Patent Application
20250059889
The present disclosure relates to the technical field of overburden separation grouting, and in particular to a method for screening a key stratum for overburden separation grouting in a coal mine.
China has abundant coal resources, but a considerable portion of them are buried under buildings, railways, and water bodies. In the main coal producing areas of East China, where there are densely populated villages and buildings on the ground, the problem of coal mining under buildings is prominent. Ground subsidence caused by coal mining will ultimately lead to many catastrophic consequences such as damage to surface buildings, water bodies, farmland, railways, and bridges, etc. As a result, a series of social and environmental problems will arise, seriously affecting the sustainable economic development of mining areas.
After mining, due to the accumulative effect of expansion induced by stress relief in the overburden stratum, the separation space is suppressed, that is, the separation layer is replaced by fractured rock masses in the caving and fissure zones. The separation layer can only exist for a period of time as the underlying rock mass is compacted when there is a typical key stratum in the formation that can control the overburden stratum. The distribution of separation layers before and after a key stratum breakage is shown in
The application status and progress of key stratums in mining subsidence has been studied (Chen Chao, Hu Zhenqi. Application Status and Progress of Key Stratum Theory in Mining Subsidence [J]. Journal of Mining Science and Technology, 2017,2 (03): 209-218). However, the grouting layers in the key stratums have not been studied, making it impossible to conduct reasonable grouting for the key stratums of different analysis objects in the mining area, leading to the failure of solving the problem of ground subsidence with low cost and high efficiency.
A technical problem to be solved by the present disclosure is that the prior art lacks a method for screening a key stratum for overburden separation grouting in a coal mine and thus is unable to solve the problem of ground subsidence with low cost and high efficiency.
The present disclosure solves the above-mentioned technical problem through the following technical means. A method for screening a key stratum for overburden separation grouting in a coal mine includes the following steps:
Further, the method for screening a key stratum for overburden separation grouting in a coal mine further include step 7:
Further, step 1 includes:
Further, step 2 includes:
Further, step 3 includes:
Further, step 4 includes: determining, by mining key stratum discrimination software KSPB, the key stratums for the screened-in analysis objects.
Further, in step 4, the step of prioritizing the key stratums based on the number of separation spaces and the range of the separation height includes:
Further, in step 4, the step of prioritizing the numbers of groutable layers includes:
Further, step 5 includes:
Further, step 6 includes:
The present disclosure has the following advantages:
(1) The present disclosure takes the scope of the subsidence zone and whether there is an old goaf as the prerequisites for screening and can quickly screening a large number of working faces in the mining area, thereby improving the efficiency of key stratum screening. The present disclosure proposes grading indicators for key stratums, groutable layers, and faults, and comprehensively ranks the advantageous target areas for grouting based on the grading indicators. Finally, the present disclosure performs reasonable grouting operations on the key stratums of different analysis objects in the mining area in order of priority, thereby solving the problem of ground subsidence with low cost and efficiency.
(2) The present disclosure comprehensively considers safety factors and the requirements of the mining party for gas protection, and performs necessary downgrading and exclusion on the selected advantageous target areas, namely the separation layers of the selected key stratums.
In order to make the objectives, technical solutions, and advantages of embodiments of the present disclosure clearer, the following clearly and completely describes the technical solutions in the embodiments of the present disclosure with reference to the embodiments of the present disclosure. Apparently, the described embodiments are some rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present disclosure without creative efforts should fall within the protection scope of the present disclosure.
The present disclosure provides a method for screening a key stratum for overburden separation grouting in a coal mine. As shown in
S1. Overall analysis objects are selected based on coal mine planning. The selection principles are as follows.
(1) A working face under an existing subsidence zone is not selected as the analysis object. When the key stratum of the overburden stratum in the subsidence zone has suffered varying degrees of damage, it is impossible to implement separation grouting or the effect of separation grouting will be weak.
(2) A mining-completed working face is not selected as the analysis object. The mining-completed working face has basically formed a stable static mining basin and the separation space there usually tends to be closed, so the actual benefits of grouting are relatively low.
(3) By comparison, a planned-mining working face is selected as the analysis object. Studying the groutability of the separation layer in the overburden stratum of the upcoming working face has high economic and social value.
(4) Based on the characteristics of gas in the mining area, for a working face with a protective layer, the conditions for overburden separation grouting are analyzed, and a mining party can comprehensively consider the necessity of overburden separation grouting according to safety management and subsidence reduction needs.
According to the above selection principles, the priority of overburden separation grouting can be determined according to the workflow in
S2. The scope of a subsidence zone in a mining area is determined based on collected data (geophysical prospecting, drilling, mining conditions, testing and observation data) and on-site investigations (surface plant and mining surface). Based on the scope of the subsidence zone, analysis objects are screened. An analysis object located within or at a boundary of the subsidence zone is excluded and an analysis object outside the boundary of the subsidence zone is retained.
S3. Based on geological mining data, it is determined whether there is an old goaf in the analysis object retained in step S2. If yes, the analysis object is excluded, and an analysis object without an old goaf is retained.
S4. Key stratums of the screened-in analysis objects are determined. The key stratums are prioritized based on a number of separation spaces and a range of a separation height. Based on a diversion fissure zone, a safe height of about 50 m is set. Based on a potential separation space and a water resistance of a rock stratum, the number of groutable layers is prioritized. Specifically:
The drilling data and rock physical and mechanical property test results provided by the mining party are organized as basic data (if the data is missing, reference is made to the lithology parameters of the surrounding area or empirical values are taken). The basic data is input into mining key stratum discrimination software KSPB.
Step 401. In the present disclosure, among the selected working faces, the Zhangji Mine 1616(3) working face is taken as an example for key stratum discrimination. The data shown in Table 1 is input into the mining key stratum discrimination software KSPB, as shown in
Step 402. Step 401 is repeated on the analysis objects selected in step S3 to acquire key stratums for different analysis objects.
Step 403. The prioritization of the key stratums is conducted based on a number of separation spaces and a range of a separation height.
A key stratum with more than 5 separation spaces and a total separation height greater than 200 m is determined as a superior key stratum.
A key stratum with 3-5 separation spaces and a total separation height of 100-200 m is determined as a medium key stratum.
A key stratum with less than 3 separation spaces or a total separation height less than 100 m is determined as an inferior key stratum.
All the key stratums are prioritized in the order of priority: superior, medium, and inferior, with the order of each key stratum at a same level being random.
Step 404. Numbers of groutable layers are prioritized. That is, based on a height of a diversion fissure zone, a protective height of 50 m is set. Based on a potential separation space and a water resistance of a rock stratum, the numbers of grouting separation layers are selected. The formula for the diversion fissure zone is selected according to the “Code for Coal Pillar Setting and Coal Mining under Buildings, Water Bodies, Railways, and Main Tunnels”.
A key stratum with more than 5 groutable layers is determined as a superior key stratum.
A key stratum with 1-5 groutable layers is determined as a medium key stratum.
A key stratum without any groutable layer is determined as an inferior key stratum.
All the key stratums are prioritized in the order of priority: superior, medium, and inferior, with the order of each key stratum at a same level being random, where for an inferior key stratum determined by the prioritization based on the numbers of groutable layers, there are no groutable layers in the inferior key stratum and there is no need for analysis. Therefore, the analysis object is directly excluded.
S5. The groutable layers are prioritized based on a fault impact. Specifically, the faults for the groutable layers are analyzed.
A key stratum with groutable layers not subjected to a fault is determined as a superior key stratum.
A key stratum with at least one groutable layer cut by the fault is determined as a medium key stratum.
A key stratum with all groutable layers cut by the fault is determined as an inferior key stratum.
All the key stratums are prioritized in the order of priority: superior, medium, and inferior, with the order of each key stratum at a same level being random.
S6. Grouting priority levels of the key stratums are comprehensively analyzed based on results of the three prioritizations, and separation layers of the key stratums are grouted in order of the priority levels. Specifically, it is determined that a same level to which a key stratum is assigned in at least two of the three prioritizations as the grouting priority level of the key stratum. It is determined that the grouting priority level of a key stratum is medium if the results of the three prioritizations on the key stratum are superior, medium, and inferior, respectively, and the separation layers of the key stratums are grouted in order of grouting priority. This step does not consider a separation layer and a fault impact of a key stratum with inferior groutable layers, but directly excludes the key stratum. For example, for the same key stratum, if the discrimination results of steps 403, 404, and S5 are superior, superior, and medium, then the grouting priority level of that key stratum is superior. For the same key stratum, if the discrimination results of steps 403, 404, and S5 are medium, superior, and medium, then the grouting priority level of that key stratum is medium. For the same key stratum, if the discrimination results of steps 403, 404, and S5 are medium, superior, and inferior, then the grouting priority level of that key stratum is medium.
S7. A selected groutable layer of the separation layer is downgraded or excluded if the screened-in separation layer involves a gas protection layer.
Taking the Huainan mining area as an example, the benefits of the method of the present disclosure are described below.
A large amount of coal resources in the Huainan mining area are buried under buildings, water bodies, and railways. If these coal resources are mined, it will inevitably involve a series of difficulties such as village relocation, ground subsidence, and land reclamation. If these coal resources are not mined, it will cause resource waste and affect the normal succession of the mining area. The overburden separation grouting technology can effectively release the coal resources buried under buildings, water bodies, and railways and increase the amount of mineable coal resources. At present, the average annual land acquisition and relocation cost of Huainan Mining Group is about 600-800 million yuan. If traditional relocation methods are adopted, the group will face a series of problems such as high investment costs, difficulty in selecting resettlement sites, and complex communication and coordination between mining areas. After the implementation of the overburden separation grouting project, the subsidence around the mining area has been significantly reduced, effectively reducing the relocation of towns and villages, thereby significantly reducing land acquisition and relocation expenses. Meanwhile, the separation grouting technology is beneficial for the production capacity replacement of coal enterprises. The implementation of separation grouting technology in the Huainan mining area can effectively reduce farmland damage, thereby effectively reducing the group's expenditure on crop compensation in subsidence zones.
There are a large number of towns and villages distributed above the working faces of some coal mines in the Huainan mining area. The continuous mining work will inevitably cause ground subsidence, affecting the normal production and life of surrounding residents. The present disclosure can solve the problem of building subsidence, and protect buildings and farmland above the coal working faces, bringing about significant social benefits. Table 2 provides grading results of the key stratums obtained from step 403, Table 3 provides grading results of the groutable layers obtained from step 404, Table 4 provides grading results of the faults for the working faces obtained from step S5, and Table 5 provides the grouting priority levels of the working faces obtained from step S6.
The working principle of the present disclosure is as follows. After mining, due to the accumulative effect of expansion induced by stress relief in the overburden stratum, the formation of separation layers is suppressed, that is, the separation layer is replaced by fractured rock masses in the caving and fissure zones. The separation layer can only exist for a period of time as the underlying rock mass is compacted when there is a typical key stratum in the formation that can control the overburden stratum. If no effective intervention is implemented in the separation layer, it will be hard to achieve a high injection-production ratio or subsidence reduction ratio.
The overburden grouting requires enclosed separation spaces, and the upper and lower rock stratums that are adjacent to each other maintain continuous movement as a whole to avoid fracture type damage, in order to form suitable separation spaces for grouting. Therefore, water in the slurry will not leak into the mining area, avoiding affecting normal and safe mining.
Based on the above working principle, the present disclosure takes the scope of the subsidence zone and whether there is an old goaf as two important indicators. Firstly, based on the scope of the subsidence zone and whether there is an old goaf, all working faces in the mining area are analyzed to efficiently select valuable working faces in the mining area. For the selected working face, the key stratums are selected based on the conditions of the separation layer, groutable layer, and fault, as well as the condition of the gas protection layer designated in the mining area, in order to obtain a suitable target area for grouting. Before the key stratum is broken, high-pressure grouting is applied to the separation layer to compact the underlying fractured rock mass, thereby expanding the grouting space and increasing the injection-production ratio. In this way, a compacted bearing structure is formed in the goaf to effectively support the key stratum, improving the subsidence reduction ratio, reducing grouting costs, and enhancing the grouting effect.
The foregoing embodiments are only used to explain the technical solutions of the present disclosure, and are not intended to limit the same. Although the present disclosure is described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent substitutions on some technical features therein. These modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202311020718.2 | Aug 2023 | CN | national |
This application is the continuation application of International Application No. PCT/CN2023/118090, filed on Sep. 11, 2023, which is based upon and claims priority to Chinese Patent Application No. 202311020718.2, filed on Aug. 14, 2023, the entire contents of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/CN2023/118090 | Sep 2023 | WO |
| Child | 18633548 | US |
