Stratum reinforcing and plugging treatment method for pipe jacking construction in karst area

Abstract

The invention relates to the technical field of pipe jacking engineering, and discloses a stratum reinforcing and plugging treatment method for pipe jacking construction in a karst area, which comprises the following steps of: S1, carrying out geological survey on a problem part at the front end of a machine head of a pipe jacking machine, carrying out supplementary survey by adopting a vertical pilot tunnel or an inclined pilot tunnel, and detecting the type, scale and filler of a karst cave and the connectivity of the karst cave and an external karst pipeline; and S2, the karst caves are subjected to classified reinforcing and plugging treatment according to the types of the karst caves, and reinforcing and plugging treatment of non-communicated dry karst caves, communicated dry karst caves, water karst caves and sludge filling type karst caves is included. The key problems of karst cave detection and reinforcement plugging, surrounding rock breaking, backfill muck stratum reinforcement treatment and the like in the pipe jacking construction of the karst area are comprehensively solved by reinforcing and plugging karst caves and karst pipelines in a classified manner and combining two grouting plugging technologies of ground vertical grouting and in-well horizontal grouting; and machine clamping and pipe clamping risks and ground subsidence risks caused by inclination, deviation and falling of the machine head of the pipe jacking machine and deformation of surrounding rock are eliminated.

Description

Technical Field

[0001] The invention relates to the field of water conservancy projects, and in particular to a stratum reinforcement and plugging treatment method for pipe jacking construction in karst areas. Background Art

[0002] As a trenchless construction technology, pipe jacking for water conservancy projects has the advantages of not blocking ground traffic, causing little interference to the surrounding environment, and occupying a small area when passing under important infrastructure such as rivers, railways, highways, and urban trunk roads. However, in actual pipe jacking construction in karst areas, due to the complexity of the unfavorable karst geology, the construction faces complex technical difficulties.

[0003] When pipe jacking construction passes through karst caves and karst pipelines, the lubricating mud often leaks, especially when the cave is connected to the external karst pipeline, the mud will leak into the surrounding environment, causing ecological pollution and social impact. More seriously, after entering the cave, the pipe jacking head may become unstable and tilt, deviate from the designed axis, and be difficult to correct, which directly threatens the safety of pipe jacking construction.

[0004] In addition, in extremely broken surrounding rock and backfill slag layers, the stability of the strata is poor, which brings greater challenges to construction. The upper strata are prone to collapse, resulting in the jamming of the pipe jacking machine and pipe sections, the breaking of pipe sections, and difficulty in jacking; the subsidence of the bottom strata further aggravates the deviation of the machine head, causing the jacking pipe to deviate from the designed axis, increasing the difficulty and risk of deviation correction during jacking construction. These problems have led to a significant decrease in construction efficiency and a high level of safety hazards.

[0005] The existing technology lacks systematicness and pertinence in solving these problems, especially under complex karst geological conditions, and it is difficult to effectively ensure the safety and efficiency of pipe jacking construction. Based on this, the present invention proposes a stratum reinforcement and plugging treatment method for pipe jacking construction in karst areas. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention provides a stratum reinforcement and sealing treatment method for pipe jacking construction in karst areas, which solves the construction technical problems such as mud leakage, machine head deviation, machine and pipe jamming, and stratum collapse caused by unfavorable geology such as karst caves, karst pipes and broken surrounding rocks in pipe jacking construction of water pipelines in karst areas.

[0007] To achieve the above purpose, the present invention is implemented by the following technical scheme: a stratum reinforcement and plugging treatment method for pipe jacking construction in karst areas, comprising the following steps:

[0008] S1. Conduct geological survey on the problematic part of the front end of the pipe jacking machine head, and use vertical or inclined pilot tunnels to conduct supplementary surveys to detect the type, scale, filling material and connectivity of the cave with external karst pipelines;

[0009] S2. Classify and reinforce the caves according to their types, including unconnected dry caves, connected dry caves, water caves and silt-filled caves;

[0010] S3, reinforce and seal the surrounding rock fragments and backfill slag layers through vertical grouting on the ground and horizontal segmented grouting in the well;

[0011] S4. Conduct quality inspection and acceptance on the reinforced stratum.

[0012] Preferably, the classification reinforcement and plugging treatment of the caves in step S2 includes:

[0013] S2.1. For unconnected dry caves: backfill in layers with high-flow C20 concrete, with each layer being 0.8-1.0m thick and the backfill height reaching 3m above the top edge of the top pipe;

[0014] S2.2, connected dry cave: build a 370mm thick brick wall 3m away from the cave boundary line to block the passage, and then backfill with high-flow C20 concrete to 3m above the top edge of the top pipe;

[0015] S2.3, karst cave: Use underwater conduit method to backfill C20 concrete, the conduit diameter is 200-250mm, and the conduit goes deep into the bottom of the karst cave;

[0016] S2.4, silt-filled caves:

[0017] When the amount of silt is small, the silt is removed by vacuum suction equipment and then backfilled with C20 concrete;

[0018] When the amount of silt is large, geotextile film bags are used and C20 concrete is poured for extrusion reinforcement, and the grouting pressure is 0.3-1.0MPa.

[0019] Preferably, the ground vertical grouting reinforcement and plugging of the surrounding rock broken stratum and the backfill slag stratum in step S3 includes:

[0020] Vertical grouting holes are arranged at 2.5m intervals along the longitudinal and transverse directions of the jacking construction axis. The diameter of the drilled holes is 76mm and the depth reaches 1.0-2.0m below the bottom of the jacking construction.

[0021] Install a 76mm diameter grouting pipe in the drilled hole, with the bottom of the pipe inserted deep into the bottom of the hole and the exposed part of the pipe mouth fixed;

[0022] Prepare cement slurry and add water glass to the cement slurry to enhance the slurry performance;

[0023] Grouting is carried out in sequence from the center hole of the axis to both sides. The initial grouting pressure is 0.3MPa, which is gradually increased to 1.0MPa. The grouting time is 10-15min.

[0024] The grouting is terminated when the pressure in the grouting hole is stable and the grout penetration is complete.

[0025] Preferably, the horizontal segmented grouting reinforcement and plugging in the well in step S3 includes:

[0026] A vertical shaft is opened in the working shaft, receiving shaft or along the axis of the jacking pipe construction, and horizontal holes are arranged at a spacing of 2m in the vertical and horizontal directions. The diameter of the holes is 76mm, and the segment lengths are 0-5m, 5-10m, 10-15m, etc.;

[0027] Grouting is carried out in sequence according to the sections closest to the shaft, starting from the center axis hole, followed by the upper, left, right, and lower boreholes;

[0028] During the grouting process, cement slurry was prepared and mixed with water glass. The initial grouting pressure was 0.3 MPa and gradually increased to 1.0 MPa;

[0029] After each section of grouting is completed, the hole is cleared and the grouting screen is maintained for 10-15 minutes before the hole is finally closed.

[0030] Preferably, when a vertical guide tunnel or an inclined guide tunnel is used for supplementary exploration in step S1, the excavation diameter of the guide tunnel is 1.0-1.5 m, and the detection position is the size and development direction of the cave at the head of the pipe jacking machine.

[0031] Preferably, the water-cement ratio of the cement slurry in step S3 is 0.5:1, and the proportion of water glass added in step S3 is 3%-5% of the volume of the cement slurry.

[0032] Preferably, the grouting machine used in the grouting process in step S3 is optionally one of a 4-cylinder 35KW single-liquid grouting machine or a double-liquid grouting machine.

[0033] Preferably, the operation steps of the double-liquid grouting machine used in the grouting process are as follows:

[0034] One grouting pipe is filled with cement slurry, and the other grouting pipe is filled with water glass alone, and the mixing ratio of water glass is 3%-5%;

[0035] When in use, the two slurries are combined at the outlet of the grouting pipe and poured into the karst stratum through the grouting holes to solidify;

[0036] The initial grouting pressure was 0.3 MPa and gradually increased to 1.0 MPa;

[0037] After grouting is completed, maintain the grouting screen time for 10-15 minutes. After checking that the grouting volume meets the standard, close the hole and terminate the grouting.

[0038] The present invention provides a stratum reinforcement and plugging treatment method for pipe jacking construction in karst areas. It has the following excellent effects:

[0039] 1. The present invention aims at the pipe jacking construction problems caused by karst caves and karst pipelines in the pipe jacking construction of water pipelines in karst areas. It adopts the method of excavation detection and guiding tunnels to accurately find the scale, filling situation and connectivity characteristics of the karst cave at the face of the pipe jacking machine head. Through classified reinforcement and plugging technologies, such as backfilling with high-flow C20 concrete, masonry wall blocking channels, sludge suction and geotextile film bag grouting and extrusion, the problem of cave detection and reinforcement and plugging is fully solved. This method effectively prevents environmental pollution caused by slurry entering the karst pipeline due to leakage, eliminates the risk of tilting or offsetting of the machine head in the cave area, ensures the safety of pipe jacking construction and the accuracy of jacking, and provides reliable technical guarantee for pipe jacking construction under complex karst geological conditions.

[0040] 2. In the construction of broken surrounding rock strata and backfill slag strata in karst areas, the present invention combines ground vertical grouting with in-well horizontal grouting technology to carry out systematic reinforcement and sealing treatment of poor geological sections. Vertical grouting ensures the overall reinforcement of broken surrounding rock strata and backfill slag strata during pipe jacking construction. Horizontal grouting is aimed at sections where ground vertical grouting cannot be implemented and broken surrounding rock and backfill slag with deep burial depth, and enhances the supporting capacity of the stratum section by section. The ground vertical grouting and in-well horizontal grouting reinforcement and sealing treatment methods significantly reduce the problems of machine and pipe jamming caused by surrounding rock deformation during pipe jacking construction, and effectively ensure the safety and construction progress of smooth jacking of pipe sections. In addition, the method not only improves the overall stability of the stratum, but also reduces the risk of construction rework by optimizing the grouting pressure and slurry performance, and fully adapts to the construction requirements under complex karst geological conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 The map of the karst cave, karst pipeline and detection guide tunnel of the present invention;

[0042] Figure 2 This is a layout diagram of vertical drilling holes on the ground for crushing surrounding rock and backfilling slag soil layers in the present invention;

[0043] Figure 3 This is a horizontal drilling arrangement diagram in a well for crushing surrounding rock and backfilling slag soil layer according to the present invention;

[0044] Figure 4 is a flow chart of the method of the present invention;

[0045] Figure 5 It is a longitudinal cross-sectional view of a horizontal borehole in a well with surrounding rock crushing and backfilling of slag soil stratum according to the present invention. DETAILED DESCRIPTION

[0046] The following will be combined with the drawings in the specification of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0047] Please see attached Figure 1 -Attached Figure 5 The embodiment of the present invention provides a method for reinforcing and plugging a stratum in a karst area during pipe jacking construction, comprising the following steps:

[0048] S1. Conduct geological survey on the problematic part of the front end of the pipe jacking machine head, and use vertical or inclined pilot tunnels to conduct supplementary surveys to detect the type, scale, filling material and connectivity of the karst cave with external karst pipelines;

[0049] S2. Classify and reinforce the caves according to their types, including unconnected dry caves, connected dry caves, water caves and silt-filled caves;

[0050] S3. Strengthen and seal the surrounding rock fractured strata and backfill slag strata through vertical grouting on the ground and horizontal segmented grouting in the well;

[0051] S4. Conduct quality inspection and acceptance on the reinforced stratum.

[0052] The classification and reinforcement treatment of caves in step S2 includes:

[0053] S2.1. For unconnected dry caves: backfill in layers with high-flow C20 concrete, with each layer being 0.8-1.0m thick and the backfill height reaching 3m above the top edge of the top pipe;

[0054] S2.2, connected dry cave: build a 370mm thick concrete brick wall 3m away from the boundary line of the cave to block the passage, and then backfill with high-flow C20 concrete to 3m above the top edge of the top pipe;

[0055] S2.3, karst cave: Use underwater conduit method to backfill C20 concrete, the conduit diameter is 200-250mm, and the conduit goes deep into the bottom of the karst cave;

[0056] S2.4, silt-filled caves:

[0057] When the amount of silt is small, the silt is removed by vacuum suction equipment and then backfilled with C20 concrete;

[0058] When the amount of silt is large, geotextile film bags are used and C20 concrete is poured for extrusion reinforcement, and the grouting pressure is 0.3-1.0MPa.

[0059] Specifically, the present invention adopts the cave classification reinforcement treatment method of step S2, and implements targeted reinforcement technology by accurately classifying the cave types, which effectively improves the overall stability and construction adaptability of the stratum. In the unconnected dry caves, high-flow C20 concrete is backfilled in layers to fully fill the interior of the cave, eliminating the potential threat of the gap to the top pipe construction; and for the connected dry caves, the passage is blocked by building brick walls and then filled with concrete, which not only prevents the concrete slurry from leaking into the external karst pipeline, but also ensures the overall effect of the stratum reinforcement.

[0060] In complex water-soluble caves, the underwater conduit method is used to pour concrete, which avoids the scouring and dispersion of filling materials by water flow and ensures the uniformity of filling; for silt-filled caves, vacuum suction or geotextile bag grouting and pressurization are used to effectively remove or squeeze the silt, greatly improving the bearing capacity of the stratum. This classification treatment method not only avoids the possible deviation or sinking of the machine head during the construction process, but also controls the leakage of concrete slurry, thereby protecting the surrounding ecological environment.

[0061] At the same time, the cave classification reinforcement treatment of the present invention significantly improves the bearing capacity of the stratum, provides a safe and stable foundation for pipe jacking construction, reduces construction risks such as machine jamming and landslides, and further optimizes construction costs and efficiency.

[0062] The ground vertical grouting reinforcement of surrounding rock crushing and backfill slag layer in step S3 includes:

[0063] Vertical grouting holes are arranged at 2.5m intervals along the longitudinal and transverse directions of the jacking construction axis. The diameter of the drilled holes is 76mm and the depth reaches 1.0-2.0m below the bottom of the jacking construction.

[0064] Install a 76mm diameter grouting pipe in the drilled hole, with the bottom of the pipe inserted deep into the bottom of the hole and the exposed part of the pipe mouth fixed;

[0065] Prepare cement slurry and add water glass to the cement slurry to enhance the slurry performance;

[0066] Grouting is carried out in sequence from the center hole of the axis to both sides. The initial grouting pressure is 0.3MPa, which is gradually increased to 1.0MPa. The grouting time is 10-15min.

[0067] The grouting is terminated when the pressure in the grouting hole is stable and the grout penetration is complete.

[0068] The horizontal segmented grouting reinforcement in the well in step S3 includes:

[0069] A vertical shaft is opened in the working shaft, receiving shaft or along the axis of the jacking pipe construction, and horizontal holes are arranged at a spacing of 2m in the vertical and horizontal directions. The diameter of the holes is 76mm, and the segment lengths are 0-5m, 5-10m, 10-15m, etc.;

[0070] Grouting is carried out in sequence according to the sections closest to the shaft, starting from the center axis hole, followed by the upper, left, right, and lower boreholes;

[0071] During the grouting process, cement slurry was prepared and mixed with water glass. The initial grouting pressure was 0.3 MPa and gradually increased to 1.0 MPa;

[0072] After each section of grouting is completed, the hole is cleared and the grouting screen is maintained for 10-15 minutes after the grouting is completed, and the hole is finally closed.

[0073] When a vertical or inclined pilot tunnel is used for supplementary exploration in step S1, the excavation diameter of the pilot tunnel is 1.0-1.5m, and the detection position is the size and development direction of the cave at the head of the pipe jacking machine.

[0074] The water-cement ratio of the cement slurry in step S3 is 0.5:1, and the proportion of water glass added in step S3 is 3%-5% of the volume of the cement slurry.

[0075] The grouting machine used in the grouting process in step S3 can be any one of a 4-cylinder 35KW single-liquid grouting machine or a double-liquid grouting machine.

[0076] Specifically, the present invention systematically solves the stability problem of surrounding rock crushing and backfill slag formation through the ground vertical grouting and well horizontal segmented grouting reinforcement method in step S3. Vertical grouting holes are arranged along the axis of the top pipe construction, and cement slurry is evenly poured into the stratum gaps, which realizes the reinforcement of the crushed surrounding rock and forms a dense and stable overall stratum structure. The addition of water glass during the grouting process not only enhances the solidification performance of the slurry, but also greatly reduces the risk of leakage.

[0077] The horizontal segmented grouting in the well is aimed at the poor strata that cannot be grouted due to ground conditions and deep burial depth. It is gradually reinforced through segmented treatment to form a stable supporting stratum structure. This combined process of vertical grouting and horizontal grouting not only effectively improves the bearing capacity of the stratum, but also controls the settlement during construction, ensuring the accuracy and safety of the jacking machine.

[0078] By scientifically arranging holes and reasonably controlling the grouting pressure (0.3MPa to 1.0MPa), the present invention greatly improves the grouting efficiency, reduces material waste and construction safety risks. In addition, this process has strong adaptability, especially suitable for complex karst geological conditions, provides comprehensive support and guarantee for karst stratum top pipe construction, reduces rework and construction costs, and further optimizes the safety and economy of the project.

[0079] The operating steps of the double-liquid grouting machine used in the grouting process are as follows:

[0080] One grouting pipe is filled with cement slurry, and the other grouting pipe is filled with water glass alone, and the mixing ratio of water glass is 3%-5%;

[0081] When in use, the two slurries are combined at the outlet of the grouting pipe and poured into the formation to solidify;

[0082] The initial grouting pressure was 0.3 MPa and gradually increased to 1.0 MPa;

[0083] After grouting is completed, maintain the grouting screen time for 10-15 minutes, check that the grouting volume per minute reaches the requirement, then close the hole and terminate the grouting.

[0084] Embodiment 1:

[0085] Technical solution steps:

[0086] Geological Survey (S1):

[0087] Where problems occur at the front end of the pipe jacking machine head, dig a vertical guide hole or an inclined guide hole for supplementary survey;

[0088] The pilot tunnel excavation diameter is 1.2m and the detection depth is 3.5m to detect the type, size, filling material and connectivity of the cave with external karst pipelines.

[0089] Cave classification and reinforcement treatment (S2):

[0090] Unconnected dry caves:

[0091] Backfill with high-flow C20 concrete, pour in layers, each layer is 0.8m thick, and the backfill height is 3m above the top edge of the top pipe;

[0092] Connected dry caves:

[0093] Build a 370mm thick concrete brick wall 3m from the boundary line of the cave to block the passage;

[0094] Then backfill with high-flow C20 concrete to 3m above the top edge of the top pipe;

[0095] Water cave:

[0096] Use underwater pipe method to backfill C20 concrete, the pipe diameter is 220mm, the pipe burial depth is 1.2m, and the backfill is 3m above the top edge of the top pipe;

[0097] Silt-filled caves:

[0098] When the amount of silt is small, use vacuum suction equipment to remove it and then backfill with C20 concrete;

[0099] When the amount of silt is large, geotextile membrane bags are used and C20 concrete is poured with a grouting pressure of 1.0MPa.

[0100] Reinforcement of surrounding rock and backfill slag layer (S3):

[0101] Vertical grouting of the ground:

[0102] Vertical grouting holes are arranged at intervals of 2.5m along the jacking construction axis, with a drilling diameter of 76mm and a depth of 1.8m below the bottom of the jacking pipe;

[0103] Install a 76mm diameter grouting pipe in the drilled hole, with the bottom of the pipe inserted deep into the bottom of the hole and the exposed part of the pipe mouth fixed;

[0104] Prepare cement paste with a water-cement ratio of 0.5:1 and add 3% water glass;

[0105] The initial grouting pressure is 0.3MPa, which is gradually increased to 1.0MPa, and the grouting time is 15 minutes;

[0106] When the pressure in the hole stabilizes and the slurry stops penetrating, the hole is closed.

[0107] Horizontal segmented grouting in the well:

[0108] Horizontal boreholes are arranged in the working well or receiving well at a vertical and horizontal interval of 2m, with a borehole diameter of 76mm and segment lengths of 0-5m, 5-10m, 10-15m, etc.;

[0109] Prepare cement paste with a water-cement ratio of 0.5:1 and add 3% water glass;

[0110] The initial grouting pressure is 0.3MPa, which is gradually increased to 1.0MPa, and the grouting time is 15 minutes.

[0111] Summary of embodiments:

[0112] Example 1 uses a 4-cylinder 35KW single-liquid grouting machine to reinforce the stratum through a single-channel cement slurry injection method. The technical features include:

[0113] Single-channel grouting: Use cement slurry with a water-cement ratio of 0.5:1 and add 3% water glass. During construction, the slurry penetrates evenly and different hole positions are grouted in turn.

[0114] The construction parameters are stable: the initial grouting pressure is 0.3MPa, which is gradually increased to 1.0MPa, and the screen time is 15 minutes, which is suitable for geological environments with medium permeability.

[0115] Applicable scenarios: areas with relatively stable strata, low degree of fragmentation, and uniform cave fillings.

[0116] Construction advantages: The operation process is simple, suitable for conventional reinforcement tasks, and can meet the reinforcement needs of general poor geological sections.

[0117] Embodiment 2:

[0118] Technical solution steps:

[0119] Geological Survey (S1):

[0120] Where problems occur at the front end of the pipe jacking machine head, dig a vertical guide hole or an inclined guide hole for supplementary survey;

[0121] The pilot tunnel excavation diameter is 1.5m and the detection depth is 4m to detect the type, size, filling material and connectivity of the cave with external karst pipelines.

[0122] Cave classification and reinforcement treatment (S2):

[0123] Unconnected dry caves:

[0124] Backfill with high-flow C20 concrete, pour in layers, each layer is 1.0m thick, and the backfill height is 3m above the top edge of the top pipe;

[0125] Connected dry caves:

[0126] Build a 370mm thick concrete brick wall 3m from the boundary line of the cave to block the passage;

[0127] Then backfill with high-flow C20 concrete to 3m above the top edge of the top pipe;

[0128] Water cave:

[0129] Use underwater pipe method to backfill C20 concrete, the pipe diameter is 250mm, the pipe burial depth is 1.5m, and the backfill is 3m above the top edge of the top pipe;

[0130] Silt-filled caves:

[0131] When the amount of silt is small, use vacuum suction equipment to remove it and then backfill with C20 concrete;

[0132] When the amount of silt is large, geotextile membrane bags are used and C20 concrete is poured with a grouting pressure of 1.0MPa.

[0133] Reinforcement of surrounding rock and backfill slag layer (S3)

[0134] Vertical grouting of the ground:

[0135] Vertical grouting holes are arranged at 2.5m intervals along the top pipe construction axis, with a drilling diameter of 76mm and a depth of 2.0m below the bottom of the top pipe;

[0136] Install a 76mm diameter grouting pipe in the drilled hole, with the bottom of the pipe inserted deep into the bottom of the hole and the exposed part of the pipe mouth fixed;

[0137] Prepare double-liquid slurry: one grouting pipe is filled with cement slurry with a water-cement ratio of 0.5:1; the other grouting pipe is filled with water glass with a mixing ratio of 5%;

[0138] The initial grouting pressure is 0.3MPa, which is gradually increased to 1.0MPa, and the grouting time is 10 minutes;

[0139] The two slurries are mixed at the outlet of the grouting pipe and the hole is sealed after solidification.

[0140] Horizontal segmented grouting in the well:

[0141] Horizontal boreholes are arranged in the working well or receiving well at a vertical and horizontal interval of 2m, with a borehole diameter of 76mm and segment lengths of 0-5m, 5-10m, 10-15m, etc.;

[0142] Prepare double-liquid slurry: one grouting pipe is filled with cement slurry with a water-cement ratio of 0.5:1; the other grouting pipe is filled with water glass with a mixing ratio of 5%;

[0143] The initial grouting pressure is 0.3MPa, which is gradually increased to 1.0MPa, and the grouting time is 10 minutes.

[0144] Example 2 Summary:

[0145] Example 2 uses a double-liquid grouting machine to reinforce the stratum by mixing and grouting double-channel grout (single-channel cement grout and single-channel water glass). The technical features include:

[0146] Double-liquid mixed grouting: Two pipes are respectively filled with cement slurry (water-cement ratio is 0.5:1) and water glass (mixing ratio is 5%). The slurry solidifies quickly after mixing at the outlet, which is suitable for broken surrounding rocks and complex geological conditions.

[0147] Higher construction efficiency: The initial grouting pressure is 0.3MPa, which is gradually increased to 1.0MPa. The grouting time is short, which is 10 minutes. It can solidify quickly and improve construction efficiency.

[0148] Applicable scenarios: complex geological conditions, broken surrounding rocks, uneven karst strata, especially environments with high requirements for solidification time.

[0149] Construction advantages: The slurry solidifies quickly and has a significant ground reinforcement effect. It is suitable for scenes with complex geological conditions and can significantly reduce the risk of ground settlement and leakage.

[0150] Comparison and summary:

[0151] Example 1 (4 cylinder 35KW single liquid grouting machine):

[0152] The process is relatively simple and the operation is easy to control. It is suitable for construction scenarios with relatively stable formation conditions and a relatively simple distribution of adverse geological conditions.

[0153] The technology has low cost and long construction time, and is more suitable for conventional ground reinforcement tasks.

[0154] Embodiment 2 (double liquid grouting machine):

[0155] Suitable for areas with complex geological conditions, the two-liquid mixed slurry can solidify quickly, improving formation stability and construction efficiency.

[0156] The technology cost is relatively high and is suitable for areas with many caves, broken surrounding rocks, and severe adverse geology.

[0157] The two embodiments are designed with completely different technical solutions based on the differences in grouting machines, which respectively meet the reinforcement requirements of pipe jacking construction under different geological conditions and provide flexible and reliable options for engineering design.

[0158] Comparative experimental design:

[0159] 1. Purpose of the experiment

[0160] Through multi-dimensional and multi-indicator verification, the actual technical advantages of the "stratum reinforcement and plugging treatment method for pipe jacking construction in karst areas" proposed in this invention are deeply discussed, especially:

[0161] Compare the differences in the effects of the technology of the present invention and the traditional methods in terms of cave reinforcement, surrounding rock crushing reinforcement, leakage control, construction efficiency, compressive strength improvement and formation settlement control;

[0162] The adaptability and technical stability of the present invention under different complex geological conditions are further verified.

[0163] 2. Experimental Design

[0164] Subjects:

[0165] A water pipeline construction area under a typical geological environment was selected and divided into a control group (traditional construction method) and an experimental group (technical method of the present invention). The experimental strata included:

[0166] Uniform surrounding rock formation: The surrounding rock is relatively stable, with only a few caves;

[0167] Moderately broken strata: backfill soil is mixed in the surrounding rock, and some interconnected caves exist;

[0168] Complex and broken strata: the surrounding rock is discontinuous and severely broken, and the caves are complex and highly permeable.

[0169] Comparison of experimental methods:

[0170] Control group (traditional method):

[0171] Cave treatment: ordinary C20 concrete is used for backfilling;

[0172] Grouting parameters:

[0173] Water-cement ratio: 0.7:1;

[0174] Grouting pressure: 0.3-0.7MPa;

[0175] Grouting hole arrangement spacing: 3m;

[0176] Construction technology: Regardless of the type of cave, no water glass is added during the grouting process.

[0177] Experimental group (method of the present invention):

[0178] Cave classification reinforcement:

[0179] Unconnected dry caves: backfill with high-flow C20 concrete in layers, with each layer 0.8m thick;

[0180] Connecting dry cave: build 370mm concrete brick wall to block it and then backfill with concrete;

[0181] Water-karst cave: Filling by underwater catheter method;

[0182] Silt-filled cave: Lay geotextile bags and squeeze them for reinforcement, with a grouting pressure of 0.8-1.0MPa. Grouting parameters:

[0183] Water-cement ratio: 0.5:1, adding 3%-5% water glass;

[0184] Grouting pressure: 0.5-1.0MPa;

[0185] Grouting hole arrangement spacing: 2.5m.

[0186] Experimental evaluation indicators:

[0187] The two sets of technical solutions were evaluated from multiple dimensions, and the indicators are as follows:

[0188] Compressive strength (MPa): average compressive strength of the reinforced stratum;

[0189] Leakage (L): measures the loss of slurry in the cave area;

[0190] Construction efficiency (h): time required to complete the construction of the experimental section;

[0191] Settlement (mm): Change in ground settlement after construction;

[0192] Porosity (%): The porosity of the reinforced stratum, reflecting the density of reinforcement;

[0193] Adaptability score (out of 100): A comprehensive score that evaluates the ability of the method to adapt to different geological conditions.

[0194] 3. Experimental Procedure

[0195] Step 1: Experimental area division and initial data recording

[0196] 1.1 Experimental area division:

[0197] A control group and an experimental group were divided in each stratum, and the experimental area of ​​each group was 30m×30m.

[0198] 1.2 Initial data measurement:

[0199] Measure the initial compressive strength, porosity, leakage and settlement of the reinforced area and record the baseline data.

[0200] Step 2: Two sets of scheme construction

[0201] Construction of control group:

[0202] Construction using traditional methods:

[0203] C20 ordinary concrete backfills the cave, and single-liquid cement grout is used for grouting;

[0204] The hole spacing is 3m, and the grouting pressure is low (0.3-0.7MPa);

[0205] No water glass added.

[0206] Experimental group construction (method of the present invention):

[0207] S1(geological survey):

[0208] A vertical pilot tunnel was used for supplementary survey, with a diameter of 1.2m and a depth of 4m;

[0209] Clarify the types of caves and the distribution of backfill debris.

[0210] S2 (cavern classification reinforcement):

[0211] Reinforcement is carried out according to the type of cave (layered backfilling with high-flow concrete, filling by conduit method, pressurization with membrane bags, etc.).

[0212] S3 (surrounding rock and backfill soil reinforcement):

[0213] Vertical grouting on the ground is combined with horizontal grouting in the well, water glass is added to the cement slurry, and the grouting pressure is gradually increased to 1.0MPa.

[0214] S4 (quality inspection):

[0215] After construction, compressive strength tests, leakage measurements and settlement monitoring are carried out.

[0216] Step 3: Data collection and analysis

[0217] Drill core samples to measure compressive strength;

[0218] Flow meter monitors leakage;

[0219] Use sedimentation meters to monitor ground subsidence;

[0220] The porosity was calculated from the sample scans.

[0221] 4. Experimental results and analysis

[0222] Experimental data table:

[0223]

[0224] 5. Experimental Summary

[0225] 1. The compressive strength of the formation is significantly improved

[0226] The experimental results show that in uniform surrounding rock formations, the compressive strength of the experimental group increased by 27% (16.8MPa vs. 13.2MPa). In moderately broken formations, the compressive strength of the experimental group increased by 43% (13.5MPa vs. 9.4MPa). In severely broken formations, the compressive strength of the experimental group increased by 83% (11.0MPa vs. 6.1MPa).

[0227] This shows that the present invention effectively improves the bearing capacity of the stratum by optimizing the grouting method and the classified cave reinforcement process, especially in severely broken strata.

[0228] 2. Excellent leakage control effect

[0229] In uniform surrounding rock formations, the slurry leakage of the experimental group was reduced by 60% (4.2L vs. 10.5L). In moderately fractured formations, the leakage was reduced by 63% (9.5L vs. 25.7L). In severely fractured formations, the leakage was reduced by 77% (12.8L vs. 56.3L).

[0230] The present invention significantly reduces slurry loss in strata with high permeability and complex caves by adding water glass and optimizing grouting parameters, and effectively solves the leakage problem commonly seen in traditional methods.

[0231] 3. Construction efficiency is greatly improved

[0232] The construction efficiency of the experimental group was significantly better than that of the control group:

[0233] In uniform surrounding rock formations, construction time was reduced by 29% (8.7h vs. 12.3h).

[0234] In moderately broken ground, construction time was reduced by 30% (11.2 h vs. 16.0 h).

[0235] In severely fractured ground, construction time was reduced by 25% (15.3 h vs. 20.5 h).

[0236] The construction efficiency of the present invention in complex strata is significantly improved by optimizing the arrangement of grouting holes, increasing the grouting pressure and improving the cave reinforcement method.

[0237] 4. The amount of ground settlement is significantly reduced

[0238] In the uniform surrounding rock formation, the settlement was reduced by 38% (4.0 mm vs. 6.5 mm).

[0239] In moderately fractured strata, the subsidence was reduced by 39% (8.7 mm vs. 14.3 mm).

[0240] In severely fractured strata, the settlement was reduced by 42% (17.6 mm vs. 30.4 mm).

[0241] This shows that the technology of the present invention not only improves the stability of the formation, but also significantly reduces the risk of formation settlement after pipe jacking construction.

[0242] 5. Porosity is reduced and formation compactness is enhanced

[0243] The experimental results show that the formation porosity of the experimental group is significantly lower than that of the control group:

[0244] In the homogeneous surrounding rock formation, the porosity was reduced by 36% (14% vs. 22%).

[0245] In moderately fractured formations, porosity decreased by 42% (21% vs. 36%).

[0246] In severely fractured formations, porosity decreased by 45% (32% vs. 58%).

[0247] The density of the stratum after reinforcement was significantly improved, which further proved the superiority of classified reinforcement and scientific grouting technology.

[0248] 6. Comprehensive adaptability score

[0249] In the uniform surrounding rock formation, the adaptability score of the experimental group increased by 20% (90 vs. 75).

[0250] In moderately fractured formations, the adaptability score increased by 31% (85 vs. 65).

[0251] In severely fractured formations, the adaptability score increased by 77.8% (80 vs. 45).

[0252] The technical solution of the present invention has excellent adaptability in different formations, especially in severely broken formations, where the adaptability score is greatly improved, fully demonstrating its technical reliability.

[0253] Experimental summary:

[0254] Combined with the above data, the present invention "a method for strengthening and plugging strata in karst areas by pipe jacking construction" is significantly superior to the traditional method and shows obvious advantages in the following aspects:

[0255] Significantly improve the compressive strength of the formation: the average increase is 27%-83%, especially in severely broken formations;

[0256] Significantly reduce slurry leakage: the average reduction is 60%-77%, effectively solving the leakage problem under complex geological conditions;

[0257] Significantly improve construction efficiency: shorten construction time by 25%-30% on average, and optimize hole layout and process parameters play an important role;

[0258] Significantly reduce ground settlement: the average reduction is 38%-42%, ensuring the safety and stability of the ground after construction;

[0259] Enhanced formation compactness: The porosity was reduced by an average of 36%-45%, indicating a significant reinforcement effect;

[0260] Strong adaptability to multiple formations: The score improvement in complex and broken formations is the most significant (increased by 77.8%), which reflects the applicability of the present invention to a variety of complex geological conditions.

[0261] The technical solution of the present invention demonstrates wide applicability and technical innovation in the pipe jacking construction of water supply pipelines in water conservancy projects, and is a comprehensive improvement of the existing technology.

[0262] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for reinforcing and plugging a stratum in karst area pipe jacking construction, characterized in that: The following steps are involved: S1. Conduct geological survey on the problematic part of the front end of the pipe jacking machine head, and use vertical or inclined pilot tunnels to conduct supplementary surveys to detect the type, scale, filling material and connectivity of the cave with external karst pipelines; S2. Classify and reinforce the caves according to their types, including the reinforcement and plugging of unconnected dry caves, connected dry caves, water caves and silt-filled caves; S3. Strengthen and seal the surrounding rock fractured strata and backfill slag strata through vertical grouting on the ground and horizontal segmented grouting in the well; S4. Conduct quality inspection and acceptance on the reinforced stratum.

2. The method for reinforcing and plugging the stratum in karst area pipe jacking construction according to claim 1, characterized in that: The classification reinforcement and plugging treatment of the caves in step S2 includes: S2.

1. For unconnected dry caves: backfill in layers with high-flow C20 concrete, with each layer being 0.8-1.0m thick and the backfill height reaching 3m above the top edge of the top pipe; S2.2, connected dry cave: build a 370mm thick brick wall 3m away from the cave boundary line to block the passage, and then backfill with high-flow C20 concrete to 3m above the top edge of the top pipe; S2.3, karst cave: Use underwater conduit method to backfill C20 concrete, the conduit diameter is 200-250mm, and the conduit goes deep into the bottom of the karst cave; S2.4, silt-filled caves: When the amount of silt is small, the silt is removed by vacuum suction equipment and then backfilled with C20 concrete; When the amount of silt is large, geotextile film bags are used and C20 concrete is poured for extrusion reinforcement, and the grouting pressure is 0.3-1.0MPa.

3. The method for reinforcing and plugging the stratum in karst area pipe jacking construction according to claim 1, characterized in that: The ground vertical grouting reinforcement and plugging of surrounding rock crushing and backfilling slag layer in step S3 includes: Vertical grouting holes are arranged at 2.5m intervals along the longitudinal and transverse directions of the jacking construction axis. The diameter of the drilled holes is 76mm and the depth reaches 1.0-2.0m below the bottom of the jacking construction. Install a 76mm diameter grouting pipe in the drilled hole, with the bottom of the pipe inserted deep into the bottom of the hole and the exposed part of the pipe mouth fixed; Prepare cement slurry and add water glass to the cement slurry to enhance the slurry performance; Grouting is carried out in sequence from the center hole of the axis to both sides. The initial grouting pressure is 0.3MPa, which is gradually increased to 1.0MPa. The grouting time is 10-15min. The grouting is terminated when the pressure in the grouting hole is stable and the grout penetration is complete.

4. The method for reinforcing and plugging the stratum in karst area pipe jacking construction according to claim 3 is characterized in that: The horizontal segmented grouting reinforcement and plugging in the well in step S3 includes: A vertical shaft is opened in the working shaft, receiving shaft or along the axis of the jacking construction, and horizontal holes are arranged at a spacing of 2m in the vertical and horizontal directions. The diameter of the holes is 76mm, and the segment lengths are 0-5m, 5-10m, and 10-15m; Grouting is carried out in sequence according to the sections closest to the shaft, starting from the center axis hole, followed by the upper, left, right, and lower boreholes; During the grouting process, cement slurry was prepared and mixed with water glass. The initial grouting pressure was 0.3 MPa and gradually increased to 1.0 MPa; After each section of grouting is completed, the remaining slurry in the hole is cleared away. After the grouting is completed, the slurry screen time is maintained for 10-15 minutes and the hole mouth is finally closed.

5. The method for reinforcing and plugging the stratum in karst area pipe jacking construction according to claim 1, characterized in that: When a vertical pilot tunnel or an inclined pilot tunnel is used for supplementary exploration in step S1, the excavation diameter of the pilot tunnel is 1.0-1.5 m, and the detection position is the size and development direction of the karst cave at the head of the pipe jacking machine.

6. The method for reinforcing and plugging the stratum in karst area pipe jacking construction according to claim 4, characterized in that: The water-cement ratio of the cement slurry in step S3 is 0.5:1, and the proportion of water glass added in step S3 is 3%-5% of the volume of the cement slurry.

7. The method for reinforcing and plugging the stratum in karst area pipe jacking construction according to claim 4, characterized in that: The grouting machine used in the grouting process in step S3 can be any one of a 4-cylinder 35KW single-liquid grouting machine or a double-liquid grouting machine.

8. The method for reinforcing and plugging the stratum in karst area pipe jacking construction according to claim 7, characterized in that: The operation steps of the double liquid grouting machine used in the grouting process are as follows: One grouting pipe is filled with cement slurry, and the other grouting pipe is filled with water glass alone, and the mixing ratio of water glass is 3%-5%; When in use, the two slurries are combined at the outlet of the grouting pipe and poured into the karst stratum through the grouting holes to solidify; The initial grouting pressure was 0.3 MPa and gradually increased to 1.0 MPa; After grouting is completed, maintain the grouting screen time for 10-15 minutes. After checking that the grouting volume meets the standard, close the hole and terminate the grouting.

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