Vacuum combined preloading sand-free cushion semi-fluid solidified soil construction method

Abstract

The invention discloses a vacuum combined preloading sand-cushion-free semi-fluid solidified soil construction method, which adopts semi-fluid solidified soil to replace a vacuum combined preloading sand cushion on a film for solidified soil construction, that is to say, a soil body is in a fluid state during manufacture and construction of the solidified soil, and the poured soil body is in a semi-fluid state during pouring. And the flowability is lost in a short time and the intensity is gradually generated. High-strength solidified soil is formed on the sealing film through the semi-flow solidified soil construction technology, a sand cushion layer on the film is replaced, the reliability of the later strength of the solidified soil is further guaranteed while the construction convenience of the solidified soil is guaranteed, and the method has wide application prospects in the field of blow-filling soft soil through vacuum combined surcharge preloading treatment.

Description

Technical Field

[0001] The present invention relates to the technical field of soft foundation reinforcement in geotechnical engineering, and more specifically, to a construction method of semi-fluid solidified soil with vacuum combined loading preloading and sand-free cushion. Background Art

[0002] There are large areas of mudflats in the coastal areas of East my country and South China. When carrying out land reclamation or soft foundation reinforcement in the offshore, the vacuum combined loading and preloading method is often used to treat the high-water content mudflats. The loading and vacuum preloading together reduce the water content of the high-water content mud, thereby improving the strength of the soft soil. In order to avoid the penetration and damage of the load to the sealing membrane, a layer of sand cushion is laid on the sealing membrane as a protective layer before loading, and then graded loading and preloading are carried out to achieve the effect of reinforcing the high-water content soft soil. Therefore, when using vacuum combined loading and preloading to reinforce the soft soil of the filling, a large amount of sand resources are required as a cushion layer. The filling area is generally full of mud and lacks sand. Sand resources mainly rely on purchasing from other places, which greatly increases the cost of soft foundation treatment construction; in addition, the current main method is to manually lay the sand cushion layer, which is inefficient and costly. The vacuum combined loading and preloading membrane protective layer not only increases the construction cost, but also increases the construction period to a certain extent, which seriously limits the application and promotion of this technology. Fluidized solidified soil can replace the sand cushion as a protective layer on the vacuum combined loading preloading membrane. Patents CN202122478068.9 and CN202311225609.4 disclose the production and construction methods of fluidized soil. Patent CN202211189277.4 replaces the sand cushion with fluidized soil as a protective layer on the vacuum combined loading preloading membrane. These inventions increase the fluidity of the solidified soil by increasing its water content, solving the problem of the difficulty of solidified soil construction, but at the same time bring some disadvantages. The fluidized solidified soil has a high water content in the later stage, which makes its strength increase slowly or even not harden. The soil body always remains in a fluid or semi-fluid state, which ultimately leads to a low foundation bearing capacity formed by the solidified soil. If the water content of the solidified soil is reduced, the development of its later strength can be guaranteed, but the soil body does not show "fluidity" during construction, which greatly reduces the convenience of the solidified soil in use. Therefore, the "high fluidity" of fluidized solidified soil during construction and the "low strength" during use are the unresolved contradictions in the current public patents.

[0003] Therefore, in view of the current situation of vacuum combined loading preloading on the protective layer of the membrane, the present application proposes a vacuum combined loading preloading sand-free cushion layer semi-fluid solidified soil construction method. Summary of the invention

[0004] One object of the present invention is to provide a vacuum combined loading and preloading method for constructing semi-fluidized solidified soil without a sand cushion layer. Semi-fluidized solidified soil construction technology is used to form solidified soil with higher strength on a sealing membrane to replace the sand cushion layer on the membrane. While ensuring the convenience of solidified soil construction, the reliability of the later strength of the solidified soil is also ensured. The method has broad application prospects in the field of vacuum combined loading and preloading for treating soft fill soil.

[0005] In order to solve the above technical problems, the present invention provides a vacuum combined loading preloading and sand-free cushion layer semi-fluid solidified soil construction method, in which semi-fluid solidified soil is used to replace the sand cushion layer on the vacuum combined loading preloading membrane for solidified soil construction, that is, the soil is in a fluid state during the production and construction of the solidified soil, and is in a semi-fluid state during and after pouring, and loses fluidity in a short time and gradually generates strength.

[0006] Preferably, the method specifically comprises the following steps:

[0007] Step 1: Use waste soil resources at the application site as the main raw material to prepare fluidized soil, and control the moisture content of the fluidized soil within a set range, and control the fluidity of the fluidized soil to 180-240 mm;

[0008] Step 2, prepare curing agent main material slurry and activator slurry separately for standby use;

[0009] Step 3: Use a semi-fluid solidified soil conveying device to pump and convey the prepared fluidized soil. During the conveying process, add a curing agent main material slurry and an activator slurry to the fluidized soil in sequence, so that the fluidized soil or the solidified soil exhibits different fluidities. After the solidified soil is conveyed to the terminal of the semi-fluid solidified soil conveying device, the semi-fluid solidified soil is formed.

[0010] Step 4: pouring the semi-fluid solidified soil at the application site;

[0011] Step 5: After the semi-fluid solidified soil is filled to the set application elevation, the semi-fluid solidified soil conveying device is closed and pumping is stopped;

[0012] Step 6: Manually assist in leveling the areas where the solidified soil elevation does not meet the requirements, and then maintain the solidified soil;

[0013] Step 7: After the maintenance is completed, check whether the bearing capacity of the solidified soil foundation meets the bearing capacity requirements for the pile load;

[0014] Step 8. After the requirements are met, load the surface of the solidified soil and carry out subsequent construction of vacuum combined loading preloading.

[0015] Preferably, the semi-fluid solidified soil conveying device is used to achieve control of the fluidity of the solidified soil and conveyance of the solidified soil, comprising a mud conveying pipeline, a curing agent main material conveying pipeline, a water adding pipeline and an activator conveying pipeline which are sequentially connected to the mud conveying pipeline along the conveying direction of the mud conveying pipeline, and a plurality of mixing and stirring heads arranged in the mud conveying pipeline, the plurality of mixing and stirring heads are respectively and one by one arranged behind the curing agent main material conveying pipeline, the water adding pipeline and the activator conveying pipeline, a mud slurry pump is provided at the inlet end of the mud conveying pipeline for driving mud conveyance, and the water adding pipeline is used to selectively add water according to the fluidity of the mud in the mud conveying pipeline.

[0016] Preferably, the curing agent main material delivery pipeline, the water supply pipeline and the activator delivery pipeline are all provided with control valves, and a control system is also provided, which is used to control the opening and closing and the opening size of the control valves on each pipeline respectively. After the fluidity of the fluidized soil is controlled within the set range in the step one, it is transported through the mud delivery pipeline, and all control valves except the control valve of the curing agent main material delivery pipeline are controlled to be closed. After the fluidized soil is transported to the end of the mud delivery pipeline, the fluidity of the fluidized soil is detected and compared with the fluidity of the fluidized soil at the beginning of the pipeline. If the difference is within the set error range, the next construction is carried out, and the water supply pipeline control valve is not opened; if the difference exceeds the set error range, the water supply pipeline control valve is controlled to be gradually opened until it is detected that the error between the fluidity of the fluidized soil at the end of the mud delivery pipeline and the fluidity of the fluidized soil at the beginning of the mud delivery pipeline is within the set range, and the opening size of the water supply pipeline control valve is recorded at this time. In the subsequent transportation process, the water supply pipeline control valve is controlled to be opened to this recorded size through the control system.

[0017] Preferably, the diameter of the mud conveying pipeline of the semi-fluid solidified soil conveying device is 200-500 mm, the diameter of the curing agent main material conveying pipeline is 50-120 mm, the diameter of the water adding pipeline is 50-100 mm, and the diameter of the activator conveying pipeline is 30-50 mm.

[0018] Preferably, the distance between the outlet of the curing agent main material delivery pipeline and the nearest mixing head is not less than 40 mm, the distance between the outlet of the water adding pipeline and the mixing head is not less than 400 mm, the distance between the outlet of the activator delivery pipeline and the nearest mixing head is not less than 400 mm, and the distance between the mixing heads is not less than 800 mm.

[0019] Preferably, the main material of the curing agent includes mineral powder and additives, and the additives include one or more of kaolin, silica fume, fly ash, steel slag, and rice husk ash, and the total mass of the additives does not exceed 40% of the total dosage of the main material of the curing agent; the main material of the curing agent is in a liquid fluid state during transportation, and the water-cement ratio is 0.6-1; the curing agent dosage, that is, the ratio of the dry mass of the main material of the curing agent to the mass of the mud is 5-15%.

[0020] Preferably, the activator is a combination of one or more substances selected from the group consisting of sodium hydroxide, sodium sulfate, cement, lime, and carbide slag; sodium sulfate cannot be used alone but must be used together with other activators; the activator must be dissolved in water in advance during transportation, and the mass fraction of the activator during dissolution is 5 to 30%.

[0021] Preferably, the control system is also used to control and select the diameters of the curing agent main material delivery pipeline and the activator delivery pipeline according to the fluidity and semi-fluidity of the fluidized soil, and set the diameters of the curing agent main material delivery pipeline and the activator delivery pipeline to 1.5 times the calculated theoretical diameters. The theoretical diameter of the curing agent main material delivery pipeline is determined by the set curing agent dosage, that is, the ratio of the dry mass of the curing agent main material to the mud mass, and the theoretical diameter of the activator delivery pipeline is determined by the theoretical diameter of the curing agent main material delivery pipeline and the mass ratio of the curing agent main material to the activator; the control valves of the curing agent main material delivery pipeline and the activator delivery pipeline are controlled to be fully opened by the control system, and the opening sizes of the control valves of the curing agent main material delivery pipeline and the activator delivery pipeline are adjusted by judging whether the end port of the mud delivery pipeline is blocked and the degree of blockage, and the opening sizes are reduced in turn until the end port of the mud delivery pipeline is just not blocked, and the opening size is calculated by the opening size The delivery flow of the curing agent main material delivery pipeline and the activator delivery pipeline is then converted into the maximum pipe diameter corresponding to when the control valves of the curing agent main material delivery pipeline and the activator delivery pipeline are fully opened; the control valves of the curing agent main material delivery pipeline and the activator delivery pipeline are controlled by the control system to open one-fifth, and the fluidity of the fluid soil at the end of the mud delivery pipeline is detected and the opening size of the control valves of the curing agent main material delivery pipeline and the activator delivery pipeline is adjusted, and the opening size is increased in sequence until the fluidity of the fluid soil at the end of the mud delivery pipeline meets the set semi-fluid soil fluidity size range, and the delivery flow of the curing agent main material delivery pipeline and the activator delivery pipeline is calculated according to the opening size, and then converted into the minimum pipe diameter corresponding to when the control valves of the curing agent main material delivery pipeline and the activator delivery pipeline are fully opened; the pipe diameters of the curing agent main material delivery pipeline and the activator delivery pipeline are set within the minimum and maximum pipe diameters obtained by the above adjustment.

[0022] Preferably, the pipe at the end of the mud conveying pipe adjacent to the stirring head is detachably connected with an auxiliary pipe, which includes a pair of pipe bodies with semicircular cross-sections, one of which is fixedly provided with a pair of arc-shaped positioning plates on two side edges along the length direction, and the pair of arc-shaped positioning plates just fit with the two side edges of the other pipe body along the length direction to combine the pair of pipe bodies into a complete pipe body, and a pair of pipe bodies are matched with a fixing sleeve, and a pair of grooves are relatively arranged in the fixing sleeve and just fit with a pair of arc-shaped positioning plates, and the fixing sleeve extends to one end of the pipe body to the outside to form an extension sleeve, which has an internal thread and fits on the external thread at the end of the mud conveying pipe. After the auxiliary pipe is installed, it forms a part of the end of the mud conveying pipe. When it is detected that the degree of blockage in the mud conveying pipe needs to adjust the pipe diameter, the fixing sleeve and the auxiliary pipe are removed, and the blockage is quickly cleared by high-pressure water so that the next adjustment and detection can be quickly carried out.

[0023] The present invention has at least the following beneficial effects:

[0024] (1) The present invention mainly uses excavated waste soil or waste soil around the application site as raw material to make mud, thereby improving the utilization rate of construction waste, saving resources, and reducing project costs.

[0025] (2) The present invention adopts the method of fluidized soil transportation combined with semi-fluidized soil pouring for construction, which is convenient to construct, has good uniformity of fluidized soil / semi-fluidized soil, and can effectively protect the vacuum pre-pressed sealing membrane.

[0026] (3) The present invention adds the main material of the curing agent and the activator into the mud separately, which not only ensures the fluidity required in the mud transportation process, but also takes into account the strength development of the cured soil in the later stage.

[0027] (4) The present invention prepares and obtains semi-fluid solidified soil through a semi-fluid solidified soil conveying device, and at the same time controls the amount of water added and adjusts the size of the pipeline through the coordinated control and adjustment of the control system, thereby achieving simple control and reasonable setting of the conveying device, improving construction efficiency, and reducing the difficulty and cost of adjustment and control.

[0028] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a construction effect diagram of the semi-fluid solidified soil of the present invention;

[0030] Figure 2 This is a schematic diagram of the structure of the semi-fluid solidified soil conveying device of the present invention;

[0031] Figure 3 This is a dimensional diagram of the semi-fluid solidified soil conveying device of the present invention;

[0032] Figure 4 This is a cross-sectional explosion diagram of the auxiliary pipe and the fixed sleeve of the present invention. DETAILED DESCRIPTION

[0033] In order to better understand the purpose, structure and function of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings so that those skilled in the art can implement it according to the description.

[0034] It should be noted that the experimental methods described in the following embodiments are conventional methods unless otherwise specified, and the reagents and materials are commercially available unless otherwise specified; in the description of the present invention, the terms "lateral", "longitudinal", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0035] The technical principle of the present invention is as follows: the soil solidifying agent is divided into a main material and an activator. The main material of the solidifying agent includes mineral powder and a certain amount of one or more substances selected from kaolin, silica fume, fly ash, steel slag and rice husk ash. After the main material of the solidifying agent is mixed with the sludge / mud, it will not affect the physical properties and mechanical properties of the sludge / mud. The activator is generally cement, lime, sodium hydroxide, sodium sulfate, carbide slag and other substances, which can activate the activity of the main material of the solidifying agent, so that it has a solidifying effect on the sludge / mud. After the activator contacts the main material of the solidifying agent, it can be hydrated and ionized to produce a large number of high-valent cations (mainly Ca 2+ ), which can effectively compress the double-layer structure of soil particles, significantly change the physical properties of silt / mud, and has the function of reducing the fluidity of mud. The purpose of using a semi-fluid solidified soil conveying device is to add the main material of the curing agent and the activator separately into the fluidized soil, so that the fluidized soil / solidified soil exhibits different fluidities. When the mud begins to be conveyed, the main material of the curing agent is added from the main material conveying pipe of the curing agent, and is stirred evenly through a mixing and stirring head. The main material of the curing agent does not change the fluidity of the fluidized soil, so the fluidized soil still exhibits good fluidity during the conveying process; when the fluidized soil is about to be output from the pipeline, the activator is added to the fluidized soil through the activator conveying pipe, and the activator is mixed evenly with the mud and the main material of the curing agent through the stirring head. The activator will immediately change the fluidity of the mud, causing the fluidized soil at the conveying outlet to lose fluidity in a short period of time and become a semi-fluid paste. Under the action of the water reaction and volcanic ash reaction of the curing agent in the later stage, the strength of the soil increases and the soil gradually becomes a solid.

[0036] The technical problem to be solved by the present invention is to use solidified soil to replace the sand cushion layer of vacuum combined preloading, and to use fluidized soil technology to solve the problem of difficult construction of solidified soil, so that the solidified soil is easy to pour; at the same time, since the moisture content and fluidity of the soil are closely related, the moisture content of the fluidized soil needs to be strictly controlled to ensure that the soil after pouring has high strength and meets the use requirements. Therefore, the present invention provides a semi-fluid solidified soil construction method, in which the soil presents a fluid state during the production and construction of the solidified soil, and the soil presents a semi-fluid state during and after pouring, and loses fluidity in a short time and gradually generates strength, that is, semi-fluid solidified soil is used to replace the sand cushion layer on the vacuum combined preloading membrane.

[0037] Waste soil resources are mainly high-water content silt, which is difficult to use directly due to its high water content and low strength, and is generally landfilled as waste soil. Waste soil can also be slag that is difficult to reuse after on-site excavation. Specific embodiment:

[0039] A coastal mudflat in Wenzhou, Zhejiang, needs to be treated for foundation treatment, and the method of this application is used for sandless cushion construction. The abandoned mudflat on site is used as the main raw material of semi-fluid soil. The moisture content of the abandoned mudflat on site is 67-88%, the porosity is 2.46-3.12, the soil is in a fluid state, has no strength, and the organic matter content is 6.8%.

[0040] The present invention requires the use of a semi-fluid solidified soil conveying device to complete the construction of the semi-fluid solidified soil without a sand cushion layer, thereby achieving control of the fluidity of the solidified soil and conveying of the solidified soil. Figure 2 As shown, the semi-fluid solidified soil conveying device is composed of a mud pump 1, a mud conveying pipeline 7, a curing agent main material conveying pipeline 2, a curing agent main material conveying pipeline control valve 6, an activator conveying pipeline 4, an activator conveying pipeline control valve 8, a water pipe 3, a water pipe control valve 9 and a plurality of mixing and stirring heads 5. The various components of the semi-fluid solidified soil conveying device are in the order of mud pumping, curing agent main material conveying pipeline, mixing and stirring head, water pipe, mixing and stirring head, activator conveying pipeline, mixing and stirring head along the mud conveying direction, and the order cannot be changed. The water pipe determines whether to add water according to the fluidity of the mud in the pipe. If the fluidity of the mud in the pipe is too poor, add a little water to dilute it, and then stir it evenly; if the fluidity of the mud in the pipe is good, do not add water to dilute it. The activator conveying pipeline is placed at the end because once the activator is added to the mixture of mud and curing agent, a hydration reaction occurs immediately, the fluidity of the fluid in the pipe becomes poor, and it is easy to block the pipe. Therefore, it is placed at the end of the mud conveying pipeline. Even if it blocks the pipe, it only blocks a little bit and does not affect the pouring.

[0041] The diameter of each pipe and the spacing of the components are shown in the attached Figure 3As shown. The diameter of the mud conveying pipeline is 200-500mm, the diameter of the curing agent main material conveying pipeline is 50-120mm, the diameter of the water adding pipeline is 50-100mm, and the diameter of the activator conveying pipeline is 30-50mm. The distance between the pipe opening of the curing agent main material conveying pipeline and the nearest mixing head is not less than 40mm, the distance between the pipe opening of the water adding pipeline and the mixing head is not less than 400mm, the distance between the pipe opening of the activator conveying pipeline and the nearest mixing head is not less than 40mm, and the distance between the mixing heads is not less than 800mm. In the project corresponding to this embodiment, the diameter of the mud conveying pipeline of the semi-fluid solidified soil conveying device is 400mm, the diameter of the curing agent main material conveying pipeline is 80mm, the diameter of the water adding pipeline is 70mm, and the diameter of the activator conveying pipeline is 35mm. The distance between the outlet of the curing agent main material delivery pipeline and the nearest mixing head is 200 mm, the distance between the outlet of the water supply pipeline and the mixing head is 600 mm, the distance between the outlet of the activator delivery pipeline and the nearest mixing head is 80 mm, and the distance between the mixing heads is 1200 mm.

[0042] According to the monitoring data, the flow rate of the water pipe valve is adjusted in advance to a semi-fluid state that meets the requirements. The curing agent main material delivery pipeline, the water supply pipeline and the activator delivery pipeline are all provided with control valves, and a control system is also provided, which is used to control the opening and closing and opening size of the control valves on each pipeline respectively. After the fluidity of the fluidized soil is controlled within the set range in the step 1, it is transported through the mud delivery pipeline, and all control valves except the control valve of the curing agent main material delivery pipeline are controlled to be closed. After the fluidized soil is transported to the end of the pipeline, the fluidity of the fluidized soil is detected and compared with the fluidity of the fluidized soil at the beginning of the pipeline. If the difference is within the set error range, the next step of construction is carried out, and the water supply pipeline control valve is not opened; if the difference exceeds the set error range, the water supply pipeline control valve is controlled to be gradually opened until it is detected that the fluidity of the fluidized soil at the end of the pipeline and the fluidity of the fluidized soil at the beginning of the pipeline are within the set range, and the opening size of the water supply pipeline control valve is recorded at this time. In the subsequent transportation process, the water supply pipeline control valve is controlled to be opened to this recorded size through the control system. The opening size of the control valve of the curing agent main material conveying pipeline is such that the flow rate of the curing agent main material flowing through the mud conveying pipe satisfies the curing agent dosage, that is, the ratio of the dry mass of the curing agent main material to the mud mass is within the range of 5-15%.

[0043] The control system is also used to control and select the diameters of the curing agent main material delivery pipeline and the activator delivery pipeline according to the fluidity and semi-fluidity of the fluidized soil, and set the diameters of the curing agent main material delivery pipeline and the activator delivery pipeline to 1.5 times the calculated theoretical diameter. The theoretical diameter of the curing agent main material delivery pipeline is determined by the set curing agent dosage, that is, the ratio of the dry mass of the curing agent main material to the mud mass. The theoretical diameter of the activator delivery pipeline is determined by the theoretical diameter of the curing agent main material delivery pipeline and the mass ratio of the curing agent main material to the activator (according to the conventional ratio); the control valves of the curing agent main material delivery pipeline and the activator delivery pipeline are controlled to be fully opened by the control system, and the opening size of the control valves of the curing agent main material delivery pipeline and the activator delivery pipeline is adjusted by judging whether the end port of the mud delivery pipeline is blocked and the degree of blockage, and the opening size is reduced in turn until the end port of the mud delivery pipeline is just not blocked, and the delivery flow of the curing agent main material delivery pipeline and the activator delivery pipeline is calculated by the opening size, and then converted into the control valves of the curing agent main material delivery pipeline and the activator delivery pipeline are fully opened. The maximum pipe diameter corresponding to the time; the control valves of the curing agent main material delivery pipeline and the activator delivery pipeline are controlled by the control system to open one-fifth, and the fluidity of the fluid soil at the end of the mud delivery pipeline is detected and the opening size of the control valves of the curing agent main material delivery pipeline and the activator delivery pipeline is adjusted, and the opening size is increased in sequence until the fluidity of the fluid soil at the end of the mud delivery pipeline meets the set semi-fluid soil fluidity size range, and the delivery flow of the curing agent main material delivery pipeline and the activator delivery pipeline is calculated by the opening size, and then converted into the minimum pipe diameter corresponding to the control valves of the curing agent main material delivery pipeline and the activator delivery pipeline when they are fully opened; the pipe diameter size of the curing agent main material delivery pipeline and the activator delivery pipeline is set within the minimum pipe diameter and maximum pipe diameter range obtained by the above adjustment, so that the control valves of the curing agent main material delivery pipeline and the activator delivery pipeline can meet the requirements of semi-fluid solidified soil when they are fully opened, so that the control system only needs to control the size of the control valve of the water supply pipeline, and the control valves of the curing agent main material delivery pipeline and the activator delivery pipeline only need to control the opening and closing, and the control process is greatly reduced. In addition, if the semi-fluid solidified soil does not meet the requirements during the actual construction process, it is only necessary to fine-tune the control valves or control the fluidity of the mud. During the actual construction process, it was found that the pipe diameter size and the opening size of the control valve of the water supply pipe obtained according to the adjustment method of this application can meet the requirements of this application project.

[0044] like Figure 4As shown, the end of the mud conveying pipeline adjacent to the mixing head is detachably connected with an auxiliary pipe, which includes a pair of pipe bodies 10 with a semicircular cross section, one of which is fixedly provided with a pair of arc-shaped positioning plates 11 on the two sides along the length direction, and the pair of arc-shaped positioning plates just fit the two sides along the length direction of the other pipe body to combine the pair of pipe bodies into a complete pipe body, and a pair of pipe bodies are matched with a fixed sleeve 12, and a pair of grooves 13 are relatively provided in the fixed sleeve and just fit the pair of arc-shaped positioning plates, and the fixed sleeve extends to one end of the pipe body to form an extension sleeve, which has an internal thread and fits the external thread at the end of the mud conveying pipeline. After the auxiliary pipe is installed, it forms a part of the end of the mud conveying pipeline. When it is detected that the mud conveying pipeline needs to adjust the pipeline diameter due to the blockage degree, the fixed sleeve and the auxiliary pipe are removed, and the blockage is quickly cleared by high-pressure water, so as to quickly carry out the next adjustment test. The auxiliary pipe is composed of two pipe bodies, which is convenient to remove and clean the blockage. In addition, the auxiliary pipe is replaced after the later adjustment is completed to form a normal pipeline for actual construction.

[0045] The main material of the curing agent needs to include mineral powder, on this basis, a certain amount of kaolin, silica fume, fly ash, steel slag, and rice husk ash are additionally added. The additives can be one or more substances therein, wherein the total mass of kaolin, silica fume, fly ash, steel slag, and rice husk ash added accounts for 35% of the total mass of the main material of the curing agent; when the main material of the curing agent is transported, its state is a liquid fluid, the water-cement ratio is 0.6-1, and the preferred embodiment is 0.8, and the curing agent dosage (the ratio of the dry mass of the curing agent to the mass of the mud) is 5-15%, and the preferred embodiment is 8%; the activator is a combination of one or more substances selected from sodium hydroxide, sodium sulfate, cement, lime, and carbide slag; wherein sodium sulfate cannot be used alone and needs to be used together with other activators. In the present embodiment, the activator is a mixture of sodium hydroxide, sodium sulfate, and lime (the mass ratio of sodium hydroxide, sodium sulfate, and lime is 1:0.5:8); the activator needs to be dissolved in water in advance when transported, and the mass fraction of the activator when dissolved is 5-30%, and the preferred embodiment is 17%.

[0046] During construction, the semi-fluid solidified soil is poured to a thickness of 1m. Except for using a semi-fluid solidified soil conveying device to prepare the semi-fluid solidified soil as a vacuum combined loading preloading cushion, the remaining process steps are the same as the conventional vacuum combined loading preloading process. The foundation treatment site is 1000m×800m, and the specific construction method includes the following steps:

[0047] (1) Preliminary preparation work for vacuum preloading: construction of drainage board and sealing wall, laying and connection of horizontal drainage system, and other routine work for vacuum preloading;

[0048] (2) Using mud from the tidal flats at the application site as the main raw material, prepare fluidized soil, control the moisture content of the fluidized soil to 100-120%, and control the fluidity of the fluidized soil to 180-240 mm, to ensure that the mud has a certain pumpability;

[0049] (3) preparing curing agent main material slurry and activator slurry separately for later use;

[0050] (4) Use a semi-fluidized solidified soil conveying device to pump and convey the prepared fluidized soil, and successively turn on the slurry pump switch, the mixing head switch, the curing agent main material conveying pipeline control valve, and the activator conveying pipeline control valve;

[0051] (5) Pour the solidified soil flowing out of the terminal of the semi-fluid solidified soil conveying device pipeline at the application site. If the fluidity of the solidified soil flowing out of the terminal is too poor to be self-compacted, it is necessary to open the water pipe valve and adjust the flow rate of the water pipe valve. When the fluidity of the solidified soil is 180-200 mm, construction can continue;

[0052] (6) When the solidified soil filling elevation reaches the design elevation, all control valves of the semi-fluid solidified soil conveying device are closed, and the semi-fluid solidified soil conveying device is removed from the site. For the corners where the solidified soil elevation does not meet the standard, manual auxiliary leveling is performed;

[0053] (7) Natural curing of solidified soil;

[0054] (8) After the solidified soil is cured to the corresponding age, a core sample is taken out through drilling for unconfined compressive strength test. The strength of the core sample is converted into the bearing capacity of the foundation. When the bearing capacity of the solidified soil foundation meets the bearing capacity required for the heap load, the next step of construction can be carried out;

[0055] (9) Load the surface of the solidified soil and carry out vacuum combined loading preloading and subsequent construction.

[0056] In the above embodiment of the present application, the semi-fluid solidified soil is cured for 7 days after construction. The semi-fluid solidified soil foundation strength is 240-270 kPa as tested by the load plate test, which meets the later loading requirements. Figure 1 The unconfined compressive strength of the core sampled soil is shown in Table 1.

[0057] Table 1 Experimental values ​​of unconfined compressive strength of core samples

[0058] Checkpoint 1 Checkpoint 2 Checkpoint 3 Checkpoint 4 Checkpoint 5 Unconfined compressive strength / MPa 1.12 1.24 1.18 1.33 1.22

[0059] It is understood that the present invention is described by some embodiments, and those skilled in the art are aware that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation mode, and they can be fully applied to various fields suitable for the present invention. For those familiar with the art, other modifications can be easily implemented, so without departing from the general concept defined by the claims and the equivalent scope, the present invention is not limited to the specific details and the illustrations shown and described here.

Claims

1. A vacuum combined loading preloading method for construction of semi-fluid solidified soil without sand cushion, characterized in that: Semi-fluid solidified soil is used to replace the sand cushion layer on the vacuum combined loading preloading membrane for solidified soil construction. That is, the soil is in a fluid state during the production and construction of the solidified soil, and is in a semi-fluid state during and after pouring, and loses fluidity in a short time and gradually develops strength.

2. The vacuum combined loading preloading sandless cushion semi-fluid solidified soil construction method according to claim 1 is characterized in that: The specific steps include: Step 1: Use waste soil resources at the application site as the main raw material to prepare fluidized soil, and control the moisture content of the fluidized soil within a set range, and control the fluidity of the fluidized soil to 180-240 mm; Step 2, prepare curing agent main material slurry and activator slurry separately for standby use; Step 3: Use a semi-fluid solidified soil conveying device to pump and convey the prepared fluidized soil. During the conveying process, add a curing agent main material slurry and an activator slurry to the fluidized soil in sequence, so that the fluidized soil or the solidified soil exhibits different fluidities. After the solidified soil is conveyed to the terminal of the semi-fluid solidified soil conveying device, the semi-fluid solidified soil is formed. Step 4: pouring the semi-fluid solidified soil at the application site; Step 5: After the semi-fluid solidified soil is filled to the set application elevation, the semi-fluid solidified soil conveying device is closed and pumping is stopped; Step 6: Manually assist in leveling the areas where the solidified soil elevation does not meet the requirements, and then maintain the solidified soil; Step 7: After the maintenance is completed, check whether the bearing capacity of the solidified soil foundation meets the bearing capacity requirements for the pile load; Step 8. After the requirements are met, load the surface of the solidified soil and carry out subsequent construction of vacuum combined loading preloading.

3. The vacuum combined loading preloading sandless cushion semi-fluid solidified soil construction method according to claim 2 is characterized in that: The semi-fluid solidified soil conveying device is used to control the fluidity of the solidified soil and convey the solidified soil, including a mud conveying pipeline, a curing agent main material conveying pipeline, a water adding pipeline and an activator conveying pipeline which are sequentially connected to the mud conveying pipeline along the conveying direction of the mud conveying pipeline, and a plurality of mixing and stirring heads arranged in the mud conveying pipeline. The plurality of mixing and stirring heads are respectively and one by one arranged behind the curing agent main material conveying pipeline, the water adding pipeline and the activator conveying pipeline. A mud slurry pump is provided at the inlet end of the mud conveying pipeline for driving mud conveying, and the water adding pipeline is used to selectively add water according to the fluidity of the mud in the mud conveying pipeline.

4. The vacuum combined loading preloading sandless cushion semi-fluid solidified soil construction method according to claim 3 is characterized in that: The curing agent main material delivery pipeline, water supply pipeline and activator delivery pipeline are all provided with control valves, and a control system is also provided, which is used to control the opening and closing and the opening size of the control valves on each pipeline respectively. After the fluidity of the fluidized soil is controlled within the set range in the step one, it is transported through the mud delivery pipeline, and all control valves except the control valve of the curing agent main material delivery pipeline are controlled to be closed. After the fluidized soil is transported to the end of the mud delivery pipeline, the fluidity of the fluidized soil is detected and compared with the fluidity of the fluidized soil at the beginning of the pipeline. If the difference is within the set error range, the next construction is carried out, and the water supply pipeline control valve is not opened; if the difference exceeds the set error range, the water supply pipeline control valve is controlled to be gradually opened until it is detected that the error between the fluidity of the fluidized soil at the end of the mud delivery pipeline and the fluidity of the fluidized soil at the beginning of the mud delivery pipeline is within the set range, and the opening size of the water supply pipeline control valve is recorded at this time. In the subsequent transportation process, the water supply pipeline control valve is controlled to be opened to this recorded size through the control system.

5. The vacuum combined loading preloading sandless cushion semi-fluid solidified soil construction method as claimed in claim 3 is characterized in that: The diameter of the mud conveying pipeline of the semi-fluid solidified soil conveying device is 200-500 mm, the diameter of the curing agent main material conveying pipeline is 50-120 mm, the diameter of the water adding pipeline is 50-100 mm, and the diameter of the activator conveying pipeline is 30-50 mm.

6. The vacuum combined loading preloading sandless cushion semi-fluid solidified soil construction method according to claim 3, characterized in that: The distance between the outlet of the curing agent main material delivery pipeline and the nearest mixing and stirring head is not less than 40mm, the distance between the outlet of the water adding pipeline and the mixing and stirring head is not less than 400mm, the distance between the outlet of the activator delivery pipeline and the nearest mixing and stirring head is not less than 400mm, and the distance between the mixing and stirring heads is not less than 800mm.

7. The vacuum combined loading preloading sandless cushion semi-fluid solidified soil construction method according to claim 2, characterized in that: The main material of the curing agent includes mineral powder and additives. The additives include one or more substances of kaolin, silica fume, fly ash, steel slag, and rice husk ash. The total mass of the additives does not exceed 40% of the total dosage of the main material of the curing agent. The main material of the curing agent is in a liquid fluid state during transportation, and the water-cement ratio is 0.6-1. The curing agent dosage, that is, the ratio of the dry mass of the main material of the curing agent to the mass of the mud is 5-15%.

8. The vacuum combined loading preloading sandless cushion semi-fluid solidified soil construction method according to claim 2, characterized in that: The activator is a combination of one or more substances selected from the group consisting of sodium hydroxide, sodium sulfate, cement, lime, and carbide slag; sodium sulfate cannot be used alone but must be used together with other activators; the activator must be dissolved in water in advance during transportation, and the mass fraction of the activator during dissolution is 5 to 30%.

9. The vacuum combined loading preloading sandless cushion semi-fluid solidified soil construction method according to claim 4, characterized in that: The control system is also used to control and select the diameters of the curing agent main material delivery pipeline and the activator delivery pipeline according to the fluidity and semi-fluidity of the fluidized soil, and set the diameters of the curing agent main material delivery pipeline and the activator delivery pipeline to 1.5 times the calculated theoretical diameters. The theoretical diameter of the curing agent main material delivery pipeline is determined by the set curing agent dosage, that is, the ratio of the dry mass of the curing agent main material to the mud mass. The theoretical diameter of the activator delivery pipeline is determined by the theoretical diameter of the curing agent main material delivery pipeline and the mass ratio of the curing agent main material to the activator. The control system controls the control valves of the curing agent main material delivery pipeline and the activator delivery pipeline to be fully opened, and adjusts the opening sizes of the control valves of the curing agent main material delivery pipeline and the activator delivery pipeline by judging whether the end port of the mud delivery pipeline is blocked and the degree of blockage, and reduces the opening sizes in turn until the end port of the mud delivery pipeline is just not blocked, and calculates the curing agent through the opening size. The delivery flow of the curing agent main material delivery pipeline and the activator delivery pipeline is calculated, and then converted into the maximum pipe diameter corresponding to when the control valves of the curing agent main material delivery pipeline and the activator delivery pipeline are fully opened; the control valves of the curing agent main material delivery pipeline and the activator delivery pipeline are controlled by the control system to open one-fifth, and the fluidity of the fluid soil at the end of the mud delivery pipeline is detected and the opening size of the control valves of the curing agent main material delivery pipeline and the activator delivery pipeline is adjusted, and the opening size is increased in sequence until the fluidity of the fluid soil at the end of the mud delivery pipeline meets the set semi-fluid soil fluidity size range, and the delivery flow of the curing agent main material delivery pipeline and the activator delivery pipeline is calculated according to the opening size, and then converted into the minimum pipe diameter corresponding to when the control valves of the curing agent main material delivery pipeline and the activator delivery pipeline are fully opened; the pipe diameters of the curing agent main material delivery pipeline and the activator delivery pipeline are set within the minimum and maximum pipe diameters obtained by the above adjustment.

10. The vacuum combined loading preloading sandless cushion semi-fluid solidified soil construction method according to claim 9, characterized in that: The pipe at the end of the mud conveying pipe close to the stirring head is detachably connected with an auxiliary pipe, which includes a pair of pipe bodies with semicircular cross-sections, one of which is fixedly provided with a pair of arc-shaped positioning plates on the two side edges along the length direction of one of the pipe bodies, and the pair of arc-shaped positioning plates just fit with the two side edges of the other pipe body along the length direction to combine the pair of pipe bodies into a complete pipe body, and a pair of fixing sleeves are fitted outside the pair of pipe bodies, and a pair of grooves are relatively arranged inside the fixing sleeves and just fit with a pair of arc-shaped positioning plates, and the fixing sleeves extend to one end of the pipe body to the outside to form an extension sleeve, which has an internal thread and fits on the external thread at the end of the mud conveying pipe. After the auxiliary pipe is installed, it forms a part of the end of the mud conveying pipe. When it is detected that the degree of blockage in the mud conveying pipe needs to adjust the pipe diameter, the fixing sleeve and the auxiliary pipe are removed, and the blockage is quickly cleared by high-pressure water so that the next adjustment and detection can be quickly carried out.

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