A construction method for filling and replacing a soil cave solidified in a fluid state

Abstract

The application discloses a kind of flow state solidified soil karst cave filling replacement construction methods, in the process of filling karst cave, with the slurry of upper karst cave as raw material to prepare flow state solidified soil, flow state solidified soil is perfused to the bottom of karst cave by pipeline, and the construction procedure of circulating extraction slurry of upper karst cave, preparation flow state solidified soil and perfusion flow state solidified soil, until the specific gravity of extracted slurry of upper karst cave and the specific gravity of prepared flow state solidified soil are equal or similar, stop perfusion flow state solidified soil.The application provides a kind of flow state solidified soil karst cave filling replacement construction method, utilizes the material in karst cave and flow state solidified soil prepared by local material of construction site, by perfusion flow state solidified soil to the bottom of karst cave, utilizes the fluidity and strength of flow state solidified soil, lifts original underground water and bottom slurry in karst cave, and two are extracted to become the raw material of flow state solidified soil, by constantly extracting and perfusion, so that the filling body of backfilling karst cave is uniform and does not produce gap, guarantees karst cave backfill quality.

Description

Technical Field

[0001] This invention relates to the field of building construction technology, and more specifically, to a method for filling and replacing karst caves with fluidized solidified soil. Background Technology

[0002] The construction of underground projects, such as subways and underground buildings, increases the likelihood and frequency of encountering irregular underground sealed spaces and irregular shapes, such as soil caves and karst caves. In order to ensure the safety and structural strength of underground projects, it is necessary to use low-grade concrete or cement mortar for backfilling.

[0003] Existing backfilling methods for karst caves primarily involve layered compaction of materials such as gravel and lime-stabilized soil. This requires well-graded sandy soil or gravel to achieve high dry density and good mechanical properties. Alternatively, low-grade concrete or mortar can be used for backfilling. During the backfilling process, the contents of the karst cave must be classified and filled in layers: fully filled karst caves require cement grouting for reinforcement; partially filled karst caves require different filling methods depending on their height, such as cement grouting, cement mortar, or C15 plain concrete plus cement grouting; and unfilled karst caves require different filling methods depending on their height, such as cement grouting, cement mortar, or C15 plain concrete plus cement grouting.

[0004] The aforementioned methods for backfilling karst caves have several drawbacks. First, they require a large amount of building materials, leading to excessively high material costs. Second, the layered grouting method demands precise control over pressure and flow rate. When encountering irregularly shaped, narrow, or deep karst caves, it becomes difficult to fully fill them, resulting in uneven filling and even voids, thus affecting the quality of the backfill. Furthermore, in actual construction, the karst caves to be filled typically contain groundwater and sediment at the bottom. Using direct grouting, the injected material directly impacts the groundwater and sediment, causing the backfill material to disperse, dilute, and fail to form a cohesive shape, ultimately resulting in an uneven filling and negatively impacting the quality of the grouting backfill. Summary of the Invention

[0005] To address the problems of uneven filling and poor backfill quality caused by direct injection of filler material into karst caves in existing technologies, this invention provides a fluidized solidified soil method for karst cave filling and replacement. This method utilizes existing materials within the karst cave and locally sourced materials, adding a certain proportion of solidifying agent to form fluidized solidified soil. By injecting this fluidized solidified soil into the bottom of the karst cave, its fluidity and strength raise the existing groundwater and sediment within the cave, which are then extracted as raw materials for the fluidized solidified soil. Through continuous extraction and injection, the contents of the karst cave are completely replaced, and low-cost fluidized solidified soil with the same or similar specific gravity is then used for backfilling. This results in a uniform filler material without voids, ensuring the quality of the karst cave backfill.

[0006] The technical solution of this invention is as follows:

[0007] A method for filling and replacing karst caves with fluidized solidified soil involves preparing fluidized solidified soil using slurry from the upper part of the karst cave as one of the raw materials during the filling process. The fluidized solidified soil is then injected into the bottom of the karst cave through pipelines. The construction process of cyclically extracting slurry from the upper part of the karst cave, preparing fluidized solidified soil, and injecting fluidized solidified soil continues until the specific gravity of the extracted slurry from the upper part of the karst cave is equal to or close to that of the prepared fluidized solidified soil. At this point, the extraction of slurry from the upper part of the karst cave is stopped, and the injection of fluidized solidified soil continues until the karst cave reaches the designed height requirement.

[0008] Fluidized solidified soil is a new type of geotechnical engineering material. Its raw materials are locally sourced soil or other industrial and mining waste. Depending on the project requirements, special cementitious materials (i.e., curing agents) adapted to the properties of the soil and rock, along with necessary water and admixtures, are mixed evenly using a specific mixer to form a mixture that can be transported through pipelines or pumps and can be poured into the ground. After pouring or filling and curing, it solidifies into an engineering material with certain strength, water stability, low permeability, and long-term stability. Fluidized solidified soil has good fluidity, similar to that of concrete and other building materials, making it feasible for pouring and grouting karst caves.

[0009] Similar to concrete, the proportion of additives and the specific gravity of fluidized bed slurry can be adjusted according to project requirements, allowing it to settle at the bottom of the karst cave and raise the original groundwater and sediment. Because the fluidized bed slurry is poured directly into the bottom of the karst cave, it impacts the original contents of the cave. As a result, the raised slurry in the upper part of the cave contains groundwater, sediment, and fluidized bed slurry. In this state, the raised slurry in the upper part of the cave is extracted using the established slurry extraction holes, remixed with other soil materials and construction waste to form fluidized bed slurry, and then poured back into the bottom of the karst cave.

[0010] Through a construction process of continuous slurry pumping, preparation of fluidized solidified soil, and backfilling of the karst cave, layered backfilling is achieved while simultaneously displacing groundwater and sediment slurry from the inside of the karst cave. This eliminates the unevenness between slurries caused by the impact force of direct injection, ensuring that the filling of the karst cave is uniform and free of voids.

[0011] The above-mentioned method for filling and replacing karst caves with fluidized solidified soil uses strength, flow spread and specific gravity as the standard indicators for the preparation of fluidized solidified soil.

[0012] The raw materials for fluidized bed solidified soil are typically soil sampled on-site. A certain amount of standard building materials or slurry is added to the soil sample, followed by water and a solidifying agent, and then the mixture is stirred until homogeneous to form fluidized bed solidified soil. As a new type of environmentally friendly building material, fluidized bed solidified soil is greatly affected by the geological conditions of the construction site and the specific requirements of the construction project. This makes it difficult to establish a fixed mix proportion standard. Therefore, fluidized bed solidified soil is usually prepared on-site after testing. The finished product standard for fluidized bed solidified soil is based on the requirements of the construction project and is prepared through testing. Among many building material standards, for the application projects and construction processes of this invention, only three values ​​need to be considered: strength, flowability, and specific gravity of the fluidized bed solidified soil. The consideration of strength is based on the engineering requirements of backfilling karst caves, which need to provide support; therefore, the strength of the solidified fluidized bed solidified soil must be guaranteed. The consideration of flow spread is based on the backfilling process of the grouting process. Since the grouting of karst caves and common grouting methods are all pipeline grouting, the fluidized solidified soil has high requirements for fluidity and non-stick properties, thus there is a rigid requirement for flow spread. In addition, while considering flow spread, since this invention eliminates the unevenness caused by the impact of the fluidized solidified soil by extracting the contents of the karst cave, there is no need to consider the problem of the grouting fluidized solidified soil spreading disorderly and mixing with groundwater and bottom mud due to insufficient aggregation caused by excessive fluidity. The scope of flow spread consideration does not include the situation of scattering due to impact with the contents of the karst cave; it only needs to meet the requirements of grouting, settling to the bottom, and raising groundwater and bottom mud. The consideration of specific gravity is for the requirement of the fluidized solidified soil settling to the bottom and raising groundwater and bottom mud. If the specific gravity is too low, the technical effect of settling to the bottom and raising the contents of the karst cave cannot be achieved. If the specific gravity is too high, too much mud, solidifying agent and other materials will need to be added, increasing the raw material cost. Therefore, a comprehensive consideration is required. Beyond these three, the material preparation standard indicators are mostly determined by the construction site or can be directly reflected by the above three standard indicators. Other reference standard indicators such as water content, density, and impermeability do not need to be considered separately.

[0013] The above-mentioned method for filling and replacing karst caves with fluidized solidified soil includes the following construction process:

[0014] Step S1. Prepare and connect the construction equipment;

[0015] Step S2. Feed materials and prepare fluidized solidified soil according to the set standards;

[0016] Step S3. The fluidized solidified soil is transported to the injection hole and injected into the bottom of the karst cave;

[0017] Step S4. After injecting a certain amount of fluidized solidified soil, stop, extract the slurry from the upper part of the karst cave through the slurry extraction hole, and use the slurry from the upper part of the karst cave as one of the raw materials to prepare fluidized solidified soil;

[0018] Step S5. Inject fluidized solidified soil into the bottom of the karst cave through the injection hole;

[0019] Step S6. Repeat steps S4 to S5 until the specific gravity of the extracted grout from the upper part of the karst cave is the same as or similar to that of the fluidized solidified soil. Stop extracting the grout from the upper part of the karst cave and continue to inject the fluidized solidified soil to the designed height requirement of the karst cave.

[0020] Furthermore, before injecting the fluidized solidified soil, measuring tools are used to measure the depth of the karst cave and the height of its contents;

[0021] During the repeated extraction of grout from the upper part of the karst cave and the injection of fluidized solidified soil, measuring tools are set up at regular intervals to monitor the height of the contents of the karst cave and determine the height of the injected fluidized solidified soil.

[0022] Before grouting, use measuring tools to measure the depth of the karst cave to confirm the depth of the grouting pipe, so that the grouting pipe can reach the bottom of the karst cave and ensure that the fluidized solidified soil can fill the karst cave and raise the height of the original contents of the karst cave.

[0023] Before grouting, use measuring tools to measure the height of the original contents of the cave. This serves two purposes: first, it helps to determine the depth of the vent holes; second, it helps to determine the location of the grout extraction pipe for extracting slurry from the upper part of the cave; and third, it provides a certain understanding of the contents of the cave.

[0024] During grouting, measuring tools are used to measure the height of the contents of the karst cave. This serves two purposes: first, to monitor the grouting progress of the fluidized solidified soil and to get a brief understanding of the amount of material required for grouting; and second, to re-determine the location of the grout extraction pipe so as to accurately extract the grout from the upper part of the karst cave, rather than the fluidized solidified soil from the deeper parts of the karst cave.

[0025] The above-mentioned method for filling and replacing karst caves with fluidized solidified soil includes a fluidized solidified soil preparation device and a grouting device. The fluidized solidified soil preparation device and the grouting device are connected, so that the fluidized solidified soil prepared by the fluidized solidified soil preparation device flows from the fluidized solidified soil preparation device through the grouting device to backfill the karst cave.

[0026] The equipment for preparing fluidized solidified soil includes

[0027] Raw material pool: A deep pool used to store the raw materials for fluidized solidified soil and the mixed raw materials for preparing fluidized solidified soil.

[0028] A mixer is a device with a mixing structure used to mix all the prepared fluidized solidified soil evenly.

[0029] Injection equipment includes

[0030] A slurry extraction pipe is a pipe used to extract the upper layer of material from a karst cave into a raw material pool.

[0031] Grouting pipe: A pipe used to inject fluidized solidified soil into the bottom of a karst cave;

[0032] Under the control of the PLC control cabinet, the raw materials for fluidized solidified soil are transported from the raw material pool to the mixer and mixed evenly to form the preset fluidized solidified soil. The fluidized solidified soil is then transported through the grouting pipe and injected into the bottom of the karst cave, raising the contents of the karst cave. The contents of the karst cave are then transported through the grouting pipe to the raw material pool to become the raw material for fluidized solidified soil.

[0033] Furthermore, the raw material pool includes a slurry pool and a solid material pool. The slurry pool contains slurry extracted from the upper part of the karst cave and slurry materials taken from the construction site. The solid material pool contains solidified materials taken from the construction site and dehydrated. As needed, the solidified materials in the solid material pool are transported to the slurry pool to form a fluidized solidified soil mixture.

[0034] In this invention, the raw materials for the fluidized solidified soil include soil materials formed from other construction projects at the construction site and slurry extracted from the upper part of the karst cave. The specific gravity of the slurry from the upper part of the karst cave is necessarily lower than that of the fluidized solidified soil, so soil materials with a higher specific gravity need to be added. Based on this, on the one hand, it is necessary to set up an additional raw material pool to place the added soil materials, so that after these soil materials are transported to the slurry pool, they can be mixed with the slurry from the upper part of the karst cave to form a slurry that meets the requirements for the preparation of fluidized solidified soil. On the other hand, in order to reduce costs, protect the environment, and ensure the stability of the karst cave, the added soil materials are also taken from the construction site. In order to meet the specific gravity standard, this part of the soil materials needs to be dehydrated.

[0035] Furthermore, a specific gravity metering device is installed in the raw material pool. The specific gravity metering device sends the specific gravity data of the contents of the raw material pool to the PLC control cabinet. The PLC control cabinet outputs control data to the transmission equipment according to the preset mix proportion data of the fluidized solidified soil, so as to control the specific gravity of the slurry output from the raw material pool to the mixer.

[0036] The raw material pool includes a slurry pool and a solid material pool. The specific gravity of the slurry extracted from the upper part of the karst cave into the slurry pool varies at different times. On the other hand, the specific gravity of the preset fluidized solidified soil is constant. Therefore, there is a difference between the two, which leads to different amounts of solidifying material and water added to the slurry pool later. To automate the preparation of fluidized solidified soil, this invention includes a PLC control cabinet (with a built-in PLC control system). The PLC control cabinet receives the specific gravity data obtained from the specific gravity metering device and calculates the amount of solidifying material and water to be added based on multiple built-in preset schemes, thereby controlling the specific gravity of the slurry in the slurry pool transported to the mixer to be the preset specific gravity of the fluidized solidified soil raw material.

[0037] Furthermore, weight measuring devices are installed along the paths from the raw material pool to the mixer and from the curing agent fixing point to the mixer. The weight measuring devices send the weight data of the fluidized solidified soil mixture and curing agent fed to the mixer to the PLC control cabinet. The PLC control cabinet controls the operation of the feeding equipment from the raw material pool to the mixer and from the curing agent fixing point to the mixer according to the preset mixing ratio data of the fluidized solidified soil, so that the fluidized solidified soil prepared by the mixer each time meets the preset mixing ratio requirements.

[0038] The amount of material mixed in a single batch by the mixer is fixed. Therefore, the weight of the fluidized solidified soil mixture and curing agent fed into the mixer is constant. In order to ensure that the amount input to the mixer by the PLC control cabinet is constant, a weight metering device is used to obtain the weight of the material entering the mixer in real time. When the weight of the monitored material reaches the predetermined weight, a control signal is sent to control the working status of the feeding equipment and stop feeding.

[0039] Furthermore, a mud pump is installed between the raw material pool and the karst cave. The mud pump extracts the slurry from the upper part of the karst cave through the slurry extraction pipe and transports it to the raw material pool through the transport pipeline.

[0040] The above-mentioned method for filling and replacing karst caves with fluidized solidified soil involves drilling injection holes, venting holes, and grouting holes at appropriate locations within the karst cave using drilling equipment. A grouting pipe is installed in the injection hole to penetrate deep into the bottom of the karst cave and inject fluidized solidified soil into the bottom of the karst cave. An venting pipe is installed in the venting hole with its bottom position higher than the contents of the karst cave. A grouting pipe is installed in the grouting hole with its bottom position varying according to the height of the contents of the karst cave to extract grout from the upper part of the karst cave.

[0041] In this invention, the interior of the cave contains substances, commonly groundwater and sedimentary mud, both of which can be extracted using a large mud pump. The large mud pump is positioned between the cave and the slurry pool in the raw material tank. The extraction pipe extends into the cave. At regular intervals, the top position of the cave contents is determined using measuring tools such as a measuring rope. The extraction pipe is then inserted into the upper part of the slurry within the cave, and the large mud pump extracts the contents into the slurry pool.

[0042] The grouting pipe is a channel for introducing fluidized solidified soil into the bottom of the karst cave. Since this invention requires the replacement of the contents of the karst cave, the injection of the grouting pipe is necessary to raise the original contents of the karst cave, such as groundwater and sediment slurry. On the other hand, the fluidized solidified soil is the filling material for backfilling the karst cave. The grouting pipe needs to go as deep as possible into the bottom of the karst cave to better fill the cave. Therefore, the grouting pipe needs to go deep into the bottom of the karst cave.

[0043] The vent pipe is a channel for venting excess gas from the cave. It also plays an auxiliary role in controlling the stability of grouting and pumping. Gas accumulates in the upper part of the cave, and its bottom position changes as the contents of the cave rise. Therefore, the bottom positions of both the vent pipe and the pumping pipe need to change with the grouting process.

[0044] According to the above-described solution, the beneficial effects of this invention are as follows:

[0045] 1. The method of using fluidized solidified soil to backfill karst caves involves raising the level of groundwater and sediment slurry at the bottom of the cave cavity during the grouting process. This sediment is then extracted and prepared as backfill material. The grouting is stopped when the specific gravity of the extracted slurry is equal to or close to that of the prepared fluidized solidified soil. The fluidized solidified soil is then continued to be injected to backfill the karst cave, thus ensuring the uniformity and quality of the backfill material. This method also avoids the complex and difficult karst cave topographic exploration process (the internal conditions of karst caves may be complex, including irregular shapes, caves of varying sizes, rock fissures, etc. To roughly understand the internal environment, large-scale exploration and monitoring are required, but due to the high cost of monitoring, it is difficult to apply on a large scale). This method saves on the costs of detailed, complex, and expensive underground exploration.

[0046] 2. Since the original contents of the karst cave are all replaced during the backfilling process, some of the fluidized solidified soil injected in the initial stage may also be extracted and replaced. In this way, almost all factors affecting the uniformity of the karst cave filling are extracted and eliminated. Therefore, the difficulty of controlling the injection of fluidized solidified soil into the karst cave is reduced. In addition, the specific gravity of the fluidized solidified soil is greater than that of the original contents of the karst cave, and its own fluidity is good. It can achieve self-compactment and self-hardening under the action of gravity and its own physicochemical reaction. There is no need to consider the unevenness caused by the impact of fluidized solidified soil with other substances. Only the stability of fluidized solidified soil during grouting needs to be considered, which reduces the difficulty of pressure and flow control in the grouting process.

[0047] 3. Layered pressure grouting allows the karst cave filling material formed by the fluidized solidified soil to be compacted, penetrated and consolidated. The fluidized solidified soil itself has excellent fluidity and self-compacting properties, which can ensure the complete filling of the karst cave, improve construction efficiency and foundation stability.

[0048] 4. It is environmentally friendly. The material of the fluidized solidified soil used to fill the karst cave comes from the construction site and the original contents of the karst cave. It is formed by adding only solidifying agent and water. The preparation and solidification processes do not produce harmful substances, have little impact on the underground environment, and meet environmental protection standards. Attached Figure Description

[0049] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0050] Figure 1 This is a schematic diagram of the structure of the present invention.

[0051] The following are the labeling elements in the figure:

[0052] 1. Cavern; 2. Grouting pipe; 3. Pumping pipe; 4. Venting pipe; 5. Grout in the upper part of the cavern; 6. Fluidized solidified soil. Detailed Implementation

[0053] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and 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.

[0054] A method for filling and replacing karst caves with fluidized solidified soil, as shown in Figure 1, involves preparing fluidized solidified soil 6 using grout 5 from the upper part of the karst cave as one of the raw materials during the filling process. The fluidized solidified soil 6 is then injected into the bottom of the karst cave 1 through a pipeline. The construction process of cyclically extracting grout 6 from the upper part of the karst cave, preparing fluidized solidified soil, and injecting fluidized solidified soil continues until the specific gravity of the extracted grout from the upper part of the karst cave is equal to or close to the specific gravity of the prepared fluidized solidified soil. At this point, the extraction of grout from the upper part of the karst cave is stopped, and the injection of fluidized solidified soil continues until the karst cave reaches the designed height requirement.

[0055] Similar to concrete, the proportion of additives in fluidized bed grout can be modified to adjust its specific gravity according to engineering requirements, allowing it to sink to the bottom of the karst cave and raise the original groundwater and sediment. Because it is poured directly into the bottom of the karst cave, the fluidized bed grout impacts the original contents of the cave. During this process, the raised grout in the upper part of the cave contains groundwater, sediment, and fluidized bed grout (i.e., the original grout in the cave and the subsequently poured fluidized bed grout). In this state, the raised grout in the upper part of the cave is extracted using the established grout extraction holes, remixed with other soil materials, construction waste, water, and curing agents to form fluidized bed grout, which is then poured back into the bottom of the cave. Through a construction process of continuous slurry pumping, preparation of fluidized solidified soil, and backfilling of the karst cave, layered backfilling is achieved while simultaneously displacing groundwater and sediment slurry from the inside of the karst cave. This eliminates the unevenness between slurries caused by the impact force of direct injection, ensuring that the filling of the karst cave is uniform and free of voids.

[0056] The standard indicators for the preparation of fluidized solidified soil are strength, flow spread and specific gravity.

[0057] The standards for finished fluidized solidified soil products are all based on the requirements of construction projects and are tested and configured accordingly. Among many building material standards, for the application projects and construction processes of this invention, only three values ​​need to be considered: the strength, flowability, and specific gravity of the fluidized solidified soil. Additionally, for efficiency reasons, the initial setting time and final setting time of the prepared fluidized solidified soil can be used as secondary standard indicators to meet the requirements of on-site construction processes and project schedules.

[0058] The consideration of strength is based on the engineering requirements of backfilling karst caves. Backfilling karst caves needs to play a supporting role, so the strength of the solidified fluidized soil must be guaranteed.

[0059] The consideration of flow spread is based on the backfilling process of the grouting process. Since the grouting of karst caves and common grouting methods are all pipeline grouting, the fluidized solidified soil has high requirements for fluidity and non-stick properties, thus there are strict requirements for flow spread. In addition, while considering flow spread, since this invention eliminates the unevenness caused by the impact of fluidized solidified soil by extracting the contents of the karst cave, there is no need to consider the problem of the grouting fluidized solidified soil spreading disorderly in the karst cave and mixing with groundwater and bottom mud due to insufficient aggregation caused by excessive fluidity. The scope of consideration for flow spread does not include the situation of scattering due to impact with the contents of the karst cave, and only needs to meet the requirements of grouting, bottom settling, and raising groundwater and bottom mud.

[0060] The specific gravity is considered to facilitate the settling of fluidized solidified soil and the raising of groundwater and settling slurry. If the specific gravity is too low, the desired effect of settling and raising the contents of the karst cave cannot be achieved. Conversely, if the specific gravity is too high, excessive amounts of slurry, solidifying agents, and other materials will be required, increasing raw material costs. Therefore, a comprehensive consideration is necessary. As for material preparation standards beyond these three factors, since the raw materials for fluidized solidified soil largely depend on the construction site or can be directly reflected by the aforementioned three standard indicators, other material standard indicators such as moisture content, density, and impermeability do not require additional consideration.

[0061] The construction process of the fluidized solidified soil karst cave filling and replacement method includes:

[0062] Step S1. Prepare and connect the construction equipment.

[0063] Step S2. Feed the material and prepare the fluidized solidified soil according to the set standards.

[0064] Step S3. The fluidized solidified soil is transported to the injection hole and injected into the bottom of the karst cave.

[0065] Step S4. After injecting a certain amount of fluidized solidified soil, stop, extract the slurry from the upper part of the karst cave through the slurry extraction hole, and use the slurry from the upper part of the karst cave as one of the raw materials to prepare fluidized solidified soil.

[0066] Step S5. Inject fluidized solidified soil into the bottom of the karst cave through the injection hole.

[0067] Step S6. Repeat steps S4 to S5 until the specific gravity of the extracted grout from the upper part of the karst cave is the same as or similar to that of the fluidized solidified soil. Stop extracting the grout from the upper part of the karst cave and continue to inject the fluidized solidified soil to the designed height requirement of the karst cave.

[0068] Before injecting the fluidized solidified soil, use measuring tools to measure the depth of the karst cave and the height of its contents.

[0069] During the repeated extraction of grout from the upper part of the karst cave and the injection of fluidized solidified soil, measuring tools are set up at regular intervals to monitor the height of the contents of the karst cave and determine the height of the injected fluidized solidified soil.

[0070] Before grouting, use measuring tools to measure the depth of the karst cave to confirm the depth of the grouting pipe, so that the grouting pipe can reach the bottom of the karst cave and ensure that the fluidized solidified soil can fill the karst cave and raise the height of the original contents of the karst cave.

[0071] Before grouting, use measuring tools to measure the height of the original contents of the cave. This serves two purposes: first, it helps to determine the depth of the vent holes; second, it helps to determine the location of the grout extraction pipe for extracting slurry from the upper part of the cave; and third, it provides a certain understanding of the contents of the cave.

[0072] During grouting, measuring tools are used to measure the height of the contents of the karst cave. This serves two purposes: first, to monitor the grouting progress of the fluidized solidified soil and to get a brief understanding of the amount of material required for grouting; and second, to re-determine the location of the grout extraction pipe so as to accurately extract the grout from the upper part of the karst cave, rather than the fluidized solidified soil from the deeper parts of the karst cave.

[0073] In this embodiment, the measuring tool is a measuring rope.

[0074] The construction equipment includes a fluidized solidified soil preparation device and a grouting device. The fluidized solidified soil preparation device and the grouting device are connected, so that the fluidized solidified soil produced by the fluidized solidified soil preparation device flows from the fluidized solidified soil preparation device through the grouting device to backfill the karst cave.

[0075] The equipment for preparing fluidized solidified soil includes

[0076] Raw material pool: A deep pool used to store the raw materials for fluidized solidified soil and the mixed raw materials for preparing fluidized solidified soil.

[0077] A mixer is a device with a mixing structure used to mix all the prepared fluidized solidified soil evenly.

[0078] The raw material pool includes a slurry pool and a solid material pool. The slurry pool contains slurry extracted from the upper part of the karst cave and slurry materials taken from the construction site. The solid material pool contains solidified materials taken from the construction site and dehydrated. As needed, the solidified materials in the solid material pool are transported to the slurry pool to form a fluidized solidified soil mixture.

[0079] In this embodiment, mud cakes are placed in the solidification pool. The mud cakes are waste and useless soil materials generated from other projects at the construction site, such as mud slurry generated from shield tunneling, soil materials generated from on-site excavation and drilling, etc. The mud cakes are formed through flocculation, pressure filtration and dewatering processes and stored in the solidification pool.

[0080] In another embodiment, yellow mud slurry, or other types of mud slurry with a high specific gravity, is placed in the solidification pool. Yellow mud slurry is generated during the excavation process at the construction site. This yellow mud slurry has a high specific gravity, which can meet the specific gravity requirements for preparing fluidized solidified soil, so it can be used directly.

[0081] Preferably, a crusher and a linear vibrating screen are installed before the solidification tank. Soil generated at the construction site is crushed, then transported to the linear vibrating screen via conveyor belt. After being screened by the linear vibrating screen, it is transported to the solidification tank. The soil at the construction site may contain small stones or soil clumps, which do not meet the requirements for preparing mud cakes or yellow mud slurry. Furthermore, to meet the requirements for preparing fluidized solidified soil and ensure that the raw materials do not contain large lumps that would affect the quality of the fluidized solidified soil, the small stones or soil clumps are crushed and then screened to ensure that the soil in the solidification tank meets the 2 mm particle size requirement for preparing mud slurry.

[0082] The slurry stored in the slurry tank is a mixture of slurry from the upper part of the karst cave and soil from the solidification tank. It needs to be pumped to the mixer by a mud pump to prepare fluidized solidified soil. In order to ensure that it becomes a uniform and suitable raw material for fluidized solidified soil, the slurry tank needs to be equipped with a stirring device to stabilize the slurry in the slurry tank.

[0083] A specific gravity metering device is installed in the raw material tank. The specific gravity metering device sends the specific gravity data of the contents of the raw material tank to the PLC control cabinet. The PLC control cabinet outputs control data to the transmission equipment according to the preset mix proportion data of the fluidized solidified soil, so as to control the specific gravity of the slurry output from the raw material tank to the mixer.

[0084] The raw material pool includes a slurry pool and a solid material pool. The specific gravity of the slurry extracted from the upper part of the karst cave into the slurry pool varies at different times. On the other hand, the specific gravity of the preset fluidized solidified soil is constant. Therefore, there is a difference between the two, which leads to different amounts of solidifying material and water added to the slurry pool later. To automate the preparation of fluidized solidified soil, this invention includes a PLC control cabinet (with a built-in PLC control system). The PLC control cabinet receives the specific gravity data obtained from the specific gravity metering device and calculates the amount of solidifying material and water to be added based on multiple built-in preset schemes. This ensures that the specific gravity of the slurry transported to the slurry pool of the mixer is the preset specific gravity of the fluidized solidified soil mixed raw materials.

[0085] Injection equipment includes

[0086] A slurry extraction pipe is a pipe used to extract the upper layer of material from a karst cave into a raw material pool.

[0087] Grouting pipe is a pipe used to inject fluidized solidified soil into the bottom of the karst cave.

[0088] Under the control of the PLC control cabinet, the raw materials for fluidized solidified soil are transported from the raw material pool to the mixer and mixed evenly to form the preset fluidized solidified soil. The fluidized solidified soil is then transported through the grouting pipe and injected into the bottom of the karst cave, raising the contents of the karst cave. The contents of the karst cave are then transported through the grouting pipe to the raw material pool to become the raw material for fluidized solidified soil.

[0089] Weight measuring devices are installed along the paths from the raw material tank to the mixer and from the fixed point of the curing agent to the mixer. The weight measuring devices send the weight data of the fluidized solidified soil mixture and the curing agent to the PLC control cabinet. The PLC control cabinet controls the operation of the feeding equipment from the raw material tank to the mixer and from the fixed point of the curing agent to the mixer according to the preset mix proportion data of the fluidized solidified soil, so that the fluidized solidified soil prepared by the mixer each time meets the preset mix proportion requirements.

[0090] In this embodiment, the feeding equipment from the raw material tank to the mixer is a combination of a mud pump and a transport pipeline. A weighing device (which can be a weighable flow meter) is installed at the end of the transport pipeline (i.e., the connection port between the transport pipeline and the mixer). The weighing device sends the weight data of the fluidized solidified soil mixture flowing into the mixer to the PLC control cabinet, allowing the PLC control cabinet to monitor the weight of the fluidized solidified soil mixture flowing from the raw material tank into the mixer, ensuring that the amount of fluidized solidified soil mixture mixed by the mixer is quantitative each time. The feeding equipment between the curing agent fixing point and the mixer is a screw conveyor. A weighing device is installed at the end of the screw conveyor. The weighing device sends the weight data of the curing agent flowing into the mixer to the PLC control cabinet, allowing the PLC control cabinet to monitor the weight of the curing agent flowing into the mixer. In summary, by monitoring the weight of the fluidized solidified soil mixture and curing agent flowing into the mixer through the weighing device, and under the control of the PLC control cabinet, the fluidized solidified soil mixed by the mixer each time is formed in the same proportion and with the same weight.

[0091] A mud pump is installed between the raw material pool and the karst cave. The mud pump extracts the slurry from the upper part of the karst cave through the slurry extraction pipe and transports it to the raw material pool through the transport pipeline.

[0092] Before injecting the fluidized solidified soil, the drilling equipment drills injection holes, venting holes and grouting holes at appropriate locations in the karst cave. A grouting pipe 2 is installed in the injection hole, extending deep into the bottom of the karst cave and injecting the fluidized solidified soil into the bottom of the karst cave. An venting pipe 4 is installed in the venting hole, with its bottom position varying with the height of the karst cave contents, and a grouting pipe 3 is installed in the grouting hole, with its bottom position varying with the height of the karst cave contents, to extract grout from the upper part of the karst cave.

[0093] In this invention, the interior of the karst cave contains substances, commonly groundwater and sedimentary mud, both of which can be extracted using a large mud pump. The large mud pump is positioned between the karst cave and the slurry pool in the raw material tank. The extraction pipe is a conduit extending into the karst cave. At regular intervals, the top position of the karst cave contents is determined using measuring tools such as a measuring rope. The extraction pipe is then inserted into the upper part of the slurry within the cave, and the large mud pump extracts the contents into the slurry pool. The number, structure, and type of the extraction pipes are not limited and are determined based on the size of the karst cave and the construction schedule; multiple sets of extraction pipes are possible.

[0094] Grouting pipes are channels used to guide fluidized solidified soil to the bottom of a karst cave. Since this invention requires the removal of the cave's contents, the grouting pipes must first elevate the original contents within the cave, such as groundwater and sediment. Secondly, the fluidized solidified soil serves as the backfill material for the karst cave; therefore, the grouting pipes need to penetrate as deeply as possible to the bottom of the cave for better filling. The number, structure, and type of grouting pipes are not limited and are determined based on the size of the cave and the construction schedule; multiple sets of grouting pipes are possible.

[0095] The vent pipe is a channel for expelling excess gas from the cavern. It also plays a supporting role in controlling the stability of grouting and pumping. Gas accumulates in the upper part of the cavern, and its bottom position changes as the cavern contents rise. Therefore, the bottom positions of both the vent pipe and the pumping pipe need to change with the grouting process. There are no restrictions on the number, structure, or type of vent pipes; the choice depends on the size of the cavern and the construction schedule. Multiple sets of vent pipes are possible. In addition, monitoring equipment, such as measuring ropes to measure the liquid level within the cavern, can be installed inside and near the vent pipes.

[0096] In this embodiment, the pumping pipe, the injection pipe, and the venting pipe are all steel pipes. A steel funnel can be installed at the top of the injection pipe to gather the fluidized solidified soil flowing into the injection pipe.

[0097] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for filling and replacing karst caves with fluidized solidified soil, characterized in that, During the filling of the karst cave, the slurry from the upper part of the karst cave is used as one of the raw materials to prepare fluidized solidified soil. The fluidized solidified soil is then injected into the bottom of the karst cave through pipelines. The construction process of cyclically extracting the slurry from the upper part of the karst cave, preparing fluidized solidified soil, and injecting fluidized solidified soil continues until the specific gravity of the extracted slurry from the upper part of the karst cave is equal to or close to the specific gravity of the prepared fluidized solidified soil. At this point, the extraction of the slurry from the upper part of the karst cave is stopped, and the injection of fluidized solidified soil continues until the karst cave reaches the designed height requirement. The construction process includes Step S1. Prepare and connect the construction equipment; Step S2. Feed materials and prepare fluidized solidified soil according to the set standards; Step S3. The fluidized solidified soil is transported to the injection hole and injected into the bottom of the karst cave; Step S4. After injecting a certain amount of fluidized solidified soil, stop, extract the slurry from the upper part of the karst cave through the slurry extraction hole to prepare fluidized solidified soil, and use the slurry from the upper part of the karst cave as one of the raw materials to prepare fluidized solidified soil; Step S5. Inject fluidized solidified soil into the bottom of the karst cave through the injection hole; Step S6. Repeat steps S4 to S5 until the specific gravity of the extracted grout from the upper part of the karst cave is the same as or similar to that of the fluidized solidified soil. Stop extracting the grout from the upper part of the karst cave and continue to inject the fluidized solidified soil to the required design height of the karst cave. Before injecting the fluidized solidified soil, use measuring tools to measure the depth of the karst cave and the height of its contents; During the repeated extraction of grout from the upper part of the karst cave and the injection of fluidized solidified soil, measuring tools are set up at regular intervals to monitor the height of the contents of the karst cave and determine the height of the injected fluidized solidified soil.

2. The method for filling and replacing karst caves with fluidized solidified soil according to claim 1, characterized in that, The standard indicators for the preparation of fluidized solidified soil are strength, flow spread and specific gravity.

3. The method for filling and replacing karst caves with fluidized solidified soil according to claim 1, characterized in that, The construction equipment includes a fluidized solidified soil preparation device and a grouting device. The fluidized solidified soil preparation device and the grouting device are connected, so that the fluidized solidified soil produced by the fluidized solidified soil preparation device flows from the fluidized solidified soil preparation device through the grouting device to backfill the karst cave. The equipment for preparing fluidized solidified soil includes Raw material pool: A deep pool used to store the raw materials for fluidized solidified soil and the mixed raw materials for preparing fluidized solidified soil. A mixer is a device with a mixing structure used to mix all the prepared fluidized solidified soil evenly. Injection equipment includes A slurry extraction pipe is a pipe used to extract the upper layer of material from a karst cave into a raw material pool. Grouting pipe: A pipe used to inject fluidized solidified soil into the bottom of a karst cave; Under the control of the PLC control cabinet, the raw materials for fluidized solidified soil are transported from the raw material pool to the mixer and mixed evenly to form the preset fluidized solidified soil. The fluidized solidified soil is then transported through the grouting pipe and injected into the bottom of the karst cave, raising the contents of the karst cave. The contents of the karst cave are then transported through the grouting pipe to the raw material pool to become the raw material for fluidized solidified soil.

4. The method for filling and replacing karst caves with fluidized solidified soil according to claim 3, characterized in that, The raw material pool includes a slurry pool and a solid material pool. The slurry pool contains slurry extracted from the upper part of the karst cave and slurry materials taken from the construction site. The solid material pool contains solidified materials taken from the construction site and dehydrated. As needed, the solidified materials in the solid material pool are transported to the slurry pool to form a fluidized solidified soil mixture.

5. The method for filling and replacing karst caves with fluidized solidified soil according to claim 3, characterized in that, A specific gravity metering device is installed in the raw material tank. The specific gravity metering device sends the specific gravity data of the contents of the raw material tank to the PLC control cabinet. The PLC control cabinet outputs control data to the transmission equipment according to the preset mix proportion data of the fluidized solidified soil, so as to control the specific gravity of the slurry output from the raw material tank to the mixer.

6. The method for filling and replacing karst caves with fluidized solidified soil according to claim 3, characterized in that, Weight measuring devices are installed along the paths from the raw material tank to the mixer and from the fixed point of the curing agent to the mixer. The weight measuring devices send the weight data of the fluidized solidified soil mixture and the curing agent to the PLC control cabinet. The PLC control cabinet controls the operation of the feeding equipment from the raw material tank to the mixer and from the fixed point of the curing agent to the mixer according to the preset mix proportion data of the fluidized solidified soil, so that the fluidized solidified soil prepared by the mixer each time meets the preset mix proportion requirements.

7. The method for filling and replacing karst caves with fluidized solidified soil according to claim 3, characterized in that, A mud pump is installed between the raw material pool and the karst cave. The mud pump extracts the slurry from the upper part of the karst cave through the slurry extraction pipe and transports it to the raw material pool through the transport pipeline.

8. The method for filling and replacing karst caves with fluidized solidified soil according to claim 1, characterized in that, Drill injection holes, venting holes, and grouting holes at appropriate locations in the karst cave using drilling equipment. Install grouting pipes in the injection holes that extend deep into the bottom of the karst cave and inject fluidized solidified soil into the bottom of the karst cave. Install venting pipes in the venting holes that are higher than the contents of the karst cave at the bottom. Install grouting pipes in the grouting holes that are positioned at the bottom according to the height of the contents of the karst cave and extract grout from the upper part of the karst cave.

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