A method for quantitative division and quality evaluation of mine engineering geological rock formations

Abstract

The invention discloses a method for quantitative division of mine engineering geological rock groups and quality evaluation thereof, comprising the following steps: S1, performing a primary division of mine engineering geological rock groups according to the genetic type of the rock mass; S2, performing a secondary division of mine engineering geological rock groups according to the stratigraphic structural evolution, sedimentary phase and structural surface; S3, performing a tertiary division of mine engineering geological rock groups according to the curvature of the rock layers under the action of their own weight in combination with the thickness of the rock layers and the basic physical and mechanical properties according to the results of the secondary grouping; S4, taking the hardness and integrity of the rock as indicators for evaluating the mine engineering geological rock groups, and combining the results of the mine engineering geological rock group division, performing an engineering geological rock group quality evaluation. The invention can realize the scientific and reasonable division of mine engineering geological rock groups, and perform rock group quality evaluation, and provide guidance for the establishment of a three-dimensional geometric geological model.

Description

Technical Field

[0001] The invention relates to the technical field of safe mining of coal mines, and in particular to a method for quantitatively dividing engineering geological rock groups in a mine and evaluating their quality. Background Art

[0002] The special mechanical behavior of deep rock mass under mining disturbance conditions is a core scientific problem that needs to be solved urgently in deep resource mining. Under the above complex geological conditions, numerical simulation technology is one of the key means to reveal the mechanism of mine geological disasters. Among them, the establishment of a three-dimensional geometric geological model is the basis of numerical simulation. In the past, when drilling to expose the strata for geological modeling, there were often the following problems:

[0003] 1) When the model grid is densely divided, the excessive number of grids makes the grid combination diversified, the calculation process is complicated and difficult to converge.

[0004] 2) The thickness of the stratum is too small relative to the boundary length of the model, making the grid conical, and the stress distribution calculation results may not accurately reflect the actual situation.

[0005] Therefore, it is extremely important to group the overburden strata according to their natural characteristics and combination characteristics so that each rock group has unique and similar engineering geological properties. Gu Dezheng proposed the concept of "engineering geological rock group" and clarified the three principles for the division of engineering geological rock groups: geological genesis, engineering problems, and the diversity of rock group classification. In recent years, many scholars have divided engineering geological rock groups in engineering fields such as slopes, tunnels, roads, and coal mines from the perspectives of lithology, rock layer thickness, occurrence, structure, and mechanical properties based on rock genesis, occurrence, combination relationship, and properties and laws of primary structural surfaces. However, the previous grouping methods were mainly subjective qualitative divisions, and the actual geomechanical characteristics were not fully considered. Summary of the invention

[0006] Purpose of the invention: The purpose of the present invention is to provide a method for quantitative division of engineering geological rock groups in mines and their quality evaluation. On the basis of the division of engineering geological rock groups, a rock group quality evaluation method is supplemented, providing a geological data basis and basis for the prevention and control of geological disasters in mines.

[0007] Technical solution: A method for quantitative division of mine engineering geological rock groups and its quality evaluation, including the following steps:

[0008] S1, the first-level division of mine engineering geological rock groups is carried out according to the genetic type of the rock mass;

[0009] S2, based on stratigraphic structural evolution, sedimentary facies and structural planes, the first-level grouping is divided into the second-level division of mine engineering geological rock groups;

[0010] S3, based on the secondary grouping results, combined with the rock layer thickness and basic physical and mechanical properties, the mine engineering geological rock group is divided into three levels according to the curvature of the rock layer under the action of its own weight;

[0011] S4, using rock hardness and rock integrity as indicators for evaluating mine engineering geological rock formations, combined with the results of mine engineering geological rock formation division, conduct engineering geological rock formation quality assessment.

[0012] Furthermore, in step S3, assuming that the interaction between the strata within the secondary grouping is not considered, the curvature under the action of deadweight reflects the ability and properties of each stratum to resist deformation; for strata in adjacent layers, if the curvature of the lower stratum is smaller than the curvature of the upper stratum under deadweight conditions, it indicates that the two strata deform synergistically, and the adjacent strata are divided into the same rock group.

[0013] Furthermore, the curvature of the rock layer under its own weight is calculated as follows:

[0014]

[0015] In the formula, C i is the curvature of the i-th rock layer; m i is the thickness of the i-th rock layer, in m; l is the length of the rock layer, in m; γ i is the bulk density of the i-th layer of rock, in kN·m -3 ; E i is the elastic modulus of the i-th rock layer, in GPa; i = 1, 2, ..., n, where n is the total number of inner rock layers in the roof overburden rock group.

[0016] Further, in step S4, the weighted arithmetic mean method is used to comprehensively calculate the quality of the overburden rock formation:

[0017]

[0018] Where BQ represents the quantitative index of rock mass quality of each rock layer; BQ (r) is the BQ value of the roof overburden rock group with a thickness of r meters; r is the thickness of the roof overburden rock group for comprehensive evaluation, in m; BQ i is the BQ value of the i-th rock layer in the roof overburden rock group; n is the total number of inner rock layers in the roof overburden rock group, in layers.

[0019] Compared with the prior art, the present invention has the following significant effects:

[0020] 1. The present invention divides engineering geological rock groups by combining qualitative and quantitative methods, fully considers the actual geomechanical characteristics, greatly reduces the subjectivity of the original technology, and provides a more scientific and accurate method for dividing engineering geological rock groups; on the basis of engineering geological rock group division, it supplements the rock group quality evaluation method, and provides a geological data basis and basis for the prevention and control of mine geological disasters;

[0021] 2. By achieving scientific and reasonable division of mine engineering geological rock groups and conducting rock group quality evaluation, guidance is provided for the establishment of three-dimensional geometric geological models, important theoretical support is provided for transparent mine construction, and the goal of green, safe and efficient production of mines is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a flow chart of the present invention;

[0023] Figure 2 Schematic diagram of rock formation stress and deformation. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0025] According to the special engineering geological conditions and characteristics of the overburden of the mine under mining conditions, based on geology and rock mechanics, the present invention proposes a three-level classification method for the engineering geological rock formation of the mine, such as Figure 1 As shown, the steps include:

[0026] Step 1: Carry out the primary division of mine engineering geological rock groups according to the genetic type of rock mass.

[0027] Among them, rock genesis types are divided into three types: igneous rock, sedimentary rock and metamorphic rock. Since the material composition, structure and texture of rock masses of different genesis types are significantly different, the rock genesis type can be determined through the lithology of the core revealed by drilling, and the rock genesis type can be grouped into different types.

[0028] Step 2: According to the conditions of stratigraphic structural evolution, sedimentary phase, structural surface, etc., the first-level grouping results are divided into the second-level division of mine engineering geological rock groups. Among them, the stratigraphic structural evolution affects the uplift and compression of the plate, making the rock mass structure, structure and fracture joint direction in different tectonic evolution histories different. Therefore, the structural stage has a significant effect on the boundary between strata. The sedimentary phase reflects the paleogeographic environment during the diagenesis period. The rock masses of different sedimentary phases have different cementation degrees, cements and particle components. The structural surface is the product of diagenesis in the geological sedimentary process, which is generally divided into conformity surface and unconformity surface. Among them, the physical and mechanical properties of the rock mass above and below the unconformity surface are different, which affects the movement and deformation of the rock strata. Based on this, the regional geological data are investigated to understand the regional sedimentary evolution and tectonic evolution history, and the unconformity surface, structural stage and sedimentary phase between strata are used as indicators for the second-level division of engineering geological rock groups, and the second-level grouping is carried out.

[0029] The above secondary division results have divided the strata according to the differences in their geological properties. In the secondary grouping results, the differences in the mechanical properties of the strata will also lead to differences in the deformation of the strata.

[0030] Step 3: Based on the results of the secondary grouping of overburden, combined with the thickness of the rock layer and the basic physical and mechanical properties, assuming that the interaction between the layers within the secondary grouping is not considered, the curvature under the action of deadweight reflects the ability and properties of each rock layer to resist deformation. For adjacent layers, if the curvature of the lower rock layer is less than the curvature of the upper rock layer under deadweight conditions, it indicates that the two rock layers deform synergistically, and the adjacent rock layers can be divided into the same rock group, thereby performing a three-level division of the mine engineering geological rock group. The curvature calculation process is as follows:

[0031] Assume that there are n layers of rock overlying the coal seam in the study area, and the length of each rock layer is l and the width is b. Figure 2 .

[0032] When the i-th rock layer is under the action of its own weight, the rock layer is subjected to a uniformly distributed load q i for:

[0033] q i =γ i m i (1)

[0034] According to Hooke's law, the bending moment M on the middle section of the rock layer is i and moment of inertia I i The expression is:

[0035]

[0036]

[0037] According to the theory of elasticity, the rock curvature Ci for:

[0038]

[0039] Assuming that the interaction between the strata is not considered, the curvature generated only under the action of each heavy load is:

[0040]

[0041] Where i = 1, 2, ..., n, n is the total number of rock layers in the mine engineering geological rock group, in units of layers; where: C i is the curvature of the i-th rock layer, dimensionless; m i is the thickness of the i-th rock layer, in m; l is the length of the rock layer, in m; γ i is the bulk density of the i-th layer of rock, in kN·m -3 ; E i is the elastic modulus of the ith rock layer, in GPa.

[0042] Step 4: Based on the division of the mine engineering geological rock group in step 3, the quality of each mine engineering geological rock group is evaluated, and the rock hardness and rock integrity are used as indicators for the evaluation of the mine engineering geological rock group. Since each mine engineering geological rock group has multiple layers of strata, the weighted arithmetic average method is used to comprehensively calculate the rock mass quality of the mine engineering geological rock group:

[0043]

[0044] Where BQ represents the quantitative index of rock mass quality of each rock layer; BQ (r) BQ is the quality value of the mine engineering geological rock formation with a thickness of r meters, dimensionless; r is the thickness of the mine engineering geological rock formation, in m; BQ i is the BQ value of the i-th rock layer in the mine engineering geological rock formation, dimensionless; n is the total number of rock layers in the mine engineering geological rock formation, in layers.

[0045] The quality classification and stability evaluation of rock mass at each stage of engineering construction can provide important engineering geological guarantees. Furthermore, the specific calculation process is as follows:

[0046] Rock hardness is one of the most basic properties of rock mass in engineering, which is related to the rock mineral structure, composition, inter-particle bonding and water softening properties. Commonly used quantitative indicators include: scratch hardness, point load index, saturated uniaxial compressive strength of rock, etc. Among them, the saturated uniaxial compressive strength of rock (R CW ) is highly representative and can reflect the nature of rock softening by water. It is widely used in rock quality classification. The rock hardness classification standards are shown in Table 1.

[0047] Table 1 Rock mass hardness classification standards

[0048]

[0049] There are many types of quantitative indicators of rock integrity used at home and abroad, and the most commonly used is the rock volume joint number (J v ), average spacing between joints, density, rock quality index (RQD), rock cracking coefficient, rock integrity coefficient (K v ) etc. RQD is easy to obtain in the underground engineering survey stage of coal mines, but using only RQD to reflect the integrity of rocks has obvious disadvantages, ignoring the variability and hierarchy of the stratum spatial structure, and often lacks accuracy and sensitivity. Compared with the rock quality index (RQD) with a single threshold, RBI is more accurate than RQD in reflecting the characteristics of rock integrity. The rock mass block index RBI is calculated as follows:

[0050] RBI=3*C r3 +10*C r10 +30*C r30 +50*C r50 +100*C r100 (7)

[0051] Where: 3, 10, 30, 50, 100 are constants, C r3 , C r10 , C r30 , C r50 , C r100 The core lengths are 3-10 cm, 10-30 cm, 30-50 cm, 50-100 cm and greater than 100 cm, expressed as percentages. v There is a good correlation with RBI, showing the consistency of rock mass integrity. v The corresponding RBI critical value can be calculated based on the classification value, see Table 2.

[0052] Table 2 Rock mass integrity and RBI corresponding standards

[0053]

[0054] Among them, K v The K corresponding to each rock layer can be determined according to the RBI in Table 2. v Value, then the quantitative index BQ value of rock mass quality of each rock layer in the mine engineering geological rock group is calculated as follows:

[0055] BQ=90+3R cw +250K v (8)

[0056] Furthermore, based on the calculation results of the rock mass quality of the mine engineering geological rock group in formula (6), the rock mass quality classification of the rock group can be shown in Table 3.

[0057] Table 3 Rock mass quality classification of mine engineering geological rock groups

[0058]

[0059] In Table 3, the basic rock mass quality classification corresponds to five levels, and the rock mass quality evaluation conclusions of each level are respectively Level I-excellent; Level II-good; Level III-good; Level IV-medium; Level V-poor. Among them, the rock mass quality evaluation results of the mine engineering geological rock group can be used for underground mining engineering design, layout and mine geological disaster prevention and control. For example: the better the rock mass quality of the mine engineering geological rock group, the easier it is to accumulate higher elastic energy and induce strong mine earthquakes and other mine engineering geological dynamic disasters; the worse the rock mass quality of the mine engineering geological rock group, the more difficult it is to support.

[0060] A mine in Ordos Basin was selected as the research area to carry out quantitative division of mine engineering geological rock formations and its quality evaluation.

[0061] Step A1, through the drilling geological exposure in the study area, it can be known that the strata in the study area are from old to new: Hujiacun Formation (T3h) of the Upper Triassic, Fuxian Formation (J1f) of the Lower Jurassic, Yan'an Formation (J2y), Zhiluo Formation (J2z), Anding Formation (J2a), Yijun Formation (K1y) and Luohe Formation (K1l) of the Lower Cretaceous, Neogene (N) and Quaternary (Q). Therefore, the top cover rocks in the study area are all sedimentary rocks, and no metamorphic rocks and igneous rocks are found. Based on this, the first-level rock formations in the study area are all sedimentary rock formations.

[0062] Step A2, by consulting the relevant literature in the study area, the literature shows that in the Middle Jurassic, the parallel unconformity between the Zhiluo Formation and the Yan'an Formation represented the end of the Indosinian Movement, and the Late Yanshan Movement at the end of the Early Cretaceous caused the Lower Cretaceous to suffer varying degrees of denudation. Therefore, the secondary division of the mine engineering geological rock formation in the study area is: the Middle Jurassic Yan'an Formation, the Zhiluo-Anding Formation, and the Early Cretaceous Yijun-Luohe-Huachi Formation.

[0063] Step A3, according to the actual engineering layout of the study area, taking a coring ZU-1 borehole as an example, the thickness of each rock layer is obtained by coring, and the core acquisition rate of core lengths of 3-10 cm, 10-30 cm, 30-50 cm, 50-100 cm and greater than 100 cm is counted. The saturated compressive strength, density and elastic modulus of the rock are obtained through indoor experiments. Assuming that the length of each rock layer is 100 m, the curvature of the overburden within 200 m of the top plate is calculated. Based on the results of the first-level and second-level divisions, combined with the third-level division standards, the calculation of the third-level division of the overburden in the study area is shown in Table 4.

[0064] Table 4 Calculation table of three-level division of overburden in ZU-1 hole in the study area

[0065]

[0066] Taking ZU-1 hole as an example, based on the basic data of the drill core and the test results of basic physical and mechanical indicators, the RBI of each rock layer is calculated and the rock mass integrity K is converted. v The comprehensive evaluation of the rock mass quality of the overburden rock group is shown in Table 5.

[0067] Table 5 Comprehensive evaluation of rock mass quality of ZU-1 hole overburden rock group

[0068]

[0069] According to the results of the basic rock mass quality classification, the BQ value of the sandstone rock layer in the overlying rock layer on the roof is relatively high. Among them, the rock layers within 100m of the roof are mainly distributed in the Yan'an Group and the Zhiluo-Anding Group. In particular, the fine sandstone of the Yan'an Group and the fine sandstone of the Zhiluo-Anding Group have high uniaxial compressive strength, relatively high RBI, relatively complete cores, and the rock mass quality evaluation is grade II (good). During mining, a large amount of elastic energy can be accumulated, which is easy to induce high-energy mine earthquakes.

Claims

1. A method for quantitative division of mine engineering geological rock formations and its quality evaluation, characterized in that: The steps are: S1, the first-level division of mine engineering geological rock groups is carried out according to the genetic type of the rock mass; S2, based on the stratigraphic structural evolution, sedimentary facies and structural surface, the first-level grouping is divided into the second-level division of the mine engineering geological rock group; the structural surface is the product of the diagenesis of the geological sedimentary process, which is divided into two types: conformity surface and unconformity surface. The physical and mechanical properties of the rock mass above and below the unconformity surface are different, which affects the movement and deformation of the rock strata; S3, based on the secondary grouping results, combined with the rock layer thickness and basic physical and mechanical properties, the mine engineering geological rock group is divided into three levels according to the curvature of the rock layer under the action of its own weight, and the mine engineering geological rock group three-level division results are obtained; S4, taking rock hardness and rock integrity as the evaluation index of mine engineering geological rock formation, combined with the three-level classification results of mine engineering geological rock formation, the quality assessment of engineering geological rock formation is carried out; the weighted arithmetic average method is used to comprehensively calculate the rock mass quality of mine engineering geological rock formation: Where BQ represents the quantitative index of rock mass quality of each rock layer; BQ (r) is the BQ value of the mine engineering geological rock formation with a thickness of r meters; r is the thickness of the mine engineering geological rock formation, m; BQ i is the BQ value of the i-th rock layer in the mine engineering geological rock group; n is the total number of rock layers in the mine engineering geological rock group; m i is the thickness of the i-th rock layer, in meters.

2. The method for quantitative division of mine engineering geological rock formations and its quality evaluation according to claim 1 is characterized in that: In step S3, assuming that the interaction between the strata within the secondary grouping is not considered, the curvature under the action of deadweight reflects the ability and properties of each stratum to resist deformation; for strata in adjacent layers, if the curvature of the lower stratum is smaller than the curvature of the upper stratum under deadweight conditions, it indicates that the two strata deform synergistically, and the adjacent strata are divided into the same rock group.

3. The method for quantitative classification of mine engineering geological rock formations and its quality evaluation according to claim 1 is characterized in that: The formula for calculating the curvature of rock formation under its own weight is as follows: In the formula, C i is the curvature of the i-th rock layer; m i is the thickness of the i-th rock layer, in m; l is the length of the rock layer, in meters; γ i is the bulk density of the i-th layer of rock, in kN·m -3 ; E i is the elastic modulus of the i-th rock layer, in GPa; i = 1, 2, ..., n, where n is the total number of rock layers in the mine engineering geological rock group.

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