Construction method for horizontally treating karst

Abstract

The invention discloses a construction method for horizontally treating karst, which comprises the following steps: S1, in a target range of a tunnel, selecting a site for constructing a temporary vertical shaft; s2, a temporary vertical shaft is excavated in a manner of hanging the shaft wall upside down; s3, horizontal drilling is conducted in the temporary vertical shaft, and a plurality of horizontal grouting holes are formed; s4, a stop-grouting plug is arranged at the orifice section of the horizontal grouting hole, horizontal grouting is carried out in the hole, and the surrounding stratum is filled; s5, the temporary vertical shaft is subjected to concrete backfilling and compacting; and S6, a shield tunneling mode is adopted, and later shield tunnel construction is completed. The construction method for horizontally treating the karst is suitable for karst filling treatment without site operation conditions on the ground, the ground temporary vertical shaft is adopted for providing a horizontal drilling operation face, and exploration and irrigation are conducted at the same time, so that filling of cavities such as the karst possibly existing around the tunnel planned to be built in the later period is completed, and a safe and stable uniform stratum is provided for subsequent tunneling.

Description

Technical Field

[0001] The invention relates to the technical field of rail transit tunnels, and in particular to a construction method for horizontally treating karst. Background Art

[0002] With the rapid development of rail transit projects in major cities, more and more adverse geological conditions are encountered, among which adverse geological conditions represented by soluble rocks such as limestone and dolomite are emerging in various regions. There are many karst treatment methods, which need to be determined comprehensively based on site conditions, cave size, distance and other factors, such as filling, bridging in the cave and other methods. At present, the main methods of karst exploration are drilling, pit exploration, and geophysical exploration, among which geophysical exploration mainly includes electromagnetic wave CT detection, resistivity method, high-density electrical method, geological radar, shallow seismic method, etc.

[0003] In the construction of rail transit projects, electromagnetic wave CT detection is the most commonly used method for karst geophysical exploration, due to factors such as the size of the cave, the depth of the project and the surrounding environment. The main karst treatment method is "ground exploration first, then ground filling", which has been successfully applied to the construction of rail transit in various places. The premise of this treatment method is ground drilling exploration, combined with electromagnetic wave CT detection scanning. Drilling and electromagnetic wave CT detection both require certain ground site conditions. If there are no obstacles on the ground or underground, ground vertical drilling can be carried out. The net distance between boreholes is not more than 30m. Considering the drilling economy and scanning accuracy requirements, the commonly used borehole net distance is generally 20-25m, otherwise the accuracy of existing equipment is not enough to support the exploration of karst cavities. When this method is applied, it is often restricted by the ground structures and cannot be arranged with vertical boreholes. The existing drilling technology can tilt the vertical boreholes appropriately to meet the requirements of electromagnetic wave CT detection, but it still requires that the net distance between the boreholes is not more than 30m. Therefore, in actual projects, if there are large-scale structures on the ground, the ground structures need to be demolished before karst exploration can be carried out, which will lead to the demolition of a large number of structures, increase project investment and social stability risks. In addition, in some projects, although the ground drilling arrangement is available, it is often difficult to requisition the ground drilling site, so it is necessary to study a karst treatment method that overcomes the problem of ground electromagnetic wave CT detection site.

[0004] In the existing public technology, CN202311511209.X proposes a karst treatment method using a pilot tunnel as a grouting operation surface. When the upper part of the rock layer is a sand layer, there is a great safety risk in using a pilot tunnel to excavate and construct a sand layer tunnel under the action of groundwater. Once water seepage and sand leakage occur during the excavation process, the pilot tunnel heading will collapse, thereby affecting the safety of the upper structures. In addition, the excavation of the pilot tunnel for radial grouting and then filling the karst is a relatively complicated process. Therefore, it is necessary to propose a karst treatment method that is suitable for wide stratum adaptability and simple process. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the above-mentioned background technology and provide a construction method for horizontal karst treatment. The method is suitable for various tunnel engineering constructions where karst exploration cannot be carried out on the ground, and has strong adaptability to the strata, and can meet the stability of the strata around the tunnel during the later shield tunnel construction.

[0006] To achieve the above object, the present invention provides a construction method for horizontal karst treatment, comprising the following steps:

[0007] S1: Select a site within the target range of the tunnel for the construction of a temporary shaft;

[0008] S2: excavating a temporary shaft by hanging the shaft wall upside down;

[0009] S3: Horizontal drilling is performed in the temporary shaft to form a number of horizontal grouting holes;

[0010] S4: a grout stopper is set at the orifice section of the horizontal grouting hole, and horizontal grouting is carried out in the hole to fill the surrounding strata;

[0011] S5: Use concrete backfill to compact the temporary shaft;

[0012] S6: Use shield tunneling method to complete the construction of the later shield tunnel.

[0013] As a preferred implementation, in step S1, based on the geological division of the stratum area where the tunnel is located and the analysis of adjacent geological drilling holes, the tunnel range where karst may exist is taken as the target range.

[0014] As a preferred implementation, in step S2, the cross-sectional shape of the temporary shaft is rectangular; when the temporary shaft is excavated, a grid steel frame is erected every 0.5-1.0m of excavation, and the anchor support is firmly overlapped with the grid steel frame; the longitudinal spacing of the anchor support is (0.5-1)m×1m.

[0015] As a preferred embodiment, in step S2, the steel bars of the grid steel frame and the rod bodies of the anchor supports are both made of glass fiber bars.

[0016] As a preferred implementation, in step S3, the linearity of the horizontal drilling is consistent with the linearity of the shield tunnel to be constructed later.

[0017] As a preferred embodiment, in step S3, the spacing between the horizontal grouting holes is 1.5×1.5 m, and the length is 2 to 3 m of the karst development stratum under the building.

[0018] As a preferred implementation, in step S3, if karst is encountered during the drilling process, karst filling grouting is implemented; if karst is not encountered during the drilling process, formation filling grouting is implemented.

[0019] As a preferred implementation method, in step S3, the specific implementation steps of horizontal drilling are as follows: first, use a drill bit to drill a hole, then use a reaming drill bit and a spiral groove reaming drill rod to reame the hole, after cleaning the hole, place the casing horizontally and grout the casing to solidify it, and then use D76 drilling in the casing.

[0020] As a preferred embodiment, in step S3, the control standard of karst filling grouting is as follows: the grouting operation can be terminated only when the following requirements are met at the same time: 1) under the maximum design pressure, when the injection rate of the grouting hole section is not greater than 1.0L / min, the grouting operation can be terminated after continuing the grouting for 20min; 2) during the whole grouting process, if the grouting time exceeds 2 hours and the grouting volume exceeds 100m 3 , stop grouting and add horizontal drill holes on the temporary shaft for filling treatment.

[0021] As a preferred implementation, in step S5, the temporary shaft is backfilled with C10-C15 low-grade concrete.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] Firstly, the karst construction treatment method proposed in the present invention is applicable to various tunnel engineering constructions where karst exploration cannot be carried out on the ground, has strong adaptability to strata, or can be applied to karst treatment of various tunnels without field operation conditions on the ground.

[0024] Secondly, the horizontal karst treatment construction method of the present invention can overcome the difficulty in site requisition for electromagnetic wave CT detection scanning and ground drilling backfilling in karst strata represented by soluble rocks such as limestone and dolomite, so as to meet the problem of stabilization of the strata around the tunnel during the later shield tunnel construction.

[0025] Thirdly, in the construction method for horizontal karst treatment of the present invention, the excavation of the temporary shaft is carried out by excavating the shaft wall in an inverted manner to a specified elevation. To facilitate excavation and support erection, the plane size of the shaft is rectangular, and the support structure adopts a grid steel frame + anchor rods, wherein the steel bars in the grid steel frame and the rod bodies of the anchor rods are made of fiberglass bars to avoid the steel bars left in the stratum at a later stage from adversely affecting subsequent shield excavation.

[0026] Fourthly, in order to ensure dense filling during the grouting process, the horizontal karst treatment construction method of the present invention sets a grouting stopper at the orifice section to ensure the filling volume and filling pressure.

[0027] Fifthly, in the horizontal karst treatment construction method of the present invention, casing is buried and reinforced, which can improve the accuracy of long-distance horizontal drilling and prevent the occurrence of drilling collapse, etc., and is suitable for horizontal drilling in various complex strata.

[0028] Sixthly, the horizontal karst treatment construction method of the present invention is suitable for karst filling treatment methods without ground site working conditions, that is, a temporary ground shaft is used to provide a horizontal drilling working surface, and exploration and pouring are carried out at the same time, so as to fill the karst and other cavities that may exist around the tunnel to be built in the later stage, and provide a safe, stable and uniform stratum for subsequent tunnel excavation. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Karst plan layout for ground borehole filling;

[0030] Figure 2 Layout of karst profile for surface drilling and filling;

[0031] Figure 3 This is a schematic diagram of karst treatment in the cave;

[0032] Figure 4 This is the plan of the temporary shaft;

[0033] Figure 5 This is a cross-section diagram of a temporary shaft;

[0034] Figure 6 Karst profile for horizontal grouting treatment in a shaft;

[0035] In the figure, there are ground buildings 1, caves 2, temporary shafts 3, anchor support 31, grid steel frames 32, shield tunnels 4, horizontal drilling and grouting 5, concrete backfilling 6, and ground drilling 7. DETAILED DESCRIPTION

[0036] The following is a detailed description of the implementation of the present invention in conjunction with the implementation cases, but they do not constitute a limitation of the present invention and are only given as examples. At the same time, the advantages of the present invention will become clearer and easier to understand through the description.

[0037] The construction method for horizontally treating karst of the present invention comprises the following steps:

[0038] S1: Based on the geological division of the stratum area where the tunnel is located and the analysis of adjacent geological drilling holes, the tunnel range where karst may exist is taken as the target range, and a suitable site is selected for temporary shaft construction;

[0039] S2: Excavate a temporary shaft 3 by hanging the shaft wall in an inverted manner; Technical requirements for temporary shaft construction: The excavation of the temporary shaft can be excavated to a specified elevation by hanging the shaft wall in an inverted manner according to the specific stratum conditions. To facilitate excavation and erection of supports, the cross-sectional shape of the temporary shaft is rectangular, and the support structure adopts grid steel frame + anchor support. The steel bars in the grid steel frame and the rod bodies of the anchors are made of glass fiber bars to avoid the steel bars left in the stratum in the later period from causing adverse effects on subsequent shield excavation. During excavation, a grid steel frame 32 is erected for every 0.5-1.0m of excavation, and the anchor support 31 is firmly overlapped with the grid steel frame 32. The longitudinal spacing of the anchor support is 0.5-1.0m×1m, and the specific length is determined according to the stratum conditions and excavation depth.

[0040] Taking a certain project as an example, the upper soil layer support parameters are 500mm thick C25 shotcrete lining + 5.0m long D22 cement coil anchor + four-leg grid steel frame, with a vertical spacing of 500mm; the lower limestone stratum support parameters are 500mm thick C25 shotcrete lining + 3.0m long D22 cement coil anchor + four-leg grid steel frame, with a vertical spacing of 1000mm.

[0041] S3: Horizontal drilling is carried out in the temporary shaft to form several horizontal grouting holes. The linearity of the horizontal drilling is consistent with the linearity of the shield tunnel to be constructed later, and the elevation direction is a certain range of the tunnel up, down, left and right. Technical requirements for horizontal grouting: The main function of horizontal grouting is to fill the karst caves that may exist around the tunnel to be constructed later. However, due to the limitations of ground site conditions, the specific distribution of karst cannot be ascertained. Therefore, blind grouting is implemented when horizontal grouting is used in the temporary shaft, that is, horizontal grouting holes are arranged on the side wall of the temporary shaft. The spacing between the grouting holes is 1.5*1.5m, and the length is 2-3m of the karst development stratum under the building. The grouting drilling adopts D76, and the material of the grouting pipe is plastic material, with an outer diameter of 42mm and a wall thickness of 3mm. The middle opening along the longitudinal length of the grouting pipe is 8-10mm, and the hole spacing is 0.5-1.0m.

[0042] When karst is encountered during the drilling process, karst filling grouting index control is implemented; when karst is not encountered, formation filling grouting is implemented. During the grouting process, the size of the karst can be calculated based on the comparison of the volume of the drilling hole and the grouting amount.

[0043] Karst filling grouting control standard: The grouting operation can be terminated only when the following requirements are met at the same time: 1) Under the maximum design pressure, when the injection rate of the grouting hole section is not greater than 1.0L / min, the grouting operation can be terminated after grouting for 20 minutes; 2) During the whole grouting process, if the grouting time is too long (such as more than 2 hours), the grouting volume is too large (such as more than 100m 3 ), it is recommended to stop grouting and add other horizontal boreholes on the temporary shaft for filling treatment.

[0044] In order to improve the accuracy of long-distance horizontal drilling and overcome the problem of difficulty in drilling through sand layers, on the basis of the above-mentioned drilling and grouting, first use a Φ110mm drill bit to drill holes (the drilling depth is the horizontal distance between the shaft and the sand layer, which is used for the plastic casing below after the reaming drill bit is excavated, and is used to solve the problem of hole collapse in the formation with difficulty in drilling), and then use a Φ153mm reaming drill bit and a high-strength spiral groove reaming drill rod to reaming and drill, and after cleaning the hole, place a Φ146mm plastic casing horizontally and grout the casing to solidify it, and then use D76 drilling in the casing. The casing is buried and reinforced in the present invention, which can improve the accuracy of long-distance horizontal drilling, prevent the occurrence of drilling collapse, etc., and is suitable for horizontal drilling of various complex formations.

[0045] S4: After the horizontal drilling is completed, a grouting plug is set at the orifice section of the horizontal grouting hole, and horizontal grouting is carried out in the hole to fill the surrounding strata. In this process, the possible karst is filled densely; in order to ensure dense filling during the grouting process, a grouting plug is set at the orifice section to ensure the filling volume and filling pressure.

[0046] S5: After the karst is treated, the temporary shaft is backfilled with concrete to make it dense; backfilling technical requirements: After the karst treatment of the entire section is completed, in order to ensure the smooth excavation of the shield tunnel in the later stage, the temporary shaft is backfilled with C10-C15 low-grade concrete. When the backfill body reaches a certain strength, it can meet the requirements of the later shield excavation.

[0047] S6: Use shield tunneling method to complete the construction of the later shield tunnel 4.

[0048] The karst filling treatment method proposed in the present invention is suitable for various tunnel engineering constructions where karst exploration cannot be carried out on the ground, has strong adaptability to strata, or is applied to karst treatment of various tunnels without field operation conditions on the ground.

[0049] The above are only specific embodiments of the present invention. It should be pointed out that any changes or substitutions that can be easily thought of by any technician familiar with the field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention, and the rest not described in detail belong to the prior art.

Claims

1. A construction method for horizontal karst treatment, characterized in that: The steps include: S1: Select a site within the target range of the tunnel for the construction of a temporary shaft; S2: excavating a temporary shaft by hanging the shaft wall upside down; S3: Horizontal drilling is performed in the temporary shaft to form a number of horizontal grouting holes; S4: a grout stopper is set at the orifice section of the horizontal grouting hole, and horizontal grouting is carried out in the hole to fill the surrounding strata; S5: Use concrete backfill to compact the temporary shaft; S6: Use shield tunneling method to complete the construction of the later shield tunnel.

2. The construction method for horizontal karst treatment according to claim 1 is characterized by: In step S1, based on the geological division of the stratum area where the tunnel is located and the analysis of adjacent geological drilling holes, the tunnel range where karst may exist is taken as the target range.

3. The construction method for horizontal karst treatment according to claim 2 is characterized in that: In step S2, the cross-sectional shape of the temporary shaft is rectangular; when the temporary shaft is excavated, a grid steel frame is erected every 0.5-1.0m of excavation, and the anchor support is firmly overlapped with the grid steel frame; the longitudinal spacing of the anchor support is (0.5-1)m×1m.

4. The construction method for horizontal karst treatment according to claim 3 is characterized by: In the step S2, the steel bars of the grid steel frame and the rod bodies of the anchor rod supports are both made of glass fiber bars.

5. The construction method for horizontal karst treatment according to claim 4 is characterized in that: In step S3, the linearity of the horizontal drilling is consistent with the linearity of the shield tunnel to be constructed later.

6. The construction method for horizontal karst treatment according to claim 5 is characterized by: In step S3, the spacing between the horizontal grouting holes is 1.5×1.5 m, and the length is 2 to 3 m of the karst development stratum below the building.

7. The construction method for horizontal karst treatment according to claim 6 is characterized by: In step S3, if karst is encountered during the drilling process, karst filling grouting is implemented; if karst is not encountered during the drilling process, formation filling grouting is implemented.

8. The construction method for horizontal karst treatment according to claim 7 is characterized by: In step S3, the specific implementation steps of horizontal drilling are as follows: first, use a drill bit to drill a hole, then use a reaming drill bit and a spiral groove reaming drill rod to reaming the hole, after cleaning the hole, place the casing horizontally and grout the casing to solidify it, and then use D76 to drill a hole in the casing.

9. The construction method for horizontal karst treatment according to claim 8, characterized in that: In step S3, the control standard of karst filling grouting is as follows: the grouting operation can be terminated only when the following requirements are met at the same time: 1) when the injection rate of the grouting hole section is not greater than 1.0L / min under the maximum design pressure, the grouting operation can be terminated after continuing the grouting for 20min; 2) During the whole grouting process, if the grouting time exceeds 2 hours and the grouting volume exceeds 100m 3 , stop grouting and add horizontal drill holes on the temporary shaft for filling treatment.

10. The construction method for horizontal karst treatment according to any one of claims 1 to 9, characterized in that: In step S5, the temporary shaft is backfilled with C10-C15 low-grade concrete.

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