A yielding filling support structure and construction method for soft rock tunnels

Abstract

The present invention relates to the technical field of soft rock tunnel support, and particularly relates to a yielding filling support structure for soft rock tunnels and a construction method. This structure is obtained by constructing according to this method. This method includes obtaining in-situ stress data, rock stratum mechanical data, and surrounding rock deformation data; when the surrounding rock deformation data exceeds the deformation threshold, locking the surrounding rock deformation area and the amount of excavation enlargement through model simulation; increasing the length of the corresponding step according to the amount of excavation enlargement and reducing the height of the corresponding step; installing bolts to seal the surrounding rock surface; laying steel arch frames; reserving injection holes at the top of the surrounding rock deformation area, injecting filling materials to form a yielding filling layer; and spraying concrete again on the surrounding rock contour surfaces corresponding to each step to form an initial support structure. The present invention can ensure the safety of tunnel construction and operation when the deformation of soft rock tunnels is large and lasts for a long time, and reduce the construction cost and workload.

Description

Technical Field

[0001] The present invention relates to the technical field of soft rock tunnel support, and specifically relates to a yielding filling support structure for soft rock tunnels and a construction method thereof. Background Art

[0002] During the construction and excavation of high in-situ stress stratified soft rock tunnels, under the action of strong extrusion stress of weak surrounding rocks, soft rock tunnels are characterized by large deformation, high deformation rate and long deformation time. As a result, asymmetric extrusion large deformation disasters often occur in the surrounding rocks of the excavated soft rock tunnels, which will cause waste of manpower and material resources for repair in mild cases.

[0003] At present, for high in-situ stress soft rock tunnels, conventional three-step excavation is generally adopted to control the deformation of the surrounding rocks during construction. Further, on the basis of conventional three-step excavation, the industry has also proposed the support concept of "combination of yielding and resistance" for soft rock tunnels, and derived support structures such as yielding steel arches, flexible filling layers and constant resistance bolts. The combination of these support structures and conventional three-step excavation can only have good support effects when the deformation of the surrounding rocks is small; when the deformation of the soft rock tunnel is large and lasts for a long time, the combination of these support structures and conventional three-step excavation cannot well ensure the safety of tunnel construction and operation; in addition, most of these support structures are full-section support structures, which greatly increase the construction cost.

[0004] Considering that asymmetric extrusion deformation usually occurs in tunnels in stratified soft rock formations, and the deformation part often concentrates on a certain part of the surrounding rocks of the soft rock tunnel. If a full-section support structure is adopted, such as filling flexible materials in the full section, it will increase a large amount of construction economic cost and workload.

[0005] In summary, it is necessary to develop a yielding filling support structure for soft rock tunnels and a construction method thereof. On the one hand, it is necessary to solve the problem that the combination of the existing full-section support structure and conventional three-step excavation cannot ensure the safety of tunnel construction and operation when the deformation of the soft rock tunnel is large and lasts for a long time. On the other hand, it is necessary to solve the problem that the use of a full-section support structure when a certain part of the surrounding rocks of the soft rock tunnel is deformed will increase the construction cost and workload. Summary of the Invention

[0006] The purpose of the present invention is to provide a yielding filling support structure for soft rock tunnels and a construction method thereof. The specific technical solutions are as follows:

[0007] A construction method of a yielding filling support structure for soft rock tunnels. During the tunneling process of the soft rock tunnel, a three-step structure is excavated. The three-step structure includes an upper step, a middle step and a lower step. The construction method includes:

[0008] Step S1: During the excavation of a soft rock tunnel, conduct in-situ stress tests, rock mechanics experiments, and surrounding rock deformation monitoring on the excavated in-situ surrounding rock in real time to obtain in-situ stress data, rock mechanics data, and surrounding rock deformation data respectively;

[0009] Step S2: When the surrounding rock deformation data abnormally increases and exceeds the deformation threshold, use discrete element numerical calculation software to process the in-situ stress data, the rock mechanics data, and the surrounding rock deformation data at this time, and establish a numerical model of the soft rock tunnel; use the model to simulate the in-situ tunnel excavation process, and then analyze and obtain the surrounding rock deformation characteristics, and lock the surrounding rock deformation area and the amount of overexcavation; the deformation threshold is that the deformation amount corresponding to the surrounding rock deformation data is less than or equal to 80 cm;

[0010] Step S3: When the surrounding rock deformation area is locked in the surrounding rock corresponding to the upper bench, during tunneling, reduce the height of the upper bench according to the amount of overexcavation, and increase the length of the upper bench;

[0011] When the surrounding rock deformation area is locked in the surrounding rock corresponding to the lower part of the upper bench and the upper part of the middle bench, during tunneling, reduce the height of the middle bench according to the amount of overexcavation, and increase the length of the middle bench;

[0012] When the surrounding rock deformation area is locked in the surrounding rock corresponding to the lower part of the middle bench and the upper part of the lower bench, during tunneling, reduce the height of the lower bench according to the amount of overexcavation, and increase the length of the lower bench;

[0013] Step S4: Install bolts on the surrounding rock after tunneling; subsequently, spray concrete on the surrounding rock profile surfaces corresponding to the upper bench, the middle bench, and the lower bench respectively to seal the surrounding rock surface;

[0014] Step S5: Lay steel arch frames at intervals along the tunneling direction of the soft rock tunnel; arrange steel wire meshes and geotextiles between two adjacent steel arch frames in the surrounding rock deformation area; reserve injection holes at the top of the surrounding rock deformation area, inject filling materials to form a yielding filling layer; subsequently, spray concrete on the surrounding rock profile surfaces corresponding to the upper bench, the middle bench, and the lower bench respectively to form an initial support structure.

[0015] Optionally, the construction method further includes Step S6 of fabricating an invert support structure; specifically, during the excavation of the soft rock tunnel, it also includes excavating the bottom of the tunnel to form an invert, and successively installing bolts and laying segments on the invert to form an invert structure; subsequently, spraying concrete on the invert structure to obtain an invert support structure.

[0016] Optionally, the construction method further includes Step S7 of constructing a secondary lining; specifically, construct secondary linings on the initial support structure and the invert support structure respectively.

[0017] Optionally, the discrete element numerical calculation software includes 3DEC discrete element numerical calculation software or PFC discrete element numerical calculation software.

[0018] Optionally, the length of the upper bench is 5 - 7 m, and the height is 3 - 4 m; the length of the middle bench is 20 - 25 m, and the height is 2 - 3 m; the length of the lower bench is 8 - 10 m, and the height is 3 - 4 m.

[0019] Optionally, a core soil is reserved at the connection between the upper bench and the middle bench; a core soil is reserved at the connection between the middle bench and the lower bench.

[0020] Optionally, the in-situ stress data includes horizontal principal stress data and vertical principal stress data.

[0021] Optionally, the rock mass mechanical data includes rock mass compressive strength, elastic modulus, Poisson's ratio, cohesion, internal friction angle, joint normal stiffness, and normal shear stiffness.

[0022] Optionally, the aperture of the injection hole is 50 - 100 cm; the filling material includes dry sand, ceramsite, and foamed concrete.

[0023] In a second aspect, the present invention provides a yielding filling support structure for a soft rock tunnel, which is constructed by using the construction method of the yielding filling support structure for a soft rock tunnel.

[0024] [[ID=2,3]]Applying the technical solution of the present invention has at least the following beneficial effects:

[0025] A construction method for a yielding filling support structure of a soft rock tunnel provided by the present invention. When the abnormal deformation data of the surrounding rock becomes larger and exceeds the deformation threshold, a discrete element numerical calculation software is used to process the in-situ stress data, rock stratum mechanical data, and surrounding rock deformation data at this time, and a numerical model of the soft rock tunnel is established. The model is used to simulate the on-site tunnel excavation process, and then the deformation characteristics of the surrounding rock are analyzed, and the deformation area and the amount of excavation expansion of the surrounding rock are locked. According to the amount of excavation expansion, the length of the corresponding step is increased, and the height of the corresponding step is reduced, changing the conventional three-step structure. Among them, increasing the length of the corresponding step is convenient for slowly releasing the stress in the deformation area of the surrounding rock, and reducing the height of the corresponding step is convenient for excavating and processing the deformation area of the surrounding rock. An injection hole is reserved at the top of the deformation area of the surrounding rock, and a filling material is injected to form a yielding filling layer, which can better release the surrounding rock pressure and absorb the energy released by the deformation of the surrounding rock. Therefore, the present invention adopts local excavation and filling of the deformation area of the surrounding rock combined with the initial support structure, which can jointly inhibit the deformation of the surrounding rock and solve the problems of increased construction cost and workload caused by using a full-section support structure when a part of the surrounding rock of the soft rock tunnel deforms. In addition, the present invention adopts local excavation and filling of the deformation area of the surrounding rock combined with the changed three-step structure, which can ensure the safety of tunnel construction and operation when the deformation of the soft rock tunnel is large and lasts for a long time.

[0026] In addition to the purposes, features, and advantages described above, the present invention has other purposes, features, and advantages. The following will refer to the drawings for a further detailed description of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0028] Figure 1 is a flow schematic diagram of a construction method for a yielding filling support structure of a soft rock tunnel in an embodiment;

[0029] Figure 2 is the simulation result of the numerical model of the soft rock tunnel for the on-site surrounding rock (the dotted arrow outside the layered soft rock represents the direction of the vertical principal stress, and the solid arrow outside the layered soft rock represents the direction of the horizontal principal stress);

[0030] Figure 3 is a structural schematic diagram of the deformation area of the surrounding rock;

[0031] Figure 4 is a perspective view of the three-step structure adjusted according to the amount of excavation expansion;

[0032] Figure 5 is Figure 4 front view of

[0033] Figure 6 This is a structural diagram of the yielding filling support structure of a soft rock tunnel;

[0034] Among them, 1. Layered soft rock, 2. Upper step, 3. Middle step, 4. Lower step, 5. Surrounding rock deformation area, 5.1. Injection hole, 5.2. Yield filling layer, 6. Anchor rod, 7. Primary support structure, 8. Invert arch support structure, 9. Secondary lining, 10. Core soil. DETAILED DESCRIPTION

[0035] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention are within the scope of protection of the present invention.

[0036] Example

[0037] See also Figure 1 A construction method for a yielding filling support structure in a soft rock tunnel, wherein a three-step structure is excavated during tunneling in soft rock (the soft rock is layered soft rock 1, the rock layer has a 40° inclination angle, and has a high ground stress environment with a lateral pressure coefficient of 2), the three-step structure comprising an upper step 2, a middle step 3, and a lower step 4; the construction method comprises:

[0038] Step S1: During the excavation of a soft rock tunnel, in-situ stress testing, rock stratum mechanics experiments, and surrounding rock deformation monitoring are performed on the excavated surrounding rock in real time to obtain in-situ stress data, rock stratum mechanics data, and surrounding rock deformation data, respectively;

[0039] Step S2: When the surrounding rock deformation data becomes abnormally large and exceeds the deformation threshold, discrete element numerical calculation software is used to process the in-situ stress data, the rock stratum mechanics data, and the surrounding rock deformation data at this time to establish a soft rock tunnel numerical model; the model is used to simulate the on-site tunnel excavation process, and then the surrounding rock deformation characteristics are analyzed and the surrounding rock deformation area 5 (i.e., the area corresponding to the surrounding rock deformation area 5) and the excavation volume are locked; for specific simulation results, see Figure 2 The deformation threshold is that the deformation amount corresponding to the surrounding rock deformation data is less than or equal to 80cm;

[0040] Step S3: The surrounding rock deformation zone 5 is locked to the corresponding surrounding rock below the upper step 2 and above the middle step 3. Figure 3 The left arch waist in the tunnel is lowered according to the excavation amount during excavation, and the length of the middle step 3 is increased; for details, see Figures 4 to 5, the excavation depth corresponding to the additional excavation volume is 80 cm; the length of the middle bench 3 is 22 m and the height is 2.4 m; the length of the upper bench 2 is 6 m and the height is 3.7 m; the length of the lower bench 4 is 8 m and the height is 3.7 m;

[0041] Step S4, refer to Figure 6 , after tunneling, install bolts 6 (the bolts 6 are specifically mortar bolts 6 with a diameter of Φ22 mm, the length of the bolts 6 is 7 m, and the spacing between adjacent bolts 6 is 1.2 m) on the surrounding rock. Specifically, during the tunneling of the soft rock tunnel, the three benches are advanced synchronously. After each bench and the invert have advanced a distance of two sets of steel arch frames (not more than two sets), install bolts 6; subsequently, spray concrete on the contour surfaces of the surrounding rock corresponding to the upper bench 2, the middle bench 3, and the lower bench 4 respectively to seal the surrounding rock surface; among them, the excavated surrounding rock surface is relatively rough, and in order to spray the surrounding rock surface relatively flat, the thickness of the sprayed concrete needs to be controlled at 6 - 8 cm;

[0042] Step S5, lay steel arch frames (specifically I22b steel arch frames) at intervals along the tunneling direction of the soft rock tunnel; arrange steel mesh and geotextile between two adjacent steel arch frames in the surrounding rock deformation area 5; reserve injection holes 5.1 at the top of the surrounding rock deformation area 5 and inject filling materials to form a pressure-relieving filling layer 5.2; subsequently, spray concrete on the contour surfaces of the surrounding rock corresponding to the upper bench 2, the middle bench 3, and the lower bench 4 respectively to form the primary support structure 7.

[0043] The construction method further includes step S6 of fabricating an invert support structure 8; specifically, during the tunneling of the soft rock tunnel, it also includes excavating the bottom of the tunnel to form an invert, and successively installing bolts 6 (the bolts 6 are specifically mortar bolts 6 with a diameter of Φ22 and the length of the bolts 6 is 7 m, and the spacing between adjacent bolts 6 is 1.2 m) on the invert and laying segments to form an invert structure; subsequently, spray concrete on the invert structure to obtain the invert support structure 8.

[0044] Refer to Figure 6 [[ID=1{6]], the construction method further includes step S7 of constructing a secondary lining 9 (specifically a waterproof lining); specifically, construct a secondary lining 9 on the primary support structure 7 and the invert support structure 8 respectively.

[0045] The discrete element numerical calculation software is 3DEC discrete element numerical calculation software.

[0046] Reserve a core soil 10 at the connection between the upper bench 2 and the middle bench 3 to facilitate providing support force and improving the stability of the surrounding rock of the excavation face; reserve a core soil 10 at the connection between the middle bench 3 and the lower bench 4 to facilitate providing support force and improving the stability of the surrounding rock of the excavation face.

[0047] The in-situ stress data includes horizontal principal stress data and vertical principal stress data.

[0048] The rock mass mechanical data includes the uniaxial compressive strength of rock mass, elastic modulus, Poisson's ratio, cohesion, internal friction angle, normal stiffness of joints and normal shear stiffness.

[0049] The aperture of the injection hole 5.1 is 50 - 100 cm (specifically 60 cm is selected); the filling material is ceramsite.

[0050] The yielding filling support structure of the soft rock tunnel constructed by the construction method increases the length of the corresponding step according to the excavation amount and reduces the height of the corresponding step, changing the conventional three-step structure. Among them, increasing the length of the corresponding step is convenient for slowly releasing the stress in the surrounding rock deformation area 5, and reducing the height of the corresponding step is convenient for excavating the surrounding rock deformation area 5 to the excavation amount; an injection hole 5.1 is reserved at the top of the surrounding rock deformation area 5, and the filling material is injected to form a yielding filling layer 5.2, which can better release the surrounding rock pressure and absorb the energy released by the surrounding rock deformation. Therefore, adopting local excavation and filling of the surrounding rock deformation area 5 combined with the initial support structure 7 can not only jointly inhibit the surrounding rock deformation, but also reduce the workload and construction cost; in addition, adopting local excavation and filling of the surrounding rock deformation area 5 combined with the changed three-step structure can ensure the safety of tunnel construction and operation when the deformation of the soft rock tunnel is large and lasts for a long time.

[0051] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A construction method for a yielding filling support structure in a soft rock tunnel, wherein a three-step structure is excavated during the excavation of the soft rock tunnel, wherein the three-step structure comprises an upper step (2), a middle step (3) and a lower step (4); characterized in that: The construction method comprises: Step S1: During the excavation of a soft rock tunnel, in-situ stress testing, rock stratum mechanics experiments, and surrounding rock deformation monitoring are performed on the excavated surrounding rock in real time to obtain in-situ stress data, rock stratum mechanics data, and surrounding rock deformation data, respectively; Step S2: When the surrounding rock deformation data becomes abnormally large and exceeds the deformation threshold, discrete element numerical calculation software is used to process the in-situ stress data, the rock stratum mechanical data and the surrounding rock deformation data at this time, and a numerical model of a soft rock tunnel is established; the model is used to simulate the on-site tunnel excavation process, and then the surrounding rock deformation characteristics are analyzed and the surrounding rock deformation area (5) and the excavation amount are locked; the deformation threshold is that the deformation amount corresponding to the surrounding rock deformation data is less than or equal to 80 cm; Step S3: when the surrounding rock deformation area (5) is locked to the corresponding surrounding rock above the upper step (2), the height of the upper step (2) is lowered according to the excavation amount during excavation, and the length of the upper step (2) is increased; When the surrounding rock deformation zone (5) is locked to the corresponding surrounding rock below the upper step (2) and above the middle step (3), the height of the middle step (3) is lowered according to the excavation amount during excavation, and the length of the middle step (3) is increased; When the surrounding rock deformation zone (5) is locked to the corresponding surrounding rock below the middle step (3) and above the lower step (4), the height of the lower step (4) is lowered according to the excavation volume during excavation, and the length of the lower step (4) is increased; Step S4, after excavation, anchor rods (6) are installed on the surrounding rock; then, concrete is sprayed on the surrounding rock contour surfaces corresponding to the upper step (2), the middle step (3) and the lower step (4) to seal the surrounding rock surface; Step S5, laying steel arches at intervals along the excavation direction of the soft rock tunnel; placing steel mesh and geotextile in sequence between the two steel arches in the surrounding rock deformation area (5); reserving injection holes (5.1) at the top of the surrounding rock deformation area (5), injecting filling material to form a pressure-yielding filling layer (5.2); then, spraying concrete again on the surrounding rock contour surfaces corresponding to the upper step (2), the middle step (3) and the lower step (4) to form an initial support structure (7); The discrete element numerical calculation software includes 3DEC discrete element numerical calculation software or PFC discrete element numerical calculation software; The length of the upper step (2) is 5-7m and the height is 3-4m; the length of the middle step (3) is 20-25m and the height is 2-3m; the length of the lower step (4) is 8-10m and the height is 3-4m.

2. The construction method of the soft rock tunnel pressure-yielding filling support structure according to claim 1 is characterized in that: The method further includes step S6 of manufacturing an inverted arch support structure (8); specifically, during the excavation of the soft rock tunnel, the method further includes excavating the bottom of the tunnel to form an inverted arch, and sequentially installing anchor rods (6) and laying pipe segments on the inverted arch to form an inverted arch structure; and then spraying concrete on the inverted arch structure to obtain the inverted arch support structure (8).

3. The construction method of the soft rock tunnel pressure-yielding filling support structure according to claim 2 is characterized in that: The method further includes applying a secondary lining (9) in step S7; specifically, applying the secondary lining (9) on the initial support structure (7) and the invert support structure (8), respectively.

4. The construction method of the yielding filling support structure for a soft rock tunnel according to claim 1 is characterized in that: Core soil is reserved at the connection between the upper step (2) and the middle step (3); and core soil is reserved at the connection between the middle step (3) and the lower step (4).

5. The construction method of the yield filling support structure for a soft rock tunnel according to claim 1 is characterized in that: The ground stress data includes horizontal principal stress data and vertical principal stress data.

6. The construction method of the yield filling support structure for soft rock tunnel according to claim 1 is characterized in that: The rock formation mechanics data include rock mass compressive strength, elastic modulus, Poisson's ratio, cohesion, internal friction angle, joint normal stiffness and normal shear stiffness.

7. The construction method of the yielding filling support structure for a soft rock tunnel according to claim 1 is characterized in that: The injection hole (5.1) has a diameter of 50-100 cm; the filling material includes dry sand, ceramsite and foam concrete.

8. A soft rock tunnel pressure-yielding filling support structure, characterized in that: The structure is constructed by using the construction method of the soft rock tunnel pressure-yielding filling support structure according to any one of claims 1 to 7.

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