Foundation treatment method for soft soil foundation with high plasticity index

Abstract

The invention provides a high-plasticity-index soft soil foundation treatment method, and relates to the technical field of soft soil foundation treatment. According to the treatment method, sedimentation of a soft soil foundation is reduced through combined use of a vibro-replacement stone column reinforcement method and a drainage consolidation construction method; when the drainage consolidation construction method for the vibro-replacement gravel pile reinforcement method is used for treating foundation settlement, the vibro-replacement gravel pile reinforcement method enables stones to sink through vibration and impact force, meanwhile, surrounding soil is compacted, a solid foundation is formed, pressure generated when gravel pile construction operation is conducted through the vibro-replacement gravel pile reinforcement method is used as a load on the soil, and therefore the foundation settlement is treated. A water supply and drainage consolidation construction method is provided to serve as a load for drainage, the underground water level is effectively reduced, the buoyancy effect of underground water on a foundation is reduced, and therefore the risk of foundation settlement is reduced; a large amount of excavation and backfilling of soil are not needed, and damage to the environment is reduced, so that the risk of foundation settlement is reduced, the construction efficiency is improved, and the construction period is shortened.

Description

Technical Field

[0001] The invention relates to the technical field of soft soil foundation treatment, and in particular to a high plasticity index soft soil foundation treatment method. Background Art

[0002] High plasticity index soft soil foundation is a type of soft soil foundation. High plasticity index soft soil foundation refers to soft soil foundation with a high plasticity index. Plasticity index is an important parameter in soil engineering, which is used to describe the plasticity range of soil in dry and wet states. Soil with high plasticity index usually has larger particle fineness and higher cohesion, which makes the soil prone to plastic deformation when subjected to external forces. The treatment methods for settlement of high plasticity index soft soil foundation include: replacement cushion method, preloading method and composite foundation method.

[0003] When the existing high plasticity index soft soil foundation is settled by the replacement cushion method, the soil layer within a certain range under the foundation is excavated, and then backfilled with sand, gravel or ash soil with higher strength, and compacted layer by layer to the density required by the design as the bearing layer of the foundation. This method is mainly suitable for shallow foundation treatment, and the treatment depth can reach 2 to 3 meters. The main function of the replacement cushion method is to improve the deformation resistance and stability of the foundation by changing the bearing capacity characteristics of the foundation. In the actual replacement cushion construction process, this operation method has a large amount of earthwork construction, which may lead to low construction efficiency and the inability to complete the replacement cushion in a short time. The replacement cushion method cannot effectively lower the groundwater level, which increases the buoyancy of groundwater on the foundation. After the construction is completed, the soil layer needs to be subsequently drained, and the construction period is long.

[0004] If the preloading method is adopted, a large amount of load needs to be piled up on the construction site, and then removed after a period of accumulation = load removal. The construction period is long and the amount of earthwork is large, resulting in low construction efficiency. After completion, subsequent drainage treatment is required to reduce the buoyancy effect of groundwater on subsequent buildings. Summary of the invention

[0005] In order to solve the problems of large construction workload, long construction period and the need for subsequent drainage treatment after the construction of the above-mentioned traditional construction method, the present invention provides a foundation treatment method for soft soil foundation with high plasticity index.

[0006] The present invention provides a high plasticity index soft soil foundation treatment method, which reduces the settlement of the soft soil foundation by combining a vibro-stone pile reinforcement method with a drainage consolidation construction method, and comprises the following steps:

[0007] S1. Planning vertical drainage wells: survey the construction area, determine the well location and depth, formulate construction plans and drawings, prepare the required construction equipment and materials, ensure the safety and smooth progress of the construction process, and select appropriate drilling equipment and materials;

[0008] S2. Wellhead excavation: After the well position and well depth are determined, the wellhead excavation work is carried out by drilling equipment; first, the ground excavation is carried out, and then the excavation is gradually carried out downwards until the well depth required by the design is reached. During the excavation process, the stability and safety of the wellhead must be ensured to avoid collapse and accidents;

[0009] It should be noted that in step S2, when excavating the wellhead, the wellhead can be excavated quickly and efficiently by an excavator or a drill, and the excavation and cleaning work can be done delicately by a shovel or a pickaxe;

[0010] S3, set up drainage system; after the wellhead is dug, install the wellbore and cast the well wall, set up drainage blind ditch and water collection well, and install drainage facilities in the water collection well;

[0011] The wellbore is an important part of the dewatering well, which can ensure the stability of the well wall and prevent collapse. During the installation of the wellbore, attention should be paid to the verticality and sealing of the wellbore to ensure the quality and stability of the wellbore;

[0012] It should be noted that in step S3, when the wellbore is installed, the wellbore of the dewatering well is hoisted and installed by a crane;

[0013] After the wellbore is installed, grouting work is carried out on the well wall. Grouting is to reinforce the well wall and prevent groundwater leakage and damage to the well wall. During the grouting process, it is necessary to select appropriate grouting materials and construction methods to ensure the grouting effect and the stability of the well wall. The bottom of the wellbore is usually equipped with a filter screen or filter tube to prevent soil particles from entering the well.

[0014] It should be noted that in step S3, when the grouting work of the well wall is performed, cement slurry or other materials are sent into the underground soil through a grouting pump, the grouting material is transported into the underground soil through a grouting pipe, and the slurry is injected into the soil through a grouting gun;

[0015] S4. Determine the pile position: clearly mark the specific position of each pile position according to the requirements of the design drawings at the construction site. The pile position is located between the drainage wells, and the pile position number is matched with the number in the design drawings;

[0016] S5. Hole making: Turn on the vibrator and slowly sink it at a rate of 1m / min to 2m / min, and keep sufficient water during the hole making process; during the hole making process, it is necessary to control the pressure of the vibrator and the water flow rate, and the water should be sufficient so that there is sufficient water from the beginning to the end of the hole making process, thereby reducing the possibility of hole collapse and allowing the pile making process to proceed smoothly;

[0017] It should be noted that for different water pressures and different soil pressures, soil pressure and minimum value, soil strength is low, soil strength is high, and pressure is high. When the hole making work is about to be completed, the water pressure should be reduced in time to avoid impacting the original soil layer below the design elevation;

[0018] S6. Hole cleaning: When drilling with a vibrator, when the designed elevation is reached, the vibrator should be stopped and hole cleaning should be started;

[0019] S7, remove the vibrator: after the hole is cleaned, pull out the vibrator at a uniform speed to prepare for the next step of filling;

[0020] S8, filling, starting the first stage of filling work;

[0021] S9, vibrating and compacting the piles. After the first stage of filling work is completed, a vibrator needs to be placed in the filled material for vibration. After the vibrating and compacting is completed, secondary filling is performed again until the construction of one gravel pile is completed. Repeat S4-S9 to complete the construction of the remaining gravel piles.

[0022] Furthermore, in step S1, the actual deviation between the pile position and the position marked on the drawing is less than 500 mm, and each pile position is divided into areas and numbered, and the numbers of all pile positions are recorded in the construction drawings.

[0023] Furthermore, in step S6, the designed drilling depth is 30 m, and the hole cleaning time is two minutes.

[0024] Furthermore, the working height of the filler is 0.5m to 1.0m; it is based on the initial filler and can be appropriately increased.

[0025] Furthermore, the working height of the secondary filler is less than 0.5 m; the secondary filler needs to control the diameter of the gravel pile, and the filler needs to be reduced to assist in the formation of the gravel pile.

[0026] Furthermore, the wellhead spacing is 2m to 3m.

[0027] Furthermore, in step S3, when grouting the well wall is performed, cement slurry or other materials are delivered into the underground soil through a grouting pump, the grouting material is delivered into the underground soil through a grouting pipe, and the slurry is injected into the soil through a grouting gun.

[0028] Furthermore, the drainage facility includes a drainage pump, a drainage pipe and a motor.

[0029] Furthermore, the vibrator has a length of 6m to 21m.

[0030] The vibro-stone pile reinforcement method improves the bearing capacity and stability of the foundation by making a pile body composed of stone in the foundation, which together with the original foundation soil forms a composite foundation. During the vibro-stone pile reinforcement process, drainage operations are carried out at the same time to lower the groundwater level, further reduce the buoyancy of groundwater on the foundation, and help prevent foundation settlement;

[0031] The principle of vibratory stone pile reinforcement method is: vibration can effectively increase the relative density of very wet to saturated non-compacted sand. When the vibrator vibrates in the sand, the surrounding saturated sand is liquefied. The liquefied soil particles are rearranged under the action of gravity, the pressure of the upper soil layer and the squeezing force of the filler. The porosity ratio of the soil is reduced, thereby increasing the density. After vibratory compaction, the sand foundation not only improves the bearing capacity and deformation modulus, but also makes the sand experience artificial vibration liquefaction in advance, thereby improving the vibration resistance of the sand. In conjunction with the drainage well, when the vibrator vibrates in the sand, the surrounding saturated sand is liquefied. The liquefied soil particles are rearranged under the action of gravity, the pressure of the upper soil layer and the squeezing force of the filler. The porosity ratio of the soil is reduced, the pore water in the soil is discharged, the water content of the soil is reduced, and the buoyancy of groundwater on the foundation is reduced. After the construction is completed, no additional drainage construction is required, which shortens the work cycle and improves work efficiency.

[0032] Drainage facilities are set up at the bottom of the well to drain the water in the well, and the water level changes are observed during the construction of the gravel pile to continuously monitor the drainage situation.

[0033] Regularly check pumps and pipes, clean them, prevent blockage, maintain pumping efficiency, and adjust pumping strategies according to water level changes;

[0034] At the same time, the drainage well construction method should pay attention to the following points during construction:

[0035] 1. Construction safety: The first priority is to ensure the safety of the construction site. It is strictly forbidden for unauthorized personnel to enter the work area or the operating table. All construction personnel should receive safety training and abide by safety operating procedures;

[0036] 2. Underground pipeline protection: Before drilling, a detailed investigation of underground pipelines should be conducted to ensure that existing trenches, cables and other underground objects will not be damaged during the drilling process;

[0037] 3. Drilling rig operation: Drilling rig operation must be carried out by a dedicated person, and the drilling rig can only be started after ensuring that the engine is running normally;

[0038] 4. Safety protection devices: All kinds of safety protection devices on the machinery should be intact, complete, sensitive, reliable and effective;

[0039] 5. Troubleshooting: The machine must not be operated with faults. If any abnormality is found during operation, the machine should be stopped for inspection and can only be used after the fault is eliminated. If the drill is stuck, the machine should be stopped for inspection immediately. Before the cause is found and the fault is eliminated, the machine must not be forced to start.

[0040] 6. Treatment after construction: After construction is completed or after get off work, the machinery and pipes must be flushed clean. For well point pipes, coarse sand should be used and filled above the original groundwater level to prevent fine sand from entering the well point and affecting the drainage effect;

[0041] When the vibro-stone pile reinforcement method is used in conjunction with the drainage consolidation construction method, the two can produce a synergistic effect to further enhance the bearing capacity and stability of the foundation. The vibro-stone pile reinforcement method can improve the density and bearing capacity of the foundation. At the same time, the stone pile construction process helps the drainage well to drain water. Coordinated operations can lower the groundwater level and reduce the buoyancy of groundwater on the foundation. This combined effect can effectively prevent the settlement of soft soil foundations and ensure the stability and safety of large-area floors.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] The vibro-stone pile reinforcement method and the drainage consolidation construction method are used together. The pressure during the vibro-stone pile construction operation is used as a load on the soil, which is provided to the drainage consolidation construction method for drainage, effectively lowering the groundwater level and reducing the buoyancy of groundwater on the foundation, thereby reducing the risk of foundation settlement. Compared with the traditional replacement method and drainage consolidation method, the amount of excavated earth is small, and the amount of earthwork done by engineering vehicles is significantly reduced. Since it does not require a large amount of excavation and backfilling of soil, it reduces damage to the environment. The construction method of the vibro-stone pile reinforcement method combined with the precipitation well is more environmentally friendly and energy-saving. At the same time, due to its high construction efficiency, it can shorten the construction period, reduce energy consumption, improve construction efficiency, shorten the construction cycle, and improve construction efficiency. After the construction is completed, there is no need for drainage treatment, which reduces construction costs. At the same time, the installed drainage can also be used as drainage facilities for subsequent buildings, further reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0045] Figure 1Figure A is a workflow diagram of a method for treating soft soil foundation with high plasticity index. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0047] The application principle of the present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0048] The drainage well in the drainage consolidation construction method of the present invention can be replaced by a bagged sand well, and the construction steps are as follows:

[0049] S1. Planning vertical drainage wells: survey the construction area, determine the well location and depth, formulate construction plans and drawings, prepare the required construction equipment and materials, ensure the safety and smooth progress of the construction process, and select appropriate drilling equipment and materials;

[0050] S2. Wellhead excavation: After the well position and well depth are determined, a 0.5m thick sand cushion layer is laid in the construction area, and the wellhead excavation work is carried out by drilling equipment; first, the ground is excavated, and then gradually excavated downward until the well depth required by the design is reached. During the excavation process, the stability and safety of the wellhead must be ensured to avoid collapse and accidents; the sand cushion layer is mainly composed of medium sand and coarse sand with high water permeability, of which the content of sand larger than 0.5mm is greater than 50%, the mud content should be less than 3%, and the permeability coefficient should be not less than 0.005m / s. The sand should be kept dry, not wet, to prevent the wet sand from changing in volume after drying, resulting in a short well;

[0051] S3. Set up a vertical drainage system. First, drive a sleeve into the preset position, sink a bagged sand well into the sleeve, remove the sleeve after the bagged sand well is in place, process the wellhead and the sand bag mouth, move to the next location and repeat the above process after all are completed, and lay a 0.5m thick sand cushion layer again after all are completed;

[0052] The tensile strength of the outer layer of the bagged sand well must be able to ensure the deadweight of the bagged sand well, and the permeability coefficient of the sand bag after filling with sand is not less than the permeability coefficient of the sand;

[0053] S4. Determine the pile position: clearly mark the specific position of each pile position according to the requirements of the design drawings at the construction site. The pile position is located between the drainage wells, and the pile position number is matched with the number in the design drawings;

[0054] S5. Hole making: Turn on the vibrator and slowly sink it at a rate of 1m / min to 2m / min, and keep sufficient water during the hole making process; during the hole making process, it is necessary to control the pressure of the vibrator and the water flow rate, and the water should be sufficient so that there is sufficient water from the beginning to the end of the hole making process, thereby reducing the possibility of hole collapse and allowing the pile making process to proceed smoothly;

[0055] It should be noted that for different water pressures and different soil pressures, soil pressure and minimum value, soil strength is low, soil strength is high, and pressure is high. When the hole making work is about to be completed, the water pressure should be reduced in time to avoid impacting the original soil layer below the design elevation;

[0056] S6. Hole cleaning: When drilling with a vibrator, when the designed elevation is reached, the vibrator should be stopped and hole cleaning should be started;

[0057] S7, remove the vibrator: after the hole is cleaned, pull out the vibrator at a uniform speed to prepare for the next step of filling;

[0058] S8, filling, starting the first stage of filling work;

[0059] S9, vibrating and compacting the piles. After the first stage of filling work is completed, a vibrator needs to be placed in the filled material for vibration. After the vibrating and compacting is completed, secondary filling is performed again until the construction of one gravel pile is completed. Repeat S4-S9 to complete the construction of the remaining gravel piles.

[0060] When replacing vertical drainage wells with bagged sand bags, pay attention to the following points:

[0061] 1. Sand bags should be filled with dry sand;

[0062] 2. The sand well should be accurately positioned, the plane well spacing deviation should not be greater than the well diameter, and the verticality should not be greater than 1.5%;

[0063] 3. The depth of the sand well shall not be less than the design requirements, and the length of the buried sand cushion layer shall not be less than 0.5m;

[0064] 4. The inner diameter of the conduit should be slightly larger than the diameter of the sand well, and a roller should be installed at the conduit opening at the entrance of the sand bag to prevent the sand bag from being scratched;

[0065] 5. Polypropylene woven bags for sand filling should be kept away from direct sunlight for a long time;

[0066] 6. The length of the sandbag on the pulling tube should not exceed 0.50m.

[0067] The vertical drainage wells and bagged sand wells have the same function. Both are to increase the drainage path of the soil and speed up the discharge of pore water in the soil. After replacing the vertical drainage wells with bagged sand wells, it is necessary to set up a sand cushion layer on the ground as a means of water collection. During the subsequent gravel pile construction process, the vibrator continuously applies pressure to the soil, forcing the soil porosity to decrease. Under the action of load, the pore water in the foundation is discharged through the bagged sand wells, the porosity decreases, the foundation undergoes consolidation deformation, and the strength of the soil gradually increases. In this process, the discharged pore water enters the bagged sand wells. Since the gravel pile construction is from bottom to top, the pore water continues to move upward during the gravel pile construction process and eventually enters the outermost sand cushion layer, thereby reducing the water content of the soil and reducing the buoyancy effect of groundwater on the building.

[0068] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

Claims

1. A method for treating a soft soil foundation with a high plasticity index, characterized in that: The method comprises a vibro-stone column reinforcement method and a drainage consolidation method, wherein the vibro-stone column reinforcement method and the drainage consolidation method are used in combination and crosswise, and comprises the following steps: S1. Planning vertical drainage wells: survey the construction area, determine the well location and depth, formulate construction plans and drawings, prepare the required construction equipment and materials, ensure the safety and smooth progress of the construction process, and select appropriate drilling equipment and materials; S2. Wellhead excavation: After the well location and well depth are determined, the wellhead is excavated by drilling equipment; S3, set up drainage system; after the wellhead is dug, install the wellbore and cast the well wall, set up drainage blind ditch and water collection well, and install drainage facilities in the water collection well; S4. Determine the pile position: clearly mark the specific position of each pile position according to the requirements of the design drawings at the construction site. The pile position is located between adjacent drainage wells, and the pile position number is matched with the number in the design drawings; S5. Hole making: Turn on the vibrator and slowly sink at a rate of 1m / min to 2m / min, and keep sufficient water during the hole making process; S6. Hole cleaning: When drilling with a vibrator, when the designed elevation is reached, the vibrator should be stopped and hole cleaning should be started; S7, remove the vibrator: after the hole is cleaned, pull out the vibrator at a uniform speed to prepare for the next step of filling; S8, filling, starting the first stage of filling work; S9, vibrating and compacting piles. After completing the first stage of filling work, the vibrator needs to be placed in the filled material for vibration. After the compaction is completed, secondary filling is performed again until the construction of one gravel pile is completed. Repeat S4-S9 to complete the construction of the remaining gravel piles.

2. A method for treating a soft soil foundation with a high plasticity index according to claim 1, characterized in that: In step S1, the actual deviation between the pile position and the position marked on the drawing is less than 500 mm, and each pile position is divided into areas and numbered, and the numbers of all pile positions are recorded in the construction drawings.

3. A method for treating a soft soil foundation with a high plasticity index according to claim 1, characterized in that: In step S6, the designed drilling depth is 30 m, and the hole cleaning time is two minutes.

4. A method for treating a soft soil foundation with a high plasticity index according to claim 1, characterized in that: The working height of the filler is 0.5m to 1.0m.

5. The method for treating a soft soil foundation with a high plasticity index according to claim 1, characterized in that: The working height of the secondary filler is less than 0.5m.

6. A method for treating a soft soil foundation with a high plasticity index according to claim 1, characterized in that: The wellhead spacing is 2m to 3m.

7. The method for treating a soft soil foundation with a high plasticity index according to claim 1, characterized in that: In step S3, when grouting the well wall is performed, cement slurry or other materials are delivered into the underground soil through a grouting pump, the grouting material is delivered into the underground soil through a grouting pipe, and the slurry is injected into the soil through a grouting gun.

8. The method for treating a soft soil foundation with a high plasticity index according to claim 1, characterized in that: The drainage facility comprises a drainage pump, a drainage pipe and a motor.

9. The method for treating a soft soil foundation with a high plasticity index according to claim 1, characterized in that: The vibrator has a length of 6m to 21m.

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