Positionable overlying strata separation layer grouting and filling method for rock stratum reconstruction

Abstract

The invention provides a rock stratum reconstruction locatable overlying strata separation layer grouting filling method which comprises the following steps: comprehensively determining the position, thickness and physical and mechanical parameters of each rock stratum according to a geological drilling histogram to obtain the position of each key stratum and the heights of a caving zone, a fissure zone and a bending sinking zone; the nearest key layer above the fissure zone is selected as a target layer position, and directional drilling is constructed below the key layer to conduct hydraulic fracturing on the rock stratum; a low-permeability plasticized cementing material is injected into the rock stratum in a pressing mode, and the rock stratum is reconstructed into a low-permeability plastic water-resisting layer; before the goaf is generated, the separation layer grouting hole is constructed to the position above the low-permeability plastic water-resisting layer, and clear water is poured into the separation layer grouting hole; after a coal face is stoped, the low-permeability plastic water-resisting layer sinks along with collapse and sinking of overlying strata in a goaf, and a separation layer space is generated between the low-permeability plastic water-resisting layer and a key layer above the low-permeability plastic water-resisting layer; after it is observed that the water level of the grouting hole rapidly drops, bed separation grouting materials are injected into the hole in a pressure mode; when the grouting pressure reaches the designed final pressure, the grouting work of the hole can be stopped; according to the method, the low-permeability plastic waterproof rock stratum is reconstructed through hydraulic fracturing, and the method capable of accurately positioning the reasonable grouting layer position is provided for the overlying strata separation layer grouting technology of a rock stratum without obvious soft and hard rock occurrence conditions or a mine under the condition that no effective-thickness waterproof layer serves as a protective layer below the separation layer space.

Description

Technical Field

[0001] The invention belongs to the technical field of grouting and filling of overburden separation layers in coal mines, and in particular provides a rock stratum reconstruction and positionable overburden separation layer grouting and filling method for mines with rock strata without obvious soft and hard rock conditions or without an effective thickness waterproof layer as a protective layer under the separation layer space. Background Art

[0002] During coal mining, overburden with different stiffness does not sink in coordination in time and space, resulting in the formation of delamination space. Grouting filling technology for overburden delamination in coal mines is a green mining technology that uses high-pressure grouting to inject filling materials into the delamination space to prevent or slow down the further sinking and deformation of the rock layer above the delamination zone, thereby achieving surface subsidence reduction. A large number of practices have proved that this technology can achieve water-saving mining; control surface subsidence, protect surface ecology; slow down or prevent rock bursts, etc.

[0003] Delamination usually occurs at the interface between soft and hard rock layers, especially below the key layer. The key layer theory provides a calculation method for the key layer, but the existing technical means cannot quantify the fluctuations of the entire stratum, the changes in lithology and strength in a large range. Especially in the rock structure without obvious soft and hard rock conditions, the temporal and spatial multi-dimensional development law of the delamination space is more complex. In the vertical direction, delamination will appear in multiple positions. During the movement of the overburden, the delamination space is always transferred upward, and the closer to the coal seam, the greater the delamination height space. In the horizontal direction, as the coal mining face advances, the delamination volume continues to increase, and the maximum delamination volume is located in the middle of the goaf. When the working face advances to a certain extent, the key layer breaks and collapses, and the delamination volume in the middle disappears. In terms of time, the delamination zone before the initial break of the key layer is developed and the delamination volume is large, which is easy to grouting and filling; once the key layer is broken for the first time, the delamination volume under the key layer is significantly reduced, only 1 / 3 to 1 / 4 before the initial break, and the difficulty of grouting increases. Therefore, in rock structures without obvious soft and hard rock conditions, due to the high complexity of the spatiotemporal multi-dimensional dynamic development state of the stratum space, it is difficult for existing technical means to effectively and accurately predict the stratum development space state at a specific time.

[0004] In addition, the slurry in the separation layer grouting project is a pressurized grouting liquid. In order to ensure safe production underground, the slurry cannot conduct the water-conducting fracture zone. Therefore, a certain thickness of a waterproof layer must be left between the separation layer grouting position and the water-conducting fracture zone as a protective layer. In practical applications, due to the randomness of the development of the waterproof layer, it is generally difficult to find a suitable waterproof layer as a protective layer below the separation layer space, and the normal underground coal mining operation is often affected by the infiltration of the slurry into the working face.

[0005] From the above analysis, it can be seen that in coal mines without obvious soft and hard rock conditions or without an effective thick waterproof layer as a protective layer under the rock layer or the separation space, it is difficult to find a reasonable separation layer grouting layer, thereby limiting the use of overburden separation layer grouting technology. Therefore, the present invention provides a rock layer reconstruction and positionable overburden separation layer grouting filling method to solve the above problem. Summary of the invention

[0006] The purpose of the present invention is to overcome the deficiencies of the prior art and to provide a rock stratum reconstruction and positionable overburden separation grouting filling method to solve the technical problems raised in the above-mentioned background technology.

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

[0008] A rock layer reconstruction and positionable overburden separation grouting filling method comprises the following steps:

[0009] S1. According to the geological drilling column chart, the position, thickness and physical and mechanical parameters of each rock layer are comprehensively determined to obtain the position of each key layer and the height of the three zones of "collapse zone, fracture zone and curved subsidence zone";

[0010] S2. On the basis of reserving a protective layer of sufficient thickness, a key layer above the "fracture zone" is selected as the target layer, and a directional drill is constructed at a certain distance below the key layer to perform hydraulic fracturing on the rock layer;

[0011] S3, injecting low-permeability plasticized cementing material into the rock formation weakened by hydraulic fracturing through directional drilling, so that the rock formation weakened by hydraulic fracturing is reconstructed into a low-permeability plastic water-proof layer;

[0012] S4. Before the goaf is formed, the separation layer grouting hole is constructed above the low-permeability plastic water-proof layer, and clean water is poured into the separation layer grouting hole;

[0013] S5. After the coal mining face is mined, as the overburden in the goaf collapses and sinks, the low-permeability plastic impermeable layer also sinks, creating a separation space between the key layer above;

[0014] S6, after observing that the water level in the separation layer grouting hole drops rapidly, timely inject the separation layer grouting material into the separation layer grouting hole;

[0015] S7. When the grouting pressure reaches the designed final pressure, and the stable leakage is less than 100L / min, and the stabilization time is not less than 30min, the grouting work of the delamination grouting holes can be stopped, and the delamination grouting holes can be sealed with cement slurry.

[0016] In the above invention content, further, the key layer position, the heights of the three zones of "collapse zone, fracture zone, and curved subsidence zone", and the thickness of the protective layer are determined for the first time by calculating using conventional empirical formulas, and subsequently need to be further comprehensively determined in combination with mine production experience and delamination grouting experience.

[0017] In the above invention, further, the directional drilling hydraulic fracturing adopts horizontal directional drilling fracturing of ground drilling or adopts downhole directional drilling fracturing.

[0018] In the above invention, further, when performing directional drilling hydraulic fracturing, a backward staged fracturing technology or a directional deep hole full-hole fixed hole hydraulic perforating fracturing technology can be used.

[0019] In the above invention, further, the hydraulic fracturing cracks are mainly horizontal cracks along the rock formation, and the expansion and development degree of vertical interlayer cracks are controlled by adjusting the viscosity of the fracturing fluid and the fracturing pressure, thereby controlling the thickness of the reconstructed rock formation.

[0020] In the above invention, further, the suitable viscosity of the fracturing fluid is determined by experiment by combining the lithology of the rock formation, the development of primary bedding fissures and the mineral composition factors.

[0021] In the above invention, further, the low permeability plasticized binder material adopts a low permeability bindable material, and the low permeability bindable material is yellow mud slurry, cement-based plastic slurry or polymer cement-based slurry.

[0022] In the above invention, further, the injection pressure of the low-permeability plasticized cementing material should be no less than 1.5 to 2 times the hydrostatic pressure of the grouting layer.

[0023] In the above invention, further, the thickness of the low permeability plastic water-proof layer is controlled by adjusting the viscosity of the fracturing fluid and the fracturing pressure to control the range of rock formation fracturing reconstruction, and the thickness of the low permeability plastic water-proof layer should be no less than 4 to 7 times the mining thickness.

[0024] In the above invention, further, the designed final pressure of the separation grouting is not less than the overburden pressure of the grouting layer.

[0025] The beneficial effects of the present invention are:

[0026] The present invention reconstructs low-permeability plastic impermeable rock strata through hydraulic fracturing, determines a reasonable delamination grouting layer position, and provides a method for accurately locating a reasonable grouting layer position for the overburden delamination grouting process in mines with rock strata without obvious soft and hard rock conditions or without an effective thick impermeable layer as a protective layer under the delamination space, thereby ensuring safe production underground and improving the work efficiency of normal coal mining operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the rock formation structure when the rock formation is reconstructed before the working face is mined according to the present invention;

[0028] Figure 2 It is a schematic diagram of the rock formation structure during the delamination grouting construction after the rock formation reconstruction of the present invention. DETAILED DESCRIPTION

[0029] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the features in the following embodiments can be combined with each other without conflict.

[0030] Example:

[0031] As attached Figure 1 and attached Figure 2 As shown, a rock layer reconstruction and positioning overburden separation grouting filling method comprises the following steps:

[0032] S1. According to the geological drilling column chart, the position, thickness and physical and mechanical parameters of each rock layer are comprehensively determined to obtain the position of each key layer and the height of the three zones of "collapse zone, fracture zone and curved subsidence zone"; wherein, the key layer position, the height of the three zones of "collapse zone, fracture zone and curved subsidence zone" and the thickness of the protective layer are determined by first using conventional empirical formulas, which are conventional calculation formulas for calculating "collapse zone, fracture zone and curved subsidence zone"; at the same time, because the lithology of the rock layer, the mining thickness of the coal seam and the inclination angle of the coal seam are all related to the height of the three zones, the empirical formulas used are also different, and the subsequent production experience of the mine and the experience of delamination grouting need to be combined to further comprehensively determine the height of the three zones;

[0033] S2. On the basis of reserving a protective layer of sufficient thickness, a key layer closest to the "fracture zone" is selected as the target layer, and a directional drilling is constructed at a certain distance below the key layer to perform hydraulic fracturing on the rock formation; preferably, the directional drilling hydraulic fracturing can be performed by horizontal directional drilling fracturing of ground drilling or by downhole directional drilling fracturing;

[0034] When conducting directional drilling hydraulic fracturing, appropriate pressure technology can be used as needed to improve the fracturing effect of the rock formation, such as the retreat staged fracturing technology or the directional deep hole full-hole fixed hydraulic perforation fracturing technology;

[0035] S3, injecting low-permeability plasticized cementing material into the rock formation weakened by hydraulic fracturing through directional drilling, preferably, the low-permeability plasticized cementing material adopts low-permeability cementable material, and the low-permeability cementable material is yellow mud slurry, cement-based plastic slurry or polymer cement-based slurry, so that the rock formation weakened by hydraulic fracturing is reconstructed into a low-permeability plastic waterproof layer; wherein the hydraulic fracturing cracks are mainly horizontal cracks along the rock formation, and the expansion and development degree of vertical interlayer cracks is controlled by adjusting the viscosity of the fracturing fluid and the fracturing pressure, thereby controlling the thickness of the reconstructed rock formation;

[0036] The suitable viscosity of the fracturing fluid is determined through experiments based on factors such as stratum lithology, primary bedding fissure development, and mineral composition. Generally, the higher the viscosity, the greater the range of cross-layer fissure expansion.

[0037] S4. Before the goaf is formed, the separation layer grouting hole is constructed above the low permeability plastic water-proof layer, and clean water is poured into the separation layer grouting hole. By observing the water in the separation layer grouting hole, it is judged whether the low permeability plastic water-proof layer has a sinking phenomenon;

[0038] S5. After the coal mining face is mined, as the overburden in the goaf collapses and sinks, the low-permeability plastic impermeable layer also sinks, and a separation space is generated between it and the key layer above. At this time, the water level in the separation grouting hole will drop significantly. Figure 2 As shown;

[0039] S6. After the water level in the separation layer grouting hole drops rapidly, the separation layer grouting material is promptly injected into the separation layer grouting hole to fill the sinking space and increase the stability of the rock layer. In order to control the sinking of the overlying key layer, the final pressure of the separation layer grouting design should not be less than the overburden pressure of the grouting layer (i.e., the self-weight of the overburden);

[0040] S7. When the grouting pressure reaches the designed final pressure, and the stable leakage is less than 100L / min, and the stabilization time is not less than 30min, the grouting work of the delamination grouting holes can be stopped, and the delamination grouting holes can be sealed with cement slurry.

[0041] In the above embodiment, preferably, in step S3, the injection pressure of the low-permeability plasticized cementing material should be no less than 1.5 to 2 times the hydrostatic pressure of the grouting layer.

[0042] In the above embodiments, preferably, the thickness of the low permeability plastic waterproof layer is mainly controlled by adjusting the viscosity of the fracturing fluid and the fracturing pressure to control the range of rock fracturing reconstruction, which is required to meet the purpose of preventing the grouting fluid of the isolation zone from leaking downward. Generally, the thickness of the low permeability plastic waterproof layer should not be less than 4 to 7 times the mining thickness to ensure reliable support for the rock structure above the delamination zone after filling.

[0043] The present invention reconstructs low-permeability plastic impermeable rock strata through hydraulic fracturing, determines a reasonable grouting layer for delamination, and provides a method for accurately locating a reasonable grouting layer for the overburden delamination grouting process in mines with rock strata without obvious soft and hard rock conditions or without an effectively thick impermeable layer as a protective layer under the delamination space, which has strong necessity and feasibility.

[0044] The above-mentioned embodiments only express the specific implementation of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A rock layer reconstruction and positioning overburden separation grouting filling method, characterized in that: The following steps are involved: S1. According to the geological drilling column chart, the position, thickness and physical and mechanical parameters of each rock layer are comprehensively determined to obtain the position of each key layer and the height of the three zones of "collapse zone, fracture zone and curved sinking zone"; S2. On the basis of reserving a protective layer of sufficient thickness, select a key layer above the "fracture zone" as the target layer, and construct a directional drilling at a certain distance below the key layer to hydraulically fracture the rock layer; S3, injecting low-permeability plasticized cementing material into the rock formation weakened by hydraulic fracturing through directional drilling, so that the rock formation weakened by hydraulic fracturing is reconstructed into a low-permeability plastic water-proof layer; S4. Before the goaf is formed, the separation layer grouting hole is constructed above the low-permeability plastic water-proof layer, and clean water is poured into the separation layer grouting hole; S5. After the coal mining face is mined, as the overburden in the goaf collapses and sinks, the low-permeability plastic impermeable layer also sinks, and a separation space is generated between it and the key layer above; S6, after observing that the water level in the separation layer grouting hole drops rapidly, timely inject the separation layer grouting material into the separation layer grouting hole; S7. When the grouting pressure reaches the designed final pressure, and the stable leakage is less than 100L / min, and the stabilization time is not less than 30min, the grouting work of the delamination grouting holes can be stopped, and the delamination grouting holes can be sealed with cement slurry.

2. A method for grouting and filling rock layers for stratum reconstruction and positioning according to claim 1, characterized in that: The position of the key layer, the heights of the three zones of "collapse zone, fracture zone, and curved subsidence zone", and the thickness of the protective layer are determined initially by calculation using conventional empirical formulas, and will subsequently need to be further comprehensively determined in combination with mine production experience and delamination grouting experience.

3. A method for grouting and filling rock layers for stratum reconstruction and positioning according to claim 1, characterized in that: The directional drilling hydraulic fracturing adopts the horizontal directional drilling fracturing of ground drilling or the downhole directional drilling fracturing.

4. A method for grouting and filling rock layers for stratum reconstruction and positioning according to claim 3, characterized in that: When conducting directional drilling hydraulic fracturing, the backward staged fracturing technology or the directional deep hole full-hole solidification hydraulic perforating fracturing technology can be used.

5. A method for grouting and filling rock layers for stratum reconstruction and positioning according to claim 3, characterized in that: The hydraulic fracturing fractures are mainly horizontal fractures along the rock formations, and the expansion and development degree of vertical interlayer fractures are controlled by adjusting the viscosity of the fracturing fluid and the fracturing pressure, thereby controlling the thickness of the reconstructed rock formation.

6. A method for grouting and filling rock layers for stratum reconstruction and positioning according to claim 5, characterized in that: The suitable viscosity of the fracturing fluid is determined by experiments based on the lithology of the rock formation, the development of primary bedding fissures and the mineral composition factors.

7. A method for grouting and filling rock layers for stratum reconstruction and positioning according to claim 5, characterized in that: The low permeability plasticized cementitious material adopts a low permeability cementitious material, and the low permeability cementitious material is yellow mud slurry, cement-based plastic slurry or polymer cement-based slurry.

8. A method for grouting and filling rock layers for stratum reconstruction and positioning according to claim 7, characterized in that: The injection pressure of the low-permeability plasticized cementing material should be no less than 1.5 to 2 times the hydrostatic pressure of the grouting layer.

9. A method for grouting and filling rock layers for stratum reconstruction and positioning according to claim 7, characterized in that: The thickness of the low permeability plastic water-blocking layer is controlled by adjusting the viscosity of the fracturing fluid and the fracturing pressure to control the range of rock formation fracturing reconstruction, and the thickness of the low permeability plastic water-blocking layer should be no less than 4 to 7 times the mining thickness.

10. The method for grouting and filling rock layers for stratum reconstruction and positioning according to claim 1, characterized in that: The designed final pressure of the separation layer grouting shall not be less than the overburden pressure of the grouting layer.

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