Construction method for controlling large deformation of mining method tunnel soft rock

Abstract

The invention discloses a construction method for controlling large deformation of tunnel soft rock by a mining method, which comprises the following steps of: 1, determining the shape and the size of a tunnel, 2, excavating the tunnel by the mining method, judging an over-excavation construction section and carrying out fixed-interval tunnel over-excavation, 3, backfilling a tunnel over-excavation surface with foam light soil, fourthly, supporting is conducted after foam light soil is backfilled, and a construction face is closed in time; according to the method, through the construction of overbreak and foam light soil backfilling of the tunnel, the property and the structure of surrounding rock are changed, transmission of high ground stress is directly blocked structurally, the effect of controlling large deformation of soft rock is achieved, and a good effect can also be achieved on soft rock mass.

Description

Technical Field

[0001] The invention relates to the technical field of tunnel engineering, and in particular to a construction method for controlling large deformation of soft rock in a mining tunnel. Background Art

[0002] Large deformation of soft rock has always been the focus of underground engineering research. Complex geological conditions (such as under the influence of fault zones) are more unfavorable to the stability of soft rock tunnels. Soft rock refers to a complex rock mechanical medium that can produce significant plastic deformation under specific environmental conditions. Large deformation of soft rock is a deformation and destruction phenomenon of the surrounding rock mass under environmental conditions such as ground stress, engineering disturbance and groundwater activity. Its essence is that the ground stress redistribution caused by excavation of the surrounding rock exceeds the yield strength of the rock mass, causing the rock mass to become plastic, the surrounding rock's self-bearing capacity is lost or partially lost, the deformation cannot be effectively constrained, and the surrounding rock undergoes plastic deformation and destruction, resulting in varying degrees of damage to the surrounding rock support.

[0003] In the existing mining method construction, for the control of large deformation of soft rock, methods such as anchor support, increasing the length of anchor rods, reserving deformation amount, etc. are usually adopted, but there are still shortcomings. For example, for soft rock masses such as phyllite, carbonaceous shale, metamorphic sandstone, etc., which have the characteristics of native structure in structure, traditional methods such as shotcrete support are difficult to achieve ideal results. Therefore, the present invention proposes a construction method for controlling large deformation of soft rock in mining method tunnels to solve the problems existing in the prior art. Summary of the invention

[0004] In view of the above problems, the purpose of the present invention is to propose a construction method for controlling large deformation of soft rock in a mining-based tunnel. The construction method for controlling large deformation of soft rock in a mining-based tunnel changes the properties and structure of the surrounding rock by over-excavating the tunnel and backfilling with foam lightweight soil, directly blocks the transmission of high ground stress from a structural perspective, and achieves the effect of controlling large deformation of soft rock, and can also have a good effect on weak rock masses.

[0005] To achieve the purpose of the present invention, the present invention is implemented by the following technical solution: A construction method for controlling large deformation of soft rock in a mining tunnel, comprising the following steps:

[0006] Step 1: First determine the actual engineering conditions according to the tunnel construction area, and then determine the shape of the tunnel;

[0007] Step 2: Excavate the tunnel according to the mining construction process, determine the risk of large soft rock deformation based on geological survey and actual site conditions, and perform tunnel over-excavation at fixed intervals in construction sections prone to large soft rock deformation;

[0008] Step 3: Backfill the over-excavated surface with foamed lightweight soil to complete the backfill construction of the over-excavated surface;

[0009] Step 4: After backfilling, provide support and then spray concrete in time to seal the construction surface.

[0010] A further improvement is that the tunnel shape determined in step 1 is one of a circular shape and a horseshoe shape, and then the excavation span of the tunnel is determined according to actual design and use needs, and the over-excavation thickness and over-excavation interval size are determined at the same time.

[0011] Further improvements are as follows: the over-excavation thickness is uniformly selected as 50 cm; when the excavated tunnel is a two-lane tunnel and a train tunnel, the over-excavation interval is twice the excavation span size, when the excavated tunnel is a three-lane tunnel, the over-excavation interval is 1.5 times the excavation span size, and when the excavated tunnel is a four-lane tunnel, the over-excavation interval is the excavation span size.

[0012] A further improvement is that when the tunnel is circular in shape, the cross-section of the over-excavation construction section is an arc with a central angle of 270°, and the bottom arc corresponding to the central angle of 90° is the same as the original tunnel and is not over-excavated.

[0013] A further improvement is that when the tunnel is horseshoe-shaped, the cross-section of the over-excavation construction section is divided into three parts, the upper part is a semicircular arc, the middle part is a rectangle, and the bottom is the invert of the original tunnel without over-excavation.

[0014] A further improvement is that during the backfilling operation in step 3, foamed lightweight soil is quickly poured on the over-excavation surface after each over-excavation portion of the tunnel is completed, so as to quickly complete the closure of the over-excavation surface.

[0015] A further improvement is that the specific operation of step 4 is to spray concrete on the surface of the foam lightweight soil after backfilling the over-excavation surface, then install the steel mesh and the vertical steel arch frame, install the anchor rods, and then spray concrete again to complete the closure of the construction surface.

[0016] The beneficial effects of the present invention are as follows: the present invention changes the properties and structure of the surrounding rock by over-excavating the tunnel and backfilling with foam lightweight soil, directly blocks the transmission of high ground stress from a structural perspective, achieves the effect of controlling large deformation of soft rock, and can also exert a good effect on weak rock mass. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a flow chart of the construction method of the present invention.

[0018] Figure 2 This is a schematic diagram of the construction dimensions of a circular tunnel in Example 1 of the present invention.

[0019] Figure 3 Schematic diagram of the over-excavation dimensions of a circular tunnel in Example 1 of the present invention.

[0020] Figure 4 This is a schematic diagram of the over-excavation thickness of a circular tunnel in Example 1 of the present invention.

[0021] Figure 5 This is a schematic diagram of the over-excavation interval of a circular tunnel in Example 1 of the present invention.

[0022] Figure 6 This is a schematic diagram of the construction dimensions of a horseshoe-shaped tunnel according to Example 2 of the present invention.

[0023] Figure 7 Schematic diagram of the over-excavation dimensions of the horseshoe-shaped tunnel in Example 2 of the present invention.

[0024] Figure 8 This is a schematic diagram of the over-excavation thickness of the horseshoe-shaped tunnel in Example 2 of the present invention.

[0025] Fig. 9 This is a schematic diagram of the over-excavation interval of a horseshoe-shaped tunnel in Example 2 of the present invention. DETAILED DESCRIPTION

[0026] In order to deepen the understanding of the present invention, the present invention will be further described in detail below in conjunction with examples. The examples are only used to explain the present invention and do not constitute a limitation on the protection scope of the present invention.

[0027] The tunnels applicable to the present invention include single-hole double-track tunnels and double-hole single-track tunnels. When used for double-hole tunnels, the over-excavation range of the two holes should be staggered during construction to avoid interference.

[0028] Example 1

[0029] according to Figure 1-Figure 5 As shown, this embodiment provides a construction method for controlling large deformation of soft rock in a mining tunnel. The tunnel shape of this embodiment is a circular tunnel.

[0030] The actual working conditions are determined through geological surveys, and circular tunnels are selected according to engineering design. Figure 2 Shown are the dimensions of a circular tunnel of diameter D, which is one of the most common tunnel shapes in engineering and is representative.

[0031] The tunnel is constructed using the mining method. Based on geological surveys and actual on-site conditions, over-excavation of the tunnel is carried out in construction sections where large deformation of soft rock is likely to occur. Figure 3 The figure shows the over-excavation range of a circular tunnel. In the over-excavation construction section, the actual excavation section of the circular tunnel is based on the center of the tunnel, with an arc of diameter D1 excavated, and the center angle of the arc is 270°. The bottom arc corresponding to the 90° center angle on the lower side is constructed according to the original tunnel size without over-excavation.

[0032] Figure 3 The figure also includes the overbreak of the tunnel, D x The distance of tunnel overcut is determined by the size of the tunnel. The larger the size, the larger the overcut range. xThe value is selected on the basis of ensuring the anchoring effect of the system anchor rod. Tunnels of different sizes require different lengths of system anchor rods. At the same time, the surrounding rock grade will also affect the length of the system anchor rod (determined according to the "Highway Tunnel Design Rules"). The specific lengths of system anchor rods for different numbers of lanes are shown in Tables 1 to 3 below.

[0033] Table 1 Reference table of anchor lengths for dual-lane tunnel systems

[0034]

[0035] Table 2 Reference table of anchor length for three-lane tunnel system

[0036]

[0037]

[0038] Table 3 Reference table of anchor length for four-lane tunnel system

[0039]

[0040] For Grade I surrounding rock, the minimum value of Grade II surrounding rock is uniformly taken to ensure stability. For Grade VI surrounding rock, it needs to be determined according to specific conditions. For the rest, the maximum value of the system anchor length is taken to ensure the stability of the surrounding rock.

[0041] Figure 4 The figure shows the over-excavation thickness of the tunnel, which is selected as 50cm. On the premise of ensuring its effective function, considering economy and construction convenience, the over-excavation thickness is selected as 50cm.

[0042] Figure 5 The overbreak interval of the tunnel is shown, which is determined by the size of the tunnel. The overbreak interval for two-lane tunnels and railway tunnels is twice the tunnel excavation span; the overbreak interval for three-lane tunnels is 1.5 times the tunnel excavation span; the overbreak interval for four-lane tunnels is the tunnel excavation span.

[0043] After over-excavation, use foam lightweight soil for backfilling. When backfilling the over-excavation surface with foam lightweight soil, excavation and backfilling should be carried out in a timely manner to complete the closure of the over-excavation surface of the tunnel as soon as possible.

[0044] After the over-excavation surface is closed, spray concrete on the surface of the foam lightweight soil, install steel mesh, erect steel arch frames, install anchor rods, and re-spray concrete to complete the closure of the construction surface in a timely manner.

[0045] Then other normal construction sections will be constructed using conventional mining methods until the tunnel is completed.

[0046] Example 2

[0047] according to Figure 1 and Figure 6-Figure 9As shown, this embodiment provides a construction method for controlling large deformation of soft rock in a mining tunnel. The tunnel shape of this embodiment is a horseshoe-shaped tunnel.

[0048] The actual working conditions are determined through geological survey, and the horseshoe-shaped tunnel is selected according to the engineering design. Figure 6 Shown are the dimensions of a four-center horseshoe tunnel with radii R1, R2, and R3, which is one of the most common tunnel shapes in engineering and is representative.

[0049] The tunnel is constructed using the mining method. Based on geological surveys and actual on-site conditions, over-excavation of the tunnel is carried out in construction sections where large deformation of soft rock is likely to occur. Figure 7 The figure shows the over-excavation range of the four-center circular horseshoe tunnel. In the over-excavation construction section, the actual excavation section of the four-center circular horseshoe tunnel is divided into three parts. The upper part is a semicircular arc with a diameter of D1, based on the center of the upper semicircle of the tunnel; the middle part is a rectangle with a length of D1 and a height of H, where H is the height from the center of the upper semicircle of the tunnel to the top of the invert surface. The bottom of the over-excavation surface is flush with the top of the invert surface; the bottom invert part is excavated according to the original tunnel size without over-excavation. The over-excavation range of other multi-center circular horseshoe tunnels refers to the over-excavation range of the four-center circular horseshoe tunnel.

[0050] Figure 7 Also shown are the overbreak ranges for different tunnel sizes, D x The distance of tunnel overcut is determined by the size of the tunnel. The larger the size, the larger the overcut range. x The value is selected on the basis of ensuring the anchoring effect of the system anchor rod. Tunnels of different sizes require different lengths of system anchor rods. At the same time, the surrounding rock grade will also affect the length of the system anchor rod (determined according to the "Highway Tunnel Design Rules"). The maximum length of the system anchor rod is taken to ensure the stability of the surrounding rock. For details, see Tables 1 to 3 of the embodiment.

[0051] Figure 8 The figure shows the over-excavation thickness of the tunnel, which is selected as 50cm. On the premise of ensuring its effective function, considering economy and construction convenience, the over-excavation thickness is selected as 50cm.

[0052] Fig. 9 The overbreak interval of the tunnel is shown, which is determined by the size of the tunnel. The overbreak interval for two-lane tunnels and railway tunnels is twice the tunnel excavation span; the overbreak interval for three-lane tunnels is 1.5 times the tunnel excavation span; the overbreak interval for four-lane tunnels is the tunnel excavation span.

[0053] After over-excavation, use foam lightweight soil for backfilling. When backfilling the over-excavation surface with foam lightweight soil, excavation and backfilling should be carried out in a timely manner to complete the closure of the over-excavation surface of the tunnel as soon as possible.

[0054] After the over-excavation surface is closed, spray concrete on the surface of the foam lightweight soil, install steel mesh, erect steel arch frames, install anchor rods, and re-spray concrete to complete the closure of the construction surface in a timely manner.

[0055] Then other normal construction sections will be constructed using conventional mining methods until the tunnel is completed.

[0056] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the principles of the present invention, several improvements and modifications may be proposed, and these improvements and modifications shall also be regarded as the protection scope of the present invention. The protection scope of the present invention is defined by the attached claims and their equivalents.

Claims

1. A construction method for controlling large deformation of soft rock in a mining tunnel, characterized in that: The following steps are involved: Step 1: First determine the actual engineering conditions according to the tunnel construction area, and then determine the shape of the tunnel; Step 2: Excavate the tunnel according to the mining construction process, determine the risk of large soft rock deformation based on geological survey and actual site conditions, and perform tunnel over-excavation at fixed intervals in construction sections prone to large soft rock deformation; Step 3: Backfill the over-excavated surface with foamed lightweight soil to complete the backfill construction of the over-excavated surface; Step 4: After backfilling, provide support and then spray concrete in time to seal the construction surface.

2. A construction method for controlling large deformation of soft rock in a mining tunnel according to claim 1, characterized in that: The tunnel shape determined in step 1 is one of a circular shape and a horseshoe shape, and then the excavation span of the tunnel is determined according to the actual design and use requirements, and the over-excavation thickness and over-excavation interval size are determined at the same time.

3. A construction method for controlling large deformation of soft rock in a mining tunnel according to claim 2, characterized in that: The over-excavation thickness is uniformly selected as 50 cm; when the excavated tunnel is a two-lane tunnel or a train tunnel, the over-excavation interval is twice the excavation span size, when the excavated tunnel is a three-lane tunnel, the over-excavation interval is 1.5 times the excavation span size, and when the excavated tunnel is a four-lane tunnel, the over-excavation interval is the excavation span size.

4. A construction method for controlling large deformation of soft rock in a mining tunnel according to claim 2, characterized in that: When the tunnel is circular in shape, the cross-section of the over-excavation construction section is an arc with a central angle of 270°, and the bottom arc corresponding to the central angle of 90° is the same as the original tunnel and is not over-excavated.

5. A construction method for controlling large deformation of soft rock in a mining tunnel according to claim 2, characterized in that: When the tunnel is in the shape of a horseshoe, the cross section of the over-excavation construction section is divided into three parts, the upper part is a semicircular arc, the middle part is a rectangle, and the bottom is the invert of the original tunnel without over-excavation.

6. A construction method for controlling large deformation of soft rock in a mining tunnel according to claim 1, characterized in that: When backfilling is performed in step 3, foamed lightweight soil is quickly poured on the over-excavation surface after each over-excavation portion of the tunnel is completed, so as to quickly complete the closure of the over-excavation surface.

7. A construction method for controlling large deformation of soft rock in a mining tunnel according to claim 1, characterized in that: The specific operation of step 4 is to spray concrete on the surface of the foam lightweight soil after backfilling the over-excavation surface, then install the steel mesh and the vertical steel arch frame, install the anchor rod, and then spray concrete again to complete the closure of the construction surface.

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