Underground cave depot fracture surrounding rock seepage control and grouting water stop method

Abstract

The invention provides an underground cave depot fissure surrounding rock seepage control and grouting water stop method, and belongs to the technical field of underground water sealing cave depots. The method comprises the steps that a two-dimensional fissure network underground water mathematical model of a reservoir area underground water seepage field is established; simulating and calculating the water inflow in the construction period and the operation period; a linkage relation among hydrogeological conditions, grouting seepage control indexes and water inflow calculation is constructed, and the proportion of pre-grouting to post-grouting and a grouting area are designed; a three-dimensional geological comprehensive analysis platform is utilized to analyze an unfavorable geologic body and a permeable structure in advance and take targeted prevention and control measures in advance; the arrangement of pre-grouting drill holes is determined, and pre-grouting is conducted; after the primary pre-grouting drilling is finished and the slurry is finally set, an inspection hole is drilled, and the water seepage amount in the inspection hole is observed; the arrangement of post-grouting drill holes is determined, and post-grouting is carried out; and the post-grouting effect is verified. The system has the technical effects of reasonable design, high systematicness, high reliability, convenience in operation, low cost, wide application range and the like.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of underground water-sealed caverns, and particularly relates to a method for controlling seepage of fissure surrounding rock and grouting water stop of an underground cavern. BACKGROUND

[0002] At present, the grouting design and construction of underground water-sealed caverns mainly refer to the experience of water and electricity engineering and the execution of water and electricity industry standards, but the construction principles of water and electricity are different from those of underground water-sealed caverns, and the seepage control indexes of the two are also different, so a series of problems occur in the process of copying the grouting technology, and the grouting quantity of many large underground water-sealed caverns during construction exceeds the engineering quantity of the estimate and seepage control problems exist.

[0003] According to the Design Standard for Underground Water-Sealed Rock Caverns (GB / T 50455-2020), the seepage quantity of the treated cavern tank per million cubic meters of storage capacity should not be greater than 200 cubic meters per day, which is equivalent to a seepage control index of about 0.1 Lu. The low permeability of the rock mass and the seepage control index of the underground water-sealed cavern determine the complexity and difficulty of the grouting technology.

[0004] At present, the underground water-sealed caverns that have been built mainly use pre-grouting and post-grouting for water stop in oil storage caverns, which is usually a case of treating the symptoms rather than the cause, lacks systematicness, has poor overall effect, is complex to operate, and has high cost, with the cost of grouting being in the hundreds of millions of yuan.

[0005] Since the seepage control and grouting water stop of underground water are the key to the success of the entire underground water-sealed cavern, it is a core technical problem, and it is urgent to create a method for controlling seepage of fissure surrounding rock and grouting water stop of an underground cavern according to the construction principles of underground water-sealed caverns and the seepage control characteristics of fissure surrounding rock, so as to systematically improve the grouting effect, reduce the grouting cost, and provide protection for the safe construction and smooth production of underground water-sealed caverns. SUMMARY

[0006] The present application aims to at least solve one of the technical problems existing in the prior art, and provides a new technical solution for a method for controlling seepage of fissure surrounding rock and grouting water stop of an underground cavern.

[0007] According to one aspect of the present application, a method for controlling seepage of fissure surrounding rock and grouting water stop of an underground cavern is provided, comprising the following steps: Step S1, establishing a two-dimensional fissure network underground water mathematical model of the seepage field of the underground water of the cavern area according to the fissure water environment characteristics of the underground water-sealed cavern; performing pure flow analysis of underground water without considering fluid-structure coupling and simulating and calculating the water inflow during the construction period and the operation period by using the two-dimensional fissure network underground water mathematical model; Step S2, constructing the linkage relationship among the hydrogeological conditions, the grouting seepage control index, and the water inflow calculation, combining the construction efficiency and the grouting effectiveness ratio, and designing the proportion of pre-grouting and post-grouting and the grouting area; Step S3, using a three-dimensional geological comprehensive analysis platform, combined with various geophysical test results during construction, to analyze the adverse geological body and water permeable structure in advance and take targeted prevention and control measures in advance; Step S4, according to the proportion of pre-grouting and grouting area to determine the arrangement of pre-grouting drill holes and pre-grouting; after the initial pre-grouting drill hole is completed and the grout is finally cured, drill inspection holes and observe the water seepage in the inspection holes; wherein, the arrangement of the initial pre-grouting drill hole is annular; Step S5, according to the proportion of post-grouting and grouting area, grouting purpose, development degree of rock fracture, grouting pressure, and effective radius of grout diffusion to determine the arrangement of post-grouting drill holes and post-grouting; Step S6, verify the effect of post-grouting.

[0008] Optionally, in step S6, the water quantity inspection scheme or the water pressure test scheme is used to verify the effect of post-grouting; When the underground water level is higher than or equal to the water curtain system elevation, the water quantity inspection scheme is used; When the underground water level is lower than the water curtain system elevation, the water pressure test scheme is used; wherein, the number of water pressure test drill holes is not less than 10% of the number of post-grouting drill holes, and when the water permeability of the water pressure test is higher than 0.3Lu, it is qualified, otherwise, continue to carry out post-grouting seepage reduction work.

[0009] Optionally, in step S1, according to the design scheme of the underground cavern, the stratified data revealed by the site survey drill hole, and the result data of the comprehensive water pressure test, the model parameters of the two-dimensional fracture network underground water mathematical model are set; the simulation stage is divided into construction period and operation period, the water inflow of each stage is simulated and calculated to guide the subsequent seepage control and grouting work; wherein, the model parameters are optimized and adjusted according to the actual engineering situation and seepage control target.

[0010] Optionally, in step S2, according to the proportion of pre-grouting and post-grouting and grouting area, the overall surrounding rock seepage control and grouting water stopping target value of the underground water sealed cavern is set.

[0011] Optionally, in step S5, the spacing of the post-grouting drill hole is 1.5m~2.0m, the length of the post-grouting drill hole is 5m~9m, and the arrangement of the post-grouting drill hole is annular or linear.

[0012] Optionally, in step S1, after the two-dimensional fracture network underground water mathematical model is used to simulate and calculate the water inflow of the construction period and the operation period and the simulation data is obtained, the monitoring data is compared and analyzed according to the hydrological monitoring data of the construction period, and the monitoring data is used to give local value to the model, so as to optimize and adjust the final simulation result.

[0013] Optionally, in step S3, the three-dimensional geological comprehensive analysis platform is utilized to manage and analyze the mass geological information; wherein the mass geological information comprises the pre-drilling and in-hole testing data, the geophysical data, the geological surveying and mapping, and the geological sketch of the field area, which have influences on the water inflow.

[0014] Optionally, in step S6, the water pressure test adopts the single-point method, the test pressure is 80% of the grouting pressure, and is not greater than 1MPa.

[0015] Optionally, in step S4, the grouting range of the pre-grouting drilling of the oil storage cavern is 6m-8m outside the excavation contour line, the annular spacing between the two adjacent pre-grouting drillings is not greater than 3m, and the hole bottom spacing between the two adjacent pre-grouting drillings is not greater than 4m.

[0016] Optionally, in step S4, whether the secondary pre-grouting drilling needs to be arranged is determined according to the water seepage amount of the inspection hole; when the secondary pre-grouting drilling needs to be arranged, the secondary pre-grouting drilling is arranged between the primary pre-grouting drillings, or the starting position of the secondary pre-grouting drilling is retracted by 0.5m-1.0m into the hole, and the secondary pre-grouting drilling is arranged in the quincunx shape.

[0017] One technical effect of the present application is that: In the embodiments of the present application, in the first aspect, in view of the poor grouting effect and high grouting cost of the oil storage cavern of the underground water-sealed cavern, the present application relies on the two-dimensional fracture network underground water mathematical model of the underground water seepage field and the three-dimensional geological comprehensive analysis platform, constructs the linkage relationship among the hydrogeological condition, the grouting seepage control index and the water inflow calculation, combines the construction efficiency and the grouting effect ratio, reasonably designs the proportion of the pre-grouting and the post-grouting, and achieves the purpose of fine design of the proportion of the pre-grouting and the post-grouting and the grouting area.

[0018] In the second aspect, the present application solves the problems of lack of systematization of the grouting of the built underground water-sealed cavern and unclear division of the pre-grouting and the post-grouting proportion, fully considers the permeability of the surrounding rock fracture and the influence of the construction efficiency on the grouting plugging, adopts the grouting strategy of pre-grouting as the main part + post-grouting as the auxiliary part + local advanced prevention and control + post-effect test, and analyzes in detail the calculation method, the use condition of the pre-grouting and the post-grouting seepage control index, and the effect test after grouting, so as to fully improve the efficiency of the grouting water stop and reduce the grouting cost and the construction period.

[0019] In the third aspect, the present application adopts the grouting strategy of pre-grouting as the main part + post-grouting as the auxiliary part + local advanced prevention and control + post-effect test, can adjust the position, the spacing, the hole length, the hole inclination, the segmented grouting plug length, the grouting contour line and other parameters of the grouting hole according to the actual working condition, and has large optimization space.

[0020] In a fourth aspect, the underground cavern fissure surrounding rock seepage control and grouting water stopping method has the advantages of strong pertinence, good grouting effect, low grouting cost, convenient operation, wide application range, and the like, and can be quickly applied to large underground water-sealed caverns and similar underground engineering and underground space project construction in China. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 Figure 1 is a flowchart of an underground cavern fissure surrounding rock seepage control and grouting water stopping method according to an embodiment of the present application; Figure 2 Figure 2 is a water head equipotential line and flow field diagram of a cavern during construction according to an embodiment of the present application; Figure 3 Figure 3 is a water head equipotential line and flow field diagram of a cavern during operation according to an embodiment of the present application; Figure 4 Figure 4 is a statistical diagram of a natural rock mass permeability coefficient according to an embodiment of the present application; Figure 5 Figure 5 is an interface diagram of a three-dimensional geological comprehensive analysis platform according to an embodiment of the present application; Figure 6 Figure 6 is a pre-grouting layout diagram for horizontal excavation of a middle and lower step of an oil storage cavern according to an embodiment of the present application; Figure 7 Figure 7 is a pre-grouting layout diagram for vertical excavation of a middle and lower step of an oil storage cavern according to an embodiment of the present application; Figure 8 Figure 8 is a single-point post-grouting hole layout diagram according to an embodiment of the present application; Figure 9 Figure 9 is a fissure flow post-grouting hole layout diagram according to an embodiment of the present application; Figure 10 Figure 10 is a planar leakage post-grouting hole layout diagram according to an embodiment of the present application. DETAILED DESCRIPTION

[0022] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that the relative arrangement of components and steps, numerical expressions, and numerical values set forth in these embodiments are not limiting to the scope of the present application unless specifically stated otherwise.

[0023] Embodiments of the present application will be described in detail below, examples of which are shown in the accompanying drawings, in which the same or similar reference numerals represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by reference to the accompanying drawings are exemplary and are intended only for explanation of the present application, and cannot be understood as limiting the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the present application.

[0024] The terms "first", "second" in the description and claims of the present application can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise specified. In addition, "and / or" in the specification and claims means at least one of the connected objects, and the character " / ", generally represents an "or" relationship between the front and rear associated objects.

[0025] According to one aspect of the present application, a method for controlling seepage and grouting water in fractured surrounding rock of an underground cavern is provided, which systematically provides a complete technology and solution for controlling seepage and grouting water in fractured surrounding rock of an underground cavern, promotes long-term and large-scale underground storage of energy media such as crude oil and LPG (Liquefied Petroleum Gas), and ensures the safety of energy structure, and has important application value for various underground projects and underground space projects such as underground water-sealed oil storage, underground LPG storage, underground hydrogen storage, and underground compressed air energy storage.

[0026] Specifically, referring to Figure 1 The method for controlling seepage and grouting water in fractured surrounding rock of an underground cavern includes the following steps: Step S1, according to the high-buried-depth and high-pressure fissure water environment characteristics of the underground water-sealed cavern, a two-dimensional fissure network groundwater mathematical model of the groundwater seepage field in the cavern area is established; the two-dimensional fissure network groundwater mathematical model is used to analyze the pure flow of groundwater without considering fluid-solid coupling and simulate and calculate the water inflow during the construction period and the operation period. At the same time, combined with the monitoring data and other information during the construction period, the numerical model is verified, and finally the reasonable water inflow of the underground water-sealed cavern is simulated and calculated.

[0027] For example, the hydrogeological conceptual model is the basis and premise of the two-dimensional fissure network groundwater mathematical model. The hydrogeological conceptual model is: anisotropic and heterogeneous, the upper boundary is a precipitation recharge, evaporation and well discharge boundary, the lower boundary is an impermeable boundary, and the underground cavern and the water curtain are generalized as a constant water head boundary.

[0028] The two-dimensional fissure network groundwater mathematical model of the groundwater seepage field in the cavern area obtained according to the hydrogeological conceptual model is as follows: ; , ; , ; , ; W = W infil (x, y, z, t) - Wevap (x, y, z, t) + W well (x, y, z, t).

[0029] In the above formula, W is the source and sink term, including evaporation, rainfall infiltration recharge, well pumping and spring discharge, etc., with the unit of m 3 / d. Wherein W infil represents the unsaturated zone infiltration amount, which is related to the surface rainfall intensity and soil moisture content; W evap represents the phreatic evaporation amount, which is related to the groundwater level depth and vegetation transpiration; W well represents the well pumping and injection amount, and the positive value is injection and the negative value is pumping.

[0030] μ is the dynamic water storage rate, which is related to the water head, with the unit of m -1 , and the expression is: μ =μ0+β( p 0-ρgH).

[0031] Wherein, μ0is the initial water storage rate, β is the medium compression coefficient, p 0is the initial pore water pressure, ρ is the density of water, g is the acceleration of gravity, which reflects the influence of water head change on water storage capacity.

[0032] μ0can be calculated by the following formula: .

[0033] In the above formula: x, y, z are respectively the x coordinate, y coordinate and elevation z coordinate (m) of a point; t is time (d); k is a constant; K is the elastic water release coefficient; n is the normal direction outside the boundary; Ω is the groundwater seepage area; H0is the initial groundwater level (m); H1is the cave or water curtain water level (m); μ is the water storage rate (m -1 ); Kxx, Kyy, Kzz are respectively the permeability coefficients (m / d) of x, y, z main directions, which reflect the spatial difference of permeability in different directions and are affected by the fracture trend and lithologic layering; B1is the first type of boundary, indicating the position of cave and water curtain (m); B2is the second type of boundary; q(x, y, z, t) represents the flow at different positions of the boundary and at different times, with the unit of m 3 / d, negative for inflow and positive for outflow.

[0034] When the groundwater pure flow analysis is carried out without considering the fluid-solid coupling, according to the design scheme of underground cave, the stratification data revealed by field survey drilling and the result data of comprehensive water pressure test, the model parameters set by the embodiment are as follows: 1) The slightly weathered rock mass (ungrouted state) takes 8.5×10 -6cm / scm / s; the permeability coefficient after grouting is taken as 1 x 10 - 6 cm / scm / s, and the grouting contour line is 6 m; 2) The water curtain system is arranged at a position 25 m above the roof of the oil storage cavern, and the elevation is 1635 m; 3) The design water level is 1670 m, and the working pressure of the water curtain system is 0.63 MPa; 4) The water curtain hole diameter is 100 mm, and the spacing is 10 m; 5) There are totally 16 underground oil storage caverns, the total length is 12870 m, the net spacing of the caverns is 36 m, and the average length is 804 m. The working pressure of the oil storage tank during the construction period is set as 0, and the water head value around the oil storage tank is set as the cavern elevation H + 0 bar; the working pressure of the oil storage tank during the operation period is set as 15 bar, and the water head value around the oil storage tank is set as the cavern elevation H + 15 bar.

[0035] The numerical simulation calculation of the seepage field uses the groundwater flow module of the Feflow finite element software to perform the finite element simulation calculation of the two-dimensional Darcy seepage field. The boundary length of the model exceeds 300 m on both sides of the cavern, and the vertical range is from the phreatic surface to 200 m below the bottom plate of the oil storage cavern. The excavation boundary of the oil storage cavern is set as 0 m pressure water head; the water curtain (drilling hole) system is set as 1670 m total water head.

[0036] The simulation stage is divided into two stages of the construction period and the operation period, and the water inflow data of each stage is accurately calculated to guide the subsequent seepage control and grouting water stopping work. The calculation results of this embodiment are briefly described as follows: 1) The calculation results after the excavation of the main oil storage cavern during the construction period: after the excavation of the main oil storage cavern, the calculation results of the seepage field in the field area are as shown in Figure 2 .

[0037] 2) The calculation results of the oil storage cavern during the operation period: during the operation period, the oil and gas pressure of 0.20 MPa is applied to the oil storage cavern, and the water head equipotential line diagram and the flow field diagram of the calculation model are shown in Figure 3 .

[0038] Through the numerical simulation calculation, it is obtained that the water inflow of the oil storage cavern after the total excavation of the water curtain system during the construction period is 11899.2 m 3 / d; after the oil and gas pressure is applied during the operation period, the water inflow of the simulated cavern is reduced to 8361.6 m 3 / d, which is shown in Table 1.

[0039] Table 1 is a statistical table of the water inflow of the water curtain roadway and the oil storage tank calculated by the numerical simulation method

[0040] After the numerical model calculation is completed, the monitoring data (i.e. measured data) and the simulation data are compared and analyzed according to the hydrological monitoring data during the construction period, and the monitoring data is used to locally assign values to the model to optimize and adjust the final simulation results.

[0041] In step S2, the linkage among the hydrogeological conditions, the grouting seepage control index and the water inflow calculation is constructed, the construction efficiency and the grouting effectiveness ratio are combined, and the proportion of pre-grouting and post-grouting and the grouting area are designed to achieve the purpose of fine design of the proportion of pre-grouting and post-grouting and the grouting area.

[0042] The water inflow control index during the operation of the underground water-sealed cavern is that the water inflow per million cubic meters of storage capacity is not more than 200 cubic meters per day, and the seepage control index of grouting is approximately equal to improving the overall permeability coefficient to 1×10 -6 cm / scm / s.

[0043] In this embodiment, the target value of the water inflow during the operation period is 1000 m 3 / d, which is equivalent to reducing the average permeability coefficient of the entire storage area from 8.5×10 -6 cm / s to 1×10 -6 cm / scm / s, and the water inflow is reduced from the simulation value of 8361.6 m 3 / d to 1000 m 3 / d.

[0044] According to the permeability coefficient statistical graph of this embodiment, Figure 4 if the pre-grouting is used to directly control the water inflow to the target value, 99.2% of the oil storage cavern area needs pre-grouting, which affects the construction progress of the entire project.

[0045] The pre-grouting construction period is calculated as follows: the average pre-grouting length of one-time advanced pre-grouting is 20 m, the average pre-grouting time is about 3 days, the overlapping length of advanced pre-grouting is 4 m, and the pre-grouting time of a 16 m cavern section is 3 days. The length of the oil storage cavern in this embodiment is 12870 m, of which the length of about 1500 m that is in the critical path and affects the overall project construction period needs about 279 days for excavation. However, the upper excavation plan of the oil storage cavern is 5 months, so the pre-grouting proportion of 99.2% of the oil storage cavern area does not meet the project construction period, and the pre-grouting proportion needs to be reduced.

[0046] In this embodiment, the construction efficiency and the grouting effectiveness ratio are combined to control the construction period within 150 days. In addition, because the grouting efficiency of pre-grouting is much higher than that of post-grouting, pre-grouting is used as much as possible for permeability reduction treatment of the rock mass, the proportion of pre-grouting and post-grouting is reasonably designed, and it is recommended that the permeability coefficient of the rock mass is reduced to 4.18×10 -6 cm / s by using pre-grouting at the initial stage, and then post-grouting is used to reach the target value, so that the pre-grouting area accounts for 51.78%.

[0047] Table 2 is a list of pre-grouting ratio and seepage control index

[0048] According to the setting of Table 2, in this embodiment, the seepage control index of pre-grouting is set to 4.18x10 -6 cm / s, the pre-grouting ratio is set to 51.78%, the pre-grouting area is the area where the rock mass permeability coefficient is higher than 4.18x10 -6 cm / s, the post-grouting area is the area where the rock mass permeability coefficient is between 4.18x10 -6 cm / s and 1.0x10 -6 cm / s.

[0049] Step S3, using a three-dimensional geological comprehensive analysis platform, combined with various geophysical test results during construction, the adverse geological body and water permeable structure are analyzed in advance and targeted prevention and control measures are taken in advance to effectively reduce the seepage control difficulty of large water inflow section.

[0050] The foregoing steps are the method for seepage control and grouting of the whole surrounding rock of the underground water-sealed cavern, in addition, during the construction of the underground water-sealed cavern, local adverse geological structure or water permeable joint may occur, if no advance prevention and control and seepage reduction treatment are taken, large water inrush or water inflow event may be caused, which greatly increases the difficulty of in-cavern grouting.

[0051] Using the three-dimensional geological comprehensive analysis platform to integrate and manage and analyze massive geological information, including the information of pre-drilling and in-hole test data, geophysical data, geological mapping, geological sketch, etc. which have influence on water inflow of the site. Combined with various geophysical test results such as TSP seismic wave method, geological radar, transient electromagnetic method, etc. during construction, the adverse geological body and water permeable structure are analyzed in advance, targeted prevention and control measures are taken in advance to effectively reduce the seepage control difficulty of large water inflow section.

[0052] As shown in Figure 5 The interface schematic diagram of the three-dimensional geological comprehensive analysis platform of this embodiment adds the excavation information of construction roadway, water curtain roadway, water curtain connecting roadway, connecting roadway, oil storage cavern, geological sketch situation, in-cavern seepage point information, etc. With the progress of construction excavation, the rich water zone and adverse geological zone in front are timely predicted and warned, and effective control means such as advance pre-grouting and advance reinforcement are taken in advance.

[0053] It should be noted that, Figure 5The embodiment of the present application uses three-dimensional geological analysis software to input underground engineering layout information such as construction roadway, water curtain roadway, water curtain connecting roadway, connecting roadway, oil storage cavern, etc., and then superimposes the geological information (poor geological body, water permeable structure, etc.) after excavation into the model in the form of a thin plate. The size and spatial information of the thin plate are related to the actual geological data. After integrating all information management, 360-degree rotation and zooming can be realized.

[0054] During construction, targeted preventive measures are taken before excavating to the thin plate area of a certain poor geological body or water permeable structure to control construction safety.

[0055] Preventive measures for poor geological bodies: advanced pre-grouting, advanced anchor rod, advanced small catheter, advanced pipe shed, and other advanced support measures, and controlling the blasting footage, which is reduced from the normal 3m to 1-2m to control safety risks.

[0056] Preventive measures for water permeable structures: combined with water discharge conditions, advanced pre-grouting is arranged, the pre-grouting borehole length is usually between 10-20m, the borehole spacing is 1.5-2.0m, and the pre-grouting control contour is usually 3-4m outside the cavern clearance periphery. The pre-grouting is in the form of a fan-shaped claw covering the rock mass to be excavated in front, so as to control the water discharge after excavation.

[0057] Since the above measures are all conventional design schemes and are not within the protection scope of the present application, they are explained below to facilitate understanding. Figure 5

[0058] Step S4: Determine the arrangement of pre-grouting boreholes according to the proportion of pre-grouting and the pre-grouting area and perform pre-grouting; after the initial pre-grouting borehole is completed and the grout is finally cured, a check borehole is drilled and the water seepage in the check borehole is observed; wherein, the borehole arrangement mode of the initial pre-grouting borehole is annular.

[0059] According to the pre-grouting seepage control index determined in the foregoing steps, the flow control index in the pre-grouting borehole is calculated. For example, in the present embodiment, the pre-grouting seepage control index is set to 4.18x10 -6 cm / s, and the flow value in the check borehole can be calculated according to the following formula: Q=kxPxL; In the formula, Q is the flow in the check borehole, the unit is L / min; k is the target water permeability of pre-grouting, the unit is Lu, 1Lu≈10x10 -6 cm / s; P is the water pressure value in the check borehole, the unit is MPa; and L is the pre-grouting borehole length, the unit is m.

[0060] ​The length L of the pre-grouting drill hole in the embodiment is uniformly 20 m, the target permeability k is approximately 0.418 Lu, and the measured water pressure in the inspection hole is 1 MPa. Therefore, the flow control index Q in the inspection hole is approximately 0.418*1*20=0.836 L / min. If the measured value in the inspection hole exceeds the flow, pre-grouting needs to be performed.

[0061] Optionally, in step S4, the grouting range of the pre-grouting drill hole of the oil storage cavern is 6 m-8 m outside the excavation contour line, the annular spacing between the two adjacent pre-grouting drill holes is not greater than 3 m, and the hole bottom spacing between the two adjacent pre-grouting drill holes is not greater than 4 m.

[0062] In actual construction, according to the construction method and the height of each step, partial peripheral hole arrangement is adopted.

[0063] 1) If the oil storage cavern is provided with three steps and all of them are horizontally excavated, the pre-grouting hole arrangement is as shown in Figure 6 , but the hole arrangement should be matched according to the height of each step. The outer insertion angle of each pre-grouting drill hole is suggested to be parallel to the roadway axis and expanded by 10°-20°. The outer insertion angle can also be calculated according to the influence range of the actual blasting loosening circle and the pre-grouting hole length. 2) If the upper step of the oil storage cavern is horizontally excavated, the pre-grouting hole arrangement is as shown in Figure 7 , but the hole arrangement should be matched according to the height of each step. The outer insertion angle of each pre-grouting drill hole is suggested to be parallel to the roadway axis and expanded by 10°-20°. In the process of excavating the upper layer of the oil storage cavern, the middle and lower steps should be arranged with pre-grouting drill holes in the direction perpendicular to the axis of the oil storage cavern in advance. The annular spacing between the two adjacent pre-grouting drill holes is 2.5 m. The hole depth of the pre-grouting drill hole is more than 2 m above the floor of the oil storage cavern. The outer insertion angle of each pre-grouting drill hole on the left and right side walls is suggested to be expanded by 15° or more perpendicular to the axis of the oil storage cavern. The outer insertion angle of each pre-grouting drill hole on the floor is suggested to be expanded by 20° or more parallel to the axis of the oil storage cavern. The outer insertion angle can also be calculated according to the influence range of the actual blasting loosening circle and the pre-grouting hole length.

[0064] After the initial pre-grouting is completed and the slurry is initially set, an inspection hole should be drilled and the water seepage in the hole should be observed to determine whether a secondary pre-grouting drill hole needs to be arranged. The inspection hole is preferably arranged on the working face at a distance of not less than 3 m from the nearest initial pre-grouting drill hole.

[0065] If the water seepage in the inspection hole still exceeds the standard after the initial pre-grouting is completed, a secondary pre-grouting drill hole or a second circle of pre-grouting drill holes can be arranged between the initial pre-grouting drill holes according to the actual situation. The initial pre-grouting drill hole forms a first circle of pre-grouting drill holes, and the secondary pre-grouting drill hole can also form a second circle of pre-grouting drill holes.

[0066] If the second pre-grouting borehole is arranged, the opening position and hole depth should be 0.5-1.0m shorter than the first pre-grouting borehole, the angle should be slightly adjusted, the annular spacing and hole bottom spacing of the second pre-grouting borehole should be the same as the first pre-grouting borehole, and finally the first pre-grouting borehole is arranged in a plum blossom shape.

[0067] If the second pre-grouting borehole is arranged, the opening position and hole depth should be 0.5-1.0m shorter than the first pre-grouting borehole, the angle should be slightly adjusted, the annular spacing and hole bottom spacing of the second pre-grouting borehole should be the same as the first pre-grouting borehole, and finally the first pre-grouting borehole is arranged in a plum blossom shape.

[0068] After the second pre-grouting borehole is grouted, if the water inflow in the inspection hole or the advanced water detection hole is still excessive, the grouting hole can be increased in the second pre-grouting hole. Similarly, when the water inflow is excessive, the grouting hole can be continuously increased.

[0069] Step S5, according to the proportion of post-grouting, grouting area, grouting purpose, development degree of rock fissure, grouting pressure and effective radius of grout diffusion to determine the arrangement of post-grouting borehole and carry out post-grouting, so as to intersect with more fissures.

[0070] The number of post-grouting boreholes is determined according to the water leakage area and grouting diffusion radius, and the spacing between post-grouting boreholes is generally 1.5-2.0m, the length of post-grouting borehole in the chamber is generally 5-6m, and locally can be lengthened to 8-9m.

[0071] The arrangement of post-grouting borehole is annular or linear. There are usually the following situations: 1) Single point stock water, along the water point, the mouth of the grouting hole is arranged, the grouting hole is arranged in the position of wide fissure and its intersection, the hole depth is more than 6m, the hole spacing is generally 1-1.5m, and the inclination angle of the borehole should be set according to the occurrence of the actual water inflow fissure, such as shown in Figure 8 .

[0072] 2) Groundwater flows along a certain fissure, a row or several rows of grouting holes can be arranged along the direction intersecting with the water inflow fissure, the grouting holes are preferably arranged on both sides of the fissure, the borehole should be inclined through the fissure, the horizontal distance between the borehole and the fissure is preferably greater than 0.5m, the spacing between single row holes is generally 1-1.5m, the hole depth is preferably more than 6m, and the inclination angle of the borehole is generally 45°-60°, which should be adjusted according to the occurrence of the actual water inflow fissure; the water inflow fissure is buried more than 3m, such as shown in Figure 9 .

[0073] 3) The fissure condition of water leakage part is complex, and the water leakage is sheet seepage, the hole arrangement should be carried out around the water leakage area, the grouting hole can be arranged in a ring shape, the hole spacing is generally 1.5-2.0m, the post-grouting hole depth of main hole is more than 6m, the inclination angle of the borehole should be set according to the occurrence of the actual water inflow fissure, the outer ring grouting hole is first grouted, then the inner ring grouting hole is grouted, and the construction should be carried out according to the sequence between rings, the encryption in the ring and the segmentation in the hole, such as shown in Figure 10 .

[0074] Step S6, verifying the effect of post-grouting.

[0075] Optionally, in step S6, the effect of post-grouting is verified by using a water quantity inspection scheme or a water pressure test scheme; When the underground water level is higher than or equal to the water curtain system elevation, the water quantity inspection scheme is used; When the underground water level is lower than the water curtain system elevation, the water pressure test scheme is used; wherein, the number of water pressure test drillings is not less than 10% of the number of post-grouting drillings, and the water permeability of the water pressure test is higher than 0.3 Lu, which is qualified, otherwise, the post-grouting seepage reduction work is continued. The water pressure test can not only be used for inspection and supplement of post-grouting drillings, but also be used for evaluation of regional permeability, improvement of post-grouting grouting process, and improvement of grouting effect.

[0076] The control index of water inflow during the operation of the underground water sealed storage is that the water inflow per million cubic meters of storage capacity is not more than 200 cubic meters per day. When the underground water level of the entire reservoir area is higher than or equal to the water curtain system elevation, the control index of post-grouting of the oil storage cavern is set as follows: 1) There is no linear flow and mud leakage, and the single-point seepage is less than 0.5 L / min; 2) The area of a single wet spot (no open water on the surface) is less than 3m 2 , and the wet spot surface has a water flow phenomenon regardless of the water inflow; 3) The seepage per 100m of the cavern should be less than 7L / min or 10m 3 / d; 4) The average water leakage of the entire project is not more than 1L / m 2 ·d, which meets the water inflow requirements of each tank; 5) The average water leakage on any 100m 2 waterproof area is not more than 2L / m 2 ·d.

[0077] If any of the above control indexes is not met, post-grouting seepage reduction work is needed.

[0078] When the underground water level of the entire reservoir area is lower than the water curtain system elevation, especially close to or lower than the oil storage cavern elevation, the seepage fissure in the cavern is in a desaturated state due to the very low underground water level, so the water quantity inspection is easy to be distorted. After the underground water level rises, the seepage fissure may increase under the action of high underground water pressure, so that the previously qualified post-grouting area needs to be treated again by post-grouting seepage reduction.

[0079] Therefore, for the case of low groundwater level (i.e. when the groundwater level is lower than the water curtain system elevation), the pressure water test inspection scheme is adopted. The pressure water test drilling is not less than 10% of the number of post-grouting drilling, and the permeability of pressure water test is higher than 0.3 Lu, otherwise the post-grouting seepage reduction work should be continued.

[0080] In order to reduce the disturbance to the construction, the single-point method is adopted for pressure water test, the test pressure is 80% of the grouting pressure, and is not greater than 1 MPa. The pressure water test pressure of the site grouting test drilling can be optimized and adjusted according to the engineering needs and geological conditions.

[0081] The pressure water test should be measured every 1 min~3 min under stable pressure, and the difference between the maximum value and the minimum value in the continuous four readings is less than 10% of the final value, or the difference between the maximum value and the minimum value is less than 1 Lmin, the test can be ended and the final value is taken as the calculation value.

[0082] The result of pressure water test can be represented by permeability k, unit is Lu. The calculation formula is the formula Q=k×P×L in step S4.

[0083] The pressure water test can not only be used for inspection and supplement of post-grouting drilling, but also be used for evaluation of regional permeability, improvement of post-grouting process, and improvement of grouting effect, the operation steps are as follows: 1) The permeability of pressure water test is greater than 1 Lu, the permeability of this area is strong, the post-grouting drilling spacing is encrypted to 1-1.5 m, the grouting hole depth is deepened to 8 m, the mixed slurry with initial setting time not greater than 20 min and final setting time not greater than 2 h is configured, the grouting pressure is static water pressure (measured value) +2.0 MPa, and the injection rate is lower than 0.5 L / min•m, the grouting can be ended after maintaining the final pressure for 30 min.

[0084] 2) The permeability of pressure water test is between 0.3-1 Lu, the permeability of this area is medium, the post-grouting drilling spacing can be locally encrypted to 1-1.5 m according to the joint fracture distribution, the grouting hole depth can be locally deepened to 8 m, the mixed slurry with initial setting time not greater than 30 min and final setting time not greater than 2 h is configured, the grouting pressure is static water pressure (measured value) +1.5 MPa, and the injection rate is lower than 0.5 L / min•m, the grouting can be ended after maintaining the final pressure for 30 min.

[0085] 3) The permeability of pressure water test is lower than 0.3 Lu, the permeability of this area is weak, and the post-grouting waterproof work can not be carried out.

[0086] In the embodiments of the present application, in the first aspect, the present application aims at the current situation of poor grouting effect and high grouting cost of oil storage caverns of underground water-sealed caverns, relies on a two-dimensional fracture network groundwater mathematical model of a groundwater seepage field and a three-dimensional geological comprehensive analysis platform, constructs a linkage relationship among hydrogeological conditions, grouting seepage control indexes and water inflow calculation, combines construction efficiency and grouting effectiveness ratio, reasonably designs the proportion of pre-grouting and post-grouting, and achieves the purpose of fine design of the proportion of pre-grouting and post-grouting and the grouting area.

[0087] In the second aspect, the present application solves the problems of lack of systematicness of grouting of built underground water-sealed caverns and unclear division of pre-grouting and post-grouting proportion, fully considers the influence of permeability of surrounding rock fractures and construction efficiency on grouting plugging, adopts a grouting strategy of pre-grouting as the main part + post-grouting as the auxiliary part + local advanced prevention and control + post-effect test, and analyzes in detail the calculation method, use conditions and effect test after grouting of pre-grouting and post-grouting seepage control indexes, so as to fully improve the efficiency of grouting water stopping and reduce the grouting cost and construction period.

[0088] In the third aspect, the present application adopts the grouting strategy of pre-grouting as the main part + post-grouting as the auxiliary part + local advanced prevention and control + post-effect test, can adjust the position, spacing, hole length, hole inclination, segmented grouting plug length, grouting contour line and other parameters of the grouting hole according to the actual working conditions, and has large optimization space.

[0089] In the fourth aspect, the underground cavern fracture surrounding rock seepage control and grouting water stopping method has the advantages of strong pertinence, good grouting effect, low grouting cost, convenient operation and wide application range, and can be quickly applied to large underground water-sealed caverns and similar underground engineering and underground space project construction in China.

[0090] Optionally, in step S1, the model parameters of the two-dimensional fracture network groundwater mathematical model are set according to the design scheme of the underground cavern, the stratified data revealed by the site survey drilling, and the result data of the comprehensive water pressure test; the simulation stage is divided into a construction period and a running period, the water inflow of each stage is simulated and calculated to guide the subsequent seepage control and grouting water stopping work; wherein the model parameters can be optimized and adjusted according to the actual engineering profile and seepage control target.

[0091] In the above-mentioned embodiments, the accuracy of the simulation calculation is improved, so as to ensure the effectiveness of the subsequent seepage control and grouting water stopping work.

[0092] Optionally, in step S2, the overall surrounding rock seepage control and grouting water stopping target value of the underground water-sealed cavern is set according to the proportion of pre-grouting and post-grouting and the grouting area. This can realize the overall surrounding rock seepage control and grouting water stopping of the underground water-sealed cavern.

[0093] Optionally, in step S5, the spacing of the post- grouting boreholes is 1.5m-2.0m, the length of the post- grouting boreholes is 5m-9m, and the post- grouting boreholes are arranged in a ring or linear shape. The post- grouting boreholes not only improve the water stopping effect and enhance the overall water stopping effect, but also enhance the structural stability. By injecting slurry into a specific area, the underground cavern cracks can be filled and compressed, the integrity and strength of the rock-soil body can be increased, and thus the stability and bearing capacity of the underground structure can be improved.

[0094] Optionally, in step S1, after the two-dimensional fissure network groundwater mathematical model is used to simulate and calculate the water inflow during the construction period and the operation period and the simulation data are obtained, the monitoring data during the construction period are compared and analyzed with the simulation data, and the monitoring data are used to locally assign values to the model to optimize and adjust the final simulation results. This helps to ensure the accuracy of the simulation results.

[0095] Optionally, in step S3, the three-dimensional geological comprehensive analysis platform is used to integrate and manage and analyze massive geological information. The massive geological information includes the pre- drilling and in-hole test data, geophysical data, geological mapping, and geological sketching which have an impact on the water inflow in the site area.

[0096] In the above embodiments, the three-dimensional geological comprehensive analysis platform not only improves the level of geological information management, but also provides strong technical support for each stage of the engineering project. The application of this technology enables complex geological problems to be solved more scientifically and efficiently.

[0097] Optionally, in step S4, whether secondary pre- grouting boreholes need to be arranged is determined according to the water seepage in the inspection hole. When the secondary pre- grouting boreholes need to be arranged, the secondary pre- grouting boreholes can be arranged between the primary pre- grouting boreholes, or the starting position of the secondary pre- grouting boreholes is retracted into the hole by 0.5m-1.0m, and the secondary pre- grouting boreholes are arranged in a plum blossom shape.

[0098] In the embodiments of the present application, the fissure surrounding rock seepage control and grouting water stopping method of the underground cavern is based on the development of finite element numerical simulation and fissure water movement theory and seepage control principle, and creates a method of simulating seepage field, calculating water inflow, fine grouting, and checking grouting effect throughout the underground water-sealed cavern. Firstly, a seepage field model of the underground water in the cavern area is established to simulate and calculate the water inflow in the construction period and operation period. Secondly, a linkage relationship among hydrogeological conditions, grouting seepage control index, and water inflow calculation is constructed, and the proportion of pre-grouting and post-grouting is reasonably designed in combination with construction efficiency and grouting effectiveness ratio. Then, the three-dimensional geological comprehensive analysis platform is used to analyze the adverse geological body and water permeable structure in advance, and targeted prevention and control measures are taken to effectively reduce the seepage control difficulty of the large water inflow section. The pre-grouting scheme and post-grouting scheme of the oil storage cavern are fine arranged. Finally, the grouting effect is checked by water quantity test and water pressure test, and the water quantity test is suitable for the working condition that the underground water level is higher than the water curtain system elevation.

[0099] Therefore, the fissure surrounding rock seepage control and grouting water stopping method of the underground cavern has the advantages of strong systematicness, high reliability, convenient operation, low cost, wide application range, etc., solves the old and difficult problem of seepage control and grouting water stopping of the existing underground water-sealed cavern, and invents a systematic solution from seepage field simulation, water inflow calculation, grouting proportion division, seepage control index setting, grouting design to grouting effect checking. The seepage control requirements of the underground water-sealed cavern can be met by only implementing the process, the tolerance to geological conditions is extremely high, and the method is suitable for grouting water stopping of various types of high-buried-depth and low-permeability fissure surrounding rock. Moreover, by constructing the linkage relationship among hydrogeological conditions, grouting seepage control index, and water inflow calculation, and combining construction efficiency and grouting effectiveness ratio, the purposes of fine grouting and seepage control are achieved, the problems of uncontrolled water inflow and low grouting effectiveness of the previous underground water-sealed cavern are effectively solved, the control parameters can be adjusted according to the actual working condition, the optimization space is large, and the method can provide a strong systematicness, high reliability, convenient operation, low cost, and wide application range for seepage control and grouting water stopping of the underground water-sealed cavern, can be quickly applied to the construction of the underground water-sealed cavern, effectively reduces the grouting cost and construction period of the underground cavern, improves the economic benefit of the cavern construction, and guarantees the safety of energy structure.

[0100] It can be understood that the above embodiments are only exemplary embodiments for illustrating the principles of the present application, and the present application is not limited thereto. Various modifications and improvements can be made by those skilled in the art without departing from the spirit and essence of the present application, and these modifications and improvements are also considered as the protection scope of the present application.

Claims

1. A method for controlling seepage and grouting to stop water in fractured surrounding rock of underground caverns, characterized in that, Includes the following steps: Step S1: Based on the characteristics of the fissure water environment in the groundwater-sealed cavern reservoir, establish a two-dimensional fissure network groundwater mathematical model of the groundwater seepage field in the reservoir area; use the two-dimensional fissure network groundwater mathematical model to perform a pure flow analysis of groundwater without considering fluid-structure interaction and simulate the inflow during the construction and operation periods. Step S2: Establish the linkage relationship between hydrogeological conditions, grouting seepage control indicators, and water inflow calculation. Combine construction efficiency and grouting effectiveness ratio to design the ratio of pre-grouting and post-grouting and the grouting area. Step S3: Utilize the three-dimensional geological comprehensive analysis platform, combined with the results of various geophysical tests during construction, to analyze unfavorable geological bodies and permeable structures in advance and take targeted prevention and control measures in advance. Step S4: Determine the arrangement of pre-grouting boreholes based on the pre-grouting ratio and grouting area, and perform pre-grouting. After the initial pre-grouting drilling is completed and the grout has set, inspection holes are drilled and the amount of seepage in the inspection holes is observed; the initial pre-grouting drilling holes are arranged in a ring shape. Step S5: Determine the layout of post-grouting boreholes and perform post-grouting based on the post-grouting ratio, grouting area, grouting purpose, degree of rock fracture development, grouting pressure, and effective radius of grout diffusion. Step S6: Verify the post-grouting effect.

2. The method for controlling seepage and grouting to stop water in fractured surrounding rock of underground caverns according to claim 1, characterized in that, In step S6, the effect of post-grouting is verified by a water volume inspection scheme or a water pressure test scheme. When the groundwater level is higher than or equal to the elevation of the water curtain system, a water volume testing scheme shall be adopted. When the groundwater level is lower than the elevation of the water curtain system, a pressure water test scheme shall be adopted. Among them, the number of pressure water test boreholes shall not be less than 10% of the number of post-grouting boreholes, and the water permeability of the pressure water test shall be qualified if it is higher than 0.3Lu. Otherwise, the post-grouting seepage reduction work shall continue.

3. The method for controlling seepage and grouting to stop water in fractured surrounding rock of underground caverns according to claim 2, characterized in that, In step S1, the model parameters of the two-dimensional fracture network groundwater mathematical model are set according to the design scheme of the underground cavern, the layered data revealed by the on-site exploration boreholes, and the results of the comprehensive pressure test. The simulation stage is divided into two stages: the construction period and the operation period. The inflow of water in each stage is simulated and calculated to guide the subsequent seepage control and grouting water-stopping work. The model parameters are optimized and adjusted according to the actual project situation and seepage control objectives.

4. The method for controlling seepage and grouting to stop water in fractured surrounding rock of underground caverns according to claim 1, characterized in that, In step S2, the overall surrounding rock seepage control and grouting water-stopping target values ​​of the underground water-sealed cavern are set according to the ratio of pre-grouting and post-grouting and the grouting area.

5. The method for controlling seepage and grouting to stop water in fractured surrounding rock of underground caverns according to claim 1, characterized in that, In step S5, the spacing of the post-grouting boreholes is 1.5m to 2.0m, the length of the post-grouting boreholes is 5m to 9m, and the arrangement of the post-grouting boreholes is either circular or linear.

6. The method for controlling seepage and grouting to stop water in fractured surrounding rock of underground caverns according to claim 1, characterized in that, In step S1, after the two-dimensional fractured network groundwater mathematical model is used to simulate and calculate the inflow during the construction and operation periods and obtain simulation data, the monitoring data and simulation data are compared and analyzed based on the hydrological monitoring data during the construction period, and the monitoring data is used to assign local values ​​to the model in order to optimize and adjust the final simulation results.

7. The method for controlling seepage and grouting to stop water in fractured surrounding rock of underground caverns according to claim 1, characterized in that, In step S3, a three-dimensional geological integrated analysis platform is used to manage and analyze massive amounts of geological information in an integrated manner. The massive amounts of geological information include previous borehole and in-hole test data, geophysical data, geological mapping and geological sketches that affect the water inflow in the site.

8. The method for controlling seepage and grouting to stop water in fractured surrounding rock of underground caverns according to claim 2, characterized in that, In step S6, the water pressure test adopts the single-point method, and the test pressure is 80% of the grouting pressure, which is not greater than 1 MPa.

9. The method for controlling seepage and grouting to stop water in fractured surrounding rock of underground caverns according to claim 1, characterized in that, In step S4, the grouting range of the pre-grouting boreholes in the oil storage cavern is 6m-8m outside the excavation outline, the circumferential distance between two adjacent pre-grouting boreholes is no more than 3m, and the bottom distance between two adjacent pre-grouting boreholes is no more than 4m.

10. The method for controlling seepage and grouting to stop water in fractured surrounding rock of underground caverns according to claim 9, characterized in that, In step S4, it is determined whether secondary pre-grouting boreholes need to be arranged based on the amount of seepage in the inspection hole. When secondary pre-grouting boreholes need to be arranged, secondary pre-grouting boreholes are set between the primary pre-grouting boreholes, or the starting position of the secondary pre-grouting boreholes is moved back 0.5 meters to 1.0 meters into the hole. The arrangement of the secondary pre-grouting boreholes is in a quincunx pattern.

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