Method for repairing a miscellaneous fill layer

Abstract

This invention discloses a method for replacing and repairing miscellaneous fill layers, relating to the field of foundation replacement treatment technology. The method includes: dividing the replacement area into multiple construction zones; excavating and repairing the miscellaneous fill layer section by section according to the construction zones and trimming the foundation; conducting compaction tests on the trimmed foundation and cyclically treating any substandard areas until they meet the requirements; pre-adjusting the moisture content and gradation of the brick slag filler; backfilling the adjusted brick slag filler in layers and spreading it according to the construction zones to form a layer body; performing segmented compaction on the layer body; classifying and cyclically correcting areas that do not meet the requirements based on real-time compaction tests; spreading fine brick slag at the interlayer interface before spreading the upper layer; and conducting overall bearing capacity and overall uniformity tests. This invention improves the bearing capacity and uniformity of the replaced miscellaneous fill layer, reduces differential settlement, and enhances the construction quality of the miscellaneous fill layer replacement and repair.

Description

Technical Field

[0001] This invention relates to the field of foundation replacement treatment technology, and in particular to a method for replacing and repairing miscellaneous fill layers. Background Technology

[0002] Increasingly, various buildings, site slabs, roads, and municipal engineering projects encounter foundations composed of mixed fill soil consisting of construction waste, bricks, rubble, gravel, silt, and small amounts of clay. This mixed fill soil layer has a complex composition, loose structure, high porosity, and poor uniformity. It softens easily when exposed to water and cannot be used directly as a bearing layer for foundations. Reinforcement or replacement measures are usually required. Replacement, as a technically mature and relatively cost-effective foundation treatment method, involves excavating the weak mixed fill soil and backfilling it in layers with stable fill material, compacting it to ensure the treated foundation's bearing capacity meets design requirements.

[0003] Currently, the replacement and repair of miscellaneous fill layers is typically applied as follows: First, the site for replacement is cleared and excavated to the design depth. Then, the bottom of the pit is simply leveled. Next, fillers such as sand, gravel, crushed stone, or brick debris are used for layered backfilling, which is then compacted layer by layer using a road roller. Finally, a simple bearing capacity test is conducted on the surface of the replacement layer. Some projects also involve watering and sieving the filler material, and sampling tests are performed on the compaction quality to control the density of the backfill layer. This method is simple to operate, requires minimal equipment, and can complete the replacement of miscellaneous fill layers under general site conditions.

[0004] However, the existing methods still have significant shortcomings. First, the one-time excavation of the entire area leads to prolonged and large-area exposure of the excavation surface, causing surface water to flow and infiltrate disorderly along the excavation surface, easily softening the foundation. Furthermore, the lack of organized drainage control along the boundaries and perimeter of the zones results in poor working conditions and severe foundation disturbance. Second, the excavated foundation is often assessed based solely on experience or simple leveling, lacking quantitative compaction testing and cyclical treatment methods for substandard areas. Insufficient foundation bearing capacity and localized weak areas are difficult to detect and effectively address in a timely manner, easily leading to differential settlement after backfilling. Third, the brick and slag filler material to be backfilled is often used directly without particle size classification, moisture content pre-adjustment, and gradation pre-adjustment. This results in a concentration of large-diameter blocks, an imbalance in the ratio of coarse to fine particles, and large deviations in moisture content, making it difficult to maintain stable compaction quality. Fourth, during layered backfilling, there is a lack of control over paving thickness and flatness, as well as real-time compaction testing with each compaction pass. Under-compacted areas cannot be identified and corrected in a timely manner, leading to uneven compaction. Fifth, the interlayer interface is poorly treated, and the upper and lower layers are not well bonded, which easily leads to the formation of weak interlayers and seepage channels. Summary of the Invention

[0005] The main objective of this invention is to propose a method for replacing and repairing miscellaneous fill layers, which aims to improve the bearing capacity and uniformity of the miscellaneous fill layers and reduce differential settlement.

[0006] To achieve the above objectives, the present invention proposes a method for replacing and repairing miscellaneous fill layers, the method comprising: The replacement area is divided into multiple construction zones. The surface layer is sealed and compacted along the boundary of the adjacent construction zones, and drainage paths are excavated around each construction zone to divert and discharge surface water. According to the construction zone, the miscellaneous fill layer is excavated and the foundation is repaired section by section. The compaction of the repaired foundation is tested, and the foundation area that fails the test is cyclically treated until it passes the test. The brick slag filler to be backfilled is classified and graded according to its particle size, and the moisture content and gradation of the graded brick slag filler are pre-adjusted. The adjusted brick slag filler is backfilled in layers and spread according to the construction zones to form a layer. The layer is compacted in segments, and the compaction degree is monitored in real time during the compaction process; Based on the real-time detected compaction degree, areas that do not meet the requirements are graded and cyclically corrected until the compaction degree meets the requirements. After the layer below passes the acceptance test, the interlayer interface is roughened, cleaned and moistened in sequence, and fine brick chips are sprinkled on the interlayer interface before the upper layer is laid. After all the aforementioned layers have been constructed, an overall load-bearing capacity test and an overall uniformity test will be conducted.

[0007] In one embodiment, the steps of dividing the replacement area into multiple construction zones, sealing and compacting the surface layer along the boundaries of adjacent construction zones, and excavating drainage paths around each construction zone to divert surface water include: The replacement area is divided into multiple construction zones, each of which is 8 to 15m long and 4 to 6m wide. The surface layer is sealed and compacted along the boundary of the adjacent construction zones to block the flow of surface water between adjacent zones; The drainage path is excavated around each of the construction zones to divert surface water to areas outside the construction zone.

[0008] In one embodiment, before the step of excavating and repairing the miscellaneous fill layer section by section according to the construction zone, the method for replacing and repairing the miscellaneous fill layer further includes: Before the current construction zone is excavated, the boundaries of the adjacent construction zones are kept closed and compacted to prevent surface water from flowing into the current construction zone. The zoning boundary is used as the paving control boundary to constrain the backfilling and paving range of the brick slag filler.

[0009] In one embodiment, the step of excavating and removing the miscellaneous fill layer and repairing the foundation section by section according to the construction zone includes: Following the direction from high to low and from the far end to the transportation corridor, the miscellaneous fill layer was excavated section by section until the designed replacement depth was reached. The exposed base after excavation is manually trimmed to remove loose soil and particles, so that the flatness deviation of the base is no more than 20mm. The compaction of the modified substrate was tested by hammer penetration to obtain the number of hammer blows per 30cm penetration.

[0010] In one embodiment, the step of cyclically processing the substrate region that fails the test until it passes includes: When the number of hammer blows on the substrate is less than 15 blows / 30cm, the corresponding substrate area is determined to be a defective area. The unqualified area was excavated a second time, and the excavation was carried out downwards to the top surface of the dense layer. The brick slag filler was then backfilled and compacted. If the number of hammer blows in the treated non-conforming area is still less than 15 blows / 30cm, repeat the second excavation, backfilling, compaction, and retesting until the number of hammer blows is not less than 15 blows / 30cm.

[0011] In one embodiment, the steps of grading and classifying the brick slag filler material to be backfilled according to its particle size, and pre-adjusting the moisture content and gradation of the graded brick slag filler material include: The brick slag filler is divided into two grades according to the first particle size limit of 150mm and the second particle size limit of 20mm, so that large pieces with a particle size greater than 150mm, medium-grade materials with a particle size of 20 to 150mm and fine materials with a particle size less than 20mm are separated from each other. The moisture content of the graded brick slag filler was determined; When the moisture content is lower than the lower limit of the optimum moisture content, the brick slag filler is uniformly sprayed with water and left to stand for 2 to 4 hours after spraying. When the moisture content is higher than the upper limit of the optimum moisture content, the brick slag filler is spread out and dried, with a spreading thickness of 300 to 400 mm, and is turned over once every 2 hours. Repeat the moisture content test until the moisture content is within ±2% of the optimum moisture content; Adjust the gradation of the brick slag filler so that the proportion of particles with a diameter greater than 40mm is 30% to 40%, the proportion of particles with a diameter of 20 to 40mm is 25% to 35%, and the proportion of particles with a diameter less than 20mm is 30% to 40%, with a non-uniformity coefficient of not less than 5 and a curvature coefficient of 1 to 3.

[0012] In one embodiment, after the steps of grading and classifying the brick slag fill material to be backfilled according to its particle size, and pre-adjusting the moisture content and gradation of the graded brick slag fill material, the method for replacing and repairing the miscellaneous fill layer further includes: Collect the fine material with a particle size of less than 20 mm, and retain a portion of the fine material as spreading material for the interlayer interface; The large pieces of material with a particle size greater than 150mm are crushed, and the two-stage grading is repeated after crushing until all the material particles are no larger than 150mm. When the proportion of particles with a diameter of less than 20 mm in the brick slag filler is less than 30%, the remaining fine material is recycled back into the brick slag filler until the gradation meets the requirements.

[0013] In one embodiment, the steps of backfilling the adjusted brick slag filler in layers, spreading it according to the construction zones to form a layer, performing segmented compaction on the layer, and monitoring the compaction degree in real time during the compaction process include: The brick slag filler is divided into multiple layers for backfilling, with each layer having a loose thickness of 250 to 280 mm. The brick slag filler is laid in a quincunx pattern according to the construction zone, with a spacing of 2 to 3 meters between piles. After laying, it is leveled so that the flatness deviation is no more than 15 mm and the loose thickness deviation is controlled within ±5 mm. The layer is first subjected to static compaction once, then medium-energy compaction twice, and finally high-energy compaction three to five times, with a compaction speed of 1.5 to 2.2 km / h; Every 60m during the compaction process 2 up to 80m 2 Set up a test point and perform real-time compaction testing on the test point as the number of compaction passes increases.

[0014] In one embodiment, the step of classifying and cyclically correcting areas that do not meet the requirements based on the real-time detected compaction degree, until the compaction degree meets the requirements, includes: Set a design compaction degree and a second threshold that is 3 percentage points lower than the design compaction degree; When the compaction degree of the test point is not less than the design compaction degree, the test point is deemed qualified. When the compaction degree at the detection point is not less than the second threshold and is less than the design compaction degree, the detection point is determined to be locally undercompacted, the detection point is marked, and a 1m radius around the detection point is marked. Apply local compaction 2 to 4 times to a 1m area, and retest the compaction degree at the test point; When the compaction degree at the detection point is less than the second threshold, the detection point is determined to be severely undercompacted, and the area within 2 meters of the detection point is excavated. From the 2m area to the top surface of the lower layer, the paving is repaved and compacted, and the compaction degree is retested at no less than 3 test points in this area; The graded judgment and cyclical correction are repeated for the corrected area until the compaction degree of all test points is not less than the design compaction degree.

[0015] In one embodiment, the steps of roughening, cleaning, and wetting the interlayer interface after the lower layer has passed acceptance testing, and then spreading fine brick slag on the interlayer interface before laying the upper layer include: The top surface of the layer described below is roughened to a depth of 6 to 8 mm; Sweep away any loose material or dust generated during the roughening process; Sprinkle water to moisten the top surface until the moisture content is 8% and there is no visible water on the surface; Fine brick slag with a thickness of 8 to 12 mm and a particle size of no more than 20 mm is evenly spread at the interlayer interface, and the upper layer is laid while the spread fine brick slag is kept loose. Alternatively, a cement paste with a water-cement ratio of 0.4 to 0.5 can be sprayed at the interlayer interface at a rate of 0.4 kg / m³. 2 The layer above is laid before the cement paste has initially set. After all the aforementioned layers have been constructed, the steps for conducting overall bearing capacity testing and overall uniformity testing include: Apply vertical loads in stages up to not less than 360 kPa and measure settlement; the equivalent characteristic value of the foundation bearing capacity is not less than 180 kPa. The uniformity of the replacement layer is tested by hammer penetration testing, ensuring that the average number of hammer blows is not less than 20 blows / 30cm and the coefficient of variation is not greater than 0.15.

[0016] The technical solution of this invention divides the replacement area into multiple construction zones, seals and compacts the surface layer along the boundaries of adjacent construction zones, and excavates drainage paths around each construction zone to divert surface water. This intercepts and systematically diverts surface water outside the construction area before it enters the work surface. Since excavation, backfilling, and compaction operations are all confined to independent zones and carried out segment by segment, the excavation surface does not need to be exposed over a large area for extended periods. This effectively prevents disorderly surface water flow, infiltration that softens the substrate, and erosion of the fill material, keeping the substrate and fill material in a dry and controllable working state. Furthermore, the zone boundaries also serve as paving control boundaries, constraining the backfilling and paving range of the fill material. Furthermore, by conducting quantitative density testing on the repaired base and cyclically treating unqualified areas, classifying and pre-adjusting the particle size, moisture content, and gradation of the brick slag filler, layering and compacting the layer with real-time compaction testing as the number of compaction passes increases, classifying and cyclically correcting under-compacted areas, and sequentially roughening, cleaning, wetting, and spreading fine brick slag at the interlayer interfaces, the entire replacement construction process is under quantitative and closed-loop control. This eliminates reliance on empirical judgments after excavation and sampling inspections after compaction, preventing the omission of local weak bases and under-compacted areas, as well as the formation of weak interlayer layers. Finally, the quality of the replacement layer is quantitatively accepted through overall bearing capacity testing and overall uniformity testing, thereby improving the bearing capacity and uniformity of the replacement layer, reducing differential settlement, and enhancing the construction quality of the miscellaneous fill layer replacement and repair. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, 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 the structures shown in these drawings without creative effort.

[0018] Figure 1 This is a flowchart illustrating an embodiment of the method for replacing and repairing miscellaneous fill layers provided by the present invention.

[0019] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0022] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0023] Existing methods for replacing and repairing miscellaneous fill layers typically involve a one-time excavation and compaction of the entire replacement area, without segmented control over excavation, drainage, backfilling, and compaction according to construction zones. This results in prolonged exposure of the excavated surface, allowing surface water to flow disorderly along the excavation surface and infiltrate, softening the foundation. Working conditions are poor, and foundation disturbance is severe. Furthermore, there is a lack of quantitative density testing and cyclical treatment methods for the excavated foundation, making it difficult to promptly identify and effectively address areas with insufficient bearing capacity and localized weakness, easily leading to differential settlement after replacement. In addition, the brick and rubble fill material to be backfilled is often used directly without particle size classification, moisture content pre-adjustment, and gradation pre-adjustment. This results in a concentration of large-diameter blocks, an imbalance in the ratio of coarse to fine particles, and large deviations in moisture content, making it difficult to consistently control compaction quality. Existing methods lack control over paving thickness and flatness during layered backfilling, as well as real-time compaction testing with each compaction pass. Under-compacted areas cannot be identified and corrected in a timely manner, leading to uneven compaction. The interlayer interfaces are poorly treated, resulting in weak interlayers and seepage channels. Furthermore, the replacement layer lacks overall bearing capacity and uniformity testing after completion, leading to a lack of quantitative assurance regarding its quality.

[0024] To address this technical problem, this invention proposes a method for replacing and repairing miscellaneous fill layers.

[0025] Please see Figure 1 In one embodiment of the present invention, the method for replacing and repairing the miscellaneous fill layer includes: S10, the replacement area is divided into multiple construction zones, the surface layer is sealed and compacted along the boundary of the adjacent construction zones, and a drainage path is excavated outside each construction zone to drain surface water. S20, according to the construction zone, excavate the miscellaneous fill layer section by section and repair the foundation. Conduct a compaction test on the repaired foundation. For the foundation area that fails the test, carry out cyclic treatment until it passes the test. S30, the brick slag filler to be backfilled is classified and graded according to its particle size, and the moisture content and gradation of the graded brick slag filler are pre-adjusted. S40, the adjusted brick slag filler is backfilled in layers and spread according to the construction zones to form a layer; S50, the layer is compacted in segments, and the compaction degree is detected in real time during the compaction process; S60, based on the real-time detected compaction degree, the areas that do not meet the requirements are classified and cyclically corrected until the compaction degree meets the requirements; S70, after the lower layer has passed the acceptance test, the interlayer interface is roughened, cleaned and moistened in sequence, and fine brick chips are sprinkled on the interlayer interface before the upper layer is laid. S80, After all the aforementioned layers have been constructed, an overall bearing capacity test and an overall uniformity test shall be conducted.

[0026] For ease of understanding, the following explains some key terms in this embodiment: Miscellaneous fill layers refer to soil layers formed during human production and daily life activities, consisting of a mixture of construction waste, bricks, rubble, gravel, silt, clay, and a small amount of domestic waste. These soil layers are characterized by complex composition, loose structure, poor uniformity, high porosity, low bearing capacity, and are prone to softening, collapsing, or uneven deformation when exposed to water, posing a threat to the safety of the superstructure.

[0027] The replacement area refers to the planar area determined according to the survey data and design requirements where the miscellaneous fill layer needs to be excavated and replaced with qualified fill material.

[0028] Construction zoning refers to the basic operational units that divide the replacement area according to certain dimensions, and are used to organize excavation, drainage, backfilling, compaction and acceptance in stages.

[0029] The zone boundary refers to the dividing line between two adjacent construction zones, which is used as a closed compaction zone and paving control boundary during construction.

[0030] Drainage pathways refer to trenches or channels excavated outside the construction zone to collect and drain surface water.

[0031] Brick slag filler refers to backfill material made primarily of brick slag, obtained by crushing and screening bricks, masonry, and concrete fragments produced during building demolition.

[0032] A layer refers to a compacted fill layer formed by spreading brick and slag filler to a certain loose thickness and then rolling it.

[0033] Loose paving thickness refers to the thickness of the fill material after it has been laid but before compaction.

[0034] Compaction degree refers to the percentage of the measured dry density of the compacted filler to its maximum dry density, and it is a key indicator for evaluating compaction quality.

[0035] Interlayer interface refers to the joint surface between two adjacent upper and lower layers.

[0036] Fine brick slag refers to fine particles with a particle size of no more than 20mm in brick slag filler, which are used as interlayer interface spreading material.

[0037] Percussion test (PCT) is an in-situ testing method that uses a hammer of specified weight and a specified drop distance to penetrate a probe into the soil and records the number of hammer blows required to penetrate to a certain depth. It is used to evaluate the compaction and bearing capacity of the soil.

[0038] Optimal moisture content refers to the moisture content at which the filler reaches its maximum dry density under a specified compaction effort. It is an important parameter for compaction quality control.

[0039] The non-uniformity coefficient refers to the ratio of the defined particle size d60 to the effective particle size d10 in the particle gradation curve, reflecting the breadth of the particle size distribution range; the curvature coefficient refers to the ratio of the square of d30 to the product of d60 and d10 in the gradation curve, reflecting the continuity of the gradation curve and the rationality of the combination of coarse and fine particles.

[0040] Grading judgment refers to a judgment method that divides the detection area into different levels such as qualified, locally under-compaction, and severely under-compaction based on the comparison results of real-time detected compaction degree with design compaction degree and second threshold, and takes corresponding corrective measures.

[0041] Design compaction degree refers to the minimum compaction degree that should be achieved after compaction as specified in the design documents.

[0042] The second threshold is a compaction limit value that is 3 percentage points lower than the design compaction degree, used to distinguish between local under-compaction and severe under-compaction.

[0043] This embodiment provides a method for replacing and repairing miscellaneous fill layers.

[0044] First, the method involves dividing the replacement area into multiple construction zones, sealing and compacting the surface layer along the boundaries of adjacent construction zones, and excavating drainage paths around each construction zone to divert surface water. Specifically, construction technicians can divide the entire replacement area into several appropriately sized construction zones that facilitate segmented construction and independent drainage, based on the shape of the replacement area, groundwater level, topographic slope, and the location of transportation channels. Along the boundaries of adjacent construction zones, a road roller or compaction equipment is used to seal and compact the surface soil, forming a compacted zone with a certain density and water-resistant properties to prevent surface water cross-flow between adjacent zones. Simultaneously, drainage paths, such as open drainage ditches or intercepting ditches, are excavated around each construction zone with a certain longitudinal slope to divert collected surface water to existing drainage facilities or collection wells outside the construction area. As another approach, geotextile fabric can be laid within the drainage paths or temporary collection pits and pumping equipment can be installed to enhance the diversion and drainage effect. By first dividing the area into zones, then sealing them off, and finally diverting water, subsequent excavation and backfilling operations can be carried out independently and in a controlled manner within each zone, avoiding interference from surface water to the foundation pit and fill material.

[0045] Furthermore, the fill layer is excavated and the foundation is trimmed section by section according to the construction zone. The compaction of the trimmed foundation is then tested, and areas that fail the test are cyclically treated until they meet the requirements. Specifically, the fill layer is excavated section by section according to the established construction sequence to the designed replacement depth, avoiding excessive exposure and prolonged soaking of the foundation caused by simultaneous excavation of the entire area. After excavation, the exposed foundation is manually trimmed, removing loose soil, loose particles, and local disturbance layers to make the foundation flat and compacted. The compaction of the trimmed foundation is then tested, for example, using a cone penetration test to obtain the number of blows per 30cm penetration, to evaluate the compaction and bearing capacity of the foundation. When the test results indicate that a local foundation does not meet the requirements, the area is subjected to repeated excavation, replacement, and compaction, and the test is repeated until the area meets the requirements before proceeding to the subsequent backfilling process. Through quantitative testing and cyclical treatment, it is ensured that the replacement layer sits on a foundation with qualified bearing capacity and uniform stability.

[0046] Based on this, the brick slag filler material to be backfilled is graded and segmented according to its particle size, and the moisture content and gradation of the segmented brick slag filler material are pre-adjusted. Specifically, screening equipment such as vibrating screens and drum screens can be used to screen the brick slag filler material into different particle size segments according to the set particle size limits, so that large-sized blocks, medium-sized materials and fine materials are separated from each other, avoiding the concentration of large materials and the segregation of coarse and fine materials. The moisture content of the segmented brick slag filler material is measured, and water is sprayed to increase humidity or spread and dried according to the optimum moisture content, so that the moisture content is adjusted to within the allowable deviation range of the optimum moisture content. At the same time, the materials of each segment are mixed in proportion according to the target gradation, and the proportion of coarse, medium and fine particles is adjusted so that the gradation curve meets the requirements, thereby providing a good material foundation for subsequent compaction.

[0047] Subsequently, the adjusted brick slag filler is backfilled in layers and spread according to the construction zones to form a layer body. Specifically, the brick slag filler is backfilled in layers according to the set loose-lay thickness. The thickness of each layer is such that it can achieve the designed density after compaction and facilitate uniform rolling. Spreading is carried out according to the construction zones, and a reasonable material distribution method is used to ensure that the filler is evenly distributed within the zones. After spreading, the layer is leveled, and the spread flatness and loose-lay thickness deviation are controlled to form a layer body with uniform thickness and a smooth surface, creating conditions for uniform rolling.

[0048] The layer was compacted in sections, with compaction degree monitored in real time during the process. Specifically, the paved layer was compacted in sections according to construction zones, using a combination of compaction energy from weak to strong. Static compaction was first used to initially stabilize the layer, followed by progressively higher energy compaction, controlling the compaction speed to gradually densify the filler. During compaction, monitoring points were set at a predetermined density, and the compaction degree was monitored in real time with each compaction pass to promptly grasp the increase in layer compaction degree, providing a basis for subsequent grading and cyclical correction.

[0049] Based on real-time compaction measurements, areas that do not meet the requirements are graded and cyclically corrected until the compaction meets the requirements. Specifically, a design compaction degree and grading thresholds are pre-set, and the compaction degree of the test points is divided into different levels such as qualified, locally under-compacted, and severely under-compacted. For under-compacted areas of different levels, different correction measures of varying intensities are taken, such as local compaction or excavation and repaving. The corrected areas are then retested, and the judgment and correction are cyclically executed until the compaction degree of all test points meets the design compaction degree requirements, ensuring that the compaction quality of the layer is uniform and meets the standards.

[0050] After the lower layer passes the acceptance test, the interlayer interface is sequentially roughened, cleaned, and moistened. Fine brick slag is then sprinkled on the interlayer interface before the upper layer is laid. Specifically, after the lower layer passes the compaction test, its top surface is roughened to create a certain roughness, thereby increasing the mechanical interlocking force between the upper and lower layers. Subsequently, the floating slag generated from roughening is cleaned and dust is blown away to keep the interface clean. Then, the top surface is moistened with water to ensure that the interface is in a suitable moisture content without standing water. Finally, a layer of fine brick slag is evenly sprinkled on the interface, and the upper layer is laid while the fine brick slag is kept loose, thereby avoiding smooth and weak surfaces between the layers and enhancing the interlayer bonding.

[0051] After all layers are constructed, overall bearing capacity and overall uniformity testing are conducted. Specifically, overall bearing capacity testing is performed on the replaced layers, for example, by applying vertical loads in stages using a plate load test, measuring settlement, and calculating the characteristic value of the foundation bearing capacity. At the same time, overall uniformity testing is performed on the replaced layers, for example, by obtaining the number of blows at each measuring point using a hammer penetration test, calculating the average value and coefficient of variation, and comprehensively evaluating the compaction uniformity of the replaced layers to ensure that the overall replaced layers meet the design requirements.

[0052] This construction method divides the replacement area into multiple construction zones and sets closed compaction boundaries and external drainage paths, achieving organized drainage of surface water and avoiding disordered confluence at the excavation face and softening of the foundation. By excavating section by section, quantitatively testing the foundation, and cyclically treating, it ensures uniform and qualified foundation bearing capacity. By implementing particle size classification, moisture content pre-adjustment, and gradation pre-adjustment for the brick and rubble filler, it provides uniform and qualified materials for high-quality compaction. Through layered paving, segmented compaction, and real-time compaction degree testing and cyclical correction with each compaction pass, it ensures uniform and qualified compaction quality for each layer. Interlayer roughening, cleaning, wetting, and spreading of fine brick and rubble enhances interlayer bonding and avoids weak interlayers. Finally, the overall bearing capacity and uniformity testing quantitatively accepts the quality of the replacement layer. This improves the construction quality and foundation bearing capacity of miscellaneous fill layer replacement and repair, reduces differential settlement, and lowers construction risks.

[0053] In an embodiment of the present invention, the steps of dividing the replacement area into multiple construction zones, sealing and compacting the surface layer along the boundary of adjacent construction zones, and excavating drainage paths around each construction zone to divert surface water include: S11, the replacement area is divided into multiple construction zones, each construction zone having a length of 8 to 15m and a width of 4 to 6m; S12, the surface layer is sealed and compacted along the boundary of the adjacent construction zones to block the flow of surface water between adjacent zones; S13, excavate the drainage path around each of the construction zones to divert surface water to outside the construction area along the drainage path.

[0054] Specifically, the replacement area is divided into multiple construction zones, each with a length of 8 to 15 meters and a width of 4 to 6 meters. This size range was determined by comprehensively considering the operational efficiency, drainage control, compaction equipment, and testing requirements of the miscellaneous fill replacement construction. A length of 8 to 15 meters and a width of 4 to 6 meters ensures that excavation, trimming, backfilling, compaction, and testing within each zone can be completed in a short time, reducing the exposure time of the foundation and fill material. It also facilitates closed compaction and external drainage along the zone boundaries, allowing for effective interception and drainage of surface water. If the zones are too long or too wide, the working area within each zone will be too large, resulting in longer excavation exposure time, concentrated compaction and testing workload, and increased difficulty in surface water control. If the zones are too short or too narrow, the number of zones will be too large, increasing the workload of zone boundaries and drainage paths, and reducing construction efficiency. For example, zones can be divided with a length of 10 meters and a width of 5 meters, or, depending on the site topography, with a length of 8 meters and a width of 4 meters, or a length of 15 meters and a width of 6 meters.

[0055] The surface soil is sealed and compacted along the boundary of adjacent construction zones to prevent surface water flow between adjacent zones. The zone boundary is the line between two adjacent construction zones. After the zones are divided and before excavation, the surface soil is sealed and compacted along this line using equipment such as small rollers, plate compactors, or vibratory rammers, forming a compaction zone of moderate width (e.g., 0.5 to 1 m). This compaction zone increases the density and reduces the permeability of the surface soil, preventing surface water from flowing across the boundary into adjacent zones, thus ensuring that each zone has a relatively independent drainage environment during excavation and backfilling. The width and number of compaction passes can be determined based on the properties of the surface soil and the amount of water accumulation on site.

[0056] Drainage paths are excavated around each construction zone to divert surface water outside the construction area. These paths can be drainage ditches or intercepting ditches excavated around the perimeter of each construction zone, or temporary drainage channels utilizing existing low-lying terrain. The drainage paths should have a certain longitudinal slope (e.g., not less than 0.3%) and connect to existing drainage facilities, collection wells, or sedimentation tanks outside the construction area. After collecting in the drainage paths, surface water flows by gravity down the slope to outside the construction area; in areas where gravity flow is not possible, collection pits can be constructed and equipped with pumps for drainage. By using drainage paths around the zones, surface water is intercepted and diverted before entering the work surface, keeping the work surface dry.

[0057] Through the above technical solution, this application establishes a surface water control system of "zone closure + peripheral interception and drainage" by limiting the length and width of construction zones, sealing and compacting along the zone boundaries, and excavating drainage paths on the perimeter. The sealing and compaction of zone boundaries blocks the cross-flow of surface water between adjacent zones, while the peripheral drainage paths systematically divert surface water outside the construction area, preventing surface water from entering the excavation face and backfill layer. This reduces the soaking, scouring, and softening of the foundation and fill material by water at the source, ensuring the working conditions and quality of the miscellaneous fill replacement construction.

[0058] In an embodiment of the present invention, before the step of excavating and repairing the miscellaneous fill layer section by section according to the construction zone, the method for replacing and repairing the miscellaneous fill layer further includes: S101, Before the current construction zone is excavated, the boundary of the adjacent construction zones is kept closed and compacted so that the surface water in the adjacent zones does not flow into the current construction zone. S102, using the partition boundary as the paving control boundary, constrains the backfilling and paving range of the brick slag filler.

[0059] Specifically, before excavating the current construction zone, the boundaries of adjacent construction zones should be kept closed and compacted. That is, when excavating a construction zone, the closed and compacted zone at the boundary of its adjacent zone remains intact and undamaged. This prevents any surface water that may be present in the adjacent zone from flowing into the currently under-excavation zone. In this way, the current zone can remain relatively dry during excavation, preventing surface water from flowing into the pit and soaking the foundation. If it is necessary to partially cross the boundary of a zone for construction purposes, the closed and compacted state should be restored promptly afterward. The closed and compacted state can be maintained through regular inspections and re-compaction.

[0060] The zoning boundaries serve as paving control boundaries, constraining the backfilling and paving range of brick ash filler. During the backfilling and paving stage, the zoning boundaries not only serve a drainage function but also act as control boundaries for the paving operation. Construction personnel use these zoning boundaries to limit the backfilling and paving range of brick ash filler to within each zoning zone, preventing the filler from crossing the boundary and paving into adjacent zones. This ensures independent construction and acceptance for each zone, making the paving range and thickness easily controllable. Marking stakes, hanging lines, or spray-painted markings can be set on the zoning boundaries as boundary control for paving and compaction.

[0061] Through the above technical solution, this application enables the zoning boundary to play a controlling role in both the excavation and backfilling stages: maintaining a closed and compacted state during the excavation stage to prevent surface water from adjacent zoning zones from flowing into the current zoning zone; and serving as a paving control boundary during the backfilling stage to constrain the paving range of the fill material. This ensures both the independence and dryness of the construction environment for each zoning zone, and guarantees the accuracy of the paving range and uniform thickness of the layered backfilling, laying the foundation for achieving uniform compaction standards in the subsequent process.

[0062] In an embodiment of the present invention, the step of excavating and removing the miscellaneous fill layer and repairing the foundation section by section according to the construction zone includes: S21, following the direction from high to low and from the far end to the transportation channel, excavate the miscellaneous fill layer section by section to the designed replacement depth; S22, Manually trim the exposed base after excavation, remove loose soil and loose particles, and ensure that the flatness deviation of the base is no more than 20mm. S23, the compactness of the modified substrate is tested by hammer penetration to obtain the number of hammer blows required for every 30cm penetration of the substrate.

[0063] Specifically, the excavation proceeds from high to low and from the far end towards the transportation corridor, removing the miscellaneous fill layer section by section to the designed replacement depth. Excavating from high to low allows surface water and construction water to collect downwards and drain through drainage paths, preventing disorderly flow within the work area. Excavating from the far end towards the transportation corridor avoids repeated compaction of the prepared foundation by construction machinery and transport vehicles, reducing foundation disturbance and allowing the excavated miscellaneous fill to be directly transported away, shortening the transportation route. Excavation is carried out section by section, treating and backfilling each section as it is completed within a construction zone or a work segment within a zone, avoiding large-area simultaneous exposure.

[0064] The exposed base after excavation is manually trimmed. Because mechanical excavation may disturb the base or leave loose soil when approaching the design depth, a small thickness is reserved for manual trimming when excavating to near the design replacement depth. This involves removing loose soil, loose particles, tree roots, and debris to ensure a smooth and compacted base surface. The base flatness deviation should not exceed 20mm, meaning the height difference between any two points on the base surface or the deviation from the design elevation should be controlled within 20mm. This ensures uniform thickness and stress distribution of the subsequent backfill layer, preventing uneven layer thickness and differential settlement due to an uneven base.

[0065] The compaction of the prepared foundation was tested using a driven cone penetration test (DCP). DCP is an in-situ testing method that uses a hammer of specified weight to penetrate the soil from a specified distance, recording the number of blows required to reach a certain depth (30cm in this case). A higher blow count indicates a denser foundation soil and higher bearing capacity. Test points can be arranged in a grid along the foundation, for example, several points every 5 to 10 meters or in each construction zone, with increased density in weak areas. Obtaining the number of blows required for every 30cm penetration provides a quantitative basis for determining the foundation's suitability.

[0066] Through the above technical solutions, this application ensures that the excavation of the fill layer and the treatment of the foundation are orderly and controllable by specifying the excavation sequence, foundation trimming standards, and quantitative testing methods. The excavation sequence from high to low and from the far end to the transportation channel reduces disorderly water flow and mechanical disturbance to the foundation; manual trimming and 20mm flatness control ensure the flatness of the foundation; and hammer penetration testing provides a quantitative indicator for the foundation compaction, enabling the foundation quality to be objectively evaluated and providing a reliable foundation for subsequent cyclic treatment and backfilling construction.

[0067] In an embodiment of the present invention, the step of performing cyclic processing on the substrate region that fails the test until it passes includes: S24, when the number of hammer blows on the substrate is less than 15 blows / 30cm, the corresponding substrate area is determined to be a defective area; S25, re-excavating the unqualified area for a second time, excavating downward to the top surface of the dense layer, backfilling with the brick slag filler and compacting by rolling; S26, re-measuring the number of blows in the treated unqualified area; if the number of blows is still less than 15 blows / 30cm, repeating the steps of secondary re-excavation, backfilling rolling and re-measurement until the number of blows is not less than 15 blows / 30cm.

[0068] Specifically, 15 blows / 30cm is used as the qualification criterion for the compactness of the substrate. When the number of blows at a detection point is less than 15 blows / 30cm, it indicates that the compactness of the substrate soil in this area is insufficient and the bearing capacity is low. Direct backfilling of the replacement layer on it may cause differential settlement or local instability, so the substrate area corresponding to the detection point is determined as an unqualified area. The threshold of 15 blows / 30cm is a quantitative limit set based on engineering experience of miscellaneous fill substrates and the bearing requirements of the replacement layer, which facilitates rapid on-site determination. The qualification standard is that the number of blows is not less than 15 blows / 30cm.

[0069] Secondary re-excavation is performed on the unqualified area, and over-excavation is carried out downward to the top surface of the dense layer. That is, the area determined to be unqualified is re-excavated, and the loose and weak soil is further excavated downward until the top surface of the relatively dense soil layer (the top surface of the dense layer) is exposed. Then brick slag filler that has been graded and pre-conditioned is backfilled, and compaction is carried out by rolling with suitable rolling equipment, so that the substrate in this area is replaced and reinforced. The over-excavation depth is determined according to the thickness of the weak soil on site, and shall be subject to excavation to the top surface of the dense layer.

[0070] Re-measure the number of blows in the unqualified area after treatment. Re-measurement points can be arranged at the center and edge of the treated area. If the re-measured number of blows is still less than 15 blows / 30cm, it indicates that the weak layer in this area has not been completely removed or the rolling is insufficient, so the cycle of secondary re-excavation, backfilling rolling and re-measurement is repeated until the re-measured number of blows is not less than 15 blows / 30cm, then the area can be determined as qualified. Through the closed-loop cycle of "detection - determination - treatment - re-measurement", it is ensured that the next backfilling process is carried out only after every substrate area meets the qualification standard.

[0071] Through the above technical solution, the present application takes 15 blows / 30cm as the quantitative qualification limit, implements cyclic treatment of re-excavation replacement and rolling compaction for the unqualified substrate area, and ensures that the compactness of all substrate areas meets the requirements through closed-loop control of re-measurement. This method avoids the problem of omission or incomplete treatment of weak substrate areas, eliminates the hidden danger of differential settlement of the replacement layer from the source, and significantly improves the uniformity and reliability of the foundation where the replacement layer is located.

[0072] In an embodiment of the present invention, the step of grading the brick slag filler to be backfilled according to particle size thereof, and performing moisture content pre-conditioning and gradation pre-conditioning on the graded brick slag filler comprises: S31, the brick slag filler is divided into two grades according to the first particle size limit of 150mm and the second particle size limit of 20mm, so that the large material with a particle size greater than 150mm, the medium material with a particle size of 20 to 150mm and the fine material with a particle size less than 20mm are separated from each other. S32, Determine the moisture content of the graded brick slag filler; S33, when the moisture content is lower than the lower limit of the optimum moisture content, the brick slag filler is uniformly sprayed with water and left to stand for 2 to 4 hours after spraying. S34, when the moisture content is higher than the upper limit of the optimum moisture content, the brick slag filler is spread out and dried, with a spreading thickness of 300 to 400 mm, and is turned over once every 2 hours; S35, retest the moisture content until the moisture content is within ±2% of the allowable deviation of the optimum moisture content; S36, Adjust the gradation of the brick slag filler so that the proportion of particles with a diameter greater than 40mm is 30% to 40%, the proportion of particles with a diameter of 20 to 40mm is 25% to 35%, and the proportion of particles with a diameter less than 20mm is 30% to 40%, and the non-uniformity coefficient is not less than 5 and the curvature coefficient is 1 to 3.

[0073] Specifically, screening equipment such as vibrating screens and drum screens are used to classify the brick slag filler into two grades using two screen openings: 150mm and 20mm. The first grade, with 150mm as the boundary, separates large pieces with a particle size greater than 150mm. The second grade, with 20mm as the boundary, separates the remaining material into medium-grade material with a particle size of 20 to 150mm and fine material with a particle size less than 20mm. This two-stage classification separates large, medium, and fine materials, facilitating subsequent separate processing (crushing large pieces and retaining fine materials) and proportional mixing to adjust the gradation, thus avoiding the concentration of large pieces and the segregation of coarse and fine materials.

[0074] The moisture content of the brick slag filler after grading should be determined. The moisture content of each grade of material can be measured separately using a drying method or a rapid moisture content meter to provide a basis for moisture content pre-adjustment. The optimal moisture content can be determined through a compaction test.

[0075] When the moisture content is below the lower limit of the optimum moisture content (i.e., below the optimum moisture content - 2%), the filler is too dry, and there is a lack of sufficient lubricating water film between the particles, making compaction difficult. Therefore, the brick slag filler is uniformly sprayed with water. After spraying water, it is left to stand for 2 to 4 hours to allow the water to fully wet the particles, avoiding an uneven state where the surface is wet and the inside is dry, and ensuring that the moisture content is uniform and meets the requirements.

[0076] When the moisture content is higher than the upper limit of the optimum moisture content (i.e., higher than the optimum moisture content + 2%), the fill material is too wet. During compaction, "springy soil" or increased pore water pressure may occur, making it difficult to improve the compaction degree. Therefore, the brick slag fill material is spread out and dried, with a spreading thickness of 300 to 400 mm. It is turned over every 2 hours to accelerate the evaporation of moisture and make the moisture content decrease evenly.

[0077] After watering or drying, retest the moisture content. If it is still not within the allowable deviation range of ±2% of the optimum moisture content, continue to take corresponding measures and retest until the moisture content is within the allowable deviation range.

[0078] Adjust the gradation of the brick slag filler. Mix the different grades of material according to the mass ratio, so that the proportion of particles larger than 40mm is 30% to 40%, particles with a diameter of 20 to 40mm is 25% to 35%, and particles with a diameter smaller than 20mm is 30% to 40%, with a uniformity coefficient of not less than 5 and a curvature coefficient of 1 to 3. Coarse particles larger than 40mm form the skeleton, particles of 20 to 40mm fill the gaps in the skeleton, and fine particles smaller than 20mm further fill and coat the coarse particles, forming a good gradation and improving the density and strength after compaction. A uniformity coefficient of not less than 5 indicates good gradation (wide particle size distribution), and a curvature coefficient of 1 to 3 indicates a continuous particle gradation curve without gaps or missing particles. During adjustment, medium-grade material can be further sieved into two grades: 40 to 150mm and 20 to 40mm, using a 40mm sieve, to facilitate mixing according to the target proportion.

[0079] Through the above technical solution, this application transforms the incoming brick slag filler from a state of mixed composition, significant particle size variations, and large moisture content deviations into qualified backfill with clearly defined particle size classifications, suitable moisture content, and good gradation by implementing two-stage grading, moisture content pre-adjustment, and gradation pre-adjustment. Moisture content pre-adjustment ensures effective compaction, while gradation pre-adjustment ensures a reasonable combination of the skeleton and filler particles after compaction, providing a uniform and controllable material foundation for subsequent layered paving and compaction, significantly improving the compaction quality and uniformity of the replacement layer.

[0080] In embodiments of the present invention, after classifying and grading the brick slag fill material to be backfilled according to its particle size, and performing moisture content pre-adjustment and gradation pre-adjustment on the graded brick slag fill material, the method for replacing and repairing miscellaneous fill layers further includes: S301, collect the fine material with a particle size of less than 20mm, and retain a portion of the fine material as spreading material for the interlayer interface; S302, crush the large pieces of material with a particle size greater than 150mm, and then re-implement the two-stage grading until all the material particles are no larger than 150mm. S303, when the proportion of particles with a diameter less than 20mm in the brick slag filler is less than 30%, the remaining fine material is recycled back into the brick slag filler until the gradation meets the requirements.

[0081] Specifically, the fine particles with a diameter less than 20mm obtained from the two-stage sorting are collected and piled up separately, with a portion reserved for use as interlayer interface spreading material. The interlayer interface spreading material must be fine particles with a diameter no greater than 20mm, and the amount can be estimated based on the interlayer spreading thickness (8 to 12mm) and interface area. The reserved fine particles should be stored separately, protected from rain and dirt, and kept loose, clean, and with appropriate moisture content for use in interlayer spreading.

[0082] Large pieces with a particle size greater than 150mm should be crushed. Equipment such as hydraulic breakers and jaw crushers can be used to crush large pieces to below 150mm. After crushing, the material is then re-sorted in two stages (150mm and 20mm) to classify the crushed products into medium-grade or fine-grade materials. Pieces still larger than 150mm are crushed and re-sorted until all materials have a particle size no larger than 150mm. Through this crushing cycle, large pieces are utilized, preventing them from forming voids, gaps, or stress concentrations in the backfill layer.

[0083] When the proportion of particles smaller than 20mm in the brick slag filler is less than 30%, the remaining fine material should be recycled back into the brick slag filler until the gradation meets the requirements. Since some fine material is retained for interlayer spreading, the proportion of fine material in the recycled filler may be lower than the target lower limit of 30%. In this case, while ensuring the allowance for interlayer spreading, the fine material (preferably using excess fine material exceeding the allowance for spreading) should be recycled back into the brick slag filler to ensure that the proportion of particles smaller than 20mm reaches more than 30%, until the gradation meets the requirements. If the total amount of fine material is insufficient to simultaneously meet the requirements for spreading material and gradation recycling, the gradation requirements should be prioritized, and the spreading material can be supplemented through further screening or crushing.

[0084] Through the above technical solutions, this application achieves full particle size utilization and gradation compliance of brick slag filler by collecting, retaining, and re-mixing fine materials, and by crushing and recycling large materials, after grading, sorting, and pre-adjusting. Retaining fine materials provides dedicated material for interlayer spreading; crushing large materials eliminates the adverse effects of oversized particles; and re-mixing fine materials ensures that the gradation meets requirements. This balances the compaction quality of the backfill layer and the interlayer bonding quality, improving the utilization rate of brick slag filler and reducing waste and secondary transportation.

[0085] In an embodiment of the present invention, the steps of backfilling the adjusted brick slag filler in layers, spreading it according to construction zones to form a layer body, performing segmented compaction on the layer body, and detecting the compaction degree in real time during the compaction process include: S41, the brick slag filler is divided into multiple layers for backfilling, with each layer having a loose thickness of 250 to 280 mm; S42, the brick slag filler is laid in a quincunx pattern according to the construction zone, with a material pile spacing of 2 to 3m. After laying, it is leveled so that the flatness deviation of the laying is no more than 15mm and the loose thickness deviation is controlled within ±5mm. S43, the layer is first subjected to static compaction once, then medium-energy compaction twice, and then high-energy compaction three to five times, with a compaction speed of 1.5 to 2.2 km / h; S44, during the compaction process, every 60m 2 up to 80m 2 Set up a test point and perform real-time compaction testing on the test point as the number of compaction passes increases.

[0086] Specifically, the brick slag filler is backfilled in multiple layers, with each layer having a loose thickness of 250 to 280 mm. Loose thickness refers to the thickness of the layer after spreading and before compaction. A loose thickness of 250 to 280 mm ensures a suitable compaction thickness after compaction, guaranteeing that compaction energy is effectively transferred to the bottom of the layer while avoiding under-compaction at the bottom due to an excessively thick layer or low construction efficiency due to an excessively thin layer. The loose thickness of each layer should be consistent to facilitate uniform compaction.

[0087] The brick slag filler is laid in a staggered, quincunx pattern according to the construction zones. This pattern means the filler piles are arranged in a staggered, quincunx pattern on the plane, with a spacing of 2 to 3 meters. This ensures a uniform distribution of coarse and fine particles after paving and leveling, preventing localized segregation caused by concentrated piles. After paving, leveling is performed to ensure a flatness deviation of no more than 15mm and a loose-lay thickness deviation within ±5mm. A flatness deviation of no more than 15mm ensures a smooth surface and uniform stress during compaction; a loose-lay thickness deviation of ±5mm ensures uniform layer thickness, avoiding uneven compaction caused by excessively thick or thin areas.

[0088] The compaction of the layer is carried out from weak to strong. First, one pass of static compaction is applied to initially stabilize the loose layer, eliminating surface looseness and local voids. Then, two passes of medium-energy compaction are applied to further densify the layer. Finally, three to five passes of high-energy compaction are applied to achieve the designed compaction degree. The compaction speed is 1.5 to 2.2 km / h. Too fast a compaction speed will result in a short compaction time per unit area, insufficient energy transfer, and poor compaction effect; too slow a speed will result in low construction efficiency. The progressive compaction method, from weak to strong and with a increasing number of passes, avoids applying high energy at the beginning, which could cause shear damage or "over-compaction" on the layer surface, ensuring a uniform increase in compaction degree.

[0089] Every 60m during the compaction process 2 up to 80m 2Set up a monitoring point and monitor the compaction degree at the monitoring point in real time with each compaction pass. The monitoring point can be tested using the sand cone method, nuclear density meter, or nuclear-free density meter. Track the increase in compaction degree at each monitoring point with each compaction pass. Real-time monitoring allows construction personnel to promptly grasp the compaction status of different parts of the layer, and to take timely subsequent grading and cyclical correction measures for areas with slow or insufficient compaction growth, avoiding rework due to local undercompaction only after all compaction is completed.

[0090] Through the aforementioned technical solutions, this application establishes a refined construction control system for layered paving and segmented compaction by specifying the loose paving thickness, quincunx pattern of the paving material, paving flatness and thickness deviation, compaction energy combination and speed, and real-time compaction detection with each compaction pass. Uniform paving and a reasonable compaction process ensure uniform increase in compaction degree across all parts of the layer. Real-time detection allows under-compacted areas to be identified promptly during construction, providing accurate real-time data for grading and cyclical correction, thereby ensuring that the compaction quality of each layer meets the standards.

[0091] In an embodiment of the present invention, the step of classifying and cyclically correcting areas that do not meet the requirements based on the real-time detected compaction degree until the compaction degree meets the requirements includes: S61, set the design compaction degree and a second threshold that is 3 percentage points lower than the design compaction degree; S62, when the compaction degree of the test point is not less than the design compaction degree, the test point is deemed qualified; S63, when the compaction degree of the detection point is not less than the second threshold and less than the design compaction degree, the detection point is determined to be locally undercompacted, the detection point is marked, and the area within 1m of the detection point is marked. Apply local compaction 2 to 4 times to a 1m area, and retest the compaction degree at the test point; S64, when the compaction degree of the detection point is less than the second threshold, the detection point is determined to be severely under-compacted, and the area around the detection point within 2m is excavated. From the 2m area to the top surface of the lower layer, the paving is repaved and compacted, and the compaction degree is retested at no less than 3 test points in this area; S65, repeat the graded judgment and cyclic correction for the corrected area until the compaction degree of all test points is not less than the design compaction degree.

[0092] Specifically, a design compaction degree and a second threshold are set. The design compaction degree, determined by the design documents (e.g., 94%), refers to the minimum compaction degree that should be achieved after the layer is compacted. The second threshold is 3 percentage points lower than the design compaction degree (e.g., 91%), used to differentiate the severity of undercompaction. Using 3 percentage points as the grading boundary ensures both the economy of applying different treatment measures to mild and severe undercompaction, and the controllability of the corrected layer quality.

[0093] When the compaction degree at a test point is not less than the design compaction degree, the test point is deemed qualified and requires no further treatment. Qualified test points serve as the basis for layer acceptance.

[0094] When the compaction degree at the test point is not less than the second threshold but less than the design compaction degree, it indicates that although the point is close to being qualified, it is slightly insufficient, belonging to local under-compaction. At this time, mark the test point and extend the compaction degree within a 1m radius around it. Apply localized compaction 2 to 4 times to a 1m area, and retest the compaction degree of the test point after compaction. Localized compaction is highly targeted, requires less work, and is suitable for rapid correction of slightly under-compacted areas.

[0095] When the compaction degree at the test point is less than the second threshold, it indicates that the compaction degree at that point is significantly insufficient, constituting severe undercompaction. In this case, localized compaction alone is insufficient to ensure that the bottom of the layer also achieves density; therefore, the area within 2 meters of the test point is excavated. From a 2m area to the top surface of the lower layer (i.e., excavating to the top surface of the already inspected and approved lower layer), the brick slag filler was repaved and compacted, and the compaction degree was retested at no less than 3 test points in this area. By expanding the excavation area and increasing the number of test points, it was ensured that the severely under-compacted areas were thoroughly corrected and that the quality of the corrected areas was uniform.

[0096] The graded judgment and cyclical correction are repeated for the corrected area. That is, if the retest results still do not meet the requirements, the process is repeated according to S63 or S64 until the compaction degree of all test points is not less than the design compaction degree. Through the closed-loop cycle of "testing-judgment-correction-retesting", the compaction quality of the layer is ensured to meet the standards in all aspects.

[0097] Through the aforementioned technical solution, this application categorizes under-compacted areas into two levels—locally under-compacted and severely under-compacted—by setting a design compaction degree and a second threshold. It then employs graded correction measures, including localized recompaction and excavation / resurfacing, respectively. This is further supplemented by cyclical retesting and closed-loop control, achieving accurate identification and on-demand treatment of compaction defects. This method avoids excessive rework through a "one-size-fits-all" approach and prevents incomplete treatment of severely under-compacted areas, thereby improving construction efficiency and ensuring the uniformity and reliability of layer compaction.

[0098] In an embodiment of the present invention, after the lower layer passes acceptance testing, the steps of sequentially roughening, cleaning, and wetting the interlayer interface, and then spreading fine brick slag on the interlayer interface before laying the upper layer include: S71, roughen the top surface of the layer below, with a roughening depth of 6 to 8 mm; S72, sweep away the floating debris generated by the roughening process and blow away any residual dust; S73, Sprinkle water to moisten the top surface until the moisture content is 8% and there is no visible water on the surface; S74, uniformly spread fine brick slag with a thickness of 8 to 12 mm and a particle size of no more than 20 mm at the interlayer interface, and spread the upper layer while keeping the spread fine brick slag loose. S75, or, spraying a neat cement paste with a water-cement ratio of 0.4 to 0.5 at the interlayer interface at a spraying rate of 0.4 kg / m³. 2 The layer above is laid before the cement paste has initially set. After all the aforementioned layers have been constructed, the steps for conducting overall bearing capacity testing and overall uniformity testing include: S81, apply vertical loads in stages up to not less than 360 kPa and measure settlement, the equivalent characteristic value of foundation bearing capacity is not less than 180 kPa; S82, the overall uniformity of the replacement layer is tested by hammer penetration testing, so that the average number of hammer blows is not less than 20 blows / 30cm and the coefficient of variation is not greater than 0.15.

[0099] Specifically, the top surface of the lower layer is roughened to a depth of 6 to 8 mm. The surface of the lower layer is relatively smooth after compaction, and directly laying the upper layer thereafter can easily create a smooth interface and result in low interlayer shear strength. Roughening creates a uniform rough texture on the top surface, increasing the interlayer contact area and mechanical interlocking force. If the roughening depth is too shallow, the effect will be insignificant; if it is too deep, it will disturb the already compacted surface of the layer. Therefore, a depth of 6 to 8 mm is chosen.

[0100] Clean up the scum generated during the roughening process and blow away any residual dust to keep the interface clean and prevent scum and dust from forming weak interlayers or isolation layers between layers.

[0101] The top surface is moistened with water until the moisture content is 8% and there is no standing water. Appropriate interfacial moisture allows for better bonding between the upper and lower layers during compaction, preventing moisture from the upper layer from being absorbed by the dry lower surface and causing poor bonding. The absence of standing water prevents the interface from becoming too wet, forming mud or a "spring" effect. It should be noted that the 8% moisture content here refers to the moisture control at the interlayer interface, which is a different control index from the optimum moisture content used for compaction.

[0102] Fine brick fragments with a thickness of 8 to 12 mm and a particle size not exceeding 20 mm are evenly spread at the interlayer interface and laid on the upper layer while remaining loose. The fine brick fragments embed between the upper and lower layers, acting as an interlocking bond and filler, forming a transitional bonding layer after compaction, enhancing the interlayer shear strength and overall integrity. The fine brick fragments are laid loosely (without pre-compacting) on ​​the upper layer, allowing them to interlock with the upper filler during compaction, achieving effective interlayer bonding.

[0103] As another approach, a cement paste with a water-cement ratio of 0.4 to 0.5 can be sprayed at the interlayer interface at a rate of 0.4 kg / m³. 2 The upper layer is laid before the cement slurry initially sets. The cement slurry forms a thin bonding layer at the interface, which, after hardening, bonds the upper and lower layers together. A water-cement ratio of 0.4 to 0.5 ensures good fluidity and bond strength of the slurry, with a spraying rate of 0.4 kg / m³. 2 To ensure a thin and uniform layer, the paving should be completed before initial setting to guarantee full bonding between the upper filler and the grout. The two methods mentioned above—spreading fine brick fragments and spraying cement slurry—are alternative solutions. During construction, either method should be selected based on site conditions and design; both can achieve the goal of enhanced interlayer bonding.

[0104] After all layers of construction are completed, an overall bearing capacity test is conducted. A plate load test is used, applying vertical loads in stages up to a minimum of 360 kPa, and measuring the settlement under each load level. After stabilization according to specifications, load-settlement curves are plotted, and the calculated characteristic value of the foundation bearing capacity is no less than 180 kPa. The overall bearing capacity test verifies that the replacement layer meets the design requirements for foundation bearing capacity.

[0105] The overall uniformity of the replacement layer was tested using a hammer penetration test. Multiple measuring points were arranged in a grid pattern on the surface of the replacement layer. The number of blows required for each 30cm penetration at each measuring point was recorded using the hammer penetration test. The average number of blows and the coefficient of variation were calculated, ensuring that the average number of blows was not less than 20 blows / 30cm and the coefficient of variation was not greater than 0.15. The average number of blows reflects the overall density of the replacement layer, while the coefficient of variation reflects the uniformity of density. A coefficient of variation not greater than 0.15 indicates that the density dispersion of the replacement layer is small and the uniformity is good, avoiding localized weak areas.

[0106] Through the above technical solutions, this application significantly enhances the bond between upper and lower layers by interlayer roughening, cleaning, wetting, and sprinkling fine brick debris (or spraying cement slurry) interface treatment, thus avoiding the formation of weak interlayer layers. The overall bearing capacity test of the plate load test and the overall uniformity test of the hammer penetration test are used to quantitatively verify the bearing capacity and uniformity of the replacement layer, ensuring that the replacement layer as a whole meets the design requirements and provides a uniform, stable, and reliable foundation for the superstructure.

[0107] The following example will provide a more detailed explanation of the above technical solution: During the replacement and repair of miscellaneous fill layers in a certain site construction project, the engineering team faced challenges such as the complex composition and loose structure of the fill, the easy infiltration of surface water, the weak and uneven foundation, and the difficulty in controlling the compaction quality of the replacement layer. To solve these problems, the construction team adopted this method.

[0108] First, the replacement area is divided into multiple construction zones, each 12m long and 5m wide. Along the boundaries of adjacent construction zones, a small roller is used to compact the surface layer, creating a compacted zone approximately 0.8m wide to prevent surface water from flowing between adjacent zones. Drainage ditches are excavated around each construction zone, with a longitudinal slope of at least 0.3%, to divert surface water to sedimentation tanks outside the construction area. Before the current construction zone is excavated, the boundaries of adjacent zones are kept compacted to prevent surface water from flowing into the current zone. Simultaneously, the zone boundaries are used as paving control boundaries, marked with lines to constrain the backfilling and paving range of the brick and rubble filler.

[0109] Secondly, following a direction from high to low and from the far end towards the transportation corridor, the miscellaneous fill layer was excavated section by section to the designed replacement depth. The exposed foundation after excavation was manually trimmed, removing loose soil and particles; the maximum measured deviation in foundation flatness was 15mm. The trimmed foundation underwent compaction testing using a cone penetration test, obtaining the number of blows required for every 30cm penetration. During the test, a section was found to have a blow count of 11 blows / 30cm, deemed an unqualified area. This area underwent secondary excavation, over-excavating down to the top of the compacted layer, backfilling with pre-mixed graded brick slag filler, and compacting it. A retest showed a blow count of 18 blows / 30cm, deemed acceptable. Through a cycle of testing, treatment, and retesting, all foundation areas were ensured to be qualified.

[0110] Further, the brick slag filler to be backfilled is graded and classified according to its particle size. A vibrating screen with two screen apertures of 150mm and 20mm is used for two-stage classification, so that large materials with a particle size larger than 150mm, medium materials with a particle size of 20 to 150mm and fine materials with a particle size smaller than 20mm are separated from each other. The large materials with a particle size larger than 150mm are crushed, and reclassified after crushing until the particle size of all materials is not larger than 150mm. The moisture content of the classified brick slag filler is measured, and the optimal moisture content is determined to be 12% through a compaction test, with an allowable deviation range of 10% to 14%. The actually measured moisture content is 8%, which is lower than the lower limit of 10%, so water is uniformly sprinkled on the brick slag filler, and the filler is left to stand for 3 hours after sprinkling, and the re-measured moisture content is 11.5%, which is within the allowable deviation range. The gradation is adjusted so that the proportion of particles with a particle size larger than 40mm is 35%, the proportion of particles with a particle size of 20 to 40mm is 30%, and the proportion of particles with a particle size smaller than 20mm is 35%, all of which are within the required range, and the uniformity coefficient is 7 and the curvature coefficient is 1.8. Meanwhile, fine materials with a particle size smaller than 20mm are collected, and part of the fine materials are retained for spreading on the interlayer interface; when the proportion of particles with a particle size smaller than 20mm in the backfill after gradation adjustment is lower than 30%, the surplus fine materials are re-mixed on the premise of ensuring the reserved amount of spreading materials until the gradation meets the requirements.

[0111] Subsequently, the adjusted brick slag filler is backfilled in layers, and the loose paving thickness of each layer is 260mm. The brick slag filler is paved in a plum blossom distribution mode according to construction partitions, the spacing between material piles is 2.5m, and the filler is leveled after paving. The actually measured maximum paving flatness deviation is 12mm, and the loose paving thickness deviation is controlled within ±5mm. The layer is subjected to static pressure rolling for 1 pass first, then rolling with medium energy for 2 passes, and then rolling with high energy for 4 passes, with a rolling speed of 1.8km / h. Every 70m during the rolling process 2 one detection point is arranged, and the compaction degree of the detection point is detected in real time along with the number of rolling passes.

[0112] Grading judgment and cyclic correction are carried out according to the real-time detected compaction degree. The designed compaction degree is set as 94%, and the second threshold is set as 91%. The actually measured compaction degree of a certain detection point is 92%, which is judged as local under-compaction, the detection point is marked, and the area within 1m around it is subjected to local supplementary rolling for 3 passes, and the re-measured compaction degree is 95%, which is judged as qualified. The actually measured compaction degree of another detection point is 88%, which is judged as serious under-compaction, and the area within 2m around the detection point is excavated to the top surface of the lower layer, then re-paved and rolled. The re-measured compaction degrees of 3 detection points in this area are 94.5%, 95.2% and 95.6% respectively, all of which are not less than 94%, so they are judged as qualified. The graded judgment and cyclic correction are repeatedly carried out on the corrected area until the compaction degrees of all detection points are not less than 94%.

[0113] After the lower layer passes acceptance testing, the interlayer interfaces are sequentially roughened, cleaned, and moistened. The roughening depth is 7mm. The resulting slag is swept away, and residual dust is blown off. The top surface is moistened with water until the moisture content is 8% and there is no standing water. A 10mm thick layer of fine brick chips with a particle size no larger than 20mm is evenly spread on the interlayer interface, and the upper layer is laid while the fine brick chips remain loose. This process is repeated layer by layer until all layers are completed.

[0114] After all layers were constructed, overall bearing capacity and uniformity tests were conducted. A plate load test was used, applying vertical loads up to 360 kPa in stages and measuring settlement. The equivalent characteristic value of the foundation bearing capacity was 195 kPa, meeting the requirements. The uniformity of the replacement layer was tested using a hammer penetration test. The average number of blows at each measuring point was 22 blows / 30 cm, and the coefficient of variation was 0.12, meeting the requirements. The overall bearing capacity and uniformity of the replacement layer were both deemed acceptable.

[0115] Using this method, the quality of the base, filling material, layered compaction, interlayer bonding, and overall quality of the miscellaneous fill layer replacement repair in this project were quantitatively controlled and accepted. The bearing capacity and uniformity of the replacement layer met the design requirements, effectively avoiding differential settlement and localized weakness.

[0116] The above description is merely an exemplary embodiment of the present invention and does not limit the scope of protection of the present invention. Any equivalent structural transformations made based on the technical concept of the present invention and the contents of the specification and drawings of the present invention, or direct / indirect applications in other related technical fields, are included within the scope of protection of the present invention.

Claims

1. A method for replacing and repairing miscellaneous fill layers, characterized in that, The method for replacing and repairing the miscellaneous fill soil layer includes: The replacement area is divided into multiple construction zones. The surface layer is sealed and compacted along the boundary of the adjacent construction zones, and drainage paths are excavated around each construction zone to divert and discharge surface water. According to the construction zone, the miscellaneous fill layer is excavated and the foundation is repaired section by section. The compaction of the repaired foundation is tested, and the foundation area that fails the test is cyclically treated until it passes the test. The brick slag filler to be backfilled is classified and graded according to its particle size, and the moisture content and gradation of the graded brick slag filler are pre-adjusted. The adjusted brick slag filler is backfilled in layers and spread according to the construction zones to form a layer. The layer is compacted in segments, and the compaction degree is monitored in real time during the compaction process; Based on the real-time detected compaction degree, areas that do not meet the requirements are graded and cyclically corrected until the compaction degree meets the requirements. After the layer below passes the acceptance test, the interlayer interface is roughened, cleaned and moistened in sequence, and fine brick chips are sprinkled on the interlayer interface before the upper layer is laid. After all the aforementioned layers have been constructed, an overall load-bearing capacity test and an overall uniformity test will be conducted.

2. The method for replacing and repairing miscellaneous fill layers as described in claim 1, characterized in that, The steps of dividing the replacement area into multiple construction zones, sealing and compacting the surface layer along the boundaries of adjacent construction zones, and excavating drainage paths around each construction zone to divert surface water include: The replacement area is divided into multiple construction zones, each of which is 8 to 15m long and 4 to 6m wide. The surface layer is sealed and compacted along the boundary of the adjacent construction zones to block the flow of surface water between adjacent zones; The drainage path is excavated around each of the construction zones to divert surface water to areas outside the construction zone.

3. The method for replacing and repairing miscellaneous fill layers as described in claim 2, characterized in that, Before the step of excavating and repairing the miscellaneous fill layer section by section according to the construction zone, the method for replacing and repairing the miscellaneous fill layer further includes: Before the current construction zone is excavated, the boundaries of the adjacent construction zones are kept closed and compacted to prevent surface water from flowing into the current construction zone. The zoning boundary is used as the paving control boundary to constrain the backfilling and paving range of the brick slag filler.

4. The method for replacing and repairing miscellaneous fill layers as described in claim 1, characterized in that, The steps of excavating and repairing the base layer section by section according to the construction zones include: Following the direction from high to low and from the far end to the transportation corridor, the miscellaneous fill layer was excavated section by section until the designed replacement depth was reached. The exposed base after excavation is manually trimmed to remove loose soil and particles, so that the flatness deviation of the base is no more than 20mm. The compaction of the modified substrate was tested by hammer penetration to obtain the number of hammer blows per 30cm penetration.

5. The method for replacing and repairing miscellaneous fill layers as described in claim 4, characterized in that, The step of cyclically processing the substrate areas that fail the test until they pass includes: When the number of hammer blows on the substrate is less than 15 blows / 30cm, the corresponding substrate area is determined to be a defective area. The unqualified area was excavated a second time, and the excavation was carried out downwards to the top surface of the dense layer. The brick slag filler was then backfilled and compacted. If the number of hammer blows in the treated non-conforming area is still less than 15 blows / 30cm, repeat the second excavation, backfilling, compaction, and retesting until the number of hammer blows is not less than 15 blows / 30cm.

6. The method for replacing and repairing miscellaneous fill layers as described in claim 1, characterized in that, The steps of classifying and grading the brick slag filler material to be backfilled according to its particle size, and pre-adjusting the moisture content and gradation of the graded brick slag filler material include: The brick slag filler is divided into two grades according to the first particle size limit of 150mm and the second particle size limit of 20mm, so that large pieces with a particle size greater than 150mm, medium-grade materials with a particle size of 20 to 150mm and fine materials with a particle size less than 20mm are separated from each other. The moisture content of the graded brick slag filler was determined; When the moisture content is lower than the lower limit of the optimum moisture content, the brick slag filler is uniformly sprayed with water and left to stand for 2 to 4 hours after spraying. When the moisture content is higher than the upper limit of the optimum moisture content, the brick slag filler is spread out and dried, with a spreading thickness of 300 to 400 mm, and is turned over once every 2 hours. Repeat the moisture content test until the moisture content is within ±2% of the optimum moisture content; Adjust the gradation of the brick slag filler so that the proportion of particles with a diameter greater than 40mm is 30% to 40%, the proportion of particles with a diameter of 20 to 40mm is 25% to 35%, and the proportion of particles with a diameter less than 20mm is 30% to 40%, with a non-uniformity coefficient of not less than 5 and a curvature coefficient of 1 to 3.

7. The method for replacing and repairing miscellaneous fill layers as described in claim 6, characterized in that, After the steps of grading and classifying the brick slag fill material to be backfilled according to its particle size, and pre-adjusting the moisture content and gradation of the graded brick slag fill material, the method for replacing and repairing the miscellaneous fill layer further includes: Collect the fine material with a particle size of less than 20 mm, and retain a portion of the fine material as spreading material for the interlayer interface; The large pieces of material with a particle size greater than 150mm are crushed, and the two-stage grading is repeated after crushing until all the material particles are no larger than 150mm. When the proportion of particles with a diameter of less than 20 mm in the brick slag filler is less than 30%, the remaining fine material is recycled back into the brick slag filler until the gradation meets the requirements.

8. The method for replacing and repairing miscellaneous fill layers as described in claim 1, characterized in that, The steps of backfilling the adjusted brick slag filler in layers, spreading it according to the construction zones to form a layer, performing segmented compaction on the layer, and monitoring the compaction degree in real time during the compaction process include: The brick slag filler is divided into multiple layers for backfilling, with each layer having a loose thickness of 250 to 280 mm. The brick slag filler is laid in a quincunx pattern according to the construction zone, with a spacing of 2 to 3 meters between piles. After laying, it is leveled so that the flatness deviation is no more than 15 mm and the loose thickness deviation is controlled within ±5 mm. The layer is first subjected to static compaction once, then medium-energy compaction twice, and finally high-energy compaction three to five times, with a compaction speed of 1.5 to 2.2 km / h; Every 60m during the compaction process 2 up to 80m 2 Set up a test point and perform real-time compaction testing on the test point as the number of compaction passes increases.

9. The method for replacing and repairing miscellaneous fill layers as described in claim 8, characterized in that, The step of classifying and cyclically correcting areas that do not meet the requirements based on the real-time detected compaction degree, until the compaction degree meets the requirements, includes: Set a design compaction degree and a second threshold that is 3 percentage points lower than the design compaction degree; When the compaction degree of the test point is not less than the design compaction degree, the test point is deemed qualified. When the compaction degree at the detection point is not less than the second threshold and is less than the design compaction degree, the detection point is determined to be locally undercompacted, the detection point is marked, and a 1m radius around the detection point is marked. Apply local compaction 2 to 4 times to a 1m area, and retest the compaction degree at the test point; When the compaction degree at the detection point is less than the second threshold, the detection point is determined to be severely undercompacted, and the area within 2 meters of the detection point is excavated. From the 2m area to the top surface of the lower layer, the paving is repaved and compacted, and the compaction degree is retested at no less than 3 test points in this area; The graded judgment and cyclical correction are repeated for the corrected area until the compaction degree of all test points is not less than the design compaction degree.

10. The method for replacing and repairing miscellaneous fill layers as described in claim 8, characterized in that, After the lower layer passes the acceptance test, the interlayer interface is sequentially roughened, cleaned, and moistened, and fine brick slag is sprinkled on the interlayer interface before the upper layer is laid. The top surface of the layer described below is roughened to a depth of 6 to 8 mm; Sweep away any loose material or dust generated during the roughening process; Sprinkle water to moisten the top surface until the moisture content is 8% and there is no visible water on the surface; Fine brick slag with a thickness of 8 to 12 mm and a particle size of no more than 20 mm is evenly spread at the interlayer interface, and the upper layer is laid while the spread fine brick slag is kept loose. Alternatively, a cement paste with a water-cement ratio of 0.4 to 0.5 can be sprayed at the interlayer interface at a rate of 0.4 kg / m³. 2 The layer above is laid before the cement paste has initially set. After all the aforementioned layers have been constructed, the steps for conducting overall bearing capacity testing and overall uniformity testing include: Apply vertical loads in stages up to not less than 360 kPa and measure settlement; the equivalent characteristic value of the foundation bearing capacity is not less than 180 kPa. The uniformity of the replacement layer is tested by hammer penetration testing, ensuring that the average number of hammer blows is not less than 20 blows / 30cm and the coefficient of variation is not greater than 0.15.

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