Method for detecting and processing karst cave in anchor cable area of limestone stratum enclosure structure

Abstract

The invention belongs to the technical field of karst cave treatment, and discloses a limestone stratum enclosure structure anchor cable area karst cave detection and treatment method which comprises the following steps: S1, delimiting an anchor cable area karst cave treatment range; s2, drilling in advance in an anchor cable area; s3, exploring a karst cave boundary in an anchor cable area; s4, grouting treatment is conducted on the karst cave in the anchor cable area; s5, the grouting effect of the karst cave in the anchor cable area is detected; and S6, anchor cable construction and anchor cable bearing capacity detection. Through the six steps, detection and treatment of the karst cave in the limestone area can be effectively achieved, the anchoring stability of the anchor cable in the limestone stratum is guaranteed, the collapse risk of the anchor cable of the enclosure structure in the construction process can be effectively reduced, the rapid development of the karst cave under the construction disturbance of the anchor cable and the water inrush and gushing risk are reduced, and the construction efficiency is improved. The anchor cable foundation pit supporting bearing capacity and deformation resistance of the limestone stratum enclosure structure can be effectively improved, and the safety of underground structure construction is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of karst cave treatment, and in particular relates to a karst cave detection and treatment method in an anchor cable area of ​​a limestone stratum retaining structure. Background Art

[0002] When carrying out engineering construction in limestone strata, it is common to encounter the development of karst caves. Karst caves are a bad geological condition for engineering construction. When encountering karst caves, they need to be treated. If the karst caves are not handled properly, it is easy to cause accidents such as ground collapse and failure of engineering containment. Once an engineering accident occurs, it will have an adverse impact on people’s lives, property and the economy.

[0003] At present, in the construction of foundation pit projects in limestone areas, the support form of "retaining piles or underground continuous walls + internal support" is mostly used, and the treatment of karst caves is mostly in the range of retaining piles and underground continuous walls. If the pile-anchor support system is used in the limestone area, the "anchor cable anchoring section" anchored in the limestone stratum will be directly related to the retaining safety of the retaining structure. Therefore, when the pile-anchor support system is used in the limestone area, it is necessary not only to pay attention to the treatment of karst caves in the range of retaining piles and underground continuous walls, but also to focus on the "karst cave treatment in the anchor cable area" to avoid the problem of anchor failure caused by the "anchor cable anchoring section" encountering karst caves in the limestone stratum. Since the use of pile-anchor support systems in limestone strata is relatively rare, there is currently a lack of corresponding methods for the treatment of karst caves in the anchor cable area of ​​the retaining structure in limestone strata. The karst caves in the limestone strata need to be detected before being treated. That is, at present, there is a specific lack of a method for detecting and treating the karst caves in the anchor cable area of ​​the retaining structure in the limestone strata to effectively reduce the risk of collapse during the anchor cable construction of the retaining structure and water inrush and gushing during the anchor cable drilling.

[0004] Therefore, a new technology is needed to solve the problem that the prior art lacks a method for detecting and treating caves in the anchor cable area of ​​a limestone stratum retaining structure. Summary of the invention

[0005] In order to solve the above-mentioned problems in the prior art, the present invention provides a method for detecting and treating karst caves in the anchor cable area of ​​a limestone stratum retaining structure, which is mainly used for "detecting and treating karst caves in the anchor cable area" of limestone strata, and can effectively reduce the risk of collapse during anchor cable construction of the retaining structure and water inrush and gushing during anchor cable drilling.

[0006] The present invention adopts the following technical solutions:

[0007] A method for detecting and treating karst caves in an anchor cable area of ​​a limestone stratum retaining structure comprises the following steps:

[0008] S1. Delineation of the treatment scope of the cave in the anchor cable area;

[0009] S11. Determine the treatment scope of the karst cave in the anchor area according to the plane layout and vertical layout of the anchor cables;

[0010] S2, advance drilling in the anchor area;

[0011] S21. Combined with detailed drilling, several advance drilling holes are set in the anchor cable anchoring section layout area;

[0012] S3, anchor cable area to explore the cave boundary;

[0013] S31, within the scope of the karst cave treatment in the anchor cable area, for the karst caves initially revealed by detailed exploration drilling and advance drilling in the anchor cable anchoring section arrangement area, drilling edge detection holes to detect the boundaries of the karst caves;

[0014] S4, grouting treatment of cave in anchor cable area;

[0015] S41. Some of the “advance drilling holes or the edge detection holes” also serve as grouting holes. The grouting holes are divided into central holes and peripheral holes according to the cave area and boundaries; wherein some of the central holes also serve as ventilation holes;

[0016] S42, grouting the cave through the grouting hole according to the type of the cave;

[0017] S5. Detection of grouting effect in the cave of anchor cable area;

[0018] S51. After the grouting is completed, the cave filling grouting effect and the cave grouting reinforcement effect are checked;

[0019] S6. Anchor cable construction and anchor cable bearing capacity testing;

[0020] S61. After completing the cave grouting treatment and cave grouting effect detection, locate the anchor cable hole position at the retaining structure and drill to the designed depth of the anchor cable;

[0021] S62, carry out the process of laying anchor cables, grouting and constructing anchor cable waist beams;

[0022] S63. After the anchor cable waist beam concrete reaches the design strength, the anchor cable is tensioned and the pull-out resistance and locking force of the anchor cable are tested.

[0023] Furthermore, in the step S11, the anchor cable includes an anchor cable anchoring section and an anchor cable free section; the karst cave treatment range in the anchor cable area includes a plane treatment range and a vertical treatment range;

[0024] The plane processing range includes a first plane boundary, a second plane boundary, a third plane boundary and a fourth plane boundary; the first plane boundary maintains a first set distance with the first side anchor cable, the second plane boundary maintains a second set distance with the second side anchor cable, the third plane boundary maintains a third set distance with the first end of the anchor cable anchoring section, and the fourth plane boundary maintains a fourth set distance with the second end of the anchor cable anchoring section; the plane area enclosed by the first plane boundary, the second plane boundary, the third plane boundary and the fourth plane boundary is the plane processing range;

[0025] The vertical processing range includes a ground boundary, an underground boundary, a first vertical boundary and a second vertical boundary; the ground boundary is a flat ground; the underground boundary maintains a fifth set distance from the lowest point of the anchor cable anchoring section; the first vertical boundary maintains a sixth set distance from the first end of the leftmost anchor cable anchoring section; the second vertical boundary maintains a seventh set distance from the second end of the rightmost anchor cable anchoring section; the vertical area enclosed by the ground boundary, the underground boundary, the first vertical boundary and the second vertical boundary is the vertical processing range;

[0026] The three-dimensional area formed by the plane treatment range and the vertical treatment range is the anchor area cave treatment range to be determined.

[0027] Furthermore, in the S21 step, the detailed exploration drilling hole also serves as an advance drilling hole, and the advance drilling holes obtained in combination with the subsequent drilling holes are provided with a plurality of advance drilling holes, and are arranged in a row, and a plurality of the advance drilling holes are respectively adjacent to the arrangement positions of the anchor cable anchoring sections; a plurality of the advance drilling holes are perpendicular to the horizontal plane formed by the planar processing range; a set hole spacing is maintained between adjacent advance drilling holes.

[0028] Further, in the step S31, (the detailed exploration drilling hole also serves as the advance drilling hole, and thus can be described only by the advance drilling hole) when the karst cave revealed by the advance drilling hole is within the karst cave treatment range of the anchor cable area, the advance drilling hole is used as the base point of the "cross" axis, and then a sequence of exploration holes is drilled along the four axial length directions of the "cross" axis at a set interval;

[0029] If a cave is found during the exploration of the first-order edge exploration holes, the first-order edge exploration holes are used as the base point of the "cross" axis, and then one or more axial length directions of the "cross" axis are selected to drill second-order edge exploration holes at a set interval until the boundary of the cave is found or the boundary of the cave treatment range of the anchor cable area is reached.

[0030] Furthermore, in the step S41, the grouting pipe is buried in the selected grouting hole, and grouting can be performed only after the gap between the "cavern roof, grouting pipe" and the "grouting hole wall" is closed.

[0031] Furthermore, in the step S42, the cave is divided into an unfilled cave, a semi-filled cave and a fully filled cave according to the natural filling conditions inside the cave;

[0032] At the peripheral holes, the unfilled cave or the semi-filled cave is filled with cement-water glass double slurry;

[0033] At the central hole, the "said unfilled cave or the said semi-filled cave" with a height ≥3m shall be filled with cement mortar first and then compacted grouting with cement slurry; the "said unfilled cave or the said semi-filled cave" with a height less than 3m shall be filled with mortar or cement slurry; if the standard penetration value of the natural filling in the said fully filled cave is less than 10 blows, compacted grouting with cement slurry shall be used; if the standard penetration value of the natural filling in the said fully filled cave is ≥10 blows, no treatment shall be given.

[0034] Among them, cement slurry is needed to seal the holes after grouting is completed.

[0035] Furthermore, in the step S4, an on-site grouting test should be carried out before construction to determine the grouting parameters;

[0036] For the peripheral holes, the grouting pressure is 0.6Mpa to 0.8Mpa, and the number of grouting times is 3 to 4 times;

[0037] For the central hole, cement slurry should be injected three times at a grouting pressure of 0Mpa to 1.0Mpa and a grouting speed of 30L / min to 70L / min. The grouting pressure should be gradually increased. After reaching the final grouting pressure, grouting should be continued for more than 10 minutes. The slurry is made of 42.5 grade ordinary Portland cement with a water-cement ratio of 1.0 to 1.5.

[0038] Furthermore, the cave filling grouting effect inspection mentioned in the step S51 is carried out by adopting the "secondary grouting" method to check the filling rate, and the pressure is gradually increased from 0Mpa to 0.2Mpa and maintained for 10min to 15min; the density is checked by adopting the standard penetration method, and the standard penetration value reaches "hard" soil, which is excellent, and the standard penetration value reaches "hard plastic" soil, which is qualified.

[0039] Furthermore, the inspection of the grouting reinforcement effect of the cave mentioned in the S51 step adopts core drilling, and performs compression test, water pressure test and in-situ standard penetration test for inspection, and the number of inspections is not less than 1% of the number of grouting holes; each cave is required to be inspected at least once; wherein, the test blocks obtained by random drilling and coring are subjected to compression test, and the unconfined compressive strength is required to be not less than 0.2Mpa; wherein, the water pressure inspection of the quality inspection hole should be carried out at least seven days after the grouting of the unit project is completed; wherein, the water permeability of the quality inspection hole after the cave reinforcement treatment should not be greater than 10Lu, the qualified rate should be more than 85%, the maximum water permeability of the unqualified hole section should not exceed 15Lu, and should not be concentrated; wherein, during the in-situ standard penetration test, the number of standard penetration blows is required to be not less than 10 blows.

[0040] Furthermore, in the step S61, if a karst cave is found during the anchor hole drilling process, grouting treatment should be carried out in time from the anchor hole, and the drilling can be continued after the treatment is completed;

[0041] In the step S62, the effective anchoring length of the anchor cable should not be less than the designed anchoring length and should penetrate the cave into the stable rock layer for not less than 3m;

[0042] In the step S63, in order to ensure the effective bearing capacity of the anchor cable in the limestone area, the anchor cable passing through the cave, when applying prestress, includes the following steps:

[0043] B1. First determine which value is the larger one, "1.4 times Fm and 0.8 times Fn", where Fm is the "standard value of calculated tension" and Fn is the "standard value of the ultimate tensile strength of the anchor cable";

[0044] B2. If 1.4Fm is a larger value than 0.8Fn, then when applying prestress, it should be tensioned to 1.4Fm first, and then released and retracted to the locking force value;

[0045] If 0.8Fn is a larger value than 1.4Fm, then when applying prestress, it should be tensioned to 0.8Fn first, and then released and retracted to the locking force value;

[0046] Wherein, in the step S63, the number of anchor cables tested for bearing capacity is not less than 10% and not less than ten.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] The method for detecting and treating karst caves in the anchor cable area of ​​the limestone stratum retaining structure proposed by the present invention comprises six steps, which are: S1, defining the treatment range of karst caves in the anchor cable area; S2, advanced drilling in the anchor cable area; S3, detecting the boundaries of karst caves in the anchor cable area;

[0049] S4, grouting treatment of caves in anchor cable area; S5, testing of grouting effect of caves in anchor cable area; S6, anchor cable construction and anchor cable bearing capacity testing. Through these six steps, the detection and treatment of caves in limestone areas can be effectively realized, and the stability of anchor cables anchored in limestone formations can be ensured, which can effectively reduce the risk of collapse of retaining structure anchor cables during construction, reduce the risk of rapid development of caves and water inrush and gushing under the disturbance of anchor cable construction, and effectively improve the bearing capacity and anti-deformation ability of anchor cable foundation pit support of retaining structure in limestone formations, and improve the safety of underground structure construction.

[0050] The method for detecting and treating karst caves in the anchor cable area of ​​the limestone stratum retaining structure proposed in the present invention is mainly used for "detecting and treating karst caves in the anchor cable area" of the limestone stratum, and solves the problem that the anchor cable anchoring section is prone to anchor instability when encountering karst caves in the limestone stratum. To a certain extent, the method proposed in the present invention fills the gap in the current research in this field ("safe construction of pile-anchor support system in limestone strata with karst caves"), making the construction of pile-anchor support system in limestone areas more scientific and safe. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The technology of the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments:

[0052] Figure 1 This is a top view of the karst cave treatment area in the anchor cable area ( Figure 1 It is also a schematic diagram of the plane treatment range (the anchor cables are projected from a top view, which can be understood as the plane arrangement of the anchor cables. According to the plane arrangement of the anchor cables, the engineering staff can determine the plane treatment range of the karst caves in the anchor cable area. According to the plane arrangement of the anchor cables, the engineering staff can preliminarily reveal the karst caves in the anchor cable area of ​​the limestone layer through detailed exploration drilling and advance drilling).

[0053] Figure 2 yes Figure 1 Sectional view at SS ( Figure 2 It is a schematic elevation diagram of the treatment range of the karst cave in the anchor cable area)(that is, a schematic diagram of the vertical treatment range)(which shows the vertical arrangement of the anchor cables. According to the vertical arrangement of the anchor cables, the engineering personnel can determine the vertical treatment range of the karst cave in the anchor cable area, so that the engineering personnel can preliminarily reveal the karst cave in the anchor cable area of ​​the limestone layer through detailed exploration drilling and advance drilling)( Figure 1 and Figure 2 The anchor cable arrangement in the diagram is derived from the construction drawing, which must be completed before “determining the scope of the cave treatment in the anchor cable area”);

[0054] Figure 3The advance drilling is used as the base point of the "cross" axis. The engineering personnel respectively drill the schematic diagram of the "first order edge detection hole" along the four axial length directions of the "cross" axis at the set intervals (the "cross" axis is a coordinate axis designed for the convenience of description, so that the engineering personnel can understand and correctly locate the drilling position of the "first order edge detection hole");

[0055] Figure 4 The "first order edge detection hole" is used as the base point of the "cross" axis. The engineering personnel select one or more axis length directions of the "cross" axis and make a schematic diagram of the "second order edge detection hole" at a set spacing ( Figure 4 It is the first embodiment in which the "first-order edge detection hole" is used as the base point of the "cross" axis (the "cross" axis is a coordinate axis designed for the convenience of description, so as to facilitate engineers to understand and correctly locate the drilling position of the "second-order edge detection hole");

[0056] Figure 5 The "first order edge detection hole" is used as the base point of the "cross" axis. The engineering personnel select one or more axis length directions of the "cross" axis and make a schematic diagram of the "second order edge detection hole" at a set spacing ( Figure 5 This is the second embodiment in which the "first-order edge detection hole" is used as the base point of the "cross" axis (the "cross" axis is a coordinate axis designed for the convenience of description, so as to facilitate engineers to understand and correctly locate the drilling position of the "second-order edge detection hole");

[0057] Figure 6 It is a schematic diagram of some "advanced drilling holes or exploratory holes" that also serve as grouting holes for treating caves (engineering personnel first preliminarily reveal the caves through detailed exploration drilling and advance drilling, then use exploratory holes to find out the boundaries of the caves, and finally let some "advanced drilling holes or exploratory holes" also serve as grouting holes for treating caves).

[0058] Reference numerals:

[0059] 11-detailed exploration drilling hole; 12-advance drilling hole; P-hole spacing; 13-side detection hole; 131-first order side detection hole; 132-second order side detection hole; L1-spacing; L2-spacing; K-axis length direction;

[0060] 2-anchor cable; 21-anchor cable anchoring section; E-first end; F-second end; 22-anchor cable free section; C-first side anchor cable; D-second side anchor cable; X1-left; X2-right; T-vertical mark; Y-auxiliary line;

[0061] 31-anchor cable waist beam; 32-enclosing structure; 33-underground structure;

[0062] 4- grouting hole; 41- peripheral hole; 42- central hole; 421- vent hole;

[0063] 5- plane processing range; 51- first plane boundary; 52- second plane boundary; 53- third plane boundary; 54- fourth plane boundary; SS- section symbol;

[0064] 6-vertical processing range; 61-ground boundary; 62-underground boundary; 63-first vertical boundary; 64-second vertical boundary;

[0065] G1-first set distance; G2-second set distance; G3-third set distance; G4-fourth set distance; G5-fifth set distance; G6-sixth set distance; G7-seventh set distance;

[0066] M-karst cave boundary; N-karst cave treatment range boundary of anchor cable area;

[0067] 7-caves; 71-unfilled caves; 72-semi-filled caves; 73-fully-filled caves;

[0068] R1-caves within the treatment range of the anchor area; R2-caves outside the treatment range of the anchor area. DETAILED DESCRIPTION

[0069] The following will be combined with the embodiments and drawings to clearly and completely describe the concept, specific structure and technical effects of the present invention, so as to fully understand the purpose, scheme and effect of the present invention. It should be noted that the embodiments in this application and the features in the embodiments can be combined with each other without conflict. The same reference numerals used throughout the drawings indicate the same or similar parts.

[0070] It should be noted that, unless otherwise specified, when a feature is referred to as being "fixed" or "connected" to another feature, it may be directly fixed or connected to the other feature, or it may be indirectly fixed or connected to the other feature. In addition, the descriptions of up, down, left, right, etc. used in the present invention are only relative to the relative positional relationship of the components of the present invention in the drawings.

[0071] Reference Figures 1 to 6 , a method for detecting and treating karst caves in the anchor cable area of ​​a limestone stratum retaining structure, comprising the following steps:

[0072] S1. Delineation of the treatment scope of the cave in the anchor cable area;

[0073] S11. According to the plane layout and vertical layout of the anchor cables (in the anchor cable construction drawing), (demarcate) the scope of the karst cave treatment in the anchor cable area;

[0074] S2, advance drilling in the anchor area;

[0075] S21. In combination with the detailed exploration boreholes 11, a plurality of advance boreholes 12 (e.g., a row of advance boreholes 12) are set in the arrangement area of ​​the anchor cable anchoring section 21; wherein the detailed exploration boreholes 11 are obtained by the previous "large spacing" drilling, and "in combination with the detailed exploration boreholes 11, a row of advance boreholes 12 are set in the arrangement area of ​​the anchor cable anchoring section 21" is equivalent to setting advance boreholes 12 for intensified exploration in combination with the detailed exploration boreholes 11 arranged at "large spacing" (refer to Figure 1 );

[0076] S3, anchor area to explore the boundaries of cave 7;

[0077] S31, within the scope of the karst cave treatment in the anchor cable area, for the karst cave 7 initially revealed by the detailed survey drilling hole 11 and the advance drilling hole 12 in the arrangement area of ​​the anchor cable anchoring section 21, drilling a detection hole 13 to detect the karst cave boundary M;

[0078] S4, grouting treatment of cave in anchor cable area;

[0079] S41, part of the "advance drilling hole 12 or the edge detection hole 13" also serves as a grouting hole 4, and the grouting hole 4 is divided into a central hole 42 and a peripheral hole 41 according to the area and boundary of the cave 7; wherein part of the central hole 42 also serves as a vent hole 421, and the vent hole 421 can maintain the atmospheric pressure balance in the cave 7 during grouting, so that the cave 7 can be grouted normally;

[0080] S42, grouting the karst cave 7 through the grouting hole 4 according to the type of the karst cave 7;

[0081] S5. Detection of grouting effect in the cave of anchor cable area;

[0082] S51. After the grouting is completed, the cave filling grouting effect and the cave grouting reinforcement effect are checked;

[0083] S6, anchor cable 2 construction and anchor cable 2 bearing capacity test;

[0084] S61, after completing the cave grouting treatment and cave grouting effect detection, locate the anchor cable 2 hole position at the enclosure structure 33, and drill to the designed depth of the anchor cable 2;

[0085] S62, carrying out the process of laying anchor cables 2, grouting and constructing anchor cable waist beams 31;

[0086] S63, after the concrete of the anchor cable waist beam 31 reaches the design strength, the anchor cable 2 is tensioned, and the pull-out resistance and locking force of the anchor cable 2 are tested.

[0087] Among them, steps S1 to S6 specifically solve the problems of difficulty in construction of anchor cables of the pile-anchor support system in limestone areas when encountering underground caves and lack of stability guarantee after anchoring.

[0088] Reference Figures 1 to 6 In one embodiment, in the step S11, the anchor cable 2 includes an anchor cable anchoring section 21 and an anchor cable free section 22; the anchor cable area karst cave treatment range includes a plane treatment range 5 and a vertical treatment range 6;

[0089] The plane processing range 5 includes a first plane boundary 51, a second plane boundary 52, a third plane boundary 53 and a fourth plane boundary 54; the first plane boundary 51 maintains a first set distance G1 with the first side anchor cable C, the second plane boundary 52 maintains a second set distance G2 with the second side anchor cable D, the third plane boundary 53 maintains a third set distance G3 with the first end E of the anchor cable anchoring section 21, and the fourth plane boundary 54 maintains a fourth set distance G4 with the second end F of the anchor cable anchoring section 21; the plane area enclosed by the first plane boundary 51, the second plane boundary 52, the third plane boundary 53 and the fourth plane boundary 54 is the plane processing range 5;

[0090] The vertical processing range 6 includes a ground boundary 61, an underground boundary 62, a first vertical boundary 63 and a second vertical boundary 64; the ground boundary 61 is a flat ground; the underground boundary 62 maintains a fifth set distance G5 from the lowest point of the anchor cable anchoring section 21; the first vertical boundary 63 maintains a sixth set distance G6 from the first end E of the leftmost X1 anchor cable anchoring section 21; the second vertical boundary 64 maintains a seventh set distance G7 from the second end F of the rightmost X2 anchor cable anchoring section 21; the vertical area enclosed by the ground boundary 61, the underground boundary 62, the first vertical boundary 63 and the second vertical boundary 64 is the vertical processing range 6;

[0091] The three-dimensional area formed by the plane treatment range 5 and the vertical treatment range 6 (Note: to help people understand the "three-dimensional area", it can be understood as a "three-dimensional plot") is the anchor area cave treatment range to be determined, and the anchor area cave treatment range is the anchor anchoring section cave treatment range (the anchor anchoring section cave treatment range is the range to be clearly defined and treated by this method).

[0092] Reference Figures 1 to 6 In one embodiment, the first setting distance G1 and the second setting distance G2 are both 3m; the third setting distance G3 and the fourth setting distance G4 are 5m; the fifth setting distance G5, the sixth setting distance G6, and the seventh setting distance G7 are 5m (Note: refer to Figure 1 and 2 The auxiliary line Y and the vertical mark T are used to understand this).

[0093] Reference Figures 1 to 6In one embodiment, in the step S21, the detailed exploration borehole 11 also serves as the advance borehole 12, and the advance borehole 12 obtained in combination with the subsequent drilling is provided with a plurality of advance boreholes 12, which are arranged in a row, and a plurality of the advance boreholes 12 are respectively adjacent to the arrangement position of the anchor cable anchoring section 21; a plurality of the advance boreholes 12 (their hole axes) are perpendicular to the horizontal plane formed by the planar processing range 5; a plurality of the advance boreholes 12 maintain a set hole spacing P between adjacent ones.

[0094] Reference Figures 1 to 6 In one embodiment, a plurality of the advance drilling holes 12 maintain a hole spacing P of 3 m between adjacent ones; preferably, for areas with complex underground conditions or other areas that require intensive research, the hole layout range of the advance drilling holes 12 should be appropriately expanded and the hole spacing P of the advance drilling holes 12 should be reduced according to actual conditions to achieve encrypted exploration, such as increasing the number of rows of the advance drilling holes 12, such as reducing the hole spacing P of the advance drilling holes 12 to 2 m or 1.5 m.

[0095] Reference Figures 1 to 6 In one embodiment, in the step S31, (the detailed exploration drilling hole also serves as the advance drilling hole, so it can be described only by the advance drilling hole) when the cave 7 revealed by the advance drilling hole 12 is within the cave treatment range of the anchor cable area, the advance drilling hole 12 (such as its hole center) is used as the base point of the "cross" axis, and then a series of exploration holes 131 are drilled along the four axial length directions K of the "cross" axis at a set spacing L1 (such as 2m);

[0096] If the first-order edge detection hole 131 finds a cave 7 during edge detection, the first-order edge detection hole 131 is used as the base point of the "cross" axis, and then one or more axial length directions K of the "cross" axis are selected, and the second-order edge detection holes 132 are drilled at a set spacing L2 (such as 2m) until the cave boundary M is found or the anchor area cave treatment range boundary N is reached. Preferably, the set spacing L1 and the set spacing L2 maintain the same fixed value, such as 2m.

[0097] For a larger cave 7, if it is found that its scope has exceeded the scope of the anchor area cave treatment (refer to Figure 2 ), you can use the following steps to handle it:

[0098] A1. First, drill a hole at the boundary N of the cave treatment range in the anchor cable area;

[0099] A2, using quick-setting slurry to seal the edges, isolating the cave R1 within the treatment range of the cave in the anchor area and the cave R2 outside the treatment range of the cave in the anchor area;

[0100] A3. Then, grouting treatment is performed on the cave R1 within the treatment range of the cave in the anchor cable area.

[0101] Reference Figures 1 to 6 In one embodiment, in the step S41, the grouting pipe is buried in the selected grouting hole 4, and grouting can be performed only after the gap between the "cavern roof, grouting pipe" and the "grouting hole wall" is closed.

[0102] Reference Figures 1 to 6 In one embodiment, in the step S41, the size and post-treatment status of the cave 7 need to be checked while grouting. The checking method is: after preliminarily estimating the size of the cave 7 based on the grouting volume and the diameter of the cave 7 detected by the grouting hole 4, inspection holes are arranged around it; when checking the holes, it is necessary not only to check the extension of the cave 7, but also to check the grouting filling status of the cave 7; if the cave 7 is found to be not fully grouted, the inspection holes need to be used to continue grouting. Preferably, some inspection holes can be used as "quality inspection holes" (quality inspection holes are described below) later.

[0103] Reference Figures 1 to 6 In one embodiment, in the step S42, the cave 7 is divided into an unfilled cave 71, a semi-filled cave 72 and a fully filled cave 73 according to the natural filling inside the cave; wherein the natural filling refers to the filling that naturally existed inside the cave before;

[0104] At the peripheral hole 41, the unfilled cave 71 or the semi-filled cave 72 is filled with cement-water glass double slurry;

[0105] At the central hole 42, the "unfilled cave 71 or the semi-filled cave 72" with a height ≥3m is first filled with cement mortar and then compacted with cement slurry; (at the central hole 42) the "unfilled cave 71 or the semi-filled cave 72" with a height less than 3m is filled with mortar or cement slurry; (at the central hole 42) if the standard penetration value of the natural filling in the fully filled cave 73 is less than 10 blows, compacted with cement slurry; (at the central hole 42) if the standard penetration value of the natural filling in the fully filled cave 73 is ≥10 blows, no treatment is done.

[0106] Among them, cement slurry is needed to seal the holes after grouting is completed.

[0107] Reference Figures 1 to 6 In one embodiment, in the step S4, a field grouting test should be carried out before construction, and the grouting parameters are adjusted according to the test results;

[0108] For the peripheral holes 41, grouting should be performed with relatively low pressure (e.g., grouting pressure is recommended to be 0.6Mpa to 0.8Mpa), multiple times (e.g., grouting times are recommended to be 3 to 4 times), and relatively large amount of control;

[0109] For the central hole 42, cement slurry should be injected three times at a grouting pressure of 0Mpa to 1.0Mpa and a grouting speed of 30L / min to 70L / min. The grouting pressure should be gradually increased. After reaching the final grouting pressure, grouting should be continued for more than 10 minutes. The slurry is made of 42.5 grade ordinary Portland cement with a water-cement ratio of 1.0 to 1.5. The actual grouting parameters should be determined based on field tests.

[0110] If a large amount of grouting is injected during the first grouting of the peripheral holes 41 and the pressure does not meet the design requirements, the peripheral holes 41 and the central hole 42 may be grouted alternately.

[0111] Reference Figures 1 to 6 In one embodiment, the cave filling grouting effect inspection mentioned in the step S51 is carried out by using the "secondary grouting" method to check the filling rate (after grouting of cave 7), and the pressure is gradually increased from 0Mpa to 0.2Mpa and maintained for 10min to 15min; the density (after grouting of cave 7) is checked by using the standard penetration method, and the standard penetration value reaches "hard" soil, which is excellent, and the standard penetration value reaches "hard plastic" soil, which is qualified.

[0112] Reference Figures 1 to 6 In one embodiment, the cave grouting reinforcement effect inspection mentioned in the step S51 adopts core drilling, and performs compression test, water pressure test and in-situ standard penetration test for inspection. (Note: the grouting reinforcement of cave 7 is obtained by grouting several grouting holes 4. When inspecting, core drilling can be performed through the grouting holes 4 or core drilling can be performed separately. Therefore, the number of inspection positions (i.e., the number of inspections)) is not less than 1% of the number of grouting holes 4. It is required that each cave 7 should be inspected at least once. Among them, the test block obtained by random drilling and coring is subjected to compression test, and its unconfined compressive strength is required to be not less than 0.2Mpa; among them, (the quality inspection hole can be obtained by drilling, or some "grouting holes 4 or inspection holes" can also serve as quality inspection holes) the water pressure inspection of the quality inspection holes should be carried out at least seven days after the grouting of the unit project is completed; among them, the water permeability of the quality inspection holes after the cave reinforcement treatment should not be greater than 10Lu, the qualified rate should be more than 85%, and the maximum water permeability of the remaining unqualified hole sections should not exceed 15Lu, and should not be concentrated; among them, during the in-situ standard penetration test (the in-situ standard penetration test can be carried out through the grouting hole 4), the standard penetration blows are required to be not less than 10 blows.

[0113] Reference Figures 1 to 6 In one embodiment, in the step S61, if a cave 7 is found during the hole forming process of the anchor cable 2, grouting treatment should be carried out in time from the anchor cable hole, and the hole forming can be continued after the treatment is completed;

[0114] In the step S62, the anchor group effect and the adverse effects of the cave 7 should be fully considered during construction. The effective anchoring length of the anchor cable 2 should not be less than the designed anchoring length and should penetrate the cave into the stable rock layer for not less than 3m (Note: the effective anchoring length of the anchor cable = the actual length of the anchor cable anchoring section - the length of the anchor cable anchoring section passing through the cave);

[0115] In the step S63, in order to ensure the effective bearing capacity of the anchor cable 2 in the limestone area, the anchor cable passing through the cave, when applying prestress, includes the following steps:

[0116] B1. First determine which value is the larger one, "1.4 times Fm and 0.8 times Fn", where Fm is the "standard value of calculated tension" and Fn is the "standard value of the ultimate tensile strength of the anchor cable";

[0117] B2. If 1.4Fm is a larger value than 0.8Fn, then when applying prestress, it should be tensioned to 1.4Fm first, and then released and retracted to the locking force value;

[0118] If 0.8Fn is a larger value than 1.4Fm, then when applying prestress, it should be tensioned to 0.8Fn first, and then released and retracted to the locking force value;

[0119] Wherein, in the step S63, the number of anchor cable bearing capacity tests is not less than 10% and is not less than ten (Note: the anchor cable bearing capacity includes the pull-out resistance and the locking force).

[0120] Reference Figures 1 to 6 In one embodiment, the enclosure structure 32 is an underground continuous wall.

[0121] The method for detecting and treating karst caves in the anchor cable area of ​​a limestone stratum retaining structure of the present invention reduces the risk of collapse of the pile-anchor support system in the limestone stratum karst cave development area during the construction of the anchor cable 2, reduces the risk of water inrush and gushing during the construction of the anchor cable 2 and the excavation of the foundation pit, can effectively ensure the bearing capacity of the anchor cable 2 of the pile-anchor support system in the limestone stratum karst development area, and improves the safety of the construction of the underground structure 33.

[0122] For other contents of the method for detecting and treating karst caves in the anchor cable area of ​​a limestone stratum retaining structure described in the present invention, please refer to the prior art and will not be described in detail here.

[0123] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Therefore, any modification, equivalent change and modification made to the above embodiment based on the technical essence of the present invention without departing from the technical solution of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for detecting and treating karst caves in the anchor cable area of ​​a limestone stratum retaining structure, characterized in that: The following steps are involved: S1. Delineation of the treatment scope of the cave in the anchor cable area; S11. Determine the treatment scope of the karst cave in the anchor area according to the plane layout and vertical layout of the anchor cables; S2, advance drilling in the anchor area; S21. Combined with detailed drilling, several advance drilling holes are set in the anchor cable anchoring section layout area; S3, anchor cable area to explore the cave boundary; S31, within the scope of the karst cave treatment in the anchor cable area, for the karst caves initially revealed by detailed exploration drilling and advance drilling in the anchor cable anchoring section arrangement area, drilling edge detection holes to detect the boundaries of the karst caves; S4, grouting treatment of cave in anchor cable area; S41, some of the "advance drilling holes or the edge detection holes" also serve as grouting holes, and the grouting holes are divided into central holes and peripheral holes according to the cave area and boundaries; wherein, some of the central holes also serve as ventilation holes; S42, grouting the cave through the grouting hole according to the type of the cave; S5. Detection of grouting effect in the cave of anchor cable area; S51. After the grouting is completed, the cave filling grouting effect and the cave grouting reinforcement effect are checked; S6. Anchor cable construction and anchor cable bearing capacity testing; S61. After completing the cave grouting treatment and cave grouting effect detection, locate the anchor cable hole position at the retaining structure and drill to the designed depth of the anchor cable; S62, carry out the process of laying anchor cables, grouting and constructing anchor cable waist beams; S63. After the anchor cable waist beam concrete reaches the design strength, the anchor cable is tensioned and the pull-out resistance and locking force of the anchor cable are tested.

2. The method for detecting and treating karst caves in the anchor cable area of ​​the limestone stratum retaining structure according to claim 1 is characterized in that: In the step S11, the anchor cable includes an anchor cable anchoring section and an anchor cable free section; the karst cave treatment range of the anchor cable area includes a plane treatment range and a vertical treatment range; The plane processing range includes a first plane boundary, a second plane boundary, a third plane boundary and a fourth plane boundary; the first plane boundary maintains a first set distance with the first side anchor cable, the second plane boundary maintains a second set distance with the second side anchor cable, the third plane boundary maintains a third set distance with the first end of the anchor cable anchoring section, and the fourth plane boundary maintains a fourth set distance with the second end of the anchor cable anchoring section; the plane area enclosed by the first plane boundary, the second plane boundary, the third plane boundary and the fourth plane boundary is the plane processing range; The vertical processing range includes a ground boundary, an underground boundary, a first vertical boundary and a second vertical boundary; the ground boundary is a flat ground; the underground boundary maintains a fifth set distance from the lowest point of the anchor cable anchoring section; the first vertical boundary maintains a sixth set distance from the first end of the leftmost anchor cable anchoring section; the second vertical boundary maintains a seventh set distance from the second end of the rightmost anchor cable anchoring section; the vertical area enclosed by the ground boundary, the underground boundary, the first vertical boundary and the second vertical boundary is the vertical processing range; The three-dimensional area formed by the plane treatment range and the vertical treatment range is the anchor area cave treatment range to be determined.

3. The method for detecting and treating karst caves in the anchor cable area of ​​the limestone stratum retaining structure according to claim 2 is characterized in that: In the step S21, the detailed exploration drilling hole also serves as the advance drilling hole, and the advance drilling holes obtained in combination with the subsequent drilling holes are provided with a total of several advance drilling holes, and are arranged in a row, and several of the advance drilling holes are respectively adjacent to the arrangement positions of the anchor cable anchoring sections; several of the advance drilling holes are perpendicular to the horizontal plane formed by the planar processing range; and several of the advance drilling holes, between adjacent holes, maintain a set hole spacing.

4. The method for detecting and treating karst caves in the anchor cable area of ​​the limestone stratum retaining structure according to claim 3 is characterized in that: In the step S31, when the karst cave revealed by the advance drilling is within the karst cave treatment range of the anchor cable area, the advance drilling is used as the base point of the "cross" axis, and then a sequence of edge exploration holes is drilled along the four axial length directions of the "cross" axis at a set interval; If a cave is found during the exploration of the first-order edge exploration holes, the first-order edge exploration holes are used as the base point of the "cross" axis, and then one or more axial length directions of the "cross" axis are selected to drill second-order edge exploration holes at a set interval until the boundary of the cave is found or the boundary of the cave treatment range of the anchor cable area is reached.

5. The method for detecting and treating karst caves in the anchor cable area of ​​the limestone stratum retaining structure according to claim 1, characterized in that: In the step S41, the grouting pipe is buried in the selected grouting hole, and grouting can be performed only after the gap between the "cavern roof, grouting pipe" and the "grouting hole wall" is closed.

6. The method for detecting and treating karst caves in the anchor cable area of ​​the limestone stratum retaining structure according to claim 1, characterized in that: In the step S42, the cave is divided into an unfilled cave, a semi-filled cave and a fully filled cave according to the natural filling conditions inside the cave; At the peripheral holes, the unfilled cave or the semi-filled cave is filled with cement-water glass double slurry; At the central hole, the "said unfilled cave or the said semi-filled cave" with a height ≥3m shall be filled with cement mortar first and then compacted grouting with cement slurry; the "said unfilled cave or the said semi-filled cave" with a height less than 3m shall be filled with mortar or cement slurry; if the standard penetration value of the natural filling in the said fully filled cave is less than 10 blows, compacted grouting with cement slurry shall be used; if the standard penetration value of the natural filling in the said fully filled cave is ≥10 blows, no treatment shall be given.

7. The method for detecting and treating karst caves in the anchor cable area of ​​the limestone stratum retaining structure according to claim 1, characterized in that: In the step S4, a field grouting test should be carried out before construction to determine the grouting parameters; For the peripheral holes, the grouting pressure is 0.6Mpa to 0.8Mpa, and the number of grouting times is 3 to 4 times; For the central hole, cement slurry should be injected three times at a grouting pressure of 0Mpa to 1.0Mpa and a grouting speed of 30L / min to 70L / min. The grouting pressure should be gradually increased. After reaching the final grouting pressure, grouting should be continued for more than 10 minutes. The slurry is made of 42.5 grade ordinary Portland cement with a water-cement ratio of 1.0 to 1.

5.

8. The method for detecting and treating karst caves in the anchor cable area of ​​the limestone stratum retaining structure according to claim 1, characterized in that: The cave filling grouting effect inspection mentioned in the step S51 is to check the filling rate by the "secondary grouting" method, and the pressure is gradually increased from 0Mpa to 0.2Mpa, and maintained for 10min to 15min; the density is checked by the standard penetration method, and the standard penetration value reaches "hard" soil, which is excellent, and the standard penetration value reaches "hard plastic" soil, which is qualified.

9. The method for detecting and treating karst caves in the anchor cable area of ​​the limestone stratum retaining structure according to claim 1, characterized in that: The inspection of the grouting reinforcement effect of the cave mentioned in the step S51 is carried out by coring through drilling, and performing compression test, water pressure test and in-situ standard penetration test, and the number of inspections shall not be less than 1% of the number of grouting holes; each cave is required to be inspected at least once; wherein, the test blocks obtained by random drilling and coring are subjected to compression test, and their unconfined compressive strength is required to be not less than 0.2Mpa; wherein, the water pressure inspection of the quality inspection holes shall be carried out at least seven days after the grouting of the unit project is completed; wherein, the water permeability of the quality inspection holes after the karst cave reinforcement treatment shall not be greater than 10Lu, the qualified rate shall be more than 85%, the maximum water permeability of the unqualified hole sections shall not exceed 15Lu, and they shall not be concentrated; wherein, during the in-situ standard penetration test, the number of standard penetration blows is required to be not less than 10 blows.

10. The method for detecting and treating karst caves in anchor cable areas of limestone stratum retaining structures according to claim 1, characterized in that: In the step S62, the effective anchoring length of the anchor cable should not be less than the designed anchoring length and should penetrate the cave into the stable rock layer for not less than 3m; In the step S63, in order to ensure the effective bearing capacity of the anchor cable in the limestone area, the anchor cable passing through the cave, when applying prestress, includes the following steps: B1. First determine which value is the larger one, "1.4 times Fm and 0.8 times Fn", where Fm is the "standard value of calculated tension" and Fn is the "standard value of the ultimate tensile strength of the anchor cable"; B2. If 1.4Fm is a larger value than 0.8Fn, then when applying prestress, it should be tensioned to 1.4Fm first, and then released and retracted to the locking force value; If 0.8Fn is a larger value than 1.4Fm, then when applying prestress, it should be tensioned to 0.8Fn first, and then released and retracted to the locking force value; Wherein, in the step S63, the number of anchor cables tested for bearing capacity is not less than 10% and not less than ten.

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