A method for constructing ground-connected wall in water-rich gravel stratum

Abstract

The present invention relates to the technical field of ground-connected wall construction, specifically a ground-connected wall construction method in a water-rich gravel formation, including S1 construction preparation: S11 detailed geological and hydrological survey, comprehensive understanding of formation characteristics, groundwater level and confined water conditions, and providing accurate basis for subsequent construction; S12 preparation of trenching equipment, mud preparation and processing equipment, steel cage manufacturing equipment and concrete pouring equipment, and ensuring that the equipment has good performance and operates normally. The present invention optimizes the trenching sequence and improves the mud ratio by "one grab and one milling", significantly reducing the exposure time and collapse risk of the trench wall, while enhancing the wall protection performance, reducing mud loss, and improving the trench wall stability and construction quality.

Description

Technical Field

[0001] The invention relates to the technical field of ground-anchored wall construction, in particular to a ground-anchored wall construction method in a water-rich gravel stratum. Background Art

[0002] The construction of subway stations requires the excavation of deep foundation pits. In order to avoid collapse and deformation of the surrounding soil during excavation, an underground continuous wall will be pre-built outside the foundation pit. The underground continuous wall is built on the ground using trenching machinery. Along the peripheral axis of the deep excavation project, a long and narrow deep trench is excavated under the condition of mud wall protection. After the trench is cleared, a steel cage is suspended in the trench, and then underwater concrete is poured using the conduit method to form a unit trench section. This process is carried out section by section to build a continuous reinforced concrete wall underground as a water interception, anti-seepage, load-bearing, and water retaining structure.

[0003] The existing underground continuous wall trenching process adopts "two grabs and one milling" trenching, that is, in the three-sequence trenching process, the trenching machine is first used to dig the soil on both sides of the trench width, and then the double-wheel milling is replaced after entering the rock, and then the rock on both sides of the trench width is first milled, and finally the remaining partition wall in the middle is milled. When this underground continuous wall trenching method is faced with the construction of water-rich gravel formation, due to the characteristics of loose particles, abundant pressurized water, and poor self-stability of the water-rich gravel formation, the trench wall of this formation is easily affected by mud scouring and pressurized water, resulting in the following problems:

[0004] The bonding force between particles in the water-rich gravel layer is weak. During the trench grabbing and milling process, the scouring effect of the mud can easily cause the gravel to fall off and the trench wall to become unstable, especially in the "two grabbing and one milling" trenching. The trench wall exposed for a long time during trench grabbing lacks effective support and is more likely to cause collapse. The diluting effect of pressurized water on the mud will lead to a decrease in the mud wall protection effect and aggravate the loss of mud. The traditional mud ratio is difficult to form sufficient mud skin coverage, and thus cannot effectively prevent mud leakage. The instability of the water-rich gravel layer requires frequent shutdowns during trenching construction to repair trench wall collapse. At the same time, mud loss increases the complexity of construction and further extends the construction period. Mud scouring causes the trench wall to be uneven. Ultrasonic testing shows that there are many voids in the trench wall, which affects the construction quality of lowering the steel cage and subsequent concrete pouring. Summary of the invention

[0005] In order to overcome the above-mentioned technical problems, the purpose of the present invention is to provide a method for constructing ground-anchored wall in water-rich gravel formation, so as to solve the problems raised in the above-mentioned background technology that the current method of "two grabs and one milling" to form grooves for the construction of ground-anchored wall in water-rich gravel formation has various problems.

[0006] To achieve the above object, the present invention provides the following technical solution: a method for constructing a ground-connected wall in a water-rich gravel stratum, comprising the following steps:

[0007] S1 Construction preparation: S11 Detailed survey of geological and hydrological conditions, comprehensive understanding of stratum characteristics, groundwater level and confined water conditions, to provide accurate basis for subsequent construction; S12 Prepare trenching equipment, mud preparation and processing equipment, steel cage production equipment and concrete pouring equipment, and ensure that the equipment is in good performance and operates normally; S13 Prepare mud liquid, preferably using Weifang bentonite as the main material, in each cubic meter of mud, the bentonite input is 186kg, clean water is 955kg, and soda ash 11.16kg, CMC5.58kg, light-burned magnesia 1.49kg, and adhesive 1.40kg are added at the same time; S14 According to the designed position of the ground-connected wall, cast the concrete guide wall; S15 Use the prepared mud liquid to circulate in the concrete guide wall; S2 Trenching construction: S21 First use the trenching machine to dig the water-rich gravel soil layer in the first sequence trench, and dig When the designed rock entry position is reached, the double-wheel milling slot is replaced to remove the water-rich gravel rock layer in the first sequence slot; S22 Use the trough grabber to dig the water-rich gravel soil layer in the second sequence slot, and when the rock entry position is reached, the double-wheel milling slot is replaced to remove the water-rich gravel rock layer in the second sequence slot; S23 Use the trough grabber to dig the water-rich gravel soil layer in the third sequence slot, and when the rock entry position is reached, the double-wheel milling slot is replaced to remove the water-rich gravel rock layer in the third sequence slot, completing the troughing operation of the entire slot section; S3 Steel cage production and hoisting: S31 According to the design requirements, the size and reinforcement of the steel cage are accurately calculated, and the steel cage is produced at the processing site; S32 Use appropriate hoisting equipment and hoists, and formulate a detailed hoisting plan to ensure that the steel cage is lowered smoothly and accurately into the slot section; S4 Concrete pouring: Use the conduit method for concrete pouring, and the conduit should be checked for sealing in advance to ensure that there is no water leakage.

[0008] Preferably, the grooving equipment in S12 includes a grooving machine, a double-wheel milling machine, etc., the mud preparation and processing equipment in S12 includes a stirring device, a mud purifier, a centrifuge, etc., the steel cage making equipment in S12 includes an electric welder, a steel bar cutting machine, etc., and the concrete pouring equipment in S12 includes a conduit, a concrete tank truck, etc.

[0009] Preferably, the soda ash in S13 can reduce water loss, increase stability, static shear force and pH value, the CMC in S13 helps to reduce water loss and enhance stability and static shear force, and the light-burned magnesium in S13 is used to increase the viscosity and stability of the slurry.

[0010] Preferably, S2 controls the lifting and lowering speed of the grab bucket and the milling wheel during the trenching process to avoid excessive speed causing the trench wall to collapse or excessive mud disturbance.

[0011] Preferably, before pouring, the lower end of the conduit is inserted into S4 to a distance of about 0.3-0.5m from the bottom of the trench, and then concrete pouring is started. During the concrete pouring process, the conduit must be always buried in the concrete to a certain depth (generally controlled at 2-6m) to prevent the conduit from being pulled out of the concrete surface and causing broken piles.

[0012] Preferably, the pouring speed of concrete should be controlled in S4 to make it rise evenly to avoid quality problems such as mud inclusion caused by excessive height difference of concrete surface. At the same time, the concrete should be poured continuously until the top surface of the concrete is higher than the design elevation by a certain height (generally 0.3-0.5m) to ensure the quality of the underground continuous wall.

[0013] Preferably, after S4 is completed, the top of the ground-connected wall is cleaned and trimmed to make it meet the flatness and elevation required by the design.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] 1. The slotting sequence optimization of "one grabbing and one milling" effectively reduces the exposure time of the slot wall. Double-wheel slot milling is performed immediately after the slotting of one side is completed to prevent the slot wall from becoming unstable due to long-term exposure. At the same time, the sequential construction reduces the exposed area of ​​the slot wall and significantly reduces the risk of collapse;

[0016] 2. The performance of mud wall protection has been significantly improved. Weifang bentonite is selected as the main material, and admixtures such as soda ash, CMC and light-burned magnesium are added to effectively reduce the water loss of mud and enhance the viscosity, stability and anti-scouring performance of mud. Through the innovative addition of sawdust, the pores in the gravel layer are effectively filled to further reduce mud leakage. At the same time, the mud wall protection effect and trench wall stability are improved. The mud circulation is combined with performance optimization to ensure that the mud can form a stable wall protection layer in the water-rich gravel formation to resist the dilution effect of pressurized water. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a topological schematic diagram of the overall construction method of the present invention;

[0018] Figure 2 This is a schematic structural diagram of S15 of the present invention;

[0019] Figure 3 This is a schematic structural diagram of S21 of the present invention;

[0020] Figure 4 This is a schematic structural diagram of S22 of the present invention;

[0021] Figure 5 It is a structural schematic diagram of S23 of the present invention.

[0022] In the figure: 11, water-rich gravel soil layer; 12, water-rich gravel rock layer; 21, first sequence groove; 22, second sequence groove; 23, third sequence groove; 31, concrete guide wall; 32, mud liquid. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments 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.

[0024] See also Figure 1-5 , an embodiment provided by the present invention: a method for constructing a ground-connected wall in a water-rich gravel stratum, comprising the following steps:

[0025] S1 Construction Preparation:

[0026] S11 Conduct detailed geological and hydrological surveys to fully understand the characteristics of the strata, groundwater levels and confined water conditions, providing an accurate basis for subsequent construction;

[0027] S12 prepare the trenching equipment, mud preparation and processing equipment, steel cage manufacturing equipment and concrete pouring equipment, and ensure that the equipment is in good performance and operates normally;

[0028] S13 prepares mud liquid 32, preferably using Weifang bentonite as the main material, and in each cubic meter of mud, the input amount of bentonite is 186kg, and the amount of clean water is 955kg. At the same time, 11.16kg of soda ash, 5.58kg of CMC, 1.49kg of light-burned magnesia, and 1.40kg of adhesive are added;

[0029] S14 pouring concrete guide wall 31 according to the designed position of the ground-connected wall;

[0030] S15 uses the prepared mud liquid 32 to circulate in the concrete guide wall 31;

[0031] S2 trenching construction:

[0032] S21: First, use a trenching machine to dig the water-rich gravel soil layer 11 in the first sequence trench 21, dig to the designed rock entry position, replace the double-wheel milling machine to dig out the water-rich gravel rock layer 12 in the first sequence trench 21;

[0033] S22: using a trenching machine to dig the water-rich gravel soil layer 11 in the second sequence trench 22, digging to the designed rock entry position, replacing the double-wheel milling machine to dig out the water-rich gravel rock layer 12 in the second sequence trench 22;

[0034] S23: using a trenching machine to dig the water-rich gravel soil layer 11 in the third sequence trench 23, digging to the designed rock entry position, replacing the double-wheel milling trench to dig out the water-rich gravel rock layer 12 in the third sequence trench 23, and completing the trenching operation of the entire trench section;

[0035] S3 steel cage production and hoisting:

[0036] S31According to the design requirements, the size and reinforcement of the steel cage are accurately calculated, and the steel cage is manufactured at the processing site;

[0037] S32 Use appropriate lifting equipment and lifting tools, formulate a detailed lifting plan, and ensure that the steel cage is lowered into the slot section smoothly and accurately;

[0038] S4 Concrete pouring: Use the conduit method for concrete pouring, and the conduit should be checked for sealing in advance to ensure there is no water leakage.

[0039] The troughing equipment in S12 includes trough grabbing machine, double-wheel milling machine, etc. The mud preparation and processing equipment in S12 includes mixing equipment, mud purifier, centrifuge, etc. The steel cage making equipment in S12 includes electric welding machine, steel bar cutting machine, etc. The concrete pouring equipment in S12 includes conduit, concrete tank truck, etc.

[0040] The soda ash in S13 can reduce water loss, increase stability, static shear force and pH value. The CMC in S13 helps to reduce water loss and enhance stability and static shear force. The light-burned magnesium in S13 is used to increase the viscosity and stability of the slurry.

[0041] S2 controls the lifting and lowering speed of the grab bucket and milling wheel during the trenching process to avoid excessive speed causing trench wall collapse or excessive mud disturbance.

[0042] S4 Before pouring, insert the lower end of the conduit to about 0.3-0.5m from the bottom of the trench, and then start pouring concrete. During the concrete pouring process, the conduit should always be buried in the concrete to a certain depth (generally controlled at 2-6m) to prevent the conduit from being pulled out of the concrete surface and causing broken piles.

[0043] In S4, the pouring speed of concrete should be controlled to make it rise evenly to avoid excessive height difference of concrete surface causing mud inclusion and other quality problems. At the same time, pouring should be continued until the top surface of concrete is higher than the design elevation by a certain height (generally 0.3-0.5m) to ensure the quality of underground continuous wall.

[0044] After S4 is completed, the top of the ground-connected wall is cleaned and trimmed to make it meet the flatness and elevation requirements of the design.

[0045] Working principle: Through detailed geological and hydrological surveys, the characteristics of water-rich gravel formations can be accurately understood, including information such as formation structure, groundwater level, and confined water conditions. This information is crucial for determining subsequent construction parameters, selecting construction techniques, and predicting and preventing risks. For example, if it is known that the groundwater level is high and the self-stability of the water-rich gravel formation is poor, targeted methods need to be adopted in mud preparation and trench wall stabilization measures.

[0046] The cast concrete guide wall provides guidance and support for the subsequent trenching, ensuring the accuracy of the trenching position and the stability of the trench wall. It also provides a certain closed space for mud circulation, ensuring that the mud forms an effective wall protection pressure around the trench wall.

[0047] Weifang bentonite is selected as the main material and mixed with a variety of admixtures. The suspension and adhesion of bentonite are used to form the basic properties of mud, and the admixtures further optimize the mud performance. For example, soda ash changes the chemical properties of mud, reduces water loss, increases stability, static shear force and pH value, so that the mud can better form mud skin in water-rich formations to prevent water and particles in the formation from entering the tank; CMC enhances the viscosity and stability of the mud, further preventing the mud from losing water; lightly burned magnesium increases the viscosity of the slurry, which helps to form a more stable wall protection structure on the tank wall; adhesives increase the viscosity of the slurry and improve the overall performance of the mud, and work together to maintain the stability of the tank wall and prevent collapse.

[0048] The "one grab and one milling" three-sequence trenching method (S21-S23) is adopted. The order of grabbing the trencher first and then the double-wheel milling is based on the different characteristics of the water-rich gravel soil layer and the rock layer. The grabbing trencher is suitable for digging relatively loose water-rich gravel soil layers, and can efficiently remove part of the soil layer; while the double-wheel milling is used to deal with water-rich gravel rock layers with higher hardness and better integrity, breaking the rock by milling to ensure the flatness and verticality of the trench wall. The lifting and lowering speed of the grab bucket and the milling wheel (mentioned in S2) during the construction process is controlled to avoid excessive impact and disturbance caused by excessive speed, and to prevent the trench wall from collapsing and excessive disturbance of the mud from losing the wall protection effect.

[0049] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A method for constructing a ground-connected wall in a water-rich gravel stratum, characterized in that: The following steps are included: S1 Construction Preparation: S11 Conduct detailed geological and hydrological surveys to fully understand the characteristics of the strata, groundwater levels and confined water conditions, providing an accurate basis for subsequent construction; S12 prepare the trenching equipment, mud preparation and processing equipment, steel cage manufacturing equipment and concrete pouring equipment, and ensure that the equipment is in good performance and operates normally; S13 prepares mud liquid, preferably using Weifang bentonite as the main material, and in each cubic meter of mud, the input amount of bentonite is 186kg, and the amount of clean water is 955kg. At the same time, 11.16kg of soda ash, 5.58kg of CMC, 1.49kg of light-burned magnesia, and 1.40kg of adhesive are added; S14 pours concrete guide wall according to the designed position of ground-connected wall; S15 uses the prepared slurry to circulate the slurry in the concrete guide wall; S2 trenching construction: S21: First, use a trenching machine to dig the water-rich gravel soil layer in the first sequence trench, dig to the designed rock entry position, replace the double-wheel milling machine to dig out the water-rich gravel rock layer in the first sequence trench; S22 uses a trenching machine to dig the water-rich gravel soil layer in the second sequence trench, digs to the designed rock entry position, replaces the double-wheel milling machine to dig out the water-rich gravel rock layer in the second sequence trench; S23 uses a trenching machine to dig the water-rich gravel soil layer in the third sequence trench, digs to the designed rock entry position, replaces the double-wheel milling machine to dig out the water-rich gravel rock layer in the third sequence trench, and completes the trenching operation of the entire trench section; S3 steel cage production and hoisting: S31According to the design requirements, the size and reinforcement of the steel cage are accurately calculated, and the steel cage is manufactured at the processing site; S32 Use appropriate lifting equipment and lifting tools, formulate a detailed lifting plan, and ensure that the steel cage is lowered into the slot section smoothly and accurately; S4 Concrete pouring: Use the conduit method for concrete pouring, and the conduit should be checked for sealing in advance to ensure there is no water leakage.

2. A method for constructing a ground-connected wall in a water-rich gravel formation according to claim 1, characterized in that: The grooving equipment in S12 includes a grooving machine, a double-wheel milling machine, etc. The mud preparation and processing equipment in S12 includes a stirring device, a mud purifier, a centrifuge, etc. The steel cage making equipment in S12 includes an electric welder, a steel bar cutting machine, etc. The concrete pouring equipment in S12 includes a conduit, a concrete tanker, etc.

3. A method for constructing a ground-connected wall in a water-rich gravel formation according to claim 1, characterized in that: The soda ash in the S13 can reduce water loss, increase stability, static shear force and pH value, the CMC in the S13 helps to reduce water loss and enhance stability and static shear force, and the light-burned magnesium in the S13 is used to increase the viscosity and stability of the slurry.

4. A method for constructing a ground-connected wall in a water-rich gravel formation according to claim 1, characterized in that: The S2 controls the lifting speed of the grab bucket and the milling wheel during the trenching process to avoid excessive speed causing the trench wall to collapse or excessive mud disturbance.

5. The method for constructing a ground-connected wall in a water-rich gravel stratum according to claim 1, characterized in that: Before pouring, the lower end of the conduit is inserted to about 0.3-0.5m from the bottom of the trench, and then concrete pouring begins. During the concrete pouring process, the conduit must be kept buried in the concrete to a certain depth to prevent the conduit from being pulled out of the concrete surface and causing broken piles.

6. A method for constructing a ground-connected wall in a water-rich gravel formation according to claim 5, characterized in that: In the above-mentioned S4, the pouring speed of concrete should be controlled to make it rise evenly to avoid excessive height difference of concrete surface causing mud inclusion and other quality problems. At the same time, continuous pouring should be carried out until the top surface of concrete is higher than the design elevation by a certain height to ensure the quality of the underground continuous wall.

7. A method for constructing a ground-connected wall in a water-rich gravel formation according to claim 1, characterized in that: After the completion of S4, the top of the ground-connected wall is cleaned and trimmed to make it meet the flatness and elevation required by the design.

Images