CN114622917A - Construction Methods for Handling Tunnel Collapse - Google Patents

Abstract

The invention discloses a construction method for treating tunnel collapse, which comprises the steps of marking, covering and intercepting drainage in a tunnel surface subsidence area, cleaning an excavated section of the tunnel, constructing a back pressure soil body, wall corner concrete in front of a tunnel face and grout stopping wall concrete, constructing a temporary support above the back pressure soil body in time, embedding a two-liquid grouting guide pipe on the grout stopping wall, performing water stopping and reinforcement on soil body surrounding rocks behind the grout stopping wall, constructing a guide wall in front of the grout stopping wall, constructing large pipe shed grouting, further performing grouting reinforcement on the soil body surrounding rocks above the back of the grout stopping wall, arranging small advanced guide pipes between grouting large pipe sheds below the subsidence area and grouting, simultaneously reinforcing vault surrounding rocks by adopting two methods of large pipe shed grouting and small advanced guide pipe grouting, excavating, spraying, supporting and supporting the tunnel face, and backfilling the subsidence area. The invention has the advantages of convenient construction, high disposal speed and high construction efficiency, effectively shortens the construction period and improves the construction safety.

Description

Construction Methods for Handling Tunnel Collapse

technical field

The invention relates to the technical field of tunnel excavation, in particular to a construction method for dealing with tunnel collapse.

Background technique

During the construction of the tunnel entrance section in summer, there is a great risk of landslides in case of continuous heavy rainfall. Due to the obvious boundary between soil and stone on the tunnel face, the precipitation continuously penetrates and soaks the covering soil layer on the top of the tunnel, the soil on the face gradually tends to be saturated and softened, the self-weight increases, the friction and cohesion of the soil decreases, and it is easy to produce plasticity. Deformation; further, under the action of blasting vibration in the rock distribution area of the face, the vault soil began to fall down along the soil-rock boundary, eventually causing the soil to collapse, resulting in the partial compression of the steel arch at the collapsed site. Bending and breaking; more seriously, if the tunnel is in the water-rich sand layer, when the tunnel is treated, water will continue to flow on the tunnel face, and secondary sand collapse will occur at any time, which cannot guarantee the safety of personnel and equipment, and construction risks. too high. The two-step method, three-step method, CD method, and CRD method adopted in order to reduce the risk are used to support the excavation construction.

SUMMARY OF THE INVENTION

In order to solve the above-mentioned problems, the present invention provides a construction method for dealing with tunnel collapse. Specifically, the following technical solutions can be adopted:

The construction method for processing tunnel collapse according to the present invention comprises the following steps:

The first step is to identify, cover and intercept and drain the tunnel in the subsidence area of the tunnel surface;

The second step is to clean up the excavated section of the tunnel, replace the backpressure soil while clearing the silt, backfill a mechanical equipment construction channel with backpressure, and then construct the corner concrete in front of the front of the tunnel and the concrete for the grout wall, and construct the backpressure in time. Temporary support above the soil mass;

The third step is to embed a double-liquid grouting conduit on the grouting wall, and perform water-stop reinforcement on the surrounding rock of the soil behind the grouting wall;

The fourth step is to construct a guide wall in front of the grout stop wall, and install the pipe shed orifice pipe extending to the back of the grout stop wall at the top of the guide wall in an oblique upward direction, and then construct a large pipe shed grouting, and further grouting the back of the grout stop wall. The upper soil surrounding rock shall be grouted for reinforcement;

The fifth step is to excavate the reinforced soil in front of the constructed initial support section in turn, and when it reaches the bottom of the collapse area, arrange and grouting between the grouting large pipe sheds, and use large pipe shed grouting and advanced small pipes The two methods of grouting reinforce the surrounding rock of the vault at the same time, and carry out the excavation and jetting support of the tunnel face;

The sixth step, repeat the construction according to the fifth step, and carry out the secondary lining construction and the backfilling of the surface subsidence area.

In the second step, when constructing the corner concrete in front of the face, firstly, a vertical grouting conduit is embedded in the back pressure soil body in front of the grouting wall, and then grouting reinforcement is performed to prevent the back of the grouting wall from being caused by the grouting pressure. Soil pressure pushes the grout wall.

The temporary support in the second step is connected to the upper step arch by welding, and the distance between adjacent temporary supports is 1m.

In the third step, when grouting is carried out through the double-liquid grouting conduit, the grout first fills the pores of the silt body behind the grouting wall, and then continuously fills the soil layer until the surrounding rock of the soil body behind the tunnel face is filled. reinforced state.

In the fourth step, each large grouting pipe shed is passed through the orifice pipe on the top of the guide wall.

In the fourth step, the grouting large pipe shed is continuously grouted for at least 10 minutes, and the grouting speed is 1/4 of the initial grouting speed or the grouting ends when the grouting amount reaches the designed grouting amount.

In the fifth step, the spray thickness of the initial concrete is 28cm.

The specific construction steps of backfilling in the surface subsidence area in the sixth step are as follows:

The first step is to select a relatively flat area within 50m of the collapse pit for ground hardening as a site for processing and mixing backfill;

The second step is to use P.O42.5 ordinary silicate bagged cement and blended foaming agent for backfill mixing after the mixing and backfilling machinery enters the site;

The third step is to install a foaming machine 30m outside the collapse pit, and pour the backfill to 10m below the original surface to complete the first backfill;

The fourth step is to use plain soil for secondary backfilling until it is flush with the original surface;

The fifth step is to apply 30cm thick lime soil above the plain soil for capping and water-proofing.

During the first backfilling, the foaming machine backfills 2 meters each time.

The construction method for dealing with tunnel collapse provided by the present invention reinforces the soil in the collapsed section by grouting in various ways, and performs backfilling and repair on the collapsed part, which fundamentally solves the secondary collapse of the tunnel; the construction is convenient. , The disposal speed is fast, the construction efficiency is high, the construction period is effectively shortened, and the construction safety is improved.

Description of drawings

Figure 1 is a schematic structural diagram of the present invention.

FIG. 2 is an A-A sectional view of the guide wall portion of FIG. 1. FIG.

FIG. 3 is a B-B sectional view in FIG. 1 .

Detailed ways

The embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. The present embodiment is implemented on the premise of the technical solution of the present invention, and provides detailed implementation methods and specific construction processes, but the protection scope of the present invention is not limited to the following described embodiment.

As shown in Figures 1-3, the construction method for dealing with tunnel collapse according to the present invention includes the following steps:

The first step is to identify, cover and intercept and drain the tunnel in the subsidence area of the tunnel surface;

Specifically, set up special safety officers around the original surface pit M (located on the surface on the right side of the tunnel face, see Figure 1) and in the tunnel, and set up safety signs such as fence railings, colorful flags, and eye-catching stickers around the pit; The topography adopts cast-in-place 60-type concrete intercepting and drainage ditch 0.4×0.6m to ensure smooth drainage of rainwater and avoid rainwater infiltration; within the impact range of the collapse pit, a steel pipe bracket is erected, which is covered with a rain-proof tarpaulin to prevent rainwater from infiltrating; at the same time, Deformation observers are arranged in the tunnel, mainly for surface settlement and displacement monitoring, tunnel vault settlement and arch convergence. During the detection process, the cumulative settlement in a single day exceeds 5mm to stop the operation in the tunnel.

The second step is to clean up the excavated section of the tunnel, replace the back pressure soil body 1 while clearing the silt, backfill a mechanical equipment construction channel with back pressure, and then construct the front corner concrete 3 of the tunnel face 2, and the mortar stop wall 4 concrete, and Temporary support 5 above the back pressure soil is constructed in time to control vertical settlement;

Specifically, when cleaning the excavated section of the tunnel, about 1500 cubic meters of sandy mudstone cave slag was reserved in advance for the back pressure of the tunnel face to ensure the safety and stability of the tunnel face and to avoid the occurrence of larger-scale mud and gushing. Mud incident. The above-mentioned back pressure soil body 1 extends all the way to the stop wall 4, its cross-section shall not be less than 2/3 of the tunnel excavation area, and its length shall not be less than 20m.

In order to ensure the stability of the tunnel face and provide a safe and sufficient construction space for subsequent construction, C30 concrete with an impermeability grade of P8 was used to cast the grout stop wall 4 to seal the tunnel collapse body and the tunnel face 2. Further, in order to ensure the stability of the grout stop wall 4 and to provide an installation platform for the construction equipment, cement-water glass double slurry is poured into the soil in front of the grout stop wall 4 and in the lower part to carry out the construction of the corner concrete 3 . During the construction of the above-mentioned corner concrete 3, 22 vertical grouting pipes (φ60mm, length 6m) are pre-buried at the foot of the grouting wall 4. The grouting material adopts cement-water glass double-liquid slurry, and the water-cement ratio of cement slurry is W:C =1:1, the volume ratio of cement slurry and water glass slurry is 1:1, and the cement adopts 42.5 grade Portland cement. The grouting pressure is 0.5-1.5Mpa, and the initial setting time of the slurry is required to be 3-5 minutes. When grouting, the mix ratio should be appropriately adjusted according to the actual situation on site.

A plurality of temporary supports 5 are constructed within 10m of the back pressure soil body 1 in the excavated section of the tunnel adjacent to the grout wall 4. Each temporary support 5 is welded to the upper step arch, and the adjacent temporary supports 5 The spacing is 1m. If necessary, increase the vertical support to control the vertical settlement, and at the same time, set 2 Φ42 locking foot anchor pipes on both sides of each truss, with a length of 6m and grouting reinforcement.

The third step is to embed a double-liquid grouting conduit 6 on the grouting wall 4, and perform water-stop reinforcement on the soil surrounding rock behind the grouting wall 4;

Specifically, the double-liquid grouting conduit 6 is a grouting pipe with a diameter of 42 mm and a length of 6 m, and 18 are evenly buried on the grouting wall 4 along the horizontal direction. Inside the rock. In the initial stage of grouting, the grout is mainly used to fill the pores of the soil layer. When the pores of the soil layer are filled and compacted by the injected grout, the grouting pressure continues to rise, and the injected grout in the later stage continues to fill the soil layer until it reaches an over-consolidated state.

In the fourth step, the guide wall 7 is constructed on the front side of the slurry stop wall 4, and the pipe shed orifice pipe extending to the back of the slurry stop wall 4 is installed on the top of the guide wall 7 along the oblique upward direction, and then the large pipe shed 8 is constructed for grouting, Further grouting reinforcement is performed on the soil surrounding rock above and behind the grout stop wall 4;

Since the constructed initial support section cannot meet the section size of the guide wall, it is necessary to break the original initial support surface, remove the original steel arch and stirrup mesh, and then construct the guide wall 7. Specifically, first install the orifice pipe used to pass through the grouting large pipe shed 8, then install two temporary I20a steel arches according to the longitudinal spacing of 50cm, and circumferentially connect Q235 steel plates 260×240mm, t=12mm, and M20 high-strength bolts For reinforcement, HRB400Φ22 connecting steel bars are used to connect the arches longitudinally, and the inner side is arranged in a single layer with a circumferential spacing of 1m, and the construction of the guide wall 7 is completed. The distance between the guide wall 7 and the grouting wall 4 is 1/5 of the pipe length of the grouting large pipe shed 8 .

The large grouting pipe shed 8 adopts 37 Φ89 grouting pipes with a length of 20m. After respectively passing through the orifice pipes, they are driven into the face 2 obliquely upward. Each of the above-mentioned grouting large pipe sheds 8 is passed through the orifice pipe on the top of the guide wall 7, the large pipe sheds 8 are circumferentially spaced 35cm, and three Φ22 steel bars are arranged in each large pipe shed 8 for reinforcement. After that, the sediment in the pipe is washed first, and then grouting is carried out according to the order from bottom to top. The single-hole grouting pressure is carried out according to the design requirements, and the grouting is continued for 10 minutes. When the grouting speed is 1/4 of the initial grouting speed or the grouting amount reaches the designed grouting amount, the grouting can end. Under normal circumstances, the grouting of the grouting large pipe shed 8 adopts a cement slurry with a water-cement ratio of 1:1 (weight ratio), the initial grouting pressure is 0.5-1.0 MPa, and the final grouting pressure reaches 2.0 MPa.

The fifth step is to excavate the reinforced soil in front of the constructed initial support section in turn, until below the subsidence area, arrange the advanced small conduits 9 between the grouting large pipe sheds 8 and grouting, and use the large pipe shed 8 for grouting and grouting. Two methods of grouting ahead of the small conduit 9 simultaneously reinforce the surrounding rock of the vault, and carry out excavation and jetting support for the tunnel face 2;

The above-mentioned small leading conduits 9 are conduits of Φ42*4mm, the longitudinal distance is 2m (longitudinal overlap is 1.5 meters), the circumferential distance is 35cm, the driving angle is 30-45°, 3.5m/piece, and the initial concrete spray thickness of the collapse section is is 28cm.

The sixth step, repeat the construction according to the fifth step, and carry out the secondary lining construction and the backfilling of the surface subsidence area.

In the fifth step, if it is confirmed that the tunnel face 2 can be excavated normally, then repeat the fifth step to carry out tunnel excavation according to the normal construction process, strengthen monitoring and measurement during construction, and excavate the middle and lower steps and the inverted arch at the same time. , Continue to follow up the construction of the second lining, the second lining construction adopts the form of composite lining, and the integral hydraulic formwork trolley is used for construction. After the initial support is completed, in order to effectively control the deformation of the tunnel body, the inverted arch is constructed as closely as possible to the excavation surface, and the invert arch is filled with a trestle platform to solve the transportation problem in the tunnel, and a full-width one-time construction is carried out.

During tunnel excavation, backfilling of the surface subsidence area should also be carried out. The specific construction steps are as follows:

S1, select a relatively flat area within 50m of the collapse pit, and perform ground hardening as a site for processing and mixing backfill;

S2, after the mixing and backfilling machinery enters the site, use P.O42.5 ordinary silicate bagged cement and admixed foaming agent to mix backfilling, the above-mentioned backfilling has the characteristics of self-leveling and self-compacting;

S3, install a foaming machine 30m away from the collapsed pit, and according to the working standard of 2m per injection height, inject the backfill to 10m below the original surface to complete the first backfill work;

S4, use plain soil for secondary backfill until it is flush with the original surface;

S5, apply 30cm thick lime soil above the plain soil for capping and water-proof treatment.

It should be noted that, in the description of the present invention, the orientations or positions indicated such as "front", "rear", "left", "right", "vertical", "horizontal", "inner", "outer", etc. The terminology of the relationship is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operate in a particular orientation , so it should not be construed as a limitation of the present invention.

Claims (9)

1. A construction method for treating tunnel collapse is characterized by comprising the following steps:

firstly, marking, covering and intercepting drainage in a tunnel surface subsidence area;

secondly, cleaning the excavated section of the tunnel, filling the back pressure soil body while cleaning sludge, back pressure filling a mechanical equipment construction channel, constructing corner concrete and grout stop wall concrete in front of the tunnel face, and constructing temporary supports above the back pressure soil body in time;

thirdly, embedding a double-liquid grouting guide pipe in the grout stopping wall, and performing water stopping reinforcement on the soil body surrounding rock behind the grout stopping wall;

fourthly, constructing a guide wall in front of the grout stop wall, installing a pipe shed orifice pipe extending to the back of the grout stop wall on the top of the guide wall along the obliquely upward direction, constructing large pipe sheds for grouting, and further grouting and reinforcing the soil body surrounding rock above the back of the grout stop wall;

fifthly, excavating a reinforced soil body in front of the constructed primary support section in sequence until the reinforced soil body is below a subsidence area, laying a small advanced guide pipe between the grouting large pipe sheds and grouting, reinforcing vault surrounding rock simultaneously by adopting two methods of large pipe shed grouting and small advanced guide pipe grouting, and excavating and spraying support on a tunnel face;

and sixthly, repeating the construction according to the fifth step, and carrying out secondary lining construction and backfilling of the surface subsidence area.

2. The construction method for treating tunnel collapse according to claim 1, characterized in that: when the concrete of the corner in front of the tunnel face is constructed in the second step, the vertical grouting guide pipe is buried in the back-pressure soil body in front of the grout stopping wall, and then grouting reinforcement is carried out to prevent the grouting pressure from causing the pressure of the soil body behind the grout stopping wall to push the grout stopping wall.

3. The construction method for treating tunnel collapse according to claim 1, characterized in that: and the temporary supports in the second step are welded with the arch center of the upper step, and the distance between every two adjacent temporary supports is 1 m.

4. The construction method for treating tunnel collapse according to claim 1, characterized in that: and in the third step, when grouting is carried out through the double-liquid grouting guide pipe, the slurry firstly fills the soil pore space behind the grout stopping wall, and then continuously fills and extrudes the soil layer until the soil surrounding rock behind the tunnel face is reinforced.

5. The construction method for treating tunnel collapse according to claim 1, characterized in that: and in the fourth step, each grouting large pipe shed is arranged in an orifice pipe at the top of the guide wall in a penetrating mode.

6. The construction method for treating tunnel collapse according to claim 1, characterized in that: and in the fourth step, grouting the large pipe shed for at least 10min, wherein the grouting speed is 1/4 of the starting grouting speed, or the grouting is finished when the grouting amount reaches the designed grouting amount.

7. The construction method for treating tunnel collapse according to claim 1, characterized in that: and in the fifth step, the spraying thickness of the primary concrete is 28 cm.

8. The construction method for treating tunnel collapse according to claim 1, wherein the concrete construction steps of backfilling the surface collapse area in the sixth step are as follows:

firstly, selecting a relatively flat section within a range of 50m near a collapsed pit, and hardening the ground to be used as a field for processing and mixing backfill;

secondly, after the stirred backfill is mechanically fed, stirring backfill by adopting P.O42.5 common silicate bagged cement and a blended foaming agent;

thirdly, installing a foaming machine outside the collapsed pit by 30m, and filling backfill materials to a position 10m below the original surface to finish the first backfilling work;

fourthly, backfilling for the second time by adopting plain soil until the plain soil is level to the original surface;

fifthly, applying lime soil with the thickness of 30cm above the plain soil for capping and water-resisting treatment.

9. The construction method for treating tunnel collapse according to claim 8, wherein: and during the first backfilling, the foaming machine backfills for 2 meters every time.

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