A stability judgment and optimization method for roof-pillar support structure in extended mining

Abstract

The present invention discloses a method for distinguishing and optimizing the stability of a roof-pillar support structure for extended mining. The present invention discretizes the supporting structure of a goaf group according to the situation, obtains the displacement, tensile stress value, safety factor of the roof of the goaf group and the displacement, load value, and safety factor of the pillars based on the displacement continuity of the roof and the pillars and the load transfer conditions through the superposition principle, and then distinguishes the stability of the roof-pillar support structure of the goaf group, and then quantitatively optimizes the extended mining structural parameters, prevents the extended mining from causing instability of the upper goaf group, and realizes the control of the stability of the roof-pillar support structure of the goaf group by the open field method extended mining, and realizes the safe, efficient, and intelligent mining of resources. The method provided by the present invention is also applicable to mine mining design and intelligent safety control of goafs, and has wide universality.

Description

Technical Field

[0001] The present invention relates to the field of intelligent technology of underground mining data, and in particular to a method for judging and optimizing the stability of a roof-pillar support structure in extended mining. Background Art

[0002] At present, more than 50% of metal and non-metal mines adopt open-site mining, especially for ore bodies with thicker ore bodies, which often adopt layered multi-section continuous recovery. After recovery, a multi-section continuous multi-span goaf group is formed. The reserved roof and pillars are used as the support structure of the goaf to maintain the stability of the goaf group. Limited by the exploration of mine resource reserves, mines often adopt the method of mining and exploration in the process of mineral resource mining. Therefore, the mining depth of the mining right of the mine is related to the burial depth of resource reserve exploration. This leads to the fact that when the mine is designed for mining, it is often only for the recovery of the current mining right mining depth, while ignoring the possible extension of mining in the future.

[0003] However, as the resources in the current mining rights are exhausted, mining companies often choose extended mining in order to continue to expand resource mining, which requires extended mining design. At present, when designing extended mining, most design units either use the upper mining parameters or increase the structural parameters of the extended mining roof and pillars to improve their stability. They not only fail to judge the stability of the upper goaf group, but also ignore the impact of extended mining on the stability of the upper goaf group, which may bring serious safety hazards to extended mining and cause the problem of reduced resource mining rate.

[0004] In the actual mining process of the project, as the mining is extended, the number of roofs and pillars in the goaf group increases, and their displacement and stress distribution have quasi-static changes. The unreasonable layout of the roof and pillar parameters may lead to low resource recovery rate and waste of resources on the one hand, and on the other hand, it is very easy to cause the unfavorable development of displacement and stress of the supporting structure, which reduces the safe mining space and even induces structural instability of the goaf group and cascading damage and collapse. Therefore, in the process of multi-stage open field mining, especially in the case of extended mining, it is an actual engineering problem that needs to be solved in the field of underground mining technology to judge the stability of the goaf group before and after the extended mining, and then take necessary safety prevention and control measures and optimize the structural parameters to prevent the safety risks that may be brought about by the extended mining and improve the recovery rate of mineral resources.

[0005] The stability of the goaf roof and pillar support structure has always been one of the hot issues in the mining industry. It mainly focuses on the single structure of the goaf roof or pillar, and the methods used include theoretical calculation, numerical simulation, similar model experiment, etc. However, the collaborative bearing relationship between the goaf roof and the pillar is rarely considered, especially in the multi-mid-section open field mining method, and only a few have been discussed through numerical simulation calculation methods. The numerical simulation calculation method first needs to perform numerical simulation modeling on the goaf group, import the model into the numerical calculation software for calculation, and analyze the displacement, stress, plastic zone and other results of the simulation calculation to determine the stability of the goaf group. The entire process of numerical modeling, calculation analysis, and stability judgment is very cumbersome, and when any structural parameter of the goaf roof or pillar is changed, a new numerical model needs to be re-established and recalculated and analyzed. At the same time, as the model volume increases, the calculation time will increase exponentially. Each calculation requires the storage of huge calculation data, which is not conducive to the comparative analysis of the calculation results and the optimization of extended mining structure parameters.

[0006] Since the roof and pillars are the main supporting structures of the goaf group, the rationality of the layout of their supporting structures directly affects the stability of the goaf group. For example, the patent document (CN 113094905 B) discloses a calculation method and system for key points of support in multiple middle-section continuous goafs, and proposes a calculation method for the position of key support points in continuous goafs based on the principle of minimum deformation energy, taking into account the relationship between the position of the support points and the inclination angle of the goaf. However, the multiple middle-sections described in the invention are layered mining of inclined ore bodies, and their goafs are distributed along the strike of the ore bodies. In fact, they belong to single-middle-section goafs distributed along the strike of the ore bodies. In the calculation process, the transferability of the load between the roof and the pillars is not considered, and the stability judgment of the goaf support structure is not considered. The position of the key support points is judged only by the minimum deformation energy. The calculation method is not suitable for multi-middle-section mining of medium-thick ore bodies. The patent document (CN 118395693 A) discloses a method, device and medium for constructing a roof-pillar mechanical model. Based on the roof-pillar rheological differential equation, the stabilization time of the roof-pillar support system is output. In the process of solving the control equation, this method unifies the supporting effect of the pillars on the roof, and does not consider the supporting effect of the differences in the distribution of the pillars on the roof. In the process of judging the stability of the goaf, the stability of the roof and pillar unit support structure cannot be taken into account.

[0007] In summary, under the conditions of multi-section extension mining, considering the coordinated bearing effect of roof and pillars, as well as the displacement continuity and load transfer between the middle sections, there is currently no definite theoretical basis and method for judging and optimizing the stability of the roof-pillar supporting structure of the goaf group.

[0008] Based on the above analysis, the prior art has the following problems and defects:

[0009] (1) The entire process of numerical simulation modeling, calculation analysis, and stability judgment in existing numerical simulation calculations is very cumbersome, time-consuming, and the amount of result data information is redundant. The result comparison and stability judgment are not intuitive enough, which is not conducive to the optimization of extended mining structure parameters and is not universal.

[0010] (2) In the existing technical methods, when judging the stability of the roof-pillar support structure, the supporting effect of the pillars on the roof is unified, and the supporting effect of the pillars on the roof is not considered. It is impossible to judge the stability of the roof and pillar unit support structure.

[0011] (3) Existing technical methods do not take into account the coordinated bearing effect of the roof and pillars, as well as the displacement continuity and load transfer between the middle sections. They do not achieve true optimization of the multi-middle section mining structure parameters. There is currently no definite theoretical basis and method for determining and optimizing the stability of the roof and pillar support structure of a multi-middle section goaf group under extended mining conditions.

[0012] In view of the above problems and defects, a method suitable for the stability judgment and optimization of the roof-pillar support structure of the goaf group in multiple middle-section extended mining is urgently needed, in order to replace the existing numerical simulation calculation process, which is cumbersome, time-consuming, has a lot of data information, and the result comparison machine stability judgment is not intuitive and has low universality. However, there is currently a lack of theoretical basis for the stability judgment and optimization of the roof-pillar support structure of the goaf group in multiple middle-section extended mining. The mechanical model of the goaf group bearing structure system under the coordinated bearing of the roof-pillar support structure has not been established, and the influence of extended mining on the stability of the upper goaf group support structure has not been considered, making the corresponding theoretical calculation method incompatible with actual engineering. Summary of the invention

[0013] The purpose of the present invention is to provide a method for distinguishing and optimizing the stability of the roof-pillar support structure of extended mining. In view of the actual situation of underground mining engineering of metal and non-metal mines, a structural system mechanical model under the condition of self-weight load of overburden in multiple middle sections of goaf groups is established, and the stress conditions and boundary conditions of the structural system mechanical model are systematically analyzed. At the same time, the coordinated bearing effect between the roof and the pillar support structure is considered, and the displacement and stress expressions of the roof and pillar of the goaf group are calculated. The correlation between the parameters of the roof and pillar support structure of the goaf group and the number of mining middle sections is quantitatively analyzed. According to the rock strength theory, the stability of the goaf group support structure before and after extended mining is determined, and then the parameters of the roof-pillar support structure of extended mining are optimized, providing a theoretical basis and method for the stability control of the goaf group of extended mining by the metal and non-metal underground open field method and the optimization of the extended mining structure parameters.

[0014] The present invention takes into account the key factors that affect the results, such as rock mass load, roof thickness-span ratio, pillar width-to-height ratio, and number of mining sections. The coordinated bearing effect of the roof and pillar support structures is taken into account in the construction of the mechanical model, so that the mechanical model construction and calculation results are more consistent with the actual engineering conditions of underground mining. At the same time, a method and basis for distinguishing the stability of goaf groups are proposed, and the stability of goaf groups is distinguished before and after extended mining of the mine, respectively, to prevent the safety risks that may be caused by extended mining, and to improve the recovery rate of mineral resources by optimizing the extended mining structural parameters. This method has the potential to replace the cumbersomeness of the numerical simulation calculation process, the unintuitiveness of the result comparison, the complexity and non-universality of the stability judgment, and supplements and improves the vacancies of the stability judgment of the goaf group support structure before and after extended mining and the optimization of the extended mining structural parameters, which is of reference significance for the safety prevention and control of extended mining of underground open field method and efficient resource mining.

[0015] The purpose of the present invention is achieved by at least one of the following technical solutions.

[0016] A method for determining and optimizing the stability of an extended mining roof-pillar support structure comprises the following steps:

[0017] Step 1: Based on the existing upper goaf group before extended mining, a mechanical model of the roof-pillar support structure system of the upper goaf group is constructed;

[0018] Step 2, obtaining the boundary conditions of the mechanical model of the upper goaf group roof-pillar support structure system described in step 1, substituting the boundary conditions into the displacement and stress expressions of the goaf group roof-pillar support structure, and then obtaining the displacement, tensile stress value and safety factor of the roof, and the displacement, load and safety factor of the pillar;

[0019] Step 3: According to the displacement, tensile stress value and safety factor of the roof, displacement, load and safety factor of the pillars calculated in step 2, the stability of the roof-pillar support structure of the upper goaf group is judged;

[0020] Step 4: Based on the analysis of the stability judgment results of the roof-pillar support structure of the upper goaf group in step 3, preliminarily determine the mining parameters under extended mining, construct a mechanical model of the roof-pillar support structure system of the goaf group after extended mining, judge the stability of the roof-pillar support structure of the goaf group after extended mining, and further optimize the mining parameters under extended mining.

[0021] Furthermore, in step 1, the mining parameters of the roof and pillars of the upper goaf group are obtained, and the mining parameters include the number of middle sections in the goaf group, the thickness of the roof, the span of the goaf (roof span), the width of the pillars, the height of the pillars, and the total span of the goaf, and a mechanical model of the roof-pillar support structure system of the upper goaf group is constructed, as follows:

[0022] In mining, after the ore body is mined, the goaf support structure is formed by reserving the roof and pillars to form a goaf group, providing a safe space for mining; the mechanical model of the roof-pillar support structure system of the goaf group includes the roof, pillars, and unmined ore body. The roof includes the overburden roof and the middle roof. The overburden roof is the roof that directly bears the overburden load, and the middle roof is the roof of the goaf above; the goaf group includes from top to bottom Each middle section includes Top plates, each mid section includes Mineral pillars;

[0023] In the mechanical model of the roof-pillar support structure system of the goaf group, the overburden roof is the direct bearing structure of the overburden load of the goaf group, and the pillar is the direct supporting structure of the roof. The overburden roof and the middle section roof are rigidly connected to the surrounding rock, and the overburden roof and the middle section roof are semi-rigidly connected to the pillar, which jointly maintain the stability of the goaf group.

[0024] According to the actual engineering situation, the load of the overburden roof includes the vertical load of the overburden and the horizontal ground stress load. The horizontal ground stress load is much smaller than the vertical load of the overburden and can be ignored. The vertical load of the overburden and its own weight are the main loads affecting the stability of the roof. For thick and large ore bodies, it is often necessary to mine in multiple layers and sections. With the increase of mining depth and the number of mining sections, the loads of the overburden roof, the middle section roof and the pillars change. The load of the overburden roof includes the self-weight of the soil and rock mass above the overburden roof and the overburden roof. The load of the middle section roof includes the self-weight of the middle section roof and the crushed stone and mechanical equipment loads accumulated on the middle section roof. As the direct supporting structure of the roof, the load of the pillar comes from the load transferred by the roof.

[0025] According to the stress condition of the roof of the goaf group, the roof load is a uniformly distributed load, Indicates the number of goaf groups from top to bottom. The middle section The load on the top plate, The value is 1, 2, 3, ... , The value is 1, 2, 3, ... , Indicates the number of middle sections of the goaf group, Indicates the number of roofs in each middle section of the goaf group. When The corresponding time is the first time from top to bottom in the goaf group. - The middle section top plate of the middle section is as follows:

[0026] ;

[0027] in, is the average bulk density of the overburden, is the average bulk density of the top plate, in kN / m 3 ; is the thickness of the overburden, in m; is the load of crushed stone and mechanical equipment accumulated on the middle top plate, in kN / m; For the The middle section The thickness of the top plate, in m;

[0028] In the process of underground open-pit strip mining, the length of the goaf is much larger than the span of the goaf. The top plate of the goaf is a plate with length and width. In order to simplify the calculation process, the plate structure is calculated using unit width. At this time, the top plate along the direction perpendicular to the goaf can be regarded as a rock beam.

[0029] Furthermore, step 2 includes the following steps:

[0030] Step 2.1, obtaining the boundary conditions of the mechanical model of the roof-pillar support structure system of the upper goaf group;

[0031] Step 2.2, discretize the mechanical model of the roof-pillar support structure system to obtain multiple unit structure models;

[0032] Step 2.3, construct a calculation unit structure expression of the mechanical model of the roof-pillar support structure system according to the unit structure model;

[0033] Step 2.4: According to the boundary conditions, substitute the calculation unit structure expression to obtain the displacement, tensile stress value and safety factor of the roof in the upper goaf group, and the displacement, load and safety factor of the pillars.

[0034] Furthermore, in step 2.1, the boundary conditions of the mechanical model of the roof-pillar support structure system of the upper goaf group are obtained, as follows:

[0035] ;

[0036] in, The goaf group is from top to bottom The displacement of the left end of the first top plate from left to right in the middle section;

[0037] The goaf group is from top to bottom From left to right The displacement of the pillars;

[0038] The mined-out area is from top to bottom From left to right The displacement of the right end of the top plate;

[0039] The goaf group is from top to bottom The corner at the left end of the first top plate from left to right in the middle section;

[0040] The goaf group is from top to bottom From left to right The corner of the pillar;

[0041] The goaf group is from top to bottom From left to right The corner at the right end of the top plate; The value is 1, 2, ... , The value is 1, 2, ... .

[0042] Furthermore, in step 2.2, the mechanical model of the roof-pillar support structure system of the upper goaf group is discretized as follows:

[0043] Considering the characteristics of displacement continuity and load transferability between the roof, pillars and surrounding rock structures, the mechanical model of the roof-pillar support structure system of the upper goaf group is discretized based on the discretization principle. According to the number of middle sections of the upper goaf group, the mechanical model of the roof-pillar support structure system of the goaf group is discretized into Unit structure model, The unit structure model includes the in the middle A top plate, supporting the top plate The pillars and the goaf below the roof. The pillars are the direct supporting structure of the roof. The right end of each roof plate is rigidly connected to the surrounding rock, and the roof plates are semi-rigidly connected to the mine pillars.

[0044] Furthermore, in step 2.3, the calculation unit structure expression of the mechanical model of the roof-pillar support structure system of the upper goaf group after discretization is constructed, which is as follows:

[0045] Take the unit structure model in step 2.2 as the calculation unit structure, and In the middle section, the expression for calculating the rotation angle and displacement of the unit structure is established as follows:

[0046] ;

[0047] Among them, the The left end of the first roof in the middle section is the coordinate origin, and the direction along the vertical goaf is x Axis (the vertical goaf direction refers to the direction from the leftmost end of the roof to the rightmost end), along the vertical upward direction is y Axis (the vertical upward refers to vertical top plate from bottom to top), establish a rectangular coordinate system; For along x The distance from the origin of the coordinate system in the axis direction, in m; The goaf group is from top to bottom The elastic modulus of the top plate of the middle section, in Pa; is the width of the top plate, in m; The goaf group is from top to bottom The thickness of the top plate in the middle section, ,in The goaf group is from top to bottom From left to right The thickness of the top plate, in m; The goaf group is from top to bottom The middle corner; The goaf group is from top to bottom The displacement of the middle section; The goaf group is from top to bottom The bending moment at the left end of the first top plate from left to right in the middle section; The goaf group is from top to bottom From left to right Bending moment at the connection between the pillar and the roof; The goaf group is from top to bottom The left end support force of the first top plate from left to right in the middle section; The goaf group is from top to bottom From left to right The supporting force (load) of each pillar; The goaf group is from top to bottom From left to right The distance from the first pillar to the left end of the first roof; The goaf group is from top to bottom The top plate load in the middle section, ; The goaf group is from top to bottom - 1 middle section passed to the The middle section The load of the pillars, = ;

[0048] The load of the calculation unit structure in the vertical direction satisfies the following formula:

[0049] ;

[0050] in, The goaf group is from top to bottom The total span of the goaf in the middle section, in m;

[0051] Substitute the rotation angle, displacement, and load boundary conditions shown in equations (1) and (2) into equation (3) and combine equation (4) to obtain The fixed end support force and fixed end bending moment of the middle section, the fixed end support force refers to the left end support force of the first top plate of the middle section and the The right end support force of the top plate, the fixed end bending moment refers to the left end bending moment of the first top plate in the middle section and the The bending moment at the right end of the top plate;

[0052] No. The left end support force of the first top plate in the middle section and The right end support force of the top plate , as follows:

[0053] ;

[0054] No. The bending moment at the left end of the first top plate in the middle section and The bending moment at the right end of the top plate , as follows:

[0055] ;

[0056] At this time, the displacement and load of the pillar are still unknown variables; according to the stress-strain constitutive model of rock uniaxial compressive strength and the Weibull distribution model, the displacement-load relationship of the pillar satisfies the following formula:

[0057] ;

[0058] in, The goaf group is from top to bottom From left to right The width of a pillar, in m; The goaf group is from top to bottom From left to right The length of a pillar, in m; is the peak displacement of the pillar, in m; The goaf group is from top to bottom From left to right The height of a pillar, in m; is the rock mass shape index; is a natural constant;

[0059] The relationship between the roof and the pillar nodes satisfies the following formula:

[0060] ;

[0061] By combining equations (1) to (8), we can further obtain the bending moment at the connection between the pillar and the roof in the calculation unit structure, the load of the pillar, and the displacement of the pillar.

[0062] Furthermore, in step 2.4, according to the boundary conditions, the calculation unit structure expression is substituted to obtain the displacement, tensile stress value and safety factor of the roof in the upper goaf group, and the displacement, load and safety factor of the pillar, as follows:

[0063] According to the discretization principle, the number of mining sections is The load of any pillar in the goaf group is , respectively, into formula (7), and the final displacement of any pillar in the goaf group is obtained , It means that after superposition, the goaf group is From left to right The final displacement of the pillars;

[0064] According to formula (7), when When the ultimate bearing capacity of any pillar in the goaf group is obtained, the safety factor of any pillar in the goaf group can be obtained from the relationship between the pillar load and its ultimate bearing capacity. for:

[0065] ;

[0066] The final displacement of any pillar in the goaf group , combined with the boundary conditions in step 2.1, and substituted into equation (3), the final displacement expression of the roof of any middle section in the goaf group is obtained: , It means that after superposition, the goaf group is From left to right in the middle section, No. 1 to The final displacement expression of the top plate is:

[0067] ;

[0068] Goaf group from top to bottom From left to right in the middle section, No. 1 to The top plate x Tensile stress in the axial direction The expression is:

[0069] ;

[0070] Safety factor of any roof of goaf group for:

[0071] ;

[0072] in, is the tensile strength of rock mass, in MPa; The goaf group is from top to bottom From left to right in the middle The maximum tensile stress value of the top plate can be obtained by formula (11) in MPa.

[0073] Furthermore, in step 3, the physical and mechanical parameters of the mine rock mass, including tensile strength, compressive strength, elastic modulus, and rock mass bulk density, are obtained through rock mass mechanics experiments. According to the displacement and tensile stress values ​​of the goaf group roof obtained in step 2, as well as the displacement, load value, and safety factor of the pillars, the stability of the goaf group roof-pillar support structure is judged, as follows:

[0074] When the tensile stress value of the roof is greater than the tensile strength of the rock mass, the roof is in an unstable state; when the load of the pillar is greater than its ultimate bearing capacity, the pillar is in an unstable state.

[0075] Furthermore, in step 4, the extended mining roof-pillar support structure parameter optimization and control includes:

[0076] S1. According to the stability determination result of the roof-pillar support structure of the upper goaf group in step S3, combined with the "Safety Risk Grading Standard for Goafs in Metal and Non-metal Mines" and the "Safety Regulations for Metal and Non-metal Mines", the ratio of the tensile strength of the rock mass to the tensile stress value of the roof and the safety factor of the pillar are used for determination. When the ratio of the tensile strength of the rock mass to the tensile stress value of the roof is less than 1.6, the roof can be regarded as a weak unit; when the safety factor of the pillar is less than 1.5, the pillar can be regarded as a weak unit; and then the weak units in the roof and the pillar are marked and focused on;

[0077] S2. According to the scope of the mining right of the mine and the extended mining depth, with reference to the mining parameters of the roof of the upper goaf group and the pillars or the actual situation of the goaf, the mining parameters under extended mining are preliminarily determined, wherein the mining parameters under extended mining include the number of middle sections under extended mining, the thickness of the roof under extended mining, the span of the goaf under extended mining, the width of the pillars under extended mining, the height of the pillars under extended mining, and the total span of the goaf under extended mining;

[0078] S3. Referring to the constructed mechanical model of the roof-pillar support structure system of the upper goaf group, according to the mining parameters under extended mining, construct a mechanical model of the roof-pillar support structure system of the goaf group after extended mining, and solve the displacement, tensile stress value and safety factor of the roof of the goaf group after extended mining, as well as the displacement, load and safety factor of the pillars, to judge the stability of the roof-pillar support structure of the goaf group after extended mining;

[0079] S4, based on the parameters of the roof-pillar support structure of the upper goaf group being predetermined values ​​and the stability of the roof-pillar support structure of the upper goaf group, according to the stability reserve size of the roof-pillar support structure of the upper goaf group, the mining parameters under extended mining are optimized in two cases;

[0080] S5. In the mining parameters under the optimized extended mining, if the ratio of the roof thickness to the span of the goaf under the extended mining is greater than 1.0, and the ratio of the pillar width to the pillar height under the extended mining is greater than 1.0, it means that the height of the goaf is relatively large, which not only increases the difficulty of the construction work, but also reduces the recovery rate. Therefore, the arrangement of the number of mining sections is unreasonable at this time. In this case, the number of extended mining sections is increased according to the mining right scope of the mine and the extended mining depth, and the process returns to step S4; otherwise, step S6 is executed;

[0081] S6. If the configuration of the middle roof needs to be adjusted during the extended mining process of the mine, it is necessary to first optimize the parameters of the middle roof, including increasing the thickness of the middle roof or increasing the width of the pillars supporting the middle roof. Then return to step S4 for stability judgment and optimization. At the same time, check and review the supporting structure parameters of the goaf group throughout the entire mining life cycle to ensure the optimization of the extended mining structure parameters and the safety and stability of the goaf group.

[0082] Further, in step S4, the stability reserve size is divided by the roof safety factor and the pillar safety factor. When the roof safety factor is greater than 3.2 and the pillar safety factor is greater than 3.0, it is defined as a large stability reserve, which meets the requirements of extended mining; otherwise, it is defined as a small stability reserve;

[0083] If the stability reserve of the roof-pillar support structure of the upper goaf group is large, then in this case, based on the stability judgment result of the roof-pillar support structure of the goaf group after the extended mining in step S3, the mining parameters under extended mining are optimized; in order to improve the resource recovery rate, according to the actual situation of the goaf, the overburden roof load is much greater than the middle roof load, the pillars are the key factors affecting the displacement and deformation of the goaf, and the overburden roof and pillars are the key bearing structures affecting the stability of the goaf; based on this, first reduce the roof thickness under extended mining, optimize the roof thickness under extended mining, and secondly, consider the continuity of the roof-pillar support structure in load and displacement, reduce the pillar width under extended mining. , optimize the width of the pillars under extended mining. After each optimization of the mining parameters under extended mining, the stability of the roof-pillar support structure of the goaf group after extended mining needs to be re-judged until the roof and the pillars are no longer in an unstable state, and step S5 is executed; during the optimization process, when there are weak units in the roof-pillar support structure of the upper goaf group, in order to improve the recovery rate of mineral resources, after taking reinforcement and support measures for the weak units, the overall stability of the goaf group is significantly improved, and the mining parameters under extended mining can be further optimized. The reinforcement and support measures include: the roof can be supported by anchor rods and anchor nets, artificial pillars, and the pillars can be reinforced by sprayed anchors and reinforced concrete circumferential reinforcement;

[0084] If the stability reserve of the roof-pillar support structure of the upper goaf group is small, then in this case, directly carrying out extended mining is very likely to cause instability of the support structure system of the upper goaf group, triggering a catastrophic accident in the goaf group; first, according to the weak units in the roof-pillar support structure of the upper goaf group identified in step S1, necessary reinforcement, support and prevention measures are taken for the weak units, and the reinforcement, support and prevention measures include that the roof can be supported by anchor rods and anchor nets, and artificial pillars, and the pillars can be reinforced by sprayed anchors and reinforced concrete circumferential reinforcement, and then the stability of the roof-pillar support structure of the upper goaf group is re-judged until the stability reserve of the roof-pillar support structure of the upper goaf group meets the requirements of extended mining, and return to step S4 to re-optimize the extended mining parameters and prevent and control.

[0085] Compared with the prior art, the present invention has the following beneficial effects:

[0086] (1) Based on the actual engineering situation, the present invention considers the coordination of displacement and deformation of the roof and pillars in multi-section mining and the synergistic bearing effect, constructs a mechanical model of the roof-pillar support structure system of multi-section continuous multi-span goaf groups, derives the displacement and stress expressions of the roof and pillars, and realizes the stability judgment of the roof-pillar support structure of the goaf group based on the rock strength theory.

[0087] (2) The present invention can identify the weak units of the upper goaf group support structure by judging the stability of the goaf group support structure before and after extended mining, thereby achieving safe prevention and control of goaf instability that may be caused by extended mining, and optimizing the extended mining structure parameters to improve the mining rate of mineral resources.

[0088] (3) The present invention takes into account the impact of extended mining on the stability of the roof-pillar support structure of the goaf group, and fills the gap in the prevention and control of the instability of the support structure of the goaf group caused by extended mining.

[0089] (4) The present invention is also applicable to the design of open-site mining and the safety control of goaf groups in mines, and can realize the stability judgment of goafs during the mining life cycle, providing a theoretical basis for mine safety control. The method is simple, practical and economical, and is in line with the development trend of deep extension mining of open-site resources and the concept of green mining. BRIEF DESCRIPTION OF THE DRAWINGS

[0090] Figure 1 It is a schematic flow chart of a method for determining and optimizing the stability of a roof-pillar support structure for extended mining in an embodiment of the present invention;

[0091] Figure 2a It is a horizontal projection structure schematic diagram of the goaf group roof-pillar support structure system model in an embodiment of the present invention, Figure 2b It is a schematic diagram of the vertical projection structure of the goaf group roof-pillar support structure system model in an embodiment of the present invention;

[0092] Figure 3 Schematic diagram of the structural mechanics model of the computing unit after discretization processing in an embodiment of the present invention;

[0093] Figure 4a It is a surface diagram showing the relationship between the peak displacement of the roof and the thickness-to-span ratio of the roof, the aspect ratio of the pillars, and the number of sections in mining in the embodiment of the present invention; Figure 4b It is a surface diagram showing the relationship between the pillar safety factor and the roof thickness-span ratio, the pillar width-height ratio, and the number of mining sections in the embodiment of the present invention; Figure 4c Schematic diagram of the relationship between the peak displacement of the roof and its thickness-to-span ratio under different mining section numbers in an embodiment of the present invention; Figure 4d This is a distribution diagram of the displacement of a lower top plate in a middle section and its thickness-to-span ratio in an embodiment of the present invention;

[0094] Figure 5 A comparison diagram of theoretical calculation and numerical simulation results in an embodiment of the present invention;

[0095] Figure 6 It is a flow chart of the stability determination steps of the roof-pillar support structure of the goaf group in an embodiment of the present invention. DETAILED DESCRIPTION

[0096] In order to better embody the purpose, technical solution and advantages of the present invention, the present invention is described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0097] Example:

[0098] A method for determining and optimizing the stability of the roof-pillar support structure in extended mining, such as Figure 1 As shown, the following steps are included:

[0099] Step 1: Based on the existing upper goaf group before extended mining, a mechanical model of the roof-pillar support structure system of the upper goaf group is constructed;

[0100] The mining parameters of the roof and pillars of the upper goaf group are obtained, including the number of middle sections in the goaf group, the thickness of the roof, the span of the goaf (roof span), the width of the pillars, the height of the pillars, and the total span of the goaf. The mechanical model of the roof-pillar support structure system of the upper goaf group is constructed, such as Figure 2a and Figure 2b As shown, the details are as follows:

[0101] In mining, after the ore body is mined, the goaf support structure is formed by reserving the roof and pillars to form a goaf group, providing a safe space for mining; the mechanical model of the roof-pillar support structure system of the goaf group includes the roof, pillars, and unmined ore body, the roof includes the overburden roof and the middle section roof, the overburden roof is the roof that directly bears the overburden load, and the middle section roof is the roof with the goaf above; the goaf group includes I middle sections from top to bottom, each middle section includes J roofs, and each middle section includes K pillars;

[0102] In the mechanical model of the roof-pillar support structure system of the goaf group, the overburden roof is the direct bearing structure of the overburden load of the goaf group, and the pillar is the direct supporting structure of the roof. The overburden roof and the middle section roof are rigidly connected to the surrounding rock, and the overburden roof and the middle section roof are semi-rigidly connected to the pillar, which jointly maintain the stability of the goaf group.

[0103] According to the actual engineering situation, the load of the overburden roof includes the vertical load of the overburden and the horizontal ground stress load. The horizontal ground stress load is much smaller than the vertical load of the overburden and can be ignored. The vertical load of the overburden and its own weight are the main loads affecting the stability of the roof. For thick and large ore bodies, it is often necessary to mine in multiple layers and sections. With the increase of mining depth and the number of mining sections, the loads of the overburden roof, the middle section roof and the pillars change. The load of the overburden roof includes the self-weight of the soil and rock mass above the overburden roof and the overburden roof. The load of the middle section roof includes the self-weight of the middle section roof and the crushed stone and mechanical equipment loads accumulated on the middle section roof. As the direct supporting structure of the roof, the load of the pillar comes from the load transferred by the roof.

[0104] According to the stress condition of the roof of the goaf group, the roof load is a uniformly distributed load, Indicates the number of goaf groups from top to bottom. The middle section The load on the top plate, The value is 1, 2, 3, ... , The value is 1, 2, 3, ... , Indicates the number of middle sections of the goaf group, Indicates the number of roofs in each middle section of the goaf group. When The corresponding time is the first time from top to bottom in the goaf group. - The middle section top plate of the middle section is as follows:

[0105] ;

[0106] in, is the average bulk density of the overburden, is the average bulk density of the top plate, in kN / m 3 ; is the thickness of the overburden, in m; is the load of crushed stone and mechanical equipment accumulated on the middle top plate, in kN / m; For the The middle section The thickness of the top plate, in m;

[0107] In the process of underground open-pit strip mining, the length of the goaf is much larger than the span of the goaf. The top plate of the goaf is a plate with length and width. In order to simplify the calculation process, the plate structure is calculated using unit width. At this time, the top plate along the direction perpendicular to the goaf can be regarded as a rock beam.

[0108] Step 2: Obtain the boundary conditions of the mechanical model of the upper goaf group roof-pillar support structure system described in step 1, substitute the boundary conditions into the displacement and stress expressions of the goaf group roof-pillar support structure, and then obtain the displacement, tensile stress value and safety factor of the roof, and the displacement, load and safety factor of the pillar, including the following steps:

[0109] Step 2.1, obtaining the boundary conditions of the mechanical model of the roof-pillar support structure system of the upper goaf group;

[0110] The boundary conditions of the mechanical model of the roof-pillar support structure system of the upper goaf group are obtained as follows:

[0111] ;

[0112] in, The goaf group is from top to bottom The displacement of the left end of the first top plate from left to right in the middle section;

[0113] The goaf group is from top to bottom From left to right The displacement of the pillars;

[0114] The mined-out area is from top to bottom From left to right The displacement of the right end of the top plate;

[0115] The goaf group is from top to bottom The corner at the left end of the first top plate from left to right in the middle section;

[0116] The goaf group is from top to bottom From left to right The corner of the pillar;

[0117] The goaf group is from top to bottom From left to right The corner at the right end of the top plate; The value is 1, 2, ... , The value is 1, 2, ... .

[0118] Step 2.2: Discretize the mechanical model of the roof-pillar support structure system to obtain multiple unit structure models, as follows:

[0119] like Figure 3 As shown in the figure, considering the characteristics of displacement continuity and load transfer between the roof, pillars and surrounding rock structures, based on the discretization principle, the mechanical model of the roof-pillar support structure system of the upper goaf group is discretized. According to the number of middle sections of the upper goaf group, the mechanical model of the roof-pillar support structure system of the goaf group is discretized into Unit structure model, The unit structure model includes the in the middle A top plate, supporting the top plate The pillars and the goaf below the roof. The pillars are the direct supporting structure of the roof. The right end of each roof plate is rigidly connected to the surrounding rock, and the roof plates are semi-rigidly connected to the mine pillars.

[0120] Step 2.3: Based on the unit structure model, construct the calculation unit structure expression of the mechanical model of the roof-pillar support structure system, as follows:

[0121] Take the unit structure model in step 2.2 as the calculation unit structure, and In the middle section, the expression for calculating the rotation angle and displacement of the unit structure is established as follows:

[0122] ;

[0123] Among them, the The left end of the first roof in the middle section is the coordinate origin, and the direction along the vertical goaf is x Axis (the vertical goaf direction refers to the direction from the leftmost end of the roof to the rightmost end), along the vertical upward direction is y Axis (the vertical upward refers to vertical top plate from bottom to top), establish a rectangular coordinate system; For along x The distance from the origin of the coordinate system in the axis direction, in m; The goaf group is from top to bottom The elastic modulus of the top plate of the middle section, in Pa; is the width of the top plate, in m; The goaf group is from top to bottom The thickness of the top plate in the middle section, ,in The goaf group is from top to bottom From left to right The thickness of the top plate, in m; The goaf group is from top to bottom The top corner of the middle section; The goaf group is from top to bottom The top plate displacement of the middle section; The goaf group is from top to bottom The bending moment at the left end of the first top plate from left to right in the middle section; The goaf group is from top to bottom From left to right Bending moment at the connection between the pillar and the roof; The goaf group is from top to bottom The left end support force of the first top plate from left to right in the middle section; The goaf group is from top to bottom From left to right The supporting capacity of each pillar; The goaf group is from top to bottom From left to right The distance from the first pillar to the left end of the first roof; The goaf group is from top to bottom The top plate load of the middle section, ; The goaf group is from top to bottom - 1 middle section passed to the The middle section The load of the pillars, = ;

[0124] The load of the calculation unit structure in the vertical direction satisfies the following formula:

[0125] ;

[0126] in, The goaf group is from top to bottom The total span of the goaf in the middle section, in m;

[0127] Substitute the rotation angle, displacement, and load boundary conditions shown in equations (1) and (2) into equation (3) and combine equation (4) to obtain The fixed end support force and fixed end bending moment of the middle section, the fixed end support force refers to the left end support force of the first top plate of the middle section and the The right end support force of the top plate, the fixed end bending moment refers to the left end bending moment of the first top plate in the middle section and the The bending moment at the right end of the top plate;

[0128] No. The left end support force of the first top plate in the middle section and The right end support force of the top plate , as follows:

[0129] ;

[0130] No. The bending moment at the left end of the first top plate in the middle section and The bending moment at the right end of the top plate , as follows:

[0131] ;

[0132] At this time, the displacement and load of the pillar are still unknown variables; according to the stress-strain constitutive model of rock uniaxial compressive strength and the Weibull distribution model, the displacement-load relationship of the pillar satisfies the following formula:

[0133] ;

[0134] in, The goaf group is from top to bottom From left to right The width of a pillar, in m; The goaf group is from top to bottom From left to right The length of a pillar, in m; is the peak displacement of the pillar, in m; The goaf group is from top to bottom From left to right The height of a pillar, in m; is the rock mass shape index; is a natural constant;

[0135] The relationship between the roof and the pillar nodes satisfies the following formula:

[0136] ;

[0137] By combining equations (1) to (8), we can further obtain the bending moment at the connection between the pillar and the roof in the calculation unit structure, the load of the pillar, and the displacement of the pillar.

[0138] Step 2.4: According to the boundary conditions, substitute the calculation unit structure expression to obtain the displacement, tensile stress value and safety factor of the roof in the upper goaf group, and the displacement, load and safety factor of the pillar, as follows:

[0139] According to the discretization principle, the number of mining sections is The load of any pillar in the goaf group is , respectively, into formula (7), and the final displacement of any pillar in the goaf group is obtained , It means that after superposition, the goaf group is From left to right The final displacement of the pillars;

[0140] According to formula (7), when When the ultimate bearing capacity of any pillar in the goaf group is obtained, the safety factor of any pillar in the goaf group can be obtained from the relationship between the pillar load and its ultimate bearing capacity. for:

[0141] ;

[0142] The final displacement of any pillar in the goaf group , combined with the boundary conditions in step 2.1, and substituted into equation (3), the final displacement expression of the roof of any middle section in the goaf group is obtained: , It means that after superposition, the goaf group is From left to right in the middle section, No. 1 to The final displacement expression of the top plate is:

[0143] ;

[0144] Goaf group from top to bottom From left to right in the middle section, No. 1 to The top plate x Tensile stress in the axial direction The expression is:

[0145] ;

[0146] Safety factor of any roof of goaf group for:

[0147] ;

[0148] in, is the tensile strength of rock mass, in MPa; The goaf group is from top to bottom From left to right in the middle The maximum tensile stress value of the top plate can be obtained by formula (11) in MPa.

[0149] In one embodiment, taking a two-span three-section goaf group support structure as an example, the goaf span is 15m, the pillar height is 12m, the roof thickness-span ratios are 0.3, 0.4, ..., 1.0, and the pillar width-height ratios are 0.5, 0.6, ..., 1.0, respectively. The relationship curves of the roof thickness-span ratio, the pillar width-height ratio and the number of mining sections are calculated, as well as the relationship curves of the pillar safety factor and the roof thickness-span ratio and the pillar width-height ratio are obtained, see Figure 4a , Figure 4b , Figure 4c and Figure 4d As shown. With the increase of the roof thickness-span ratio and the pillar width-height ratio, the peak displacement of the roof changes in a decreasing manner, and its change rate decreases with the increase of the roof thickness-span ratio. When the roof thickness-span ratio is greater than 0.6, the change of the roof peak displacement is less affected by the thickness-span ratio. When the pillar width-height ratio is greater than 0.7, the change of the roof peak displacement is less affected by the width-height ratio. With the increase of the roof thickness-span ratio and the pillar width-height ratio, the pillar safety factor changes in an increasing manner, and its change rate gradually increases. At the same time, under the condition that the structural parameters of the goaf are the same, the peak displacement of the entire goaf is located in the overburden roof structure, and the minimum safety factor of the pillar is located in the deepest pillar.

[0150] The reliability of the calculation method is verified by numerical simulation. The numerical model of the roof-pillar support structure system of the upper goaf group is constructed by MIDAS or Rhion software. The constructed numerical model is imported into the FLAC3D numerical simulation calculation software. The excavation command of the FLAC3D numerical simulation calculation software is called to perform calculations to obtain the displacement and tensile stress values ​​of the roof in the roof-pillar support structure system of the upper goaf group, as well as the displacement and load values ​​of the pillars. The displacement and tensile stress values ​​of the roof, the displacement and load values ​​of the pillars are derived, and the fitting curve is drawn.

[0151] According to the theoretical calculation and numerical simulation conditions, the theoretical calculation and numerical simulation results were compared and analyzed respectively, and the RMRE method was used to analyze the error of the calculation results of the two methods. The change trends of the two calculation results are basically the same, and the RMRE calculation errors are less than 10%. Relative to the entire goaf, the errors are within the allowable range, so the theoretical calculation method can be used to obtain the displacement and tensile stress values ​​of the roof of the goaf group, as well as the displacement and load values ​​of the pillars.

[0152] In one embodiment, taking the support structure of a two-span and one-middle goaf group as an example, the goaf span is 15m, the pillar height is 12m, the roof thickness-span ratio is 0.4, and the pillar width-height ratio is 0.6, theoretical calculations and numerical simulations are performed respectively, and the results are compared and analyzed. The RMRE method is used to analyze the errors of the two calculation results. The results show that the change trends of the two calculation results are basically consistent. The RMRE calculation result is 4.1%, and the error is less than 10%. Relative to the entire goaf, the error is within the allowable range. Therefore, the theoretical calculation method can be used to obtain the displacement and tensile stress values ​​of the roof of the goaf group, as well as the displacement and load values ​​of the pillars. Figure 5 shown.

[0153] Step 3: According to the displacement, tensile stress value and safety factor of the roof, displacement, load and safety factor of the pillars calculated in step 2, the stability of the roof-pillar support structure of the upper goaf group is judged;

[0154] like Figure 6 As shown in the figure, the physical and mechanical parameters of the mine rock mass are obtained through rock mass mechanics experiments, including tensile strength, compressive strength, elastic modulus, and rock and soil bulk density. According to the displacement and tensile stress values ​​of the goaf roof obtained in step 2, as well as the displacement, load value, and safety factor of the pillars, the stability of the goaf roof-pillar support structure is judged, as follows:

[0155] When the tensile stress value of the roof is greater than the tensile strength of the rock mass, the roof is in an unstable state; when the load of the pillar is greater than its ultimate bearing capacity, the pillar is in an unstable state.

[0156] In one embodiment, a limestone mine goaf group is taken as an example. The mine adopts the strip-type open-field mining method. Currently, multiple goaf middle sections have been formed. The calculation is based on the structural parameters of the two middle sections of +10m and -25m. The on-site investigation results show that the top plate thickness of the goaf in the +10m middle section is 21.8m, the spans are 14.2m and 17.3m respectively, the pillar width is 18.9m, and the pillar height is 11.5m; the top plate thickness of the goaf in the -25m middle section is 20.2m, the spans are 16.0m and 15.4m respectively, the pillar width is 17.2m, and the pillar height is 14.2m. The goaf is buried at a depth of about 190m, and the average bulk density of the overburden is 19.8kN / m 3 The average bulk density of limestone ore body is 26.3kN / m 3 , elastic modulus is 20GPa, tensile strength is 7.6MPa, and compressive strength is 82.3MPa. According to step 1, a mechanical model of the roof-pillar support structure system of the two-span and two-middle sections of the goaf group is constructed, and the displacement and tensile stress values ​​of the goaf group roof, as well as the displacement and load values ​​of the pillars are calculated according to step 2; the calculation results show that: the peak displacement of the +10m middle section roof is 0.13cm, the maximum tensile stress of the two spans is 3.1MPa and 4.2MPa, and the pillar load is 18.3kN; the peak displacement of the -25m middle section roof is 0.06cm, the maximum tensile stress of the two spans is 2.3MPa and 2.1MPa, and the pillar load is 20.9kN.

[0157] The on-site displacement and stress monitoring results show that the peak displacement of the roof in the +10m middle section is 0.14cm, the tensile stress of the roof is 3.0MPa and 4.3MPa respectively, and the pillar load is 18.4kN; the peak displacement of the roof in the -25m middle section is 0.05cm, the tensile stress of the roof is 1.2MPa and 2.3MPa respectively, and the pillar load is 21.0kN.

[0158] The calculation results of the above examples are basically consistent with the on-site monitoring results. The maximum tensile stress of the roof of the goaf is less than the rock mass tensile strength of 7.6MPa, the pillar displacement is less than its critical displacement, the pillar load is less than its ultimate bearing capacity, and the goaf is in a stable state, which is in line with the actual on-site engineering conditions.

[0159] Step 4: Based on the analysis of the stability judgment results of the roof-pillar support structure of the upper goaf group in step 3, the mining parameters under extended mining are preliminarily determined, and a mechanical model of the roof-pillar support structure system of the goaf group after extended mining is constructed. The stability of the roof-pillar support structure of the goaf group after extended mining is judged, and the mining parameters under extended mining are further optimized, including:

[0160] S1. According to the stability determination result of the roof-pillar support structure of the upper goaf group in step S3, combined with the "Safety Risk Grading Standard for Goafs in Metal and Non-metal Mines" and the "Safety Regulations for Metal and Non-metal Mines", the ratio of the tensile strength of the rock mass to the tensile stress value of the roof and the safety factor of the pillar are used for determination. When the ratio of the tensile strength of the rock mass to the tensile stress value of the roof is less than 1.6, the roof can be regarded as a weak unit; when the safety factor of the pillar is less than 1.5, the pillar can be regarded as a weak unit; and then the weak units in the roof and the pillar are marked and focused on;

[0161] S2. According to the scope of the mining right of the mine and the extended mining depth, with reference to the mining parameters of the roof of the upper goaf group and the pillars or the actual situation of the goaf, the mining parameters under extended mining are preliminarily determined, wherein the mining parameters under extended mining include the number of middle sections under extended mining, the thickness of the roof under extended mining, the span of the goaf under extended mining, the width of the pillars under extended mining, the height of the pillars under extended mining, and the total span of the goaf under extended mining;

[0162] S3. Referring to the constructed mechanical model of the roof-pillar support structure system of the upper goaf group, according to the mining parameters under extended mining, construct a mechanical model of the roof-pillar support structure system of the goaf group after extended mining, and solve the displacement, tensile stress value and safety factor of the roof of the goaf group after extended mining, as well as the displacement, load and safety factor of the pillars, to judge the stability of the roof-pillar support structure of the goaf group after extended mining;

[0163] S4, based on the parameters of the roof-pillar support structure of the upper goaf group being predetermined values ​​and the stability of the roof-pillar support structure of the upper goaf group, according to the stability reserve size of the roof-pillar support structure of the upper goaf group, the mining parameters under extended mining are optimized in two cases;

[0164] The stability reserve size is divided by the roof safety factor and the pillar safety factor. When the roof safety factor is greater than 3.2 and the pillar safety factor is greater than 3.0, it is defined as a large stability reserve, which meets the requirements of extended mining; otherwise, it is defined as a small stability reserve.

[0165] In one embodiment, if the stability reserve of the roof-pillar support structure of the upper goaf group is large, then for this situation, based on the stability judgment result of the roof-pillar support structure of the goaf group after the extended mining in step S3, the mining parameters under the extended mining are optimized; in order to improve the resource recovery rate, according to the actual situation of the goaf, the overburden roof load is much greater than the middle roof load, the pillar is the key factor affecting the displacement and deformation of the goaf, and the overburden roof and the pillar are the key bearing structures affecting the stability of the goaf; based on this, firstly, the roof thickness under the extended mining is reduced, and the roof thickness under the extended mining is optimized; secondly, considering the continuity of the roof-pillar support structure in load and displacement, the pillar width under the extended mining is reduced, and the pillar width under the extended mining is optimized; after each optimization of the mining parameters under the extended mining, the stability of the roof-pillar support structure of the goaf group after the extended mining needs to be re-judged until the roof and the pillar are no longer in an unstable state, and step S5 is executed;

[0166] In one embodiment, during the optimization process, when there are weak units in the roof-pillar support structure of the upper goaf group, in order to improve the recovery rate of mineral resources, after taking reinforcement and support measures for the weak units, the overall stability of the goaf group is significantly improved, and the mining parameters under extended mining can be further optimized. The reinforcement and support measures include: the roof can be supported by anchor rods and anchor nets, and artificial pillars, and the pillars can be reinforced by sprayed anchors and reinforced concrete circumferential reinforcement;

[0167] In one embodiment, if the stability reserve of the roof-pillar support structure of the upper goaf group is small, then in this case, directly carrying out extended mining is very likely to cause instability of the support structure system of the upper goaf group, triggering a catastrophic accident in the goaf group; first, according to the weak units in the roof-pillar support structure of the upper goaf group identified in step S1, necessary reinforcement, support and prevention measures are taken for the weak units, and the reinforcement, support and prevention measures include that the roof can be supported by anchor rods and anchor nets, and artificial pillars, and the pillars can be reinforced by sprayed anchors and reinforced concrete circumferential reinforcement, and then the stability of the roof-pillar support structure of the upper goaf group is re-judged until the stability reserve of the roof-pillar support structure of the upper goaf group meets the requirements of extended mining, and return to step S4 to re-optimize and prevent the extended mining parameters.

[0168] S5. In one embodiment, in the mining parameters of the extended mining after optimization, if the ratio of the roof thickness to the span of the goaf under the extended mining is greater than 1.0, and the ratio of the pillar width to the pillar height under the extended mining is greater than 1.0, it means that the height of the goaf is relatively large, which not only increases the difficulty of the construction work, but also reduces the recovery rate. Therefore, the arrangement of the number of mining sections is unreasonable at this time. In this case, the number of the extended mining sections is increased according to the mining right scope of the mine and the extended mining depth, and the process returns to step S4; otherwise, step S6 is executed;

[0169] S6. In one embodiment, if the configuration of the middle section roof needs to be adjusted during the extended mining process of the mine, it is necessary to first optimize the parameters of the middle section roof, including increasing the thickness of the middle section roof or increasing the width of the pillars supporting the middle section roof, and then return to step S4 for stability judgment and optimization. At the same time, the supporting structure parameters of the goaf group during the entire mining life cycle are verified and reviewed to ensure the optimization of the extended mining structure parameters and the safety and stability of the goaf group.

[0170] In the description of the present invention, unless otherwise specified, all terms are used for the purpose of facilitating the description of the present invention and are not specific, and therefore cannot be understood as limiting the present invention.

[0171] It should be understood that the present invention is not limited to the above-mentioned specific embodiments. Any modification, substitution, combination, simplification, etc. made by any technician familiar with the technical field within the technical scope disclosed by the present invention in accordance with the spirit and principle of the present invention are equivalent replacement methods and should be included in the protection scope of the present invention.

Claims

1. A method for determining and optimizing the stability of the roof-pillar support structure in extended mining, characterized in that: The following steps are involved: Step 1: Based on the existing upper goaf group before extended mining, a mechanical model of the roof-pillar support structure system of the upper goaf group is constructed; the mining parameters of the roof and pillars of the upper goaf group are obtained, and the mining parameters include the number of middle sections in the goaf group, the thickness of the roof, the span of the goaf, the width of the pillar, the height of the pillar and the total span of the goaf, and the mechanical model of the roof-pillar support structure system of the upper goaf group is constructed, as follows: The goaf support structure is formed by reserving the roof and pillars to form a goaf group, providing a safe space for mining; the mechanical model of the roof-pillar support structure system of the goaf group includes the roof, pillars, and unmined ore bodies. The roof includes the overburden roof and the middle roof. The overburden roof is the roof that directly bears the overburden load, and the middle roof is the roof of the goaf above; the goaf group includes from top to bottom Each middle section includes Top plates, each mid section includes Mineral pillars; In the mechanical model of the roof-pillar support structure system of the goaf group, the overburden roof is the direct bearing structure of the overburden load of the goaf group, the pillar is the direct supporting structure of the roof, the overburden roof and the middle roof are rigidly connected to the surrounding rock, and the overburden roof and the middle roof are semi-rigidly connected to the pillar; The load of the overburden roof includes the deadweight of the soil and rock mass above the overburden roof and the deadweight of the overburden roof; the load of the middle section roof includes the deadweight of the middle section roof and the load of the crushed stones and mechanical equipment accumulated on the middle section roof; the load of the pillar as the direct supporting structure of the roof comes from the load transferred by the roof; According to the stress condition of the roof of the goaf group, the roof load is a uniformly distributed load, Indicates the number of goaf groups from top to bottom. The middle section The load on the top plate, The value is 1, 2, 3, ... , The value is 1, 2, 3, ... , Indicates the number of middle sections of the goaf group, Indicates the number of roofs in each middle section of the goaf group. When The corresponding time is the first time from top to bottom in the goaf group. - The middle section top plate of the middle section is as follows: in, is the average bulk density of the overburden, is the average bulk density of the top plate; is the thickness of the overburden; The loads are the rubble and mechanical equipment piled on the top plate of the middle section; For the The middle section The thickness of the top plate; Step 2, obtaining the boundary conditions of the mechanical model of the upper goaf group roof-pillar support structure system described in step 1, substituting the boundary conditions into the displacement and stress expressions of the goaf group roof-pillar support structure, and then obtaining the displacement, tensile stress value and safety factor of the roof, and the displacement, load and safety factor of the pillar; Step 3: According to the displacement, tensile stress value and safety factor of the roof, displacement, load and safety factor of the pillars calculated in step 2, the stability of the roof-pillar support structure of the upper goaf group is judged; Step 4: Based on the analysis of the stability judgment results of the roof-pillar support structure of the upper goaf group in step 3, preliminarily determine the mining parameters under extended mining, construct a mechanical model of the roof-pillar support structure system of the goaf group after extended mining, judge the stability of the roof-pillar support structure of the goaf group after extended mining, and further optimize the mining parameters under extended mining.

2. The method for determining and optimizing the stability of the extended mining roof-pillar support structure according to claim 1, characterized in that: Step 2 specifically includes the following steps: Step 2.1, obtaining the boundary conditions of the mechanical model of the roof-pillar support structure system of the upper goaf group; Step 2.2, discretize the mechanical model of the roof-pillar support structure system to obtain multiple unit structure models; Step 2.3, construct a calculation unit structure expression of the mechanical model of the roof-pillar support structure system according to the unit structure model; Step 2.4: According to the boundary conditions, substitute the calculation unit structure expression to obtain the displacement, tensile stress value and safety factor of the roof in the upper goaf group, and the displacement, load and safety factor of the pillars.

3. The method for determining and optimizing the stability of the extended mining roof-pillar support structure according to claim 2, characterized in that: In step 2.1, the boundary conditions of the mechanical model of the roof-pillar support structure system of the upper goaf group are obtained, as follows: in, The goaf group is from top to bottom The displacement of the left end of the first top plate from left to right in the middle section; The goaf group is from top to bottom From left to right The displacement of the pillars; The mined-out area is from top to bottom From left to right The displacement of the right end of the top plate; The goaf group is from top to bottom The corner at the left end of the first top plate from left to right in the middle section; The goaf group is from top to bottom From left to right The corner of the pillar; The goaf group is from top to bottom From left to right The corner at the right end of the top plate; The value is 1, 2, ... , The value is 1, 2, ... .

4. The method for determining and optimizing the stability of the extended mining roof-pillar support structure according to claim 3, characterized in that: In step 2.2, the mechanical model of the roof-pillar support structure system of the upper goaf group is discretized as follows: The mechanical model of the roof-pillar support structure system of the upper goaf group is discretized. According to the number of middle sections of the upper goaf group, the mechanical model of the roof-pillar support structure system of the goaf group is discretized into Unit structure model, The unit structure model includes the in the middle A top plate, supporting the top plate The pillars and the goaf below the roof. The pillars are the direct supporting structure of the roof. The right end of each roof plate is rigidly connected to the surrounding rock, and the roof plates are semi-rigidly connected to the mine pillars.

5. The method for determining and optimizing the stability of the extended mining roof-pillar support structure according to claim 4, characterized in that: In step 2.3, the calculation unit structure expression of the mechanical model of the roof-pillar support structure system of the upper goaf group after discretization is constructed, as follows: Take the unit structure model in step 2.2 as the calculation unit structure, and In the middle section, the expression for calculating the rotation angle and displacement of the unit structure is established as follows: Among them, the The left end of the first roof in the middle section is the coordinate origin, and the direction along the vertical goaf is x Axis, vertically upward direction y Axis, establish a rectangular coordinate system; For along x The distance from the origin of the coordinate system to the axis direction; The goaf group is from top to bottom The elastic modulus of the top plate in the middle section; is the width of the top plate; The goaf group is from top to bottom The thickness of the top plate in the middle section, ,in The goaf group is from top to bottom From left to right The thickness of the top plate; The goaf group is from top to bottom The top corner of the middle section; The goaf group is from top to bottom The top plate displacement of the middle section; The goaf group is from top to bottom The bending moment at the left end of the first top plate from left to right in the middle section; The goaf group is from top to bottom From left to right Bending moment at the connection between the pillar and the roof; The goaf group is from top to bottom The left end support force of the first top plate from left to right in the middle section; The goaf group is from top to bottom From left to right The supporting capacity of each pillar; The goaf group is from top to bottom From left to right The distance from the first pillar to the left end of the first roof; The goaf group is from top to bottom The top plate load in the middle section, ; The goaf group is from top to bottom - 1 middle section passed to the The middle section The load of the pillars, = ; The load of the calculation unit structure in the vertical direction satisfies the following formula: in, The goaf group is from top to bottom The total span of the goaf in the middle section; Substitute the rotation angle, displacement, and load boundary conditions shown in equations (1) and (2) into equation (3) and combine equation (4) to obtain The fixed end support force and fixed end bending moment of the middle section, the fixed end support force refers to the left end support force of the first top plate of the middle section and the The right end support force of the top plate, the fixed end bending moment refers to the left end bending moment of the first top plate in the middle section and the The bending moment at the right end of the top plate; No. The left end support force of the first top plate in the middle section and The right end support force of the top plate , as follows: No. The bending moment at the left end of the first top plate in the middle section and The bending moment at the right end of the top plate , as follows: At this time, the displacement and load of the pillar are still unknown variables; according to the stress-strain constitutive model of rock uniaxial compressive strength and the Weibull distribution model, the displacement-load relationship of the pillar satisfies the following formula: in, The goaf group is from top to bottom From left to right The width of the pillars; The goaf group is from top to bottom From left to right The length of the pillar; is the peak displacement of the pillar; The goaf group is from top to bottom From left to right The height of the pillars; is the rock mass shape index; is a natural constant; The relationship between the roof and the pillar nodes satisfies the following formula: By combining equations (1) to (8), we can obtain the bending moment at the connection between the pillar and the roof in the calculation unit structure, the load of the pillar, and the displacement of the pillar.

6. A method for determining and optimizing the stability of an extended mining roof-pillar support structure according to claim 5, characterized in that: In step 2.4, according to the boundary conditions, the calculation unit structure expression is substituted to obtain the displacement, tensile stress value and safety factor of the roof in the upper goaf group, and the displacement, load and safety factor of the pillar, as follows: According to the discretization principle, the number of mining sections is The load of any pillar in the goaf group is , respectively, into formula (7), and the final displacement of any pillar in the goaf group is obtained , It means that after superposition, the goaf group is from top to bottom. From left to right The final displacement of the pillars; According to formula (7), when When the ultimate bearing capacity of any pillar in the goaf group is obtained, the safety factor of any pillar in the goaf group can be obtained from the relationship between the pillar load and its ultimate bearing capacity. for: The final displacement of any pillar in the goaf group , combined with the boundary conditions in step 2.1, and substituted into equation (3), the final displacement expression of the roof of any middle section in the goaf group is obtained: , It means that after superposition, the goaf group is from top to bottom. From left to right in the middle section, No. 1 to The final displacement expression of the top plate is: Goaf group from top to bottom From left to right in the middle section, No. 1 to The top plate x Tensile stress in the axial direction The expression is: Safety factor of any roof of goaf group for: in, is the tensile strength of rock mass; The goaf group is from top to bottom From left to right in the middle The maximum tensile stress value of the top plate is obtained by formula (11).

7. A method for determining and optimizing the stability of an extended mining roof-pillar support structure according to any one of claims 1 to 6, characterized in that: In step 3, the physical and mechanical parameters of the mine rock mass, including tensile strength, compressive strength, elastic modulus and bulk density of the rock mass, are obtained through rock mass mechanics experiments. According to the displacement and tensile stress values ​​of the goaf roof obtained in step 2, as well as the displacement, load value and safety factor of the pillars, the stability of the goaf roof-pillar support structure is judged, as follows: When the tensile stress value of the roof is greater than the tensile strength of the rock mass, the roof is in an unstable state; when the load of the pillar is greater than its ultimate bearing capacity, the pillar is in an unstable state.

8. The method for determining and optimizing the stability of the extended mining roof-pillar support structure according to claim 7, characterized in that: In step 4, the extended mining roof-pillar support structure parameter optimization and control includes: S1, according to the stability judgment result of the roof-pillar supporting structure of the upper goaf group in step 3, the ratio of the tensile strength of the rock mass to the tensile stress value of the roof and the safety factor of the pillar are used for judgment. When the ratio of the tensile strength of the rock mass to the tensile stress value of the roof is less than 1.6, the roof is regarded as a weak unit; when the safety factor of the pillar is less than 1.5, the pillar is regarded as a weak unit; and then the weak units in the roof and the pillar are marked; S2. According to the scope of the mining right of the mine and the extended mining depth, with reference to the mining parameters of the roof of the upper goaf group and the pillars or the actual situation of the goaf, preliminarily determine the mining parameters under extended mining, wherein the mining parameters under extended mining include the number of middle sections under extended mining, the thickness of the roof under extended mining, the span of the goaf under extended mining, the width of the pillars under extended mining, the height of the pillars under extended mining and the total span of the goaf under extended mining; S3. Referring to the constructed mechanical model of the roof-pillar support structure system of the upper goaf group, according to the mining parameters under extended mining, construct a mechanical model of the roof-pillar support structure system of the goaf group after extended mining, and solve the displacement, tensile stress value and safety factor of the roof of the goaf group after extended mining, as well as the displacement, load and safety factor of the pillars, to judge the stability of the roof-pillar support structure of the goaf group after extended mining; S4, based on the parameters of the roof-pillar support structure of the upper goaf group being predetermined values ​​and the stability of the roof-pillar support structure of the upper goaf group, according to the stability reserve size of the roof-pillar support structure of the upper goaf group, the mining parameters under extended mining are optimized in two cases; S5. In the mining parameters under the optimized extended mining, if the ratio of the roof thickness to the span of the goaf under the extended mining is greater than 1.0, and the ratio of the pillar width to the pillar height under the extended mining is greater than 1.0, it means that the goaf height is relatively large and the arrangement of the number of mining sections is unreasonable. Then, the number of the extended mining sections is increased according to the mining right scope of the mine and the extended mining depth, and the process returns to step S4; otherwise, step S6 is executed; S6. If the configuration of the middle roof needs to be adjusted during the extended mining process of the mine, it is necessary to first optimize the parameters of the middle roof, including increasing the thickness of the middle roof or increasing the width of the pillars supporting the middle roof. Then return to step S4 for stability judgment and optimization. At the same time, check and review the supporting structure parameters of the goaf group throughout the entire mining life cycle to ensure the optimization of the extended mining structure parameters and the safety and stability of the goaf group.

9. A method for determining and optimizing the stability of an extended mining roof-pillar support structure according to claim 8, characterized in that: In step S4, the stability reserve size is divided by the roof safety factor and the pillar safety factor. When the roof safety factor is greater than 3.2 and the pillar safety factor is greater than 3.0, it is defined as a large stability reserve, which meets the requirements of extended mining; otherwise, it is defined as a small stability reserve; If the stability reserve of the roof-pillar support structure of the upper goaf group is large, then in view of this situation, based on the stability judgment result of the roof-pillar support structure of the goaf group after extended mining in step S3, the mining parameters under extended mining are optimized; first, the roof thickness under extended mining is reduced to optimize the roof thickness under extended mining, and the pillar width under extended mining is reduced to optimize the pillar width under extended mining. After each optimization of the mining parameters under extended mining, the stability of the roof-pillar support structure of the goaf group after extended mining needs to be re-judged until the roof and the pillar are not in an unstable state, and step S5 is executed; during the optimization process, when there are weak units in the roof-pillar support structure of the upper goaf group, after taking reinforcement and support measures for the weak units, the mining parameters under extended mining are further optimized, and the reinforcement and support measures include: the roof is supported by anchor rods and anchor nets and artificial pillars, and the pillars are reinforced by sprayed anchors and reinforced concrete circumferential reinforcement; If the stability reserve of the roof-pillar supporting structure of the upper goaf group is small, then in this case, first, according to the weak units in the roof-pillar supporting structure of the upper goaf group identified in step S1, necessary reinforcement, support and control measures are taken for the weak units. The reinforcement, support and control measures include supporting the roof with anchor rods and anchor nets and artificial pillars, and reinforcing the pillars with sprayed anchors and reinforced concrete circumferential reinforcement. Then, the stability of the roof-pillar supporting structure of the upper goaf group is re-judged until the stability reserve of the roof-pillar supporting structure of the upper goaf group meets the requirements of extended mining, and then return to step S4 to re-optimize the extended mining parameters and control.

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