Vacuum preloading and positive pressure air bag air outlet rod combined soft soil foundation drainage reinforcement method

Abstract

The invention discloses a drainage reinforcement method for a soft soil foundation by combining vacuum preloading with positive-pressure air bag air outlet rods. An air outlet rod with an air bag is arranged at the center position of every four plastic drainage plates which are arranged in a square shape; and the top ports of all the air outlet rods with the air bags are connected with a positive pressure supply device. The positive pressure supply device inputs high-pressure gas to the air outlet rods with the air bags through the transverse pipelines, so that the air holes of the air outlet rods with the air bags blow out the high-pressure gas outwards in the transverse direction, the high-pressure gas moves towards the plastic drainage plates on the periphery, and then the high-pressure gas and the negative pressure working state of the vacuum preloading foundation drainage system cooperate to promote drainage. Meanwhile, the air bags on the air outlet rods with the air bags are inflated and expanded to compact surrounding soil under the action of positive pressure, so that ultra-static pore water pressure is generated in the extruded soil, and the drainage and reinforcement effect of the foundation is further improved.

Description

Technical Field

[0001] The invention belongs to the technical field of soft soil foundation reinforcement, and in particular relates to a soft soil foundation drainage reinforcement method using a vacuum preloading combined with a positive pressure air bag outlet rod. Background Art

[0002] In recent years, with the continued vigorous development of port trade, the existing port yards and berths can no longer meet the needs of shipping. As a result, large-scale land reclamation and yard repair (expansion) projects have emerged. However, the water level in coastal areas is high, the physical and mechanical properties of the soil layer are poor, and the soft soil area is widely distributed. These have always been difficult problems that restrict the effect and quality of soft foundation reinforcement. Engineering accidents caused by uneven settlement and large post-construction settlement in existing yards and docks are common.

[0003] The traditional vacuum preloading soft foundation reinforcement method is widely used in my country's coastal and riverside areas. It has significant advantages such as short construction period, significant reinforcement effect, small impact on the environment, and high construction safety. However, it also has some disadvantages, such as limited reinforcement depth. The reinforcement depth of the vacuum preloading method is usually limited by the effective drainage depth of the drainage system. Since the traditional vacuum preloading process is limited by the vacuum degree (usually 80~90kPa) and its transmission efficiency (the study of vacuum degree attenuation law is usually within the range of 2~7kPa / m), its effective reinforcement depth is generally about 10m. For deep soft foundation, the reinforcement depth is limited to 10m. Soil layer, the reinforcement effect is not ideal, usually need to be combined with other reinforcement methods to achieve the reinforcement depth required by the design; the scope of application is limited, although the vacuum preloading method has certain applicability to a variety of soft soil foundations, but for some special geological conditions, such as deep soft soil layers, soft soil foundations with extremely high water content, etc., its reinforcement effect may be affected to a certain extent, and it needs to be used in combination with other methods; in addition, with the continuous improvement of soft foundation reinforcement technology, the reinforcement mechanism and effect of traditional processes are constantly being refreshed, so the traditional vacuum preloading process also needs to be continuously improved and improved to meet the needs of key projects for soft foundation reinforcement efficiency.

[0004] Therefore, there are still many problems and challenges in the application and development of traditional vacuum preloading soft foundation reinforcement technology, and there is still a long way to go in the research and innovation of new soft foundation reinforcement technology. In this regard, a new soft foundation reinforcement method based on vacuum preloading technology is proposed. Summary of the Invention

[0005] The purpose of the present invention is to provide a soft soil foundation drainage reinforcement method with vacuum preloading combined with positive pressure air bag outlet rod in order to address the technical deficiencies in the prior art.

[0006] The present invention is achieved through the following technical solutions: A method for draining and reinforcing a soft soil foundation using vacuum preloading combined with a positive pressure airbag outlet rod comprises the following steps: Step 1: Lay the cushion layer in the soft soil foundation area to be treated; Step 2: Install plastic drainage boards and air outlet rods with air bags in the soft soil foundation area to be treated; the plastic drainage boards are arranged in a lattice, and an air outlet rod with an air bag is placed at the center of every four plastic drainage boards arranged in a square; Step 3: Lay a sand layer, lay out horizontal drainage pipes and horizontal pipelines in the sand layer, and connect the top ports of all the air outlet rods with air bags to the horizontal pipelines; Step 4: Lay a sealing film on the sand layer, and dig a film pressing trench around the soft soil foundation to be treated, and seal the sealing film around to form a closed environment in the soft soil foundation area to be treated; Step 5: Lead the drainage collecting pipe upward out of the sealing membrane through the first vertical pipe and the first membrane outlet device and connect it to the air extraction and drainage device; lead the horizontal pipe upward out of the sealing membrane through the second vertical pipe and the second membrane outlet device and connect it to the positive pressure supply device; Step 6: Use the vacuum drainage device and positive pressure supply device to drain and reinforce the soft soil foundation.

[0007] In the above technical solution, in step 6, the drainage reinforcement process is carried out according to the following steps: Step 6.1: Only start the vacuum drainage device to perform vacuum preloading foundation drainage; Step 6.2: After the drainage rate is less than the set threshold, proceed to step 6.2; in step 6.2, simultaneously start the air extraction and drainage device and the positive pressure supply device to drain the foundation; the positive pressure supply device inputs high-pressure gas to each air outlet rod with an air bag through a horizontal pipeline, so that the air holes of the air outlet rod with the air bag blow out high-pressure gas laterally outward, and the high-pressure gas moves toward the surrounding plastic drainage boards. At the same time, under the synergistic effect of the air extraction and drainage device applying negative pressure to the foundation through the plastic drainage boards, the air outlet rod with the air bag and the four surrounding Many tiny channels are formed in the soil between the surrounding plastic drainage boards, and airflow is generated in the tiny channels from the air outlet rod with air bags to the plastic drainage boards around it, so that the moisture in the soil moves along these tiny channels and the airflow toward the plastic drainage boards and enters the plastic drainage boards; at the same time, the air bags on the air outlet rod with air bags are inflated and expanded under the action of positive pressure to compact the surrounding soil, so that excess pore water pressure is generated in the squeezed soil, which promotes the precipitation of water from the soil and further improves the foundation drainage reinforcement effect; Step 6.3: After step 6.2 has run for the set time, stop the positive pressure supply device and only open the air extraction and drainage device to perform vacuum preloading and drainage again. At this time, since many tiny channels have been formed in the foundation in step 6.2, only opening the air extraction and drainage device in step 6.3 can not only take advantage of the formation of tiny channels, but also greatly increase the negative pressure in the foundation, thereby improving the drainage effect. Step 6.4: Repeat steps 6.2 and 6.3 alternately several times; Step 6.5: Stop the positive pressure supply device and only start the air extraction and drainage device to carry out foundation drainage and reinforcement.

[0008] In the above technical solution, during the joint operation of the air extraction and drainage device and the positive pressure supply device, the negative pressure provided by the air extraction and drainage device is greater than the positive pressure provided by the positive pressure supply device, so that during the joint operation of the two, the entire foundation remains in a negative pressure state.

[0009] In the above technical solution, the air outlet rod structure with an airbag is as follows: it includes a steel pipe main body, the bottom of the steel pipe main body is a closed tip structure, a plurality of air holes are opened on the tube wall of the steel pipe main body, and an airbag is mounted on the steel pipe main body, and the airbag is connected to the inside of the steel pipe main body through an airway.

[0010] In the above technical solution, a woven cloth or a non-woven cloth is also laid on the lower layer of the sealing membrane as a protection to prevent the sealing membrane and the sand layer from being squeezed and ruptured.

[0011] In the above technical solution, water holes are distributed on the drainage and water collecting pipes, and the water holes are wrapped with filter cloth.

[0012] In the above technical solution, there are multiple airbags on the air outlet rod with airbags, which are arranged at intervals along the length direction of the steel pipe body.

[0013] The advantages and beneficial effects of the present invention are: Based on the vacuum preloading foundation drainage technology, the present invention combines an air outlet rod with an air bag and a positive pressure supply device, and arranges an air outlet rod with an air bag at the center position of every 4 plastic drainage boards arranged in a square; the top ports of all the air outlet rods with air bags are connected to the horizontal pipeline, and the horizontal pipeline is buried in the sand layer of the vacuum preloading foundation drainage system. The horizontal pipeline leads the sealing film upward through the vertical pipeline and the film outlet device and is connected to the positive pressure supply device. During operation, the positive pressure supply device inputs high-pressure gas to each air outlet rod with an air bag through a transverse pipeline, so that the air holes of the air outlet rod with the air bag blow out high-pressure gas laterally outward, and these high-pressure gases move toward the surrounding plastic drainage boards, and then cooperate with the negative pressure working state of the vacuum preloading foundation drainage system, so that many tiny channels are formed in the soil between the air outlet rod with the air bag and the plastic drainage boards around it, and air flows from the air outlet rod with the air bag to the plastic drainage boards around it, so that the moisture in the soil moves along the tiny channels and the air flow toward the plastic drainage boards, and enters the plastic drainage boards, which promotes drainage; at the same time, the air bags on the air outlet rod with the air bag are inflated and expanded under the action of positive pressure to compact the surrounding soil, so that excess pore water pressure is generated in the squeezed soil, which promotes the precipitation of moisture from the soil, and further improves the foundation drainage and reinforcement effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The present invention is a flow chart of the soft soil foundation drainage reinforcement method using vacuum preloading combined with a positive pressure air bag outlet rod.

[0015] Figure 2 This is a structural schematic diagram of a soft soil foundation reinforcement system constructed by the method of the present invention.

[0016] Figure 3 It is a top view schematic diagram of the arrangement between the air outlet rod with air bag and the plastic drainage board.

[0017] Figure 4 It is a three-dimensional schematic diagram of the arrangement between the air outlet rod with air bag and the plastic drainage board.

[0018] Figure 5 It is a structural diagram of the air outlet rod with an air bag.

[0019] For ordinary technicians in this field, other relevant drawings can be obtained based on the above drawings without any creative work. DETAILED DESCRIPTION

[0020] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0021] The present invention provides a soft soil foundation drainage reinforcement method using vacuum preloading combined with positive pressure airbag outlet rod, see attached Figure 1 and attached Figure 2 , including the following steps: Step 1: Lay a cushion layer in the soft soil foundation area to be treated to meet the mechanical working conditions.

[0022] Step 2: Install plastic drainage board 3 and air outlet rod 1 with air bag in the soft soil foundation area to be treated; see attached Figure 3 The plastic drainage boards 3 are arranged in a lattice, and an air outlet rod 1 with an air bag is arranged at the center of every four plastic drainage boards 3 arranged in a square.

[0023] See attached Figure 5 The structure of the air outlet rod 1 with an airbag is as follows: it includes a steel pipe body 101, the bottom of the steel pipe body 101 is a closed tip structure, which is convenient for inserting it into the foundation, and a plurality of air holes 102 are opened on the tube wall of the steel pipe body 101, and an airbag 103 is set on the steel pipe body 101. The airbag 103 is connected to the inside of the steel pipe body 101 through an airway. There are multiple airbags 103, which are arranged at intervals along the length direction of the steel pipe body 101.

[0024] Step 3: Lay a sand layer 4 , lay a horizontal drainage collection pipe 5 and a horizontal pipeline 10 in the sand layer 4 , and connect the top ports of all the air outlet rods 1 with air bags to the horizontal pipeline 10 .

[0025] Step 4: A sealing film 6 is laid on the sand layer 4 (preferably, a woven cloth or non-woven fabric can also be laid under the sealing film 6 as a protection to prevent the sealing film 6 and the sand layer from being squeezed and ruptured), and a film pressing trench 7 is excavated around the soft soil foundation to be treated to seal the sealing film 6 around, thereby forming a closed environment in the soft soil foundation area to be treated.

[0026] Step 5: Lead the drainage collection pipe 5 upward through the first vertical pipeline and the first film outlet device 81 to the sealing membrane 6 and connect it to the air extraction and drainage device 9 (also known as the water vapor separation pump); lead the horizontal pipeline 10 upward through the second vertical pipeline and the second film outlet device 82 to the sealing membrane 6 and connect it to the positive pressure supply device 2. The final system structure is shown in the attached figure. Figure 2 .

[0027] Step 6: Use the air extraction and drainage device 9 and the positive pressure supply device 2 to drain and reinforce the soft soil foundation.

[0028] Furthermore, preferably, the drainage reinforcement process is carried out according to the following steps: Step 6.1: Only the vacuum drainage device 9 is started to perform traditional vacuum preloading foundation drainage. At this stage, since there is a lot of water vapor in the soft soil foundation in the initial state, rapid and efficient foundation drainage can be performed. Specifically, during operation, the vacuum drainage device 9 generates negative pressure, which is transmitted to the soft soil foundation through the drainage collection pipe 5, the sand layer 4 and the plastic drainage board 3. Under the action of the negative pressure, the water and air in the soft soil foundation enter the plastic drainage board 3, and are collected upward along the plastic drainage board 3 to the drainage collection pipe 5, and finally enter the vacuum drainage device along the drainage collection pipe 5, thereby achieving drainage reinforcement of the soft soil foundation.

[0029] Step 6.2: As vacuum preloading foundation drainage proceeds, the foundation moisture content gradually decreases, the drainage rate also gradually decreases, and the energy consumption of the air extraction and drainage device 9 increases. Therefore, after the drainage rate falls below a certain threshold, step 6.2 is performed. In step 6.2, the air extraction and drainage device 9 and the positive pressure supply device 2 are simultaneously activated. The two work together to drain the foundation, which can greatly improve the drainage rate and drainage effect.

[0030] Specifically, when the two work together, the positive pressure supply device 2 inputs high-pressure gas to each air outlet rod 1 with an air bag through the horizontal pipeline 10, so that the air hole 102 of the air outlet rod 1 with an air bag blows out the high-pressure gas horizontally (see the attached Figure 4 The air bags on the upper and lower parts of the soil are then blown away by the air inlets which are then pulled out of the soil and the water inlets are pulled out of the soil and the soil is pumped in. As shown by the arrows in the figure, these high-pressure gases move toward the plastic drainage boards 3 around them. At the same time, the air bags on the air bags on the upper and lower parts of the soil will be inflated and expanded to compact the surrounding soil under the action of positive pressure, so that excess pore water pressure is generated in the squeezed soil, which promotes the precipitation of water from the soil, thereby further improving the drainage and reinforcement effect of the foundation.

[0031] Furthermore, during the joint operation of the air extraction and drainage device 9 and the positive pressure supply device 2, the negative pressure provided by the air extraction and drainage device 9 is greater than the positive pressure provided by the positive pressure supply device 2, so that during the joint operation of the two, the entire foundation remains in a negative pressure state.

[0032] Step 6.3: Since the vacuum drainage device 9 and the positive pressure supply device 2 are turned on at the same time in step 6.2, although many tiny channels can be formed in the foundation, the input of positive pressure gas in the foundation will reduce the negative pressure in the foundation. Therefore, if step 6.2 is continued for a long time, the drainage effect is not optimal.

[0033] Therefore, after step 6.2 has run for a period of time, the positive pressure supply device 2 is stopped and step 6.3 is performed. In step 6.3, only the air extraction and drainage device 9 is activated, and the traditional vacuum preloading and drainage process is performed again. At this time, since many tiny channels have been formed in the foundation in step 6.2, only the air extraction and drainage device 9 is activated in step 6.3. This can not only take advantage of the formation of tiny channels, but also greatly increase the negative pressure in the foundation, thereby improving the drainage effect.

[0034] Step 6.4: Repeat steps 6.2 and 6.3 alternately several times.

[0035] Step 6.5: Stop the positive pressure supply device 2 and activate only the air extraction and drainage device 9 to perform foundation drainage and reinforcement. This step is to finally extract the water and gas from the foundation. This is because the operation of the positive pressure supply device 2 increases the gas content in the foundation. Therefore, in the final stage, the positive pressure supply device 2 is stopped and only the air extraction and drainage device 9 is activated.

[0036] For ease of explanation, spatial relative terms such as "upper", "lower", "left", and "right" are used in the embodiments to illustrate the relationship between one element or feature shown in the figures and another element or feature. It should be understood that, in addition to the orientation shown in the figures, spatial terms are intended to include different orientations of the device in use or operation. For example, if the device in the figure is inverted, the element described as being "under" other elements or features will be positioned "above" other elements or features. Therefore, the exemplary term "under" can include both upper and lower orientations. The device can be positioned in other ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used here can be interpreted accordingly.

[0037] Moreover, relational terms such as “first” and “second” are merely used to distinguish one component from another having the same name, but do not necessarily require or imply any actual relationship or order between these components.

[0038] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for draining and reinforcing soft soil foundation using vacuum preloading combined with a positive pressure airbag outlet rod, characterized in that: The following steps are involved: Step 1: Lay the cushion layer in the soft soil foundation area to be treated; Step 2: Install plastic drainage boards and air outlet rods with air bags in the soft soil foundation area to be treated; the plastic drainage boards are arranged in a lattice, and an air outlet rod with an air bag is placed at the center of every four plastic drainage boards arranged in a square; Step 3: Lay a sand layer, lay out horizontal drainage pipes and horizontal pipelines in the sand layer, and connect the top ports of all the air outlet rods with air bags to the horizontal pipelines; Step 4: Lay a sealing film on the sand layer, and dig a film pressing trench around the soft soil foundation to be treated, and seal the sealing film around to form a closed environment in the soft soil foundation area to be treated; Step 5: Lead the drainage collecting pipe upward out of the sealing membrane through the first vertical pipe and the first membrane outlet device and connect it to the air extraction and drainage device; lead the horizontal pipe upward out of the sealing membrane through the second vertical pipe and the second membrane outlet device and connect it to the positive pressure supply device; Step 6: Use the vacuum drainage device and positive pressure supply device to drain and reinforce the soft soil foundation.

2. The soft soil foundation drainage reinforcement method using vacuum preloading combined with positive pressure airbag outlet rod according to claim 1 is characterized in that: In step 6, the drainage reinforcement process is carried out as follows: Step 6.1: Only start the vacuum drainage device to perform vacuum preloading foundation drainage; Step 6.2: After the drainage rate is less than the set threshold, proceed to step 6.2; in step 6.2, simultaneously start the air extraction and drainage device and the positive pressure supply device to drain the foundation; the positive pressure supply device inputs high-pressure gas to each air outlet rod with an air bag through a transverse pipeline, so that the air holes of the air outlet rod with the air bag blow out high-pressure gas laterally, and the high-pressure gas moves to the surrounding plastic drainage boards. At the same time, under the synergistic effect of the air extraction and drainage device applying negative pressure to the foundation through the plastic drainage board, the air outlet rod with the air bag and its surrounding Many tiny channels are formed in the soil between the surrounding plastic drainage boards, and air flows from the air outlet rod with air bags to the surrounding plastic drainage boards, causing the moisture in the soil to move along these tiny channels and the air flow toward the plastic drainage boards and enter the plastic drainage boards. At the same time, the air bags on the air outlet rod with air bags are inflated and expanded under the action of positive pressure to compact the surrounding soil, generating excess pore water pressure in the squeezed soil, promoting the precipitation of water from the soil, and further improving the foundation drainage reinforcement effect. Step 6.3: After step 6.2 has run for the set time, stop the positive pressure supply device and only open the air extraction and drainage device to perform the vacuum pre-pressure drainage work again; Step 6.4: Repeat steps 6.2 and 6.3 alternately several times; Step 6.5: Stop the positive pressure supply device and only start the air extraction and drainage device to carry out foundation drainage and reinforcement.

3. The soft soil foundation drainage reinforcement method using vacuum preloading combined with positive pressure airbag outlet rod according to claim 1 is characterized in that: During the joint operation of the air extraction and drainage device and the positive pressure supply device, the negative pressure provided by the air extraction and drainage device is greater than the positive pressure provided by the positive pressure supply device.

4. The soft soil foundation drainage reinforcement method using vacuum preloading combined with positive pressure airbag outlet rod according to claim 1 is characterized in that: The structure of the air outlet rod with an airbag includes a steel pipe body, the bottom of the steel pipe body is a closed tip structure, a plurality of air holes are opened on the tube wall of the steel pipe body, and an airbag is mounted on the steel pipe body, and the airbag is connected to the inside of the steel pipe body through an airway.

5. The soft soil foundation drainage reinforcement method using vacuum preloading combined with positive pressure airbag outlet rod according to claim 1 is characterized in that: The lower layer of the sealing membrane is also paved with woven cloth or non-woven fabric.

6. The method for draining and reinforcing soft soil foundation using vacuum preloading combined with positive pressure airbag outlet rod according to claim 1 is characterized in that: The drainage collecting pipe is provided with water-permeable holes, which are wrapped with filter cloth.

7. The method for draining and reinforcing soft soil foundation using vacuum preloading combined with positive pressure airbag outlet rod according to claim 4 is characterized in that: There are multiple air bags on the air outlet rod with air bags, which are arranged at intervals along the length direction of the steel pipe body.

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