has been accumulated, and the social benefits are remarkable.

2) Economic benefits

The arch change of Shuozhou Tunnel Entrance Dk128+832～Dk128+856 of Zhunchi Railway in shallow buried partial pressure aeolian sandy loess section adopts Mai-style pipe shed construction. Comparison of economic benefits, only the scope of the arch, large pipe shed plan: 60 φ108 steel pipes x 12m/piece x 300 yuan/m=216,000 yuan, machinery rental 180,000 yuan per month, 24m treatment requires three times of large pipes The shed can only be passed, 216,000 yuan × 3 = 648,000 yuan, more than 60 days of construction is required, and the mechanical cost is 360,000 yuan, a total of 1.008 million yuan. The arch of the Mai-type anchor pipe shed according to the present invention: 5 times of double-layer drilling, 84 R51L self-propelled anchors × 2 layers × 5 times = 840, 840 × 7.5m/root × 60 yuan/m =378,000 yuan, 180,000 yuan for machinery, 450,000 yuan for saving machinery and materials, and can be completed in only 28 days, saving machinery and working days, saving 30 working days, and saving more than 400,000 yuan in labor costs.

The method has the advantages of fast construction speed, economy, safety and environmental protection. The method has been successfully applied in the construction, effectively solving the pressure of the construction period. The tunnel required a construction period of only 574 days.

3) Environmental benefits

Compared with the use of machinery in the construction hole of the large pipe shed, this method has less sewage discharge and less noise, can reduce mechanical exhaust emissions, has little harm to the operators, and has created good environmental protection benefits for the construction.

Claims (5)

1. formula pipe canopy processing aeolian accumulation chiltern loess tunnel advanced in years subsides to sink to invading a limit construction method, it is characterized in that comprising the following steps:

1) surface cracks (6) is processed, and first along crack excavation groove, then with the direct grout injection of spacing fracture about 30cm, after grouting, ground, crack adopts cement sand plaster, makes circular-arc;

2) backfill in hole, preliminary bracing (11) sinks to invading limit section backfill hole slag (12), and 1.5m high scope in arch adopts sprayed mortar (13) backfill closely knit;

3) sink to invading limit situation according to tunnel, in conjunction with Clearance survey data, determine the arch scope of changing;

4) excavation method adopts three benching tunnelling methods, sets radially anchor pole (7) before changing arch, adopts and steps formula anchor pole, hoop × longitudinal pitch is 100 × 40cm, quincuncial arrangement, cement injection in anchor pole, after grouting and reinforcing, change and sink to invading limit section steel arch frame again by Pin, concrete grammar is as follows:

A. take digging machine vibrating hammer to coordinate artificial pneumatic pick to remove and sink to invading the preliminary bracing of limit section by Pin, after dismounting, carry out in time just spray sealing country rock;

B. apply advance support, adopt the double-deck formula anchor pole (8) that steps, lay along 180 ° of scopes of tunnel cross-section, every layer of circumferential distance is 15～25cm, and longitudinal lap joint is no less than 2.5m, and the elevation angle is controlled at 10 °～15 °, and cement injection in anchor pole forms and steps formula pipe booth structure;

C. set up and sink to invading limit section steel arch frame (9), sink to invading limit section steel arch frame spacing identical with former construction steel bow member spacing, on lead, in lead, under lead arch springing set step formula lock foot anchoring stock, cement injection in anchor pole, adjacent sinking is invaded between limit section steel arch frame and is adopted channel-section steel (10) to connect, circumferential distance 50～70cm, sprayed mortar sealing in time;

D. immediate support after removing by Pin according to above-mentioned steps, every displacement one Pin, repeating step a, to the operation of steps d, has encircleed until change.

2. formula pipe canopy processing aeolian accumulation chiltern loess tunnel advanced in years according to claim 1 subsides and sinks to invading limit construction method, it is characterized in that the sinking of setting up in step c invades on limit section steel arch frame (9), and be fixed with fixing steel plate (3) by pasting country rock one side interval, each fixing steel plate two ends have the locating hole (4) that is positioned to sink to invading limit section steel arch frame both sides, squeeze into the formula lock foot anchoring stock advanced in years (2) of country rock in locating hole (4), be positioned to sink to invading formula lock foot anchoring stock bared end employing circular connector advanced in years (5) connection of limit section steel arch frame both sides and invade limit section steel arch frame (9) with sinking and fix.

3. formula pipe canopy processing aeolian accumulation chiltern loess tunnel advanced in years according to claim 1 and 2 subsides to sink to invading limit construction method, it is characterized in that stepping formula lock foot anchoring stock (2) and squeezes into end for the shape of a hoof.

4. formula pipe canopy processing aeolian accumulation chiltern loess tunnel advanced in years according to claim 1 and 2 subsides and sinks to invading limit construction method, it is characterized in that stepping formula lock foot anchoring stock (2) is 15～20 ° with the angle of horizontal direction, and the locating hole (4) on fixing steel plate (3) is longitudinal slotted eye.

5. formula pipe canopy advanced in years according to claim 2 is processed aeolian accumulation chiltern loess tunnel and is subsided to sink to invading limit construction method, it is characterized in that circular connector (5) be by two fixedly reinforcing bar be flexibly connected the loop configuration forming.