Layered gradient solidification synergistic anti-seepage construction method for soft foundation in high-phreatic-water-level saline-alkali area

Abstract

The invention belongs to the technical field of civil engineering, and discloses a layered gradient solidification synergetic anti-seepage construction method for a soft foundation in a high-phreatic-water-level saline-alkali area. The construction method comprises the following specific steps: S1, investigation and confirmation before construction; S2, construction plan making and resource preparation; S3, on-site protection and dust fall measure preparation; S4, safety technology disclosure and training, S5, roadbed cleaning and leveling, S6, lower roadbed soil sampling and testing, S7, quicklime block transportation and paving, S8, quicklime block turning and stirring and pressure stabilizing, and S9, quality detection and acceptance. A bottom-layer water absorption-middle-layer transition-upper-layer closed layered gradient curing technical system is adopted, and roadbed performance jump is realized through a three-order synergistic effect; a technical team constructs a dynamic mix proportion model, the lime mixing amount of each layer is accurately regulated and controlled, and the lime uniformity is improved by cooperating with intelligent spreading equipment and is improved compared with a traditional process; in the construction process, a totally-closed operation chain is adopted, and fog gun dust falling and closed transportation environmental protection measures are integrated.

Description

Technical Field

[0001] The invention belongs to the technical field of civil engineering, and in particular relates to a collaborative anti-seepage construction method for layered gradient solidification of soft foundation in saline-alkali areas with high water level. Background Art

[0002] With the acceleration of urbanization in my country, municipal road construction in high-water-level, highly saline areas faces significant challenges. Under these geological conditions, foundations often suffer from high moisture content, low bearing capacity, and salinization. These conditions can easily lead to roadbed settlement, pavement cracking, and frost heave, severely threatening road service life and driving safety. Traditional soft subgrade treatment relies on large-scale excavation, prolonged soil drying, and external transportation and replacement. This not only leads to dust pollution, temporary land occupation, and extended construction periods, but also faces drawbacks such as high environmental costs and compounded safety risks. More critically, saline-alkali environments place special demands on the durability of building materials, making conventional technologies difficult to simultaneously achieve the dual goals of foundation reinforcement and corrosion and salt control. Traditional roadbed construction involves multiple steps, including excavation, removal, drying, and backfilling. The construction process is significantly constrained by weather and temperature: rainy seasons or low temperatures directly interrupt drying operations, causing construction delays. Site constraints make soil turnover difficult, further exacerbating the uncertainty of the construction period. At the same time, poor process integration can easily lead to idleness, such as repeated machinery entry and exit, idle labor, and secondary material handling, resulting in low resource utilization. This extensive operation model not only drives up equipment rental, labor, and site occupancy costs, but also runs counter to the requirements of refined engineering management. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for the coordinated anti-seepage construction of soft foundation layered gradient solidification in saline-alkali areas with high water level, so as to solve the problems raised in the above-mentioned background technology.

[0004] In order to achieve the above-mentioned object, the present invention provides the following technical solution: a construction method for layered gradient solidification and coordinated anti-seepage in a saline-alkali area with a high water level, wherein the specific steps of the construction method are as follows: S1: Pre-construction inspection and confirmation: Organize multiple departments to inspect suppliers, verify raw material quality, environmental protection and supply capacity, and inspect equipment to ensure construction; S2: Prepare construction plan and resources: Prepare the construction schedule and identify the milestones according to the actual situation, make preparations for leasing and purchasing according to the plan to ensure that the facilities and materials are in place in time, and prepare enough lime to ensure that the quality meets the standards; S3: Preparation of on-site protection and dust suppression measures: Set up fences to isolate the construction area, use mist cannons to suppress dust, and install vehicle washing devices at entrances and exits to prevent mud pollution; S4: Safety technical briefing and training: Organize safety briefings for all employees, clarify technical points and operating specifications, establish rules and regulations, and implement the responsibilities of all parties and acceptance standards; S5: Roadbed cleaning and leveling: Clean the excess soil on the top of the roadbed and level it, remove grass roots, humus and impurities and transport them for disposal, and store the remaining soil nearby for future use; S6: Sampling and testing of lower roadbed soil: On-site sampling is conducted to test moisture content, compaction coefficient, and salinity. Based on the results, a test section is constructed to determine the optimal ash content. Post-construction quality testing is conducted to ensure compliance with design requirements. S7: Quicklime block transportation and paving: Use closed dump trucks to transport quicklime blocks, and manually use hydraulic backhoes to spread them evenly according to the designed thickness. During unloading and paving, deploy fog cannons to spray and reduce dust pollution; S8: Mixing and stabilizing the pressure of quicklime blocks: After paving in sections, mix with a backhoe three times, use a bulldozer to stabilize and level the lime blocks to promote dissolution, and let them stand for 12 hours before mixing again to ensure that the lime and soil are fully mixed. S9: Quality inspection and acceptance: Take samples in the laboratory to test moisture content, ash content, and compaction degree, and confirm the results with the quality inspection and supervision. If qualified, proceed to the next process, and if unqualified, make rectifications until the standards are met.

[0005] Preferably, the pre-construction inspection and confirmation in S1 refers to arranging the Equipment and Materials Department and the Technical Quality Department to jointly conduct on-site inspections of quicklime suppliers and equipment manufacturers, focusing on verifying raw material quality indicators, environmental certification documents and stable supply capabilities, and simultaneously conducting technical status assessments of hydraulic backhoes, bulldozers, and road rollers. Through trial operation tests, it is ensured that the equipment performance meets the standards, providing resource guarantees with controllable quality, environmental compliance, and efficient operation for subsequent construction.

[0006] Preferably, the specific steps of preparing the construction plan and preparing resources in S2 are as follows: Step 1: Prepare a construction schedule Based on the project volume, site conditions and process connection requirements, the start and end times of each sub-project are refined, the time nodes of each construction stage are clarified, and a visual schedule is formed and reviewed and confirmed by the project department; Step 2: Develop equipment and material support plan Calculate equipment lifecycle and material requirements based on the schedule, contact leasing vendors in advance to sign supply agreements, compile quicklime purchase lists, and clarify quality standards and acceptance procedures; Step 3: Implement quicklime storage and quality control Reserve sufficient quicklime according to the construction period, conduct sampling inspection on each batch of raw materials, and classify and store them in moisture-proof warehouses after passing the inspection. Establish a ledger to record batch information to ensure that the materials are traceable.

[0007] Preferably, the specific steps for preparing on-site protection and dust reduction measures in S3 are as follows: Step 1: Standardized construction fencing A prefabricated steel structure enclosure was used, with a C20 concrete foundation poured at the bottom. A sprinkler dust suppression system was installed on the top of the enclosure. Intelligent access control channels were set up at the entrances and exits, equipped with anti-collision piers, warning lights, and monitoring equipment. Project notice boards and environmental protection slogans were posted on the outside of the enclosure to form a fully enclosed construction area. Step 2: Special deployment of dust prevention and control A full-time environmental protection manager is appointed, and mobile fog cannons are equipped to dynamically track dust reduction during earthwork excavation and lime paving processes. PM2.5 online monitors are used to provide real-time data feedback. When dust concentrations exceed the standard, the fog cannon linkage system is automatically activated, and the operation of the dust reduction equipment is recorded simultaneously. Step 3: Standardized vehicle washing process A three-stage sedimentation tank-type automatic washing platform is set up at the entrance and exit, equipped with a high-pressure washing gun and a vibration mud removal device. All vehicles leaving the site are required to pass through the washing platform, and the mud cleaning rate of the body and tires must reach 100%. Special personnel are assigned to check the sealing and covering of the vehicles. Vehicles that do not meet the standards will be returned for washing, and a vehicle washing video record file will be established.

[0008] Preferably, the specific steps of safety technology briefing and training in S4 are as follows: Step 1: Implementation of graded safety technical briefing A three-level safety briefing meeting was held. In the first phase, the project manager organized management personnel to study the construction organization design and risk plan; in the second phase, the technical director explained the process difficulties to the team leader; in the third phase, the team leader conducted practical training for machine operators and operating personnel, using 3D construction animations to demonstrate key points in dust control and safe equipment operation, and all personnel signed a briefing confirmation form; Step 2: Visual control of technical difficulties Produce standardized process drawings, mark the core parameters of the number of times the bottom water absorption layer is turned over and the compaction degree of the middle transition layer, and set up a BIM technical briefing board at the construction site to display the construction progress and quality indicators of each layer in real time; Step 3: Systematize the management system A three-level management and control mechanism consisting of pre-shift inspection, process inspection and special inspection is established, an intelligent compaction monitoring system is configured to provide real-time data feedback, accountability procedures are initiated for processes that fail acceptance for three consecutive times, and a PDCA closed-loop management system is formed.

[0009] Preferably, the S5 roadbed cleaning and leveling refers to the detailed cleaning of excess earth on the top of the lower roadbed according to the design elevation, using a combination of bulldozer rough leveling and grader fine leveling to ensure that the roadbed surface flatness deviation is controlled within ±15mm, and manual trimming is used to supplement the corner areas.

[0010] Preferably, the sampling and testing of the lower roadbed soil in S6 refers to carrying out standardized sampling and testing of the lower roadbed soil, using the ring knife method to determine the natural moisture content, the standard compaction test to obtain the maximum dry density and optimal moisture content parameters, and simultaneously implementing chemical titration analysis of the saline and alkali content; formulating a special plan for the test section based on the test data, selecting representative sections for 3% to 6% gradient ash mixing, tracking the compaction change curve through a nuclear density meter, and combining the EDTA titration method to detect the ash dosage attenuation law.

[0011] Preferably, the specific steps of transporting and spreading the quicklime blocks in S7 are as follows: Step 1: Closed transportation and dynamic dust suppression Use closed dump trucks to transport quicklime blocks, with tarpaulin sealing devices installed on the top of the trucks. Mist cannon trucks are deployed along the transportation routes to start spraying dust suppression in advance at the loading and unloading points. Step 2: Mechanical paving and zoned dust control Hydraulic backhoe is used to pave the material in layers according to the designed thickness. The thickness error of each layer is controlled within ±2cm. Mobile fog cannon units are configured simultaneously to form a three-dimensional dust reduction network at the unloading port and the paving operation surface. One Type 30 fog cannon is configured for every 100 square meters of operation area, using intermittent pulse spray mode.

[0012] Preferably, the specific steps of stirring and stabilizing the quicklime blocks in S8 are as follows: Step 1: When the paving reaches the segment length, use a hydraulic backhoe to stir the material three times; Step 2: After the mixing is completed, use a bulldozer to stabilize the pressure and initially level it so that the quicklime blocks and the moisture in the soil are fully dissolved; Step 3: After standing for 12 hours, stir the soil for the second time to fully mix the lime and soil. The number of mixing times is also 3 times. Step 4: After mixing is completed, use a bulldozer to stabilize and level the surface again, and let it stand for one hour. Finally, use a single-bar wheel roller to perform static compaction three times.

[0013] Preferably, the quality inspection and acceptance in S9 refers to witness sampling of the ash soil in the bottom water-absorbing layer in the laboratory, using the drying method to detect the moisture content, the EDTA titration method to determine the ash content, and the sand injection method to verify the compaction index; after the inspection data is reviewed by professional quality inspectors, it is submitted to the supervision engineer to organize parallel inspection, focusing on checking the lime dosage attenuation curve and 7-day unconfined compressive strength.

[0014] The beneficial effects of the present invention are as follows: 1. The present invention adopts a bottom layer water absorption-middle layer transition-upper layer closed layered gradient solidification technology system to achieve a leap in roadbed performance through third-order synergy; the technical team constructs a dynamic mix ratio model to accurately control the lime dosage of each layer, and cooperates with intelligent spreading equipment to improve the uniformity of lime, which is better than traditional processes; a fully enclosed operation chain is adopted during the construction process, integrating environmental protection measures such as fog cannon dust suppression and closed transportation to reduce dust emissions and stably control PM10 concentration within the national secondary standard; for high water level environments, a two-way drainage channel is set at the bottom layer in combination with a quicklime water absorption layer, and the moisture content of the roadbed is simultaneously blocked by an ion curing agent to block the salt and alkali upward traceability path. The chloride ion migration coefficient has been tested to be reduced; this system improves the efficiency of human-machine collaboration, shortens the construction period, reduces the cost per kilometer, and achieves multi-dimensional optimization of quality-cost-progress.

[0015] 2. The present invention achieves multiple benefits through the collaborative anti-seepage technology of layered gradient solidification: On the technical level, gradient treatment is used to improve the overall performance of the roadbed, optimize the construction process, significantly shorten the construction period, and reduce the construction cost and earthwork handling cost; on the environmental protection level, through closed transportation, dynamic dust reduction and vehicle washing systems, dust emissions are effectively controlled to ensure environmental protection compliance of construction; on quality, a dual-control detection system is established, combined with intelligent monitoring to ensure compaction and lime uniformity, and significantly inhibit saline-alkali erosion; on safety, three-level briefing, visual control and closed-loop management are implemented to improve the hidden danger rectification rate and ensure construction safety; on the social level, this technology has been certified as a high-quality project, providing energy-saving and carbon reduction solutions for similar projects, and promoting technological progress in the industry.

[0016] 3. The present invention adopts layered gradient solidification treatment technology, and realizes technical and economic optimization through a three-stage coordinated system of bottom layer water absorption, middle layer transition, and upper layer closure. Compared with traditional processes, it improves construction efficiency, shortens construction period, and reduces earthwork processing costs. At the same time, relying on green construction measures such as closed transportation and precise plastering, dust emissions are reduced and resource utilization is improved. After testing, the rebound modulus of the roadbed after treatment reaches 65MPa, the salt-alkali erosion inhibition rate is improved, and the construction quality and safety are both guaranteed. This technology is convenient to construct and conforms to the concept of sustainable development. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the overall use process of the construction method of the present invention; Figure 2 This is a process flow chart of the layered gradient green construction method for soft foundation in saline-alkali areas with high water level of the present invention; Figure 3 This is a cross-sectional view of the roadbed layered gradient treatment according to the present invention; Figure 4 This is a graph showing the dry density of the lower roadbed at 50 cm and the amount of ash added; Figure 5This is a schematic diagram of the hydraulic backhoe mixing of 50cm quicklime blocks in the lower roadbed of the present invention; Figure 6 This is a schematic diagram of the lime-soil mixing and pressure stabilization construction of the intermediate transition layer of the present invention; Figure 7 This is a graph showing the dry density of the roadbed at 15 cm and the amount of ash added; Figure 8 This is a schematic diagram of the closed transportation and mechanical spreading construction of quicklime powder according to the present invention; Figure 9 This is a schematic diagram of the quicklime powder intelligent spreading control system of the present invention; Figure 10 This is a schematic diagram of the lime-soil mixing construction of the upper sealing layer of the present invention. DETAILED DESCRIPTION

[0018] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0019] like Figures 1 to 10 As shown, the embodiment of the present invention provides a method for collaborative anti-seepage construction of soft foundation layered gradient solidification in saline-alkali areas with high water level. The specific steps of the construction method are as follows: S1: Pre-construction inspection and confirmation: Organize multiple departments to inspect suppliers, verify raw material quality, environmental protection and supply capacity, and inspect equipment to ensure construction; S2: Prepare construction plan and resources: Prepare the construction schedule and identify the milestones according to the actual situation, make preparations for leasing and purchasing according to the plan to ensure that the facilities and materials are in place in time, and prepare enough lime to ensure that the quality meets the standards; S3: Preparation of on-site protection and dust suppression measures: Set up fences to isolate the construction area, use mist cannons to suppress dust, and install vehicle washing devices at entrances and exits to prevent mud pollution; S4: Safety technical briefing and training: Organize safety briefings for all employees, clarify technical points and operating specifications, establish rules and regulations, and implement the responsibilities of all parties and acceptance standards; S5: Roadbed cleaning and leveling: Clean the excess soil on the top of the roadbed and level it, remove impurities such as grass roots and humus, and transport them for disposal. The remaining soil will be stored nearby for future use; S6: Sampling and testing of lower roadbed soil: On-site sampling is conducted to test moisture content, compaction coefficient, and salinity. Based on the results, a test section is constructed to determine the optimal ash content. Post-construction quality testing is conducted to ensure compliance with design requirements. S7: Quicklime block transportation and paving: Use closed dump trucks to transport quicklime blocks, and manually use hydraulic backhoes to spread them evenly according to the designed thickness. During unloading and paving, deploy fog cannons to spray and reduce dust pollution; S8: Mixing and stabilizing the pressure of quicklime blocks: After paving in sections, mix with a backhoe three times, use a bulldozer to stabilize and level the lime blocks to promote dissolution, and let them stand for 12 hours before mixing again to ensure that the lime and soil are fully mixed. S9: Quality inspection and acceptance: Take samples in the laboratory to test moisture content, ash content, and compaction degree, and confirm the results with the quality inspection and supervision. If qualified, proceed to the next process, and if unqualified, make rectifications until the standards are met.

[0020] Among them, the pre-construction inspection and confirmation in S1 refers to arranging the Equipment and Materials Department and the Technical Quality Department to jointly conduct on-site inspections of quicklime suppliers and equipment manufacturers, focusing on verifying raw material quality indicators, environmental certification documents and stable supply capabilities, and simultaneously conducting technical status assessments of construction machinery such as hydraulic backhoes, bulldozers, and road rollers. Through trial operation inspections, it is ensured that the equipment performance meets the standards, providing resource guarantees with controllable quality, environmental compliance, and efficient operation for subsequent construction.

[0021] The specific steps for preparing the construction plan and preparing resources in S2 are as follows: Step 1: Prepare a construction schedule Based on the project volume, site conditions, and process connection requirements, the start and end times of each sub-project are refined, and the time nodes of each construction stage (such as roadbed cleaning, layered solidification, and quality inspection) are clarified. A visual schedule is formed and reviewed and confirmed by the project department; Step 2: Develop equipment and material support plan Calculate the equipment (such as hydraulic backhoes and rollers) usage cycle and material (quicklime, fuel) requirements based on the schedule, contact the leasing manufacturer in advance to sign a supply agreement, and simultaneously prepare a quicklime purchase list to clarify quality standards (such as particle size and activity index) and acceptance procedures.

[0022] Step 3: Implement quicklime storage and quality control Sufficient quicklime should be reserved according to the construction period, and each batch of raw materials should be sampled and tested (calcium content, fineness, and undigested residue content). After passing the test, they should be classified and stored in a moisture-proof warehouse. A ledger should be established to record batch information to ensure that the materials are traceable.

[0023] The specific steps for preparing on-site protection and dust suppression measures in S3 are as follows: Step 1: Standardized construction fencing Use prefabricated steel structure enclosures (height ≥ 2.5m), cast C20 concrete foundation at the bottom, install a sprinkler dust suppression system on the top of the enclosure, set up intelligent access control channels at the entrances and exits, equipped with anti-collision piers, warning lights and monitoring equipment, and post project notice boards and environmental protection slogans on the outside of the enclosure to form a fully enclosed construction area; Step 2: Special deployment of dust prevention and control Appoint a full-time environmental protection manager and equip mobile fog cannons (range ≥ 30m) to implement dynamic tracking and dust reduction for dust-generating processes such as earth excavation and lime paving. Use PM2.5 online monitors to provide real-time data feedback. When dust concentration exceeds the standard, the fog cannon linkage system is automatically activated, and the dust reduction equipment operation ledger is simultaneously recorded; Step 3: Standardized vehicle washing process A three-stage sedimentation tank-type automatic washing platform is set up at the entrance and exit, equipped with a high-pressure washing gun and a vibration mud removal device. All vehicles leaving the site are required to pass through the washing platform, and the mud cleaning rate of the body and tires must reach 100%. Special personnel are assigned to check the sealing and covering of the vehicles. Vehicles that do not meet the standards will be returned for washing, and a vehicle washing video record file will be established.

[0024] The specific steps of safety technical briefing and training in S4 are as follows: Step 1: Implementation of graded safety technical briefing A three-level safety briefing meeting was held. In the first phase, the project manager organized management personnel to study the construction organization design and risk plan. In the second phase, the technical director explained the process difficulties (such as lime dosage control and mixing depth requirements) to the team leader. In the third phase, the team leader conducted practical training for machine operators and workers, using 3D construction animations to demonstrate key points such as dust control and safe equipment operation. All personnel signed a briefing confirmation form. Step 2: Visual control of technical difficulties A standardized atlas of the construction process was created, noting key parameters such as the number of times the bottom water-absorbing layer was stirred (≥3 times) and the compaction degree of the middle transition layer (≥93%). A BIM technical briefing board was set up at the construction site to display the construction progress and quality indicators of each layer in real time. To address difficulties such as dewatering in high-water-level areas and improving saline-alkali soils, error case warning panels were created and special seminars were organized to strengthen workers' understanding of key processes such as digestion temperature control and gradient ratios. Step 3: Systematize the management system A "Quality, Safety, and Civilized Construction Management Manual" was compiled, clearly defining the project manager as the primary responsible person. Management boundaries were defined for the technical, materials, and safety departments, and 20 acceptance criteria were established, including quicklime ash content testing (EDTA titration method) and compaction testing (sand filling method). A three-tiered management and control mechanism consisting of "pre-shift inspection, process inspection, and special supervision" was established. An intelligent compaction monitoring system was deployed to provide real-time data feedback. Accountability procedures were initiated for processes that failed acceptance three times in a row, forming a closed-loop PDCA management system.

[0025] The S5 mid-roadbed cleaning and leveling process involves meticulously clearing excess earth from the top of the lower roadbed according to the design elevation. This involves a combination of rough leveling with a bulldozer and fine leveling with a motor grader to ensure the surface flatness deviation is within ±15mm, with manual trimming of corners. Simultaneously, impurity removal is carried out, using screening equipment to thoroughly remove excessively large organic matter such as grass roots and humus. Once qualified, the soil is transported to a government-approved environmentally friendly dump site using sealed dump trucks. Covering measures are implemented throughout the transportation process to prevent spillage, and dedicated vehicle washing stations are set up. The remaining qualified earth is stacked in a terraced manner on a nearby flat area, with each layer no more than three meters high and compacted layer by layer. After the top is leveled, it is covered with a double-layer six-needle dust screen, and drainage ditches are installed around the site to prevent soil erosion. A soil inventory ledger is established simultaneously to enable dynamic allocation and management.

[0026] Among them, the sampling and testing of the lower roadbed soil in S6 refers to the standardized sampling and testing of the lower roadbed soil, the use of the ring knife method to determine the natural moisture content, the standard compaction test to obtain the maximum dry density and optimal moisture content parameters, and the simultaneous implementation of chemical titration analysis of the saline and alkali content; a special plan for the test section is formulated based on the test data, and representative sections are selected for 3% to 6% gradient ash mixing. The compaction change curve is tracked by a nuclear density meter, and the ash dosage attenuation law is detected by the EDTA titration method. The ash dosage is comprehensively determined to be 4.5% as the optimal ratio; after the construction of the test section is completed, it is implemented for 7 days of saturated water curing and then subjected to deflection detection and core sampling verification to ensure that the compaction degree is ≥95%, the lime dosage deviation is ≤±1%, and the bearing ratio CBR value meets the standard before it can be promoted on a large scale.

[0027] The specific steps of transporting and paving the quicklime blocks in S7 are as follows: Step 1: Closed transportation and dynamic dust suppression Closed dump trucks are used to transport quicklime blocks, and a tarpaulin sealing device is installed on the top of the truck compartment. A fog cannon truck is used to follow the transportation route, and spray dust reduction is started in advance at the loading and unloading points to form a "transportation-dust reduction" linkage mechanism. Targeted spraying is implemented at dust-prone nodes such as vehicle turns and meeting, ensuring that the dust diffusion coefficient throughout the transportation process is ≤0.8mg / m³.

[0028] Step 2: Mechanical paving and zoned dust control Hydraulic backhoe is used to pave the material in layers according to the designed thickness. The error of the paving thickness of each layer is controlled within ±2cm. Mobile fog cannon units are installed simultaneously to form a three-dimensional dust reduction network at the unloading port and the paving work surface. One Type 30 fog cannon is installed for every 100 square meters of work area. Intermittent pulse spray mode is used to ensure that the visibility of the work surface is ≥50m. Special personnel are arranged to monitor the PM10 concentration at the same time. When the concentration exceeds the standard, the fog cannon frequency increase program will be automatically triggered.

[0029] The specific steps of stirring and stabilizing the quicklime blocks in S8 are as follows: Step 1: When the paving reaches the segment length (less than 100m), use a hydraulic backhoe to turn the material over three times; Step 2: After the mixing is completed, use a bulldozer to stabilize the pressure and initially level it so that the quicklime blocks and the moisture in the soil are fully dissolved; Step 3: After standing for 12 hours, stir the soil for the second time to fully mix the lime and soil. The number of mixing times is also 3 times. Step 4: After mixing is completed, use a bulldozer to stabilize and level the surface again, and let it stand for one hour. Finally, use a single-bar wheel roller to perform static compaction three times.

[0030] The quality inspection and acceptance in S9 involves witnessed laboratory sampling of the lime soil in the bottom water-absorbing layer. The drying method is used to test moisture content, the EDTA titration method is used to determine ash content, and the sand filling method is used to verify compaction. After review by professional quality inspectors, the test data is submitted to the supervising engineer for parallel testing, focusing on the lime dosage attenuation curve and the 7-day unconfined compressive strength. After a three-party joint inspection confirms that all parameters meet the design standards, a process acceptance form is issued and construction proceeds to the next step. If the test values do not meet the CBR value or the compaction requirement of ≥95%, the corrective procedure is immediately initiated, and the defective areas are reworked and retested until they meet the requirements.

[0031] Example 1: Application of coastal soft foundation treatment engineering In a municipal road soft foundation treatment project in Tianjin Binhai New Area, the layered gradient solidification and coordinated anti-seepage construction method was adopted. The specific implementation steps are as follows: Pre-construction inspection and confirmation: The Equipment and Materials Department, in conjunction with the Technical Quality Department, conducted on-site inspections of three quicklime suppliers to verify their ISO14001 environmental certification and their daily production capacity of 800 tons. The department also simultaneously tested the hydraulic system pressure parameters of equipment such as the hydraulic backhoe (CAT320D) and bulldozer (SD22), verifying the stability of the equipment through a two-hour continuous operation trial run.

[0032] Preparation of construction plan: Based on the construction area of 32,000 m2, a four-level schedule was prepared using Project software: S1-S3 stage (preparation period) 15 calendar days, S4-S6 stage (test section) 10 calendar days, S7-S9 stage (main construction) 45 calendar days; signed equipment leasing agreements with 5 companies, stockpiled 4,200 tons of PC32.5 grade quicklime, set up a moisture-proof warehouse and established an electronic ledger to achieve batch traceability.

[0033] On-site protection implementation: Build a 3.2km prefabricated steel structure enclosure, configure a PM2.5 online monitor (detection range 0-1000μg / m³) and 22 Type 30 fog cannons to form an intelligent dust reduction network; the three-stage sedimentation tank flushing platform uses three high-pressure water jets (pressure 12MPa) combined with a vibrating mud removal device to achieve the environmental protection requirement of vehicle mud volume ≤5g / m².

[0034] Safety technical briefing: Carry out three-level safety education: The project department organizes special learning on "Construction Organization Design", the technical person in charge demonstrates the mixing process parameters through the BIM model, and the team leader implements VR safety experience training; a standardized process atlas board is set up on site to display core indicators such as the bottom water absorption layer (mixing depth 35cm) and the middle transition layer (compaction degree ≥93%) in real time.

[0035] Roadbed treatment: Rough leveling (flatness ±10cm) was performed using a D85 bulldozer, followed by fine leveling to a deviation of ±15mm using a PY180 motor grader. The top 30cm humus soil was transported away (8km), and the lower clay was tested for moisture content at a rate of 200m³ / batch. Typical data showed a natural moisture content of 28.7% and a plasticity index of 16.2.

[0036] Construction of the test section: The K0+200-K0+400 section was selected to carry out gradient ash addition tests of 3%, 4.5%, and 6%. The use of a nuclear density meter (MC-3 type) showed that the 4.5% ash addition achieved the optimal compaction degree of 95.8% after 7 days of curing. The EDTA titration method detected the ash dosage attenuation rate, which was controlled at 8.2% / month, and was determined to be the optimal mix ratio.

[0037] Quicklime construction: 8 Shaanxi Automobile M3000 closed dump trucks (rated load 25 tons / truck) are used for transportation, and an electric tarpaulin sealing device is installed on the top of the truck compartment; a hydraulic backhoe (PC200-8) is used to pave the lime in 25cm layers, and the thickness error of each layer is controlled within ±2cm. A mist cannon is also configured to implement intermittent pulse spraying (with a water spraying interval of 8 seconds).

[0038] Mixing and pressure stabilization process: After paving a single section of 200m, a backhoe is used to mix the road three times (mixing depth 38cm), and a bulldozer is used to stabilize the pressure until K ≥ 90%; after standing for 12 hours, a second mixing is performed, and the intelligent compaction monitoring system (ICCC) is used to provide real-time data feedback. Finally, a single steel wheel roller (XS263J) is used to statically compact the road three times to achieve a flatness of ≤ 20mm / 2m ruler.

[0039] Quality acceptance: Witness sampling and testing showed that the moisture content of the ash soil was 19.3% (optimal moisture content ± 2%), the EDTA titrated ash dosage was 4.32%, and the compaction degree was 96.1%. The supervisor's parallel inspection showed that the 7-day unconfined compressive strength reached 0.82MPa, exceeding the design value by 15%. After passing the acceptance, the construction of the graded gravel layer began.

[0040] Bottom water absorption layer According to the design requirements, the excess soil above the top of the lower roadbed is cleaned and leveled (the part containing grass roots, humus, etc. that cannot be used for backfill is removed and transported away, and the other excess soil is temporarily stored nearby). The soil of the lower roadbed is sampled on site to determine the moisture content, compaction coefficient, salinity and alkali content of the soil. Based on the test results, the construction of the test section is organized to determine the optimal ash content for the final roadbed treatment.

[0041] Quicklime blocks are transported to the construction site using enclosed dump trucks. Manual labor combined with a hydraulic backhoe spreads the blocks evenly according to calculated data. Dust is generated during the unloading and paving process, and mist cannons can be deployed to suppress it. When the paving reaches the specified length (less than 100 meters), a hydraulic backhoe is used to mix the blocks (2-3 times). After mixing, a bulldozer is used to stabilize the pressure and perform preliminary leveling. After 12 hours, the quicklime blocks are allowed to fully dissolve moisture in the soil. A second mixing (2-3 times) is then performed to thoroughly mix the lime and soil. After mixing, a bulldozer is used to stabilize the pressure and level the blocks. After one hour of static stagnation, a horizontal roller is used to perform static compaction 2-3 times. On-site sampling and compaction testing are conducted in the laboratory to measure indicators such as the moisture content, ash content, and compaction of the bottom absorbent layer of lime soil. Only after approval by professional quality inspectors and the supervising engineer can the next construction step proceed.

[0042] Intermediate transition layer After the bottom absorbent layer passes inspection, the excavated and stored soil is backfilled to the working surface. The design thickness of this layer is 15 cm. For this project, the soil backfill coefficient is set at 1.25, resulting in a backfill thickness of 15 cm x 1.25 = 18.75 cm. The required amount of quicklime powder is calculated based on the construction area for this phase. Powdered quicklime is transported to the site by bulk cement trucks and conveyed via negative pressure pipes to a powder spreading vehicle. The vehicle's automatic weighing system and intelligent spreading system, combined with the results of the intelligent proportioning system, ensure precise control of the distribution of quicklime. For areas with high moisture content, quicklime blocks are added using a hydraulic backhoe and manual labor. After distribution, a stabilized soil mixer is used for mixing. Adjacent mixing sections should overlap by at least 25 cm. For staged mixing, the vertical overlap should be at least 5 m. The mixing depth and uniformity should be checked regularly throughout the mixing process, and the mixing depth should reach the bottom of the current layer of soil. After two to three passes of mixing, a bulldozer performs stabilization and preliminary leveling. Following stabilization, a 26t single-wheel roller performs two to three static passes. After static compaction, elevation points are measured according to the design (measurement points are spaced 10m apart for each lane). A scraper then levels, grades, and shapes the intermediate transition layer according to the elevations of each measured point. Once shaped to the specified elevation, slope, and road crown, the roller performs a stabilization pass, followed by a weak vibration recompaction. Then, a strong vibration rolling process is applied. Rolling is performed horizontally from low to high, overlapping the surface by 30 to 50cm. Retracting the rollers ensures that each layer is evenly compacted in thickness and width. The roller speed is 1.2 to 1.8 km / h for the first pass and 1.8 to 2.4 km / h for subsequent passes. The number of passes is controlled according to the parameters determined during the rolling test section.

[0043] Upper sealing layer 1. According to the construction procedures and process flow, the qualified middle transition layer was backfilled with bare soil, which served both as cover and maintenance and as soil for the upper sealing layer. The backfill thickness and quality met the design requirements. The loose spreading coefficient was determined based on the production test section, and the loose spreading thickness was calculated. Control lines were marked on elevation stakes on both sides of the roadbed. The design thickness of the upper sealing layer for this project was 15 cm. With the loose spreading coefficient set at 1.25, the loose spreading thickness of the bare soil backfill for the upper sealing layer was calculated to be 15 cm x 1.25 = 18.75 cm. Multiple on-site sampling of the upper sealing layer backfill soil was conducted to determine the average moisture content, compaction coefficient, and salinity. The optimal lime content was calculated based on the test results and loose spreading thickness. The required amount of quicklime powder was then calculated based on the construction area of the upper sealing layer. The quicklime powder spreading thickness was calculated using the automatic weighing system within the powder spreading vehicle, the intelligent spreading system, and the intelligent proportioning system. During construction, the spreading thickness was manually inspected and verified by verifying the lime content. After the construction of the upper sealing layer is completed, the compaction, ash content, integrity, permeability, overall uniformity, etc. are tested as the final quality control standards.

[0044] During the construction process, powdered quicklime is transported to the site via bulk cement trucks and conveyed via negative pressure pipes to the powder spreader. The spreader's intelligent control system precisely distributes the lime, and manual on-site measurement and verification of the spread thickness ensure optimal lime content. After spreading, the stabilized soil mixer is used for mixing. Adjacent mixing sections should overlap by at least 25 cm. If mixing is done in sections, the longitudinal overlap should exceed 5 m. The mixing depth and uniformity should be checked regularly throughout the mixing process, reaching the bottom of the lime layer. After two to three passes of mixing, a bulldozer is used for pressure stabilization and preliminary leveling. After pressure stabilization, a 26t single-wheel roller is used for two to three static rolls. After static rolling is complete, elevation points are measured according to the design elevation (measurement points are spaced 10 m apart for each lane). A scraper is then used to level, grade, and shape the upper sealing layer according to the elevation of each measured point. After shaping to the specified elevation, slope, and road crown, use a roller to stabilize the road surface. Then, use a weak vibration mode for recompaction. Then, use a strong vibration mode for rolling. Roll horizontally from low to high, overlapping the road surface by 30 to 50 cm. Use a reverse rotation mode to ensure uniform compaction across the entire layer. The roller speed should be between 1.2 and 1.8 km / h for the first pass, and between 1.8 and 2.4 km / h for subsequent passes. The number of passes should be controlled according to the parameters determined during the production test section.

[0045] 3. During the construction of the intermediate transition layer and the upper closed layer of ash soil, dust-free mechanical equipment is used from the transportation of quicklime powder to loading and then to spreading. Dust is easily generated only during the mixing process. Mobile fog cannons are deployed in areas prone to dust generation to move with the mixer for dust reduction. After compaction is completed, geotextile is laid on the upper closed layer and water is sprinkled for maintenance and dust reduction. Effective dust suppression measures are taken throughout the construction of the upper closed layer, which improves the environmental pollution caused by dust caused by traditional ash soil operations and achieves green construction of the entire project.

[0046] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0047] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for collaborative anti-seepage construction of soft foundation layered gradient solidification in high water table saline-alkali areas, characterized by: The specific steps of this construction method are as follows: S1: Pre-construction inspection and confirmation: Organize multiple departments to inspect suppliers, verify raw material quality, environmental protection and supply capacity, and inspect equipment to ensure construction; S2: Prepare construction plan and resources: Prepare the construction schedule and identify the milestones according to the actual situation, make preparations for leasing and purchasing according to the plan to ensure that the facilities and materials are in place in time, and prepare enough lime to ensure that the quality meets the standards; S3: Preparation of on-site protection and dust suppression measures: Set up fences to isolate the construction area, use mist cannons to suppress dust, and install vehicle washing devices at entrances and exits to prevent mud pollution; S4: Safety technical briefing and training: Organize safety briefings for all employees, clarify technical points and operating specifications, establish rules and regulations, and implement the responsibilities of all parties and acceptance standards; S5: Roadbed cleaning and leveling: Clean the excess soil on the top of the roadbed and level it, remove grass roots, humus and impurities and transport them for disposal, and store the remaining soil nearby for future use; S6: Sampling and testing of lower roadbed soil: On-site sampling is conducted to test moisture content, compaction coefficient, and salinity. Based on the results, a test section is constructed to determine the optimal ash content. Post-construction quality testing is conducted to ensure compliance with design requirements. S7: Quicklime block transportation and paving: Use closed dump trucks to transport quicklime blocks, and manually use hydraulic backhoes to spread them evenly according to the designed thickness. During unloading and paving, deploy fog cannons to spray and reduce dust pollution; S8: Mixing and stabilizing the pressure of quicklime blocks: After paving in sections, mix with a backhoe three times, use a bulldozer to stabilize and level the lime blocks to promote dissolution, and let them stand for 12 hours before mixing again to ensure that the lime and soil are fully mixed. S9: Quality inspection and acceptance: Take samples in the laboratory to test moisture content, ash content, and compaction degree, and confirm the results with the quality inspection and supervision. If qualified, proceed to the next process, and if unqualified, make rectifications until the standards are met.

2. The method for collaborative anti-seepage construction of soft foundation layered gradient solidification in high water table saline-alkali areas according to claim 1, characterized in that: The pre-construction inspection and confirmation in S1 refers to arranging the Equipment and Materials Department and the Technical Quality Department to jointly conduct on-site inspections of quicklime suppliers and equipment manufacturers, focusing on verifying raw material quality indicators, environmental certification documents and stable supply capabilities, and simultaneously conducting technical status assessments of hydraulic backhoes, bulldozers, and road rollers. Through trial operation tests, it is ensured that the equipment performance meets the standards, providing resource guarantees with controllable quality, environmental compliance, and efficient operation for subsequent construction.

3. The method for collaborative anti-seepage construction of soft foundation layered gradient solidification in high water table saline-alkali areas according to claim 1, characterized in that: The specific steps for preparing the construction plan and preparing resources in S2 are as follows: Step 1: Prepare a construction schedule Based on the project volume, site conditions and process connection requirements, the start and end times of each sub-project are refined, the time nodes of each construction phase are clarified, and a visual schedule is formed and reviewed and confirmed by the project department; Step 2: Develop equipment and material support plan Calculate equipment lifecycle and material requirements based on the schedule, contact leasing vendors in advance to sign supply agreements, compile quicklime purchase lists, and clarify quality standards and acceptance procedures; Step 3: Implement quicklime storage and quality control Reserve sufficient quicklime according to the construction period, conduct sampling inspection on each batch of raw materials, and classify and store them in moisture-proof warehouses after passing the inspection. Establish a ledger to record batch information to ensure that the materials are traceable.

4. The method for collaborative anti-seepage construction of soft foundation layered gradient solidification in high water table saline-alkali areas according to claim 1, characterized in that: The specific steps for preparing on-site protection and dust suppression measures in S3 are as follows: Step 1: Standardized construction fencing A prefabricated steel structure enclosure was used, with a C20 concrete foundation poured at the bottom. A sprinkler dust suppression system was installed on the top of the enclosure. Intelligent access control channels were set up at the entrances and exits, equipped with anti-collision piers, warning lights, and monitoring equipment. Project notice boards and environmental protection slogans were posted on the outside of the enclosure to form a fully enclosed construction area. Step 2: Special deployment of dust prevention and control A full-time environmental protection manager is appointed, and mobile fog cannons are equipped to dynamically track dust reduction during earthwork excavation and lime paving processes. PM2.5 online monitors are used to provide real-time data feedback. When dust concentrations exceed the standard, the fog cannon linkage system is automatically activated, and the operation of the dust reduction equipment is recorded simultaneously. Step 3: Standardized vehicle washing process A three-stage sedimentation tank-type automatic washing platform is set up at the entrance and exit, equipped with a high-pressure washing gun and a vibration mud removal device. All vehicles leaving the site are required to pass through the washing platform, and the mud cleaning rate of the body and tires must reach 100%. Special personnel are assigned to check the sealing and covering of the vehicles. Vehicles that do not meet the standards will be returned for washing, and a vehicle washing video record file will be established.

5. The method for collaborative anti-seepage construction of soft foundation layered gradient solidification in high water table saline-alkali areas according to claim 1, characterized in that: The specific steps of safety technology disclosure and training in S4 are as follows: Step 1: Implementation of graded safety technical briefing A three-level safety briefing meeting was held. In the first stage, the project manager organized management personnel to study the construction organization design and risk plan; in the second stage, the technical director explained the process difficulties to the team leaders; In the third phase, the team leader conducted practical training for machine operators and workers, using 3D construction animations to demonstrate key points in dust control and equipment safe operation, and all staff signed a confirmation form. Step 2: Visual control of technical difficulties Produce standardized process drawings, mark the core parameters of the number of times the bottom water absorption layer is turned over and the compaction degree of the middle transition layer, and set up a BIM technical briefing board at the construction site to display the construction progress and quality indicators of each layer in real time; Step 3: Systematize the management system A three-level management and control mechanism consisting of pre-shift inspection, process inspection and special inspection is established, an intelligent compaction monitoring system is configured to provide real-time data feedback, accountability procedures are initiated for processes that fail acceptance for three consecutive times, and a PDCA closed-loop management system is formed.

6. The method for collaborative anti-seepage construction of soft foundation layered gradient solidification in high water table saline-alkali areas according to claim 1, characterized in that: The S5 roadbed cleaning and leveling refers to the detailed cleaning of excess earth on the top of the lower roadbed according to the design elevation, using a combination of bulldozer rough leveling and grader fine leveling to ensure that the roadbed surface flatness deviation is controlled within ±15mm, and manual trimming is used to supplement the edge and corner areas.

7. The method for collaborative anti-seepage construction of soft foundation layered gradient solidification in high water table saline-alkali areas according to claim 1, characterized in that: The sampling and testing of the lower roadbed soil in S6 refers to the standardized sampling and testing of the lower roadbed soil, the use of the ring knife method to determine the natural moisture content, the standard compaction test to obtain the maximum dry density and optimal moisture content parameters, and the simultaneous implementation of chemical titration analysis of the salt and alkali content; based on the test data, a special plan for the test section is formulated, and representative sections are selected for 3% to 6% gradient ash mixing. The compaction change curve is tracked by a nuclear density meter, and the EDTA titration method is combined to detect the ash dosage attenuation law.

8. The method for collaborative anti-seepage construction of soft foundation layered gradient solidification in high water table saline-alkali areas according to claim 1, characterized in that: The specific steps of transporting and paving the quicklime blocks in S7 are as follows: Step 1: Closed transportation and dynamic dust suppression Use closed dump trucks to transport quicklime blocks, with tarpaulin sealing devices installed on the top of the trucks. Mist cannon trucks are deployed along the transportation routes to start spraying dust suppression in advance at the loading and unloading points. Step 2: Mechanical paving and zoned dust control Hydraulic backhoe is used to pave the material in layers according to the designed thickness. The thickness error of each layer is controlled within ±2cm. Mobile fog cannon units are configured simultaneously to form a three-dimensional dust reduction network at the unloading port and the paving operation surface. One Type 30 fog cannon is configured for every 100 square meters of operation area, using intermittent pulse spray mode.

9. The method for collaborative anti-seepage construction of soft foundation layered gradient solidification in high water table saline-alkali areas according to claim 1, characterized in that: The specific steps of stirring and stabilizing the quicklime blocks in S8 are as follows: Step 1: When the paving reaches the segment length, use a hydraulic backhoe to stir the material three times; Step 2: After the mixing is completed, use a bulldozer to stabilize the pressure and initially level it so that the quicklime blocks and the moisture in the soil are fully dissolved; Step 3: After standing for 12 hours, stir the soil for the second time to fully mix the lime and soil. The number of mixing times is also 3 times. Step 4: After mixing is completed, use a bulldozer to stabilize and level the surface again, and let it stand for one hour. Finally, use a single-bar wheel roller to perform static compaction three times.

10. The method for collaborative anti-seepage construction of soft foundation layered gradient solidification in high water table saline-alkali areas according to claim 1, characterized in that: The quality inspection and acceptance in S9 refers to the witnessed sampling of the ash soil in the bottom moisture-absorbing layer in the laboratory, the use of the drying method to detect the moisture content, the EDTA titration method to determine the ash content, and the sand injection method to verify the compaction index; after the inspection data is reviewed by professional quality inspection personnel, it is submitted to the supervision engineer to organize parallel inspection, with a focus on checking the lime dosage attenuation curve and the 7-day unconfined compressive strength.

Images