A method for strengthening support of cross tunnels based on reinforced roof of pile-type supports

Abstract

The present invention relates to a method for strengthening support of an intersection tunnel based on a top plate reinforced by a stacking support, which belongs to the technical field of tunnel support and solves the problem of poor tunnel stability when a new branch tunnel is excavated in the prior art. The method for strengthening support of an intersection tunnel based on a stacking support to reinforce the top plate of the present invention obtains the stress distribution characteristics of the surrounding rock of the tunnel intersection section, the range of the plastic zone, and the safety factor of the surrounding rock point based on the Mohr-Coulomb criterion through theoretical calculation before the construction of the new branch tunnel. On this basis, the range of the strengthened support area and the required working resistance of the stacking support are determined, and stacking supports are installed along the main tunnel in the tunnel intersection section. The top plate of the tunnel intersection section is reinforced by the stacking support to enhance the overall stability of the tunnel. When all the stacking supports are connected to the top plate and reach the rated working resistance, the excavation of the branch tunnel is carried out. After the mine pressure in the tunnel intersection section is stabilized, the support support is removed and recovered. The present invention achieves the stability and safety of the excavation process.

Description

[0001] The present invention claims the priority of the prior application with the application date of June 29, 2022, application number: 202210749733.X, and invention name: "A method for strengthening support of cross-tunnels based on reinforced roof of stack-type supports". Technical Field

[0002] The invention relates to the technical field of tunnel support, and in particular to a cross tunnel reinforcement support method based on a pile-type support to reinforce a roof. Background Art

[0003] In the production process of underground mines, due to the actual engineering needs of coal transportation, material transportation, ventilation and pedestrians, multiple tunnels are often designed and constructed to intersect or branch from a main tunnel. Such tunnels are called cross tunnels or tunnel intersections. Compared with ordinary tunnels, the stress concentration of the surrounding rock in the tunnel intersection section is higher, the exposed area of ​​the roof is larger, the deformation and crushing of the surrounding rock is more serious, and the tunnel support conditions are worse. Affected by the above factors, the support of the cross tunnel is more difficult and is more prone to deformation and damage during the operation period. The cross tunnel is often the throat of the mine production. Once it is deformed and unstable, it will have a serious impact on the mine production.

[0004] At present, increasing the support strength of anchor rods (cables) is the main way to solve the problem of cross tunnel support. Some mines will also arrange single pillars or flexible trusses for reinforcement in the early stage of support, but this support form still has the following defects: ① The initial support strength is insufficient. After the tunnel is excavated, the surrounding rock moves violently. The insufficient support strength of the support body cannot effectively suppress the deformation of the roof, which easily leads to roof delamination; on the other hand, it cannot effectively avoid the slab of the coal wall. After the slab is damaged, the supporting effect on the roof is reduced, which will further aggravate the sinking of the roof and cause a vicious cycle. ② The labor intensity of employees is high. The installation, daily maintenance and withdrawal of single pillars will increase the workload and labor intensity of employees, and there are great safety hazards during the support and withdrawal of single pillars. ③ The expansion and repair are frequent during the operation period. The conventional support means have weak long-term control ability for tunnel deformation. In order to ensure that the cross tunnel meets the use requirements, expansion and repair are often required, which greatly disrupts the normal production and operation of the mine.

[0005] Therefore, it is necessary to innovate the existing support technology, enhance the initial support strength of the support body, control the deformation of the tunnel, improve the long-term stability of the tunnel, and at the same time increase the mechanization degree of the construction process, reduce labor intensity, improve construction efficiency, and meet the needs of mine operation. Summary of the invention

[0006] In view of the above analysis, the present invention aims to provide a method for strengthening support of an intersection tunnel based on reinforcing the top plate with a stack-type support, so as to solve the problem of poor long-term stability of the existing intersection tunnels.

[0007] The purpose of the present invention is mainly achieved through the following technical solutions:

[0008] A method for strengthening support of an intersecting tunnel based on reinforcing the roof with a pile-type support comprises the following steps:

[0009] Step S1: Determine the scope of the enhanced support area according to the point safety factor;

[0010] Step S2: Calculate the required working resistance of the stacking bracket;

[0011] Step S3: Select a pile-type support that meets the resistance requirements to support the reinforced support area.

[0012] Furthermore, in step S1, in combination with actual engineering geological conditions, the stress distribution characteristics and plastic zone range of the surrounding rock of the tunnel intersection section are obtained through theoretical calculation, and the point safety factor of the surrounding rock is calculated in combination with the Mohr-Coulomb criterion to determine the range of the enhanced support area.

[0013] Furthermore, areas within the plastic zone and areas with point safety factors not greater than 1 should be designated as enhanced support areas.

[0014] Furthermore, in step S2, the required working resistance of the stack-type support must satisfy that the safety factor of the surrounding rock point after the supporting force is applied is greater than 1; the required working resistance of the stack-type support is obtained by reverse calculation by substituting it into the point safety factor calculation formula.

[0015] Furthermore, in step S3, appropriate stack-type supports are selected based on the theoretically calculated required working resistance of the stack-type supports and the actual spatial size of the intersection tunnel, and the required number of stack-type supports is calculated based on the width of the reinforced support area and the size of the stack-type supports. Before the construction of a new branch tunnel, stack-type supports are installed along the excavated main tunnel to reinforce the support of the top plate of the intersection section.

[0016] Furthermore, it also includes:

[0017] Step S4: After the construction of the new branch tunnel is completed, the stacked supports are recovered.

[0018] Furthermore, in the step S3, after all the stack-type supports are connected to the tunnel roof of the main tunnel and reach the rated working resistance, the excavation of the new branch tunnel is carried out; after the excavation of the new branch tunnel in the tunnel intersection section is completed and the mine pressure is stable, the dismantling and recovery of the stack-type supports and related auxiliary equipment in the tunnel is carried out, and the construction of the reinforced support section of the intersection tunnel is completed.

[0019] Furthermore, in step S3, a first stack-type support is installed in the reinforced support area of ​​the main tunnel; and 1 to 2 second stack-type supports are additionally installed on the outer side of the acute-angle side triangle area of ​​the tunnel intersection section between the main tunnel and the newly excavated branch tunnel to control the asymmetric deformation of the tunnel caused by stress concentration.

[0020] Furthermore, in step S3, if the angle between the main tunnel and the newly excavated branch tunnel is a right angle, there is no need to consider installing an additional second stack support.

[0021] Furthermore, in step S4, after the movement of the rock layer on the roof of the tunnel intersection section is stable and the stress disturbance zone at the head of the newly excavated branch tunnel is far away from the tunnel intersection section, the dismantling and recovery of each stack-type support in the main tunnel is carried out, and other auxiliary construction equipment and accessories in the construction area are recovered at the same time.

[0022] The technical solution of the present invention can achieve at least one of the following effects:

[0023] 1. The present invention adopts stack-type supports to reinforce the cross tunnel roof, which can greatly improve the initial support strength and effectively control the deformation of the tunnel.

[0024] 2. The invention provides a method for strengthening cross-tunnel support based on reinforcing the roof with stack-type supports, which provides high-strength support for the cross-tunnel roof through stack-type supports to control tunnel deformation and greatly improve the roof safety factor.

[0025] 3. The newly excavated cross tunnel of the present invention is carried out under the state of the top protection of the pile-type support. During this period, the pile-type support plays a role similar to that of a filling body, which can reduce the exposed area of ​​the top plate of the cross section of the tunnel and greatly increase the safety factor of the top plate. At the same time, compared with the traditional cross tunnel construction process, the present invention can also avoid the installation, daily maintenance, withdrawal and other heavy physical labor of the single pillar during the construction process, which not only reduces the labor intensity of employees, but also eliminates the safety hazards during the construction period.

[0026] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0028] Figure 1 It is a plan layout diagram of a cross-tunnel reinforcement support method based on a stack-type support to reinforce the roof when the tunnel intersection angle is an acute angle;

[0029] Figure 2 It is a plan layout diagram when the intersection angle of the lanes is a right angle.

[0030] Reference numerals:

[0031] 1-the first stack of supports; 2-the main tunnel; 3-the newly excavated branch tunnel; 4-the strengthened support area; 5-the second stack of supports; 6-the acute angle side triangle area; 7-the obtuse angle side triangle area. DETAILED DESCRIPTION

[0032] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0033] Example 1

[0034] A specific embodiment of the present invention discloses a method for strengthening support of an intersection tunnel based on reinforcing the roof with a stack-type support.

[0035] The following is combined with Figure 1-2 , the embodiments of the present invention are further described:

[0036] like Figure 1 , Figure 2 As shown, the method for strengthening support of an intersection tunnel based on reinforcement of the roof by stack-type supports of the present invention is as follows: before the construction of a new branch tunnel 3, the stress distribution characteristics of the surrounding rock of the tunnel intersection section, the range of the plastic zone and the point safety factor based on the Mohr-Coulomb criterion are obtained through theoretical calculation, and on this basis, the range of the strengthened support area 4, the required working resistance of the first stack-type support 1 and other parameters are determined, and then the first stack-type support 1 is installed along the main tunnel 2 at the tunnel intersection section, and the first stack-type support 1 is used to reinforce the roof of the tunnel intersection section to enhance the overall stability of the tunnel, and when all the first stack-type supports 1 are connected to the roof and reach the rated working resistance, the excavation and support operation of the new branch tunnel 3 is carried out, and after the mine pressure in the tunnel intersection section is stabilized, the first stack-type supports 1 and related auxiliary equipment in the tunnel are dismantled and recovered.

[0037] The specific steps of the support method are as follows:

[0038] S1: Determine the scope of the reinforced support area 4.

[0039] Specifically,

[0040] S11: In combination with the actual engineering geological conditions, the stress distribution characteristics of the surrounding rock of the tunnel intersection section are obtained through calculation; the stress calculation of the surrounding rock of the tunnel intersection section belongs to the technology known in the art and will not be repeated in the present invention.

[0041] S12 calculates the point safety factor of the surrounding rock based on the Mohr-Coulomb criterion, i.e., the yield criterion, to determine the scope of the reinforced support zone 4.

[0042] Among them, areas with point safety factors not greater than 1 should be designated as enhanced support areas 4.

[0043] Furthermore, the vertical stress σ in the triangle area of ​​the cross tunnel t The approximate solution of and the approximate expression of stress concentration factor K are shown in equations (1) and (2):

[0044]

[0045]

[0046] In the formula,

[0047] σ1 is the vertical stress of the original rock;

[0048] σ2 is the horizontal stress of the original rock;

[0049] α is the intersection angle between the main tunnel 2 and the newly excavated branch tunnel 3;

[0050] Polar coordinates of stress at points ρ and θ;

[0051] γ1 is the distance from the center of the intersection roadway to the boundary of the plastic deformation circle;

[0052] r1 plastic zone width;

[0053] λ=σ1 / σ2 is the lateral pressure coefficient.

[0054] The original stresses σ1 and σ2 in the above calculation formula can be expressed by P and λP, and the simplified calculation formula for the vertical stress is:

[0055]

[0056] The distance γ1 from the center of the intersection roadway to the boundary of the plastic deformation circle can be calculated using the width of the plastic failure zone of the roadway.

[0057] The width r1 of the plastic failure zone of the roadway can be calculated by the following formula:

[0058]

[0059] in:

[0060]

[0061]

[0062]

[0063]

[0064]

[0065] In the formula, γ is the bulk density of surrounding rock; h is the height of the tunnel; d is the span of the tunnel; is the internal friction angle of rock, and c is the cohesive force.

[0066] After clarifying the stress distribution characteristics of the surrounding rock in the tunnel intersection section, the point safety factor method can be used to further evaluate the stability of the rock mass, and then predict the possibility of rock mass damage outside the loosening damage range.

[0067] At present, the most commonly used strength failure criterion in geotechnical engineering is the Mohr-Coulomb criterion, which is in good agreement with laboratory experimental results.

[0068] In general, the definition of point safety factor based on the Mohr-Coulomb criterion can be expressed as:

[0069]

[0070] Where σ n and τ n are the normal stress and shear stress on the tunnel section respectively.

[0071] When F<1, the stress state of the surrounding rock at the intersection of the tunnel is outside the Mohr-Coulomb envelope, and the surrounding rock is in a broken state.

[0072] When F=1, the stress state of the surrounding rock is on the Mohr-Coulomb envelope and the surrounding rock is in a critical failure state.

[0073] When F>1, the stress of the surrounding rock at the intersection is within the Mohr-Coulomb envelope, and the surrounding rock is in a safe state.

[0074] The specific scope of the reinforced support zone 4 of the tunnel intersection section is determined by calculating the plastic zone range and the safety factor of the surrounding rock point.

[0075] Specifically, in step S1, the plastic zone range and the area where the safety factor of the surrounding rock point is not greater than 1 belong to the reinforced support area 4; the reinforced support area 4 needs to use the first stack-type support 1 for reinforced support during the excavation construction of the new branch tunnel 3.

[0076] S2: Calculate the required working resistance of the first stack support 1.

[0077] The supporting force of the first stack support 1 on the tunnel roof of the main tunnel 2 can be regarded as vertical stress, and its working resistance should ensure that the point safety factor of the surrounding rock in the reinforced support area 4 is greater than 1 after the supporting force is applied, which can be substituted into the point safety factor calculation formula and calculated by reverse calculation.

[0078] Specifically, after the first stack support 1 is supported, the point safety factor of the surrounding rock in the enhanced support area 4 is greater than 1. So far, the width of the enhanced support area 4 of the surrounding rock of the tunnel intersection section and the required maximum working resistance of the first stack support 1 are obtained.

[0079] S3: Selection and installation of the first stack support 1.

[0080] In combination with the required working resistance of the first stack type support 1 calculated in step S1 and step S2 and the actual spatial size of the reinforced support area 4, a suitable first stack type support 1 is selected, and the required number of first stack type supports 1 is calculated according to the width of the reinforced support area 4 and the size of the first stack type supports 1. Before the construction of the new branch tunnel 3, the first stack type supports 1 are installed along the excavated main tunnel 2 to reinforce the support of the cross section top plate.

[0081] In addition, considering that the stress concentration phenomenon in the acute-angle side triangle area 6 of the tunnel intersection section is more significant, and the smaller the intersection angle, the greater the tunnel deformation in the acute-angle side triangle area 6 of the main tunnel 2 and the newly excavated branch tunnel 3.

[0082] One to two additional second stack-type supports 5 are installed in the main tunnel 2 outside the acute-angle side triangle area 6 of the tunnel intersection section to control the asymmetric deformation of the tunnel, while no additional stack-type supports are required in the obtuse-angle side triangle area 7; if the tunnel angle between the main tunnel 2 and the newly excavated branch tunnel 3 is a right angle, there is no need to consider installing an additional second stack-type support 5.

[0083] Before the construction of a new branch tunnel, the present invention obtains the stress distribution characteristics of the surrounding rock of the tunnel intersection section, the range of the plastic zone and the point safety factor based on the Mohr-Coulomb criterion through theoretical calculation, and on this basis determines the range of the reinforced support area, the working resistance required by the pile-type support and other parameters; the pile-type support is installed along the main tunnel at the tunnel intersection section, and the top plate of the tunnel intersection section is reinforced by the pile-type support to enhance the overall stability of the tunnel.

[0084] S4: Excavation of new branch tunnel 3 and equipment recovery.

[0085] After all the first-stack supports 1 are connected to the tunnel roof and reach the rated working resistance, the excavation and support operation of the new branch tunnel 3 is carried out. After the excavation and support operation of the new branch tunnel 3 in the tunnel intersection section is completed and the mine pressure is stable, the dismantling and recovery of the first-stack supports 1 and related auxiliary equipment in the tunnel are carried out, and the construction of the cross tunnel reinforced support section is completed.

[0086] The invention carries out the branch tunnel excavation operation after all the pile-type supports are firmly connected to the roof and reach the rated working resistance. After the mine pressure in the tunnel intersection section is stabilized, the pile-type supports and related auxiliary equipment in the tunnel are removed and recovered, thereby ensuring the stability and safety of the branch tunnel excavation.

[0087] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for strengthening support of cross tunnels based on reinforced roof with pile-type supports, characterized in that: The following steps are involved: Step S1: Determine the scope of the enhanced support area according to the point safety factor; Step S2: Calculate the required working resistance of the stacking bracket; Step S3: Selecting a pile support that meets the resistance requirements to support the enhanced support area; In the step S1, the stress distribution characteristics and plastic zone range of the surrounding rock of the tunnel intersection section are obtained through theoretical calculation in combination with the actual engineering geological conditions, and the point safety factor of the surrounding rock is calculated in combination with the Mohr-Coulomb criterion to determine the range of the enhanced support area; The area within the plastic zone and the area with a point safety factor not greater than 1 should be designated as a strengthened support area; In the step S2, the required working resistance of the stack type support must satisfy that the safety factor of the surrounding rock point after the support force is applied is greater than 1; the required working resistance of the stack type support is obtained by reverse calculation by substituting it into the point safety factor calculation formula; In the step S3, a suitable stacking support is selected based on the theoretically calculated required working resistance of the stacking support and the actual spatial size of the intersection tunnel, and the number of stacking supports required is calculated based on the width of the reinforced support area and the size of the stacking support. Before the construction of the new branch tunnel, the stacking support is installed along the excavated main tunnel to reinforce the support of the top plate of the intersection section; In the step S3, a first stack type support is installed in the reinforced support area of ​​the main tunnel; 1 to 2 second stack type supports are additionally installed outside the acute angle side triangle area of ​​the tunnel intersection section between the main tunnel and the newly excavated branch tunnel to control the asymmetric deformation of the tunnel caused by stress concentration; no additional stack type supports are required in the obtuse angle side triangle area; In step S3, if the angle between the main tunnel and the newly excavated branch tunnel is a right angle, there is no need to consider installing the second stack support.

2. The method for strengthening support of cross tunnels based on reinforced roof with stacked supports according to claim 1, characterized in that: Also includes: Step S4: After the construction of the new branch tunnel is completed, the stacked supports are recovered.

3. The method for strengthening support of cross tunnels based on reinforced roof with stacked supports according to claim 2, characterized in that: In step S3, after all the stack-type supports are connected to the tunnel roof of the main tunnel and reach the rated working resistance, the excavation of the new branch tunnel is carried out; after the excavation of the new branch tunnel in the tunnel intersection section is completed and the mine pressure is stable, the dismantling and recovery of the stack-type supports and related auxiliary equipment in the tunnel is carried out, and the construction of the reinforced support section of the intersection tunnel is completed.

4. The method for strengthening support of cross tunnels based on reinforced roof with stacked supports according to claim 3 is characterized in that: In step S4, after the movement of the top rock layer of the tunnel intersection section is stable and the excavation head stress disturbance zone of the newly excavated branch tunnel is far away from the tunnel intersection section, the dismantling and recovery of each stack-type support in the main tunnel is carried out, and other auxiliary construction equipment and accessories in the construction area are recovered at the same time.

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