A method for judging the support mode of a tunnel with a roof spacer layer under a goaf

Abstract

The present invention discloses a method for judging the support mode of a roadway with a roof spacer layer under a goaf, which belongs to the technical field of underground engineering construction, and comprises the following steps: S1, determining the thickness of the immediate roof of the upper coal layer, and determining the basic roof structure of the upper coal layer through a rock layer column diagram; and calculating the uniformly distributed load on the lower coal roof; S2, determining the critical span-thickness ratio of the composite beam of the lower coal roadway roof, and obtaining the minimum self-stable thickness t of the roadway roof. min ; S3, determine the actual undamaged thickness of the lower coal roof t r , and through t r With t min The support method of the interlayer tunnel is judged by comparison; the present invention further optimizes the support method of the tunnel, changes the current situation that the support and reinforcement design of this type of tunnel has long relied on experience, and based on the principle of material mechanics, takes the maximum span-to-thickness ratio of the roof composite beam as the basis for judging the self-stability of the roof, thereby realizing quantitative judgment of the support method.

Description

Technical Field

[0001] The invention belongs to the technical field of underground engineering construction, and in particular relates to a method for determining a support mode of a tunnel with a roof spacing layer under a goaf. Background Art

[0002] At present, tunnels with interval layers under goafs usually bear greater pressure, so the tunnel support strength is usually relatively high. In terms of support form, active support represented by anchor (cable) support is often combined with passive support such as scaffolding and single hydraulic props. However, the roof under some goafs is relatively strong and the degree of crushing is not high. Therefore, the roof of the tunnel under such goafs does not require excessive support strength, which will cause unnecessary waste of resources. In addition, the scaffolding support, as a passive support method, needs to be assembled at the support site, and the installation process is complicated and the labor intensity of the workers is high. Most of the brackets are made of steel, with a large overall weight and high support cost.

[0003] At present, the commonly used on-site detection method for stable roof rock strata is drilling and peeping. If the thickness of the roof interval layer is large and the stable height of the roof is large, the test will consume more manpower. In addition, when the tunnel length is long, multiple measuring stations need to be selected to conduct roof drilling and peeping to confirm the development of the roof fracture area, so as to determine whether the support design needs to adopt the coupling support of active support and passive support (scaffolding, etc.). As a result, the support reinforcement design of this type of tunnel has long relied on experience. Summary of the invention

[0004] The purpose of the present invention is to provide a method for determining the support mode of a tunnel with a roof spacing layer under a goaf, so as to solve the problems raised in the above-mentioned background technology.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for determining the support mode of a tunnel with a roof spacing layer under a goaf, comprising the following steps:

[0006] S1. Determine the thickness of the immediate roof of the upper coal layer, and determine the basic roof composition of the upper coal layer through the rock layer columnar diagram; and calculate the uniformly distributed load on the roof of the lower coal layer;

[0007] S2. Determine the critical span-thickness ratio of the composite beam of the lower coal roadway roof and obtain the minimum self-stable thickness t of the roadway roof min ;

[0008] S3. Determine the actual undamaged thickness t of the lower coal roof r , and through t r With t min The support method of the interlayer tunnel can be determined by comparison.

[0009] As a preferred implementation, in step S1, the thickness of the upper coal immediate roof is determined by using a rock layer column chart and a calculation formula, and the calculation formula is:

[0010]

[0011] Among them, h is the mining height, SA is the roof settlement, and KA is the rock expansion coefficient;

[0012] The basic roof structure of the upper coal layer is determined by the rock layer column diagram, and the formula for calculating the uniformly distributed load on the lower coal roof is:

[0013] q=(M Z +M E +M J )×γ,

[0014] Where Mz is the thickness of the immediate roof of the upper coal layer, ME is the thickness of the basic roof of the upper coal layer, MJ is the thickness of the interval rock layer, and γ is the rock bulk density.

[0015] As a preferred implementation, in step S2, the calculation formula for determining the critical span-to-thickness ratio of the lower coal roadway roof composite beam is:

[0016]

[0017] Among them, l is the tunnel span, t is the thickness of the composite beam of the lower coal tunnel roof, σ max is the ultimate tensile strength of the composite beam, q is the uniformly distributed load on the lower coal roof determined in step S1, and λ is the lateral pressure coefficient;

[0018] And among them, if σ max ≤λq, at this time the tunnel roof beam does not meet the conditions for tensile failure.

[0019] As a preferred implementation, in step S3, the calculation formula for determining the actual undamaged thickness of the lower coal roof is:

[0020] t r =M J -d,

[0021] Among them, tr is the actual undamaged thickness of the roadway roof, and d is the damaged depth of the upper coal floor;

[0022] If t r ≥t min , then the tunnel roof interval layer can maintain self-stability, and the support method only adopts the active support method of anchor cable.

[0023] If t r <t min, the tunnel roof interval layer cannot maintain self-stability. In addition to the active support method of anchor cable support, the passive support method of scaffolding support should also be adopted to strengthen the support.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention further optimizes the support method of the tunnel, changes the current situation that the support and reinforcement design of this type of tunnel has long relied on experience, and based on the principle of material mechanics, uses the maximum span-to-thickness ratio of the roof composite beam as the basis for judging the self-stability of the roof, thereby realizing quantitative judgment of the support method. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A rock column diagram of the present invention;

[0027] Figure 2 This is a simplified mechanical model diagram of the top plate spacing layer of the present invention;

[0028] Figure 3 It is a support mode judgment frame diagram of the present invention. DETAILED DESCRIPTION

[0029] The present invention will be further described below in conjunction with the embodiments.

[0030] The following examples are used to illustrate the present invention, but they cannot be used to limit the scope of protection of the present invention. The conditions in the examples can be further adjusted according to specific conditions. Simple improvements to the method of the present invention under the premise of the concept of the present invention belong to the scope of protection claimed in the present invention.

[0031] Example 1

[0032] A method for determining the support mode of a tunnel with a roof spacing layer under a goaf comprises the following steps:

[0033] Step S1, the average mining height of the upper coal layer is 5.4m, the rock expansion coefficient is 1.25, and the roof subsidence is 1.08m. The thickness of the upper coal roof MZ is calculated to be 17.28m, and Figure 1 Judgment: The upper coal immediate roof is composed of 0.3m mudstone, 5.0m siltstone and 10m medium sandstone. The immediate roof thickness is determined to be 15.3m.

[0034] And through Figure 1 It is judged that the upper coal basic roof is composed of 9m fine sandstone, 1.85m medium sandstone and 2.91m sandy mudstone. The thickness of the upper coal basic roof ME is 13.76m, and the average bulk density of the rock mass is 25kN / m 3 , the thickness of the spacer layer is 5.57m, and then by the formula q=(M Z +ME +M J )×γ, the uniformly distributed load q on the roof of the lower coal tunnel is determined to be 865.75 kN / m 2 .

[0035] Step S2, the lateral pressure coefficient is 1.85, the tensile strength of the lower coal roof is 2.63MPa, through the formula:

[0036] The maximum span-thickness ratio of the composite beam is determined to be 4.75, the width of the lower coal cutting tunnel is 8.2m, and the critical interlayer spacing t to maintain the stability of the composite beam is obtained. min It is 1.73m.

[0037] Step S3: The floor destruction depth of the upper coal goaf is 1.2m. According to the formula: t r =M J -d to obtain the actual undamaged thickness t of the tunnel roof r 4.37m;

[0038] Judgement r ≥t min Therefore, only anchor cable support is used in the tunnel support method.

[0039] Example 2

[0040] A method for determining the support mode of a tunnel with a roof spacing layer under a goaf comprises the following steps:

[0041] Step S1, the average mining height of the upper coal layer is 5.4m, the rock expansion coefficient is 1.25, and the roof subsidence is 1.08m. The thickness of the upper coal roof MZ is calculated to be 17.28m, and Figure 1 Judgment: The upper coal immediate roof is composed of 0.3m mudstone, 5.0m siltstone and 10m medium sandstone. The immediate roof thickness is determined to be 15.3m.

[0042] And through Figure 1 It is judged that the upper coal basic roof is composed of 9m fine sandstone, 1.85m medium sandstone and 2.91m sandy mudstone. The thickness of the upper coal basic roof ME is 13.76m, and the average bulk density of the rock mass is 25kN / m 3 , the thickness of the spacer layer is 5.57m, and then by the formula q=(M Z +M E +M J )×γ, the uniformly distributed load q on the roof of the lower coal tunnel is determined to be 865.75 kN / m 2 .

[0043] Step S2, the lateral pressure coefficient is 1.65, the tensile strength of the lower coal roof is 1.57MPa, through the formula:

[0044] The maximum span-thickness ratio of the composite beam is determined to be 0.81, the width of the lower coal cutting tunnel is 8.2m, and the critical interlayer spacing t to maintain the stability of the composite beam is obtained. min It is 10.12m.

[0045] Step S3: The floor destruction depth of the upper coal goaf is 1.2m. According to the formula: t r =M J -d to obtain the actual undamaged thickness t of the tunnel roof r 4.37m;

[0046] Judgement r <t min , the tunnel roof interval layer cannot maintain self-stability. In addition to active support methods such as anchor cable support, passive support methods such as scaffolding support are also needed to strengthen the support.

[0047] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for determining the support mode of a tunnel with a roof spacer layer under a goaf, characterized in that: The following steps are involved: S1. Determine the thickness of the immediate roof of the upper coal layer, and determine the basic roof composition of the upper coal layer through the rock layer columnar diagram; and calculate the uniformly distributed load on the roof of the lower coal layer; S2. Determine the critical span-thickness ratio of the composite beam of the lower coal roadway roof and obtain the minimum self-stable thickness t of the roadway roof min ; In step S2, the calculation formula for determining the critical span-to-thickness ratio of the roof composite beam of the lower coal roadway is: ； Among them, l is the tunnel span, t is the thickness of the composite beam of the lower coal tunnel roof, σ max is the ultimate tensile strength of the composite beam, q is the uniformly distributed load on the lower coal roof determined in step S1, and λ is the lateral pressure coefficient; And among them, if σ max ≤ λq, at this time, the tunnel roof beam does not meet the tensile failure conditions; S3. Determine the actual undamaged thickness t of the lower coal roof r , and through t r With t min The support method of the interlayer tunnel is determined by comparison; In step S3, the calculation formula for determining the actual undamaged thickness of the lower coal roof is: ； in, is the actual undamaged thickness of the roadway roof, and d is the damaged depth of the upper coal floor; like The tunnel roof interval layer can maintain self-stability, and the support method is only the active support method of anchor cable; like The tunnel roof interlayer cannot maintain self-stability. In addition to the active support method of anchor cable support, the passive support method of scaffolding support should also be adopted to strengthen the support.

2. The method for determining the support mode of a tunnel with a roof spacer layer under a goaf according to claim 1, characterized in that: In step S1, the thickness of the upper coal layer is determined by using a rock layer column chart and a calculation formula, and the calculation formula is: ； Where h is the mining height, S A is the roof subsidence, K A is the rock expansion coefficient; The basic roof structure of the upper coal layer is determined by the rock layer column diagram, and the formula for calculating the uniformly distributed load on the lower coal roof is: ； Where M Z is the thickness of the upper coal roof, M E is the basic top thickness of the upper coal layer, M J is the thickness of the interval rock layer, and γ is the rock bulk density.

Images