Construction method of pre-tamping and combined wetting and reinforcing tamping for disorderly high fill site

Abstract

The application belongs to the technical field of geotechnical engineering construction, and specifically provides a disordered high fill site pre-ramming and humidification and dynamic compaction combined construction method, which comprises the following steps: 1) detecting cracks and cavities in the target site; 2) pre-ramming to eliminate cracks and cavities in the target site; 3) water injection and humidification of the target site after pre-ramming; and 4) dynamic compaction construction of the humidified target site until the requirements are met. The application solves the problems of uneven humidification and poor reinforcement effect in the existing dynamic compaction foundation treatment of disordered high fill soil sites, avoids the problem of uneven water injection and humidification caused by uneven upper and lower strata, and has the characteristics of good treatment effect, fast construction speed and small residual settlement.

Description

Technical Field

[0001] This invention belongs to the field of geotechnical engineering construction technology, specifically relating to a combined construction method of pre-compaction and humidification dynamic compaction for disordered high fill sites. Background Technology

[0002] The loess hilly and gully region of western my country is characterized by undulating terrain, numerous gullies, and limited flat land. Due to topographical and spatial constraints, land for construction is scarce, leading many areas to adopt excavation and filling methods for land development, resulting in numerous loess high fill projects. Loess high fill projects are unique geological formations characterized by "three sides, two bodies, and two water bodies." The "original foundation" contains a thick layer of collapsible loess, while the fill material is predominantly excavated collapsible loess. Collapsible loess possesses unique properties such as water sensitivity, macroporosity, and structural integrity. Under natural moisture conditions, it generally exhibits high strength, but once soaked in water, its structure rapidly deteriorates, its bearing capacity decreases sharply, and significant additional subsidence occurs, causing cracking and even damage to buildings and structures situated on loess sites. Therefore, engineering measures are needed to eliminate the collapsing deformation of the foundation. Among the existing high fill sites, one type is the orderly high fill project that has undergone special investigation and design, and the fill has been treated with layered compaction or dynamic tamping. The fill structure is compact and the collapsibility has been basically eliminated. The other type refers to the high fill project that has not undergone special investigation and design, and the fill has not been treated with layered compaction or dynamic tamping. The fill structure is loose and the collapsibility has not been eliminated. Once soaked in water, it will also produce large collapsibility deformation. Therefore, the foundation must be reinforced again before the project is constructed to ensure the uniformity, compactness and stability of the foundation.

[0003] Dynamic compaction is widely used in the treatment of loess fill sites due to its advantages such as simple construction, high efficiency, and short construction period. The effectiveness of dynamic compaction is closely related to the moisture content of the foundation soil. In the arid Northwest region, the moisture content of the loess fill material is usually low (natural moisture content often falls below 8%). According to the China Engineering Construction Standardization Association standard "Technical Specification for Dynamic Compaction Foundation Treatment" (CECS279-2010), when using dynamic compaction to treat collapsible loess foundations, the natural moisture content of the soil should be 1% to 3% lower than the plastic limit. Within the soil layer to be compacted, if the natural moisture content is lower than 10%, it should be moistened, ideally to near the optimum moisture content. Therefore, to ensure the effectiveness of dynamic compaction, the low-moisture loess needs to be moistened before construction. In the arid Northwest region, the low moisture content of the loess fill material in disordered high fill sites, coupled with the lack of compaction, results in a loose internal structure and the development of cracks and cavities. When using injection holes to moisten low-moisture-content fill, water seeps down along dominant channels such as cracks and cavities, while areas far from these channels remain dry. This results in localized areas reaching saturation while others remain low, which is detrimental to dynamic compaction. Therefore, there is an urgent need to develop a combined construction method for pre-compaction and moistening dynamic compaction in disordered high-fill sites to address the problems of uneven water injection and poor dynamic compaction effects caused by cracks and cavities in disordered fill sites.

[0004] Chinese patent document CN113463609A, published on April 6, 2021, discloses a "relay-style" dynamic compaction replacement method for treating deep saturated soft soil foundations. The method includes the following steps: S100 – Construction preparation: Thoroughly understand the site's geological conditions, construction conditions, the extent and thickness of the saturated soft soil to be replaced, and the groundwater level; equip the site with a crane and hammer capable of meeting the dynamic compaction replacement depth; prepare replacement materials that meet the requirements. S200 – Level the site and lay a 1.5-2.0m thick cushion layer, the same material as the dynamic compaction replacement material, meeting the construction equipment requirements. S300 – Conduct single-point dynamic compaction replacement pier impact tests. S400 – Construct the dynamic compaction replacement piers according to the construction parameters determined by the single-point dynamic compaction replacement pier tests. This method solves the problem that traditional foundation treatment methods are difficult to achieve the desired treatment effect and are costly. However, this document still does not address the problem of uneven water injection and humidification caused by cracks and cavities in disordered fill sites, resulting in poor dynamic compaction treatment effects. Summary of the Invention

[0005] The present invention provides a combined construction method of pre-compaction and humidification dynamic compaction for disordered high fill sites. The purpose is to overcome the problems of uneven humidification and poor reinforcement effect faced by existing technologies in the dynamic compaction foundation treatment of disordered high fill sites.

[0006] Therefore, the present invention provides a construction method combining pre-compaction and humidified dynamic compaction for disordered high fill sites, comprising the following steps:

[0007] 1) Detect cracks and cavities within the target site;

[0008] 2) Pre-compacting to eliminate cracks and voids in the target site;

[0009] 3) Moisten the pre-compacted target site with water;

[0010] 4) Perform dynamic compaction on the humidified target site until the requirements are met.

[0011] Preferably, step 1) includes the following steps:

[0012] 101) Clean and level the target site until it is flat;

[0013] 102) Lay out high-density electrical resistivity tomography lines on a leveled site;

[0014] 103) Connect the high-density electrical resistivity measurement line to the monitoring electrode and measure the resistivity data of the target area;

[0015] 104) Interpret the resistivity profile;

[0016] 105) Determine the distribution range and depth of cracks and cavities in the fill of the target area based on the resistivity profile.

[0017] 106) Inspect the crack and void areas identified in step 105).

[0018] Preferably, step 2) includes the following steps:

[0019] 201) Set up tamping points directly above the cracks and cavities, and determine the effective reinforcement depth of dynamic compaction based on the measured range and depth of the cracks and cavities.

[0020] 202) Set up tamping points in the horizontal direction within the range of cracks and cavities. The tamping points should be located directly above the cracks and cavities. Tamping should be carried out on the tamping points. When the tamping settlement reaches the stop tamping standard, tamping should be stopped and the tamping pit should be filled.

[0021] 203) Fully compact the surface loose soil within the compaction range of step 202), and clean and level the site after full compaction.

[0022] 204) The extent of cracks and cavities is detected again. The resistivity changes at the same depth in the backfill before and after compaction are compared to determine the extent to which the compaction has eliminated cracks and cavities. If cracks and cavities are not eliminated, repeat steps 201) to 203) until all cracks and cavities are eliminated.

[0023] Preferably, step 3) includes the following steps:

[0024] 301) Determine the humidification parameters of the target site after pre-compaction;

[0025] 302) Determine the humidification depth of the target site after pre-compaction;

[0026] 303) Determine the parameters of the water injection holes in the target site after pre-compaction;

[0027] 304) Determine the single-hole water injection volume of the target site after pre-compaction;

[0028] 305) Drill water injection holes in the target site after pre-compaction;

[0029] 306) Monitoring step 305) Soil moisture content at the target site;

[0030] 307) Inject water into the water inlet;

[0031] 308) Stop water injection when the water content in the injection hole reaches the target range.

[0032] Preferably, the method for laying out high-density electrical resistivity tomography lines in step 102) on the leveled site is as follows: multiple equidistant and parallel high-density electrical resistivity tomography lines are laid out on the leveled site in both longitudinal and transverse directions, forming a square measuring network. Equidistant high-density electrical resistivity tomography points are set on the high-density electrical resistivity tomography lines. The measuring electrodes are vertically inserted into the soil at the high-density electrical resistivity tomography points, and the measuring electrodes are connected to the position detector through an electrode conversion device.

[0033] Preferably, in step 103), the resistivity data of the target area is measured using a Winner device, and the isolation coefficient is 1 to 10 during the measurement.

[0034] Preferably, the specific method for determining the distribution range and depth of cracks and cavities in the fill of the target area based on the resistivity profile in step 105) is as follows: the average value of the resistivity measurement of the fill in the area without cracks and cavities is set as the resistivity threshold. On the resistivity profile of each detected area, a closed area with a resistivity value greater than the resistivity threshold is searched. When there is a closed area with a resistivity value greater than the resistivity threshold, this closed area is the undetermined layer of cracks and cavities in the detected area. When there is no closed area with a resistivity value greater than the resistivity threshold, there are no cracks or cavities in the detected area.

[0035] Preferably, the method for inspecting the crack and cavity areas in step 106) of step 105) is as follows: drilling and static cone penetration tests are conducted on the crack and cavity areas. The drilling and static cone penetration tests are conducted within the filling body. The maximum depth of the drilling and static cone penetration tests must penetrate the top surface of the original foundation and enter the original foundation, and exceed the effective detection depth of the high-density electrical resistivity tomography. When a sudden drop of the drill occurs during the drilling process or when the water drill causes a uniform drop of mud in the hole, and the static cone penetration resistance at the adjacent position and the target depth is reduced to the target range value, then cracks or cavities are present at that location; otherwise, cracks or cavities are not present.

[0036] Preferably, the method for determining the humidification parameters of the target site after pre-compaction in step 301) is as follows: before construction, take undisturbed soil samples from the target site after pre-compaction, with a sampling interval of 0.5m to 1.0m, and determine the natural moisture content w0 and maximum dry density ρ of the soil at different depths below the compaction surface. d and optimum moisture content w op The weighted average value w of the natural moisture content of the soil at different depths below the rammed surface was calculated using the thickness weighted method.

[0037] Preferably, the method for determining the moistening depth of the target site after pre-compaction in step 302) is as follows: based on the natural moisture content w0 of the soil in step 301), the moistening depth is determined within the required reinforcement depth range. The determination method is as follows: when the natural moisture content w0 of the soil is less than 8%, the soil needs to be moistened; when the natural moisture content w0 of the soil is less than 10%, the soil needs to be moistened to the optimal moisture content.

[0038] The beneficial effects of this invention are:

[0039] 1. The present invention provides a combined construction method for pre-compaction and humidification-based dynamic compaction of disordered high fill sites, which involves the following steps: 1) detecting cracks and cavities in the target site; 2) pre-compaction to eliminate cracks and cavities in the target site; 3) injecting water to humidify the pre-compacted target site; 4) performing dynamic compaction on the humidified target site until the requirements are met. Pre-compaction to eliminate cracks and cavities before humidification solves the problems of ground subsidence caused by water injection and humidification, sinkholes formed by water loss along cracks, and uneven humidification. This invention has high practical value, is easy to promote and apply, and solves the problems of high difficulty in treating disordered high fill sites, long construction periods, and high post-construction settlement requirements. It also has advantages such as good treatment effect, fast construction speed, and small residual settlement, and has good application prospects.

[0040] 2. The construction method of combining pre-compaction and humidification dynamic compaction for disordered high fill sites provided by this invention involves laying high-density electrical resistivity survey lines on the leveled site, connecting the high-density electrical resistivity survey lines to monitoring electrodes, measuring the resistivity data of the target area, interpreting the resistivity profile, determining the distribution range and depth of cracks and cavities in the fill of the target area based on the resistivity profile, and finally inspecting the crack and cavity areas. This method can promptly and accurately detect the distribution of cracks and cavities in the site.

[0041] 3. The construction method of combining pre-compaction and humidification dynamic compaction in disordered high fill sites provided by this invention adopts a combination of deep and shallow water injection holes when determining the parameters of the water injection holes. The deep water injection holes are used to humidify the deep strata, and the shallow water injection holes are used to humidify the shallow strata. That is, by adopting a water injection and humidification method that combines deep and shallow holes, the problem of uneven water injection and humidification caused by uneven strata between the upper and lower layers can be avoided. Attached Figure Description

[0042] The present invention will now be described in further detail with reference to the accompanying drawings.

[0043] Figure 1 This is a schematic diagram of a high-density electrical resistivity tomography (EDT) line.

[0044] Figure 2 This is a schematic diagram of high-density electrical resistivity tomography (EDT) for detecting cracks and cavities.

[0045] Figure 3 This is a schematic diagram showing the horizontal level of the compaction points during the pre-compaction of cracks and cavities;

[0046] Figure 4 This is a schematic diagram showing the depth and extent of the cracks and cavities;

[0047] Figure 5 This is a schematic diagram showing the horizontal distribution of water injection holes and monitoring holes;

[0048] Figure 6 This is a schematic diagram of the longitudinal section of the water injection hole and the monitoring hole;

[0049] Figure 7 This is a schematic diagram of the tamping point layout during the humidification and dynamic compaction construction of this invention.

[0050] Explanation of reference numerals in the attached drawings: 1. High-density electrical resistivity tomography line; 2. High-density electrical resistivity tomography point; 3. Void boundary line; 4. Fill body; 5. Top surface of original foundation; 6. Original foundation; 7. Crack; 8. Void; 9. Exploration borehole; 10. Static cone penetration test equipment; 11. First pass of pre-compaction point; 12. Second pass of pre-compaction point; 13. Third pass of pre-compaction point; 14. Fourth pass of pre-compaction point; 15. Rammer; 16. Hammer; 17-1. Deep water injection hole; 17-2. Shallow water injection hole; 18. Moisture content monitoring hole; 19. Soil moisture meter; 20. Cable; 21. Data acquisition system; 22. Pea gravel; 23. First pass of humidified ramming point; 24. Second pass of humidified ramming point; 25. Third pass of humidified ramming point. Detailed Implementation

[0051] Example 1:

[0052] A construction method combining pre-compaction and humidified dynamic compaction for disordered high-fill sites includes the following steps:

[0053] 1) Detect cracks and cavities within the target site;

[0054] 2) Pre-compacting to eliminate cracks and voids in the target site;

[0055] 3) Moisten the pre-compacted target site with water;

[0056] 4) Perform dynamic compaction on the humidified target site until the requirements are met.

[0057] This invention solves the problems of ground subsidence, sinkholes formed by water loss along cracks, and uneven humidification caused by pre-compacting to eliminate cracks and cavities before humidification. This invention has high practical value, is easy to promote and apply, and solves the problems of difficult treatment, long construction period, and high post-construction settlement requirements for disordered high fill sites. It also has the advantages of good treatment effect, fast construction speed and small residual settlement, and has good application prospects.

[0058] Example 2:

[0059] Based on Example 1, step 1) includes the following steps:

[0060] 101) Clean and level the target site until it is flat;

[0061] Specifically, construction waste, weeds, tree roots, and other debris within the construction site area will be cleared and leveled to create a flat area.

[0062] 102) Lay out high-density electrical resistivity tomography lines on a leveled site;

[0063] Preferred, such as Figure 1As shown, the method for laying out high-density electrical resistivity tomography lines 1 on the leveled site in step 102) is as follows: multiple equidistant and parallel high-density electrical resistivity tomography lines 1 are laid out on the leveled site in both longitudinal and transverse directions. The longitudinal and transverse high-density electrical resistivity tomography lines form a square measuring network. Equidistant high-density electrical resistivity tomography points 2 are set on the high-density electrical resistivity tomography lines. The measuring electrodes are vertically inserted into the soil at the high-density electrical resistivity tomography points. The measuring electrodes are connected to the position detector through the electrode conversion device.

[0064] Specifically, the spacing between adjacent high-density electrical resistivity tomography (EP tomography) lines is 2–4 m, and the spacing between adjacent high-density EPT measurement points is 1.0–2.0 m. The measuring electrodes are connected to the electrode conversion device via multi-core cables 20, and the plane coordinates and elevation of the high-density EPT measurement points are measured using GPS RTK or a total station. This method can accurately obtain the location information of the high-density EPT measurement points.

[0065] 103) Connect the high-density electrical resistivity measurement line to the monitoring electrode and measure the resistivity data of the target area;

[0066] Preferably, in step 103), the resistivity data of the target area is measured using a Winner device, and the isolation coefficient is 1 to 10 during the measurement.

[0067] Specifically, a high-density electrical resistivity tomography (EDT) instrument was used to detect high-fill sites. A Wenner device was employed for measurement, with an isolation coefficient of 1–10 to ensure the detection depth exceeded the fill thickness and the resolution was sufficient to identify cracks and voids. During measurement, multiple monitoring electrodes connected to the high-density EDT probe were energized to obtain multiple sets of resistivity data corresponding to the area under test.

[0068] 104) Interpret the resistivity profile;

[0069] Specifically, the method for interpreting resistivity profile maps is as follows: multiple sets of resistivity data obtained from each high-density electrical resistivity survey line are transmitted to a computer (data acquisition system 21). The computer performs inversion analysis on each set of resistivity data, and a resistivity profile map can be drawn from each set of resistivity data. The inversion analysis process is as follows: first, denoising technology is used to remove outliers, then preprocessing such as terrain correction and format conversion is performed, and the data is imported into CRT data processing software. Then, the data is imported into RES2DINV for two-dimensional inversion, and the inversion results are plotted as contour maps using Surfer software. Based on the variation characteristics of apparent resistivity values ​​on the contour lines, combined with existing site survey data and soil property difference points, geological interpretation is performed. Finally, the resistivity profile map is drawn using Auto-CAD software.

[0070] 105) Determine the distribution range and depth of cracks and cavities in the fill of the target area based on the resistivity profile.

[0071] Potential hazards such as cavities and cracks are mainly characterized by high resistivity, low density, and low dielectric constant. Therefore, the average resistivity measurement values ​​of the fill soil in areas without cracks and with cavities are set as the resistivity threshold.

[0072] Preferably, the specific method for determining the distribution range and depth of cracks 7 and cavities 8 in the fill of the target area based on the resistivity profile in step 105) is as follows: the average value of the resistivity measurement of the fill in the area without cracks and cavities is set as the resistivity threshold. On the resistivity profile of each detected area, a closed area (high-resistivity closed loop) with a resistivity value greater than the resistivity threshold is searched. When there is a closed area with a resistivity value greater than the resistivity threshold, this closed area is the undetermined layer of cracks and cavities in the detected area. When there is no closed area with a resistivity value greater than the resistivity threshold, there are no cracks or cavities in the detected area. Figure 1 The 3rd mark is the defined boundary line of the cavity.

[0073] 106) Inspect the crack and void areas identified in step 105).

[0074] Preferred, such as Figure 2 As shown, the method for inspecting the crack and cavity area in step 105) in step 106) is as follows: drilling (or well, trench) (using exploration borehole 9) and static cone penetration testing (using static cone penetration testing equipment 10) are carried out in the crack and cavity area. The drilling and static cone penetration testing are conducted within the fill body 4. The maximum depth of drilling and static cone penetration testing must penetrate the top surface 5 of the original foundation and enter the original foundation 6, and exceed the effective detection depth of the high-density electrical resistivity tomography. When a sudden drop of the drill bit occurs during drilling or when the water drill causes a uniform drop of mud in the hole, and the static cone penetration resistance at the adjacent position and the target depth is reduced to the target range value, then cracks or cavities are developed at that location; otherwise, cracks or cavities are not developed.

[0075] Example 3:

[0076] Based on Example 2, step 2) includes the following steps:

[0077] 201) Set up tamping points directly above the cracks and cavities, and determine the effective reinforcement depth of dynamic compaction based on the measured range and depth of the cracks and cavities.

[0078] Specifically, such as Figure 3 and Figure 4As shown, tamping points are set directly above the locations where cracks and cavities develop. Based on the crack or cavity depth H0 and range measured in step one, the dynamic tamping energy level for eliminating cracks and cavities under non-humidification conditions is determined through on-site tamping tests or regional experience. The effective reinforcement depth H of dynamic tamping is then determined. If test data or experience is lacking, it can be determined according to the "Technical Specification for Foundation Treatment of Buildings" JGJ79-2012, which requires the effective reinforcement depth H to be (1.1~1.2)H0.

[0079] 202) Set up tamping points in the horizontal direction within the range of cracks and cavities. The tamping points should be located directly above the cracks and cavities. Tamping should be carried out on the tamping points. When the tamping settlement reaches the stop tamping standard, tamping should be stopped and the tamping pit should be filled.

[0080] Specifically, the outermost edge of the crack or hole must be within the tamping area of ​​the hammer, and the spacing between tamping points must not exceed 3.5 times the diameter of the hammer.

[0081] Preferably, when compacting the points (using a tamping machine 15), the first pass involves skipping points (see the first compaction point 11 in pre-compaction), the second pass fills the gaps from the first pass (see the second compaction point 12 in pre-compaction), the third pass fills the gaps from the first and second passes (see the third compaction point 13 in pre-compaction), and after point compaction is completed, the fourth pass fills the gaps from the previous three passes along the line of the cavity development range (see the fourth compaction point 14 in pre-compaction), and finally, a low-energy full compaction is performed to achieve overlap between the hammer marks, with the overlap being no less than 1 / 4 of the diameter of the tamping hammer 16. During each pass of dynamic compaction, when the settlement of the last two blows reaches the stopping standard, the compaction pit is filled with a bulldozer.

[0082] Preferably, the cessation of compaction criteria is determined through on-site test compaction. When test data or experience is lacking, the following requirements shall be followed based on the dynamic compaction energy level E: when E < 4000 kN·m, the settlement of the last two compaction blows shall be less than 5 cm; when 4000 kN·m ≤ E < 6000 kN·m, the settlement of the last two compaction blows shall be less than 10 cm; when 6000 kN·m ≤ E < 8000 kN·m, the settlement of the last two compaction blows shall be less than 15 cm; when 8000 kN·m ≤ E < 12000 kN·m, the settlement of the last two compaction blows shall be less than 20 cm; when E ≥ 12000 kN·m, the settlement of the last two compaction blows shall be less than 25 cm.

[0083] 203) Fully compact the surface loose soil within the compaction range of step 202), and clean and level the site after full compaction.

[0084] Specifically, after the spot compaction is completed, a dynamic compaction energy level of 1000kN·m to 2000kN·m is used to fully compact the surface loose soil within the dynamic compaction range, and the site is cleaned and leveled.

[0085] 204) The extent of cracks and cavities is detected again. The resistivity changes at the same depth in the backfill before and after compaction are compared to determine the extent to which the compaction has eliminated cracks and cavities. If cracks and cavities are not eliminated, repeat steps 201) to 203) until all cracks and cavities are eliminated.

[0086] Specifically, the area of ​​cracks and cavities is re-detected after pre-compaction using a high-density electrical resistivity tomography method, following the same survey lines and survey point locations as before pre-compaction.

[0087] Example 4:

[0088] Based on Example 3, step 3) includes the following steps:

[0089] 301) Determine the humidification parameters of the target site after pre-compaction;

[0090] Preferably, the method for determining the humidification parameters of the target site after pre-compaction in step 301) is as follows: before construction, take undisturbed soil samples from the target site after pre-compaction, with a sampling interval of 0.5m to 1.0m, and determine the natural moisture content w0 and maximum dry density ρ of the soil at different depths below the compaction surface. d and optimum moisture content w op The weighted average value w of the natural moisture content of the soil at different depths below the rammed surface was calculated using the thickness weighted method.

[0091] 302) Determine the humidification depth of the target site after pre-compaction;

[0092] Preferably, the method for determining the moistening depth of the target site after pre-compaction in step 302) is as follows: based on the natural moisture content w0 of the soil in step 301), the moistening depth is determined within the required reinforcement depth range. The determination method is as follows: when the natural moisture content w0 of the soil is less than 8%, the soil needs to be moistened; when the natural moisture content w0 of the soil is less than 10%, the soil needs to be moistened to the optimal moisture content.

[0093] 303) Determine the parameters of the water injection holes in the target site after pre-compaction;

[0094] Preferably, the water injection holes adopt a combined arrangement of deep water injection holes 17-1 and shallow water injection holes 17-2, wherein the deep water injection holes are used to humidify the deep formations and the shallow water injection holes are used to humidify the shallow formations.

[0095] Preferably, the water injection hole adopts two hole depths: a deep water injection hole depth and a shallow water injection hole depth.

[0096] The depth of the deep water injection hole is determined based on the foundation reinforcement depth H, when the vertical permeability K y Greater than horizontal permeability K xIf the vertical permeability Ky of the fill soil is less than or equal to the horizontal permeability Kx, then the depth h of the injection hole should be equal to the reinforcement depth (H-1) m to (H-2) m.

[0097] The shallow water injection hole has a depth of 1 / 2 to 2 / 3 of the deep water injection hole depth;

[0098] Two hole depths, deep water injection hole and shallow water injection hole, are used to ensure convenient construction.

[0099] Preferably, the water injection holes are arranged in an equilateral triangle or square pattern, with a diameter of 130mm-160mm and a spacing of 1.0m-2.0m. This results in better water injection performance.

[0100] 304) Determine the single-hole water injection volume of the target site after pre-compaction;

[0101] Specifically, determine the water injection volume per well: Based on the total number of water injection wells in the site, determine the treatment area and wetting soil layer thickness of each well. The water injection volume of a single well can be calculated using the following formula:

[0102]

[0103] In the formula: q is the water injection rate per orifice (m³). 3 );w op The optimum moisture content (%) of natural soil within the depth range of the fill to be moistened; The weighted average (%) of the moisture content of natural soil within the depth range of the fill to be moistened; The weighted average dry density (g / cm³) of natural soil within the depth range to be moistened fill. 3 A is the treatment area of ​​a single hole (m²). 2 h represents the thickness (m) of the soil layer to be moistened in a single hole.

[0104] 305) Drill water injection holes in the target site after pre-compaction;

[0105] Preferably, the water injection holes are arranged in a square or equilateral triangular pattern.

[0106] Preferably, the hole spacing is determined based on the humidification range of a single hole. The spatial distance is 0.8m to 2.0m.

[0107] Preferably, the water injection hole is formed by drilling; this improves construction efficiency.

[0108] Preferably, for silty soil sites with a moisture content of less than 8%, drilling (hammer-driven tube drilling) is used to prevent hole collapse.

[0109] Preferably, after the water injection hole is formed, gravel (pea gravel 22) or coarse sand is poured into the water injection hole; this can prevent the water injection hole from collapsing.

[0110] 306) Monitoring step 305) Soil moisture content at the target site;

[0111] like Figure 5 and Figure 6 As shown, specifically, three types of moisture content monitoring points (moisture content monitoring holes 18) are set up at the centroid between adjacent water injection holes, at the midpoint of the line connecting the centroid and the water injection hole, and at the midpoint of the line connecting adjacent water injection holes. Soil moisture meters 19 are used to monitor the moisture content. At each monitoring point, multiple measuring points are set up along the same vertical direction, starting from a depth of 1m below the ground. The vertical spacing between the measuring points should be 1.0m to 2.0m, and the maximum monitoring depth should exceed the designed maximum humidification depth by at least 1.0m. The soil moisture meter is installed into the soil layer through drilling. After installation, it is connected to an automated monitoring system, and the change in soil moisture content is observed every 1h to 3h.

[0112] 307) Inject water into the water inlet;

[0113] Specifically, after the water injection holes are constructed, to facilitate water injection, multiple water injection holes are divided into a construction area and a cofferdam is built. The total water injection volume Q = nq required for each construction area is calculated based on the number of water injection holes (n) within the cofferdam area. To ensure the uniformity of the backfill moisture content within the intended humidification depth and to prevent excessively high or low local moisture content, the water injection process is carried out in small, frequent applications, preferably 3 to 5 times, with an interval of 1 to 2 days between each injection, ensuring sufficient time for water to seep from the water injection holes to the surrounding area.

[0114] 308) Stop water injection when the water content in the injection hole reaches the target range.

[0115] Specifically, the target range is [w op -3%,w op +3%], when the moisture content monitoring points set in step 306 observe the range of moisture content variation of fill at different depths, it is [w op -3%,w op When the humidity reaches +3%, it indicates that the humidification requirement has been met, and subsequent dynamic compaction construction can be carried out.

[0116] Example 5:

[0117] Based on Example 4, step 4) involves dynamic compaction of the humidified target site until the requirements are met.

[0118] Specifically, after the backfill soil has reached the required moisture content, the dynamic compaction level should be determined through on-site test compaction or regional experience. If test data or experience is lacking, it can be determined according to the "Technical Specification for Building Foundation Treatment" JGJ79-2012. For example... Figure 7As shown, the humidification and compaction construction of disordered high backfill sites should be carried out in four passes: (1) First pass (humidification and compaction first pass 23): the compaction points are arranged in a square, and the spacing between the compaction points can be (2.5 to 3.5) times the diameter of the hammer; (2) Second pass (humidification and compaction second pass 24): the compaction points are inserted at the centroid of the square; (3) Third pass (humidification and compaction third pass 25): the compaction points are arranged in a rhombus, that is, at the center of the four main compaction points adjacent to the first and second passes; (4) Fourth pass: full compaction, with each compaction point overlapping the other by no less than 1 / 2 of the compaction mark (hammer diameter), and the number of blows is 2. The hammer should be stopped according to step 202, or if there is excessive bulging or lateral displacement around the compaction pit, or if the compaction pit is too deep and it is difficult to start the hammer.

[0119] In the description of this invention, it should be understood that if terms such as "upper" or "lower" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, it does not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are for illustrative purposes only and should not be construed as limiting the invention.

[0120] The above examples are merely illustrative of the present invention and do not constitute a limitation on the scope of protection of the present invention. All designs that are the same as or similar to the present invention are within the scope of protection of the present invention.

Claims

1. A construction method combining pre-compaction and humidified dynamic compaction for disordered high fill sites, characterized in that: Includes the following steps: 1) Detect cracks and cavities within the target site; 2) Pre-compacting to eliminate cracks and voids in the target site; step 2) includes the following steps: 201) Set up tamping points directly above the cracks and cavities, and determine the effective reinforcement depth of dynamic compaction based on the measured range and depth of the cracks and cavities. 202) Set up tamping points in the horizontal direction within the range of cracks and cavities. The tamping points should be located directly above the cracks and cavities. Tamping should be carried out on the tamping points. When the tamping settlement reaches the stop tamping standard, tamping should be stopped and the tamping pit should be filled. The outermost edge of the crack or cavity should be within the tamping imprint of the tamping hammer, and the spacing between tamping points should not be higher than 3.5 times the diameter of the tamping hammer. 203) Fully compact the surface loose soil within the compaction range of step 202), and clean and level the site after full compaction; 204) The extent of cracks and cavities is detected again. The resistivity changes at the same depth in the backfill before and after compaction are compared to determine the extent to which the compaction has eliminated cracks and cavities. If cracks and cavities are not eliminated, repeat steps 201) to 203) until all cracks and cavities are eliminated. 3) Moisten the pre-compacted target site with water; step 3) includes the following steps: 301) Determine the humidification parameters of the target site after pre-compaction; 302) Determine the humidification depth of the target site after pre-compaction; 303) Determine the parameters of the water injection holes in the target site after pre-compaction; the water injection holes adopt a combination of deep water injection holes (17-1) and shallow water injection holes (17-2), wherein the deep water injection holes are used to moisten the deep strata, and the shallow water injection holes are used to moisten the shallow strata. 304) Determine the single-hole water injection volume of the target site after pre-compaction; 305) Drill water injection holes in the target site after pre-compaction; 306) Monitoring step 305) Soil moisture content at the target site; 307) Inject water into the water inlet; 308) Stop water injection when the water content in the injection hole reaches the target range; 4) Perform dynamic compaction on the humidified target site until the requirements are met.

2. The construction method of combined pre-compaction and humidification dynamic compaction for disordered high fill sites as described in claim 1, characterized in that: Step 1) includes the following steps: 101) Clean and level the target site to a flat surface; 102) Lay out high-density electrical resistivity tomography lines on a leveled site; 103) Connect the high-density electrical resistivity measurement line to the monitoring electrode and measure the resistivity data of the target area; 104) Deciphering the resistivity profile; 105) Determine the distribution range and depth of cracks and cavities in the fill of the target area based on the resistivity profile; 106) Inspect the crack and void areas identified in step 105).

3. The construction method of combined pre-compaction and humidification dynamic compaction for disordered high fill sites as described in claim 2, characterized in that: The method for laying out high-density electrical resistivity tomography lines in step 102) on the leveled site is as follows: multiple equidistant and parallel high-density electrical resistivity tomography lines are laid out on the leveled site in both longitudinal and transverse directions. The longitudinal and transverse high-density electrical resistivity tomography lines form a square measuring network. Equidistant high-density electrical resistivity tomography points are set on the high-density electrical resistivity tomography lines. The measuring electrodes are vertically inserted into the soil at the high-density electrical resistivity tomography points. The measuring electrodes are connected to the position detection instrument through an electrode conversion device.

4. The construction method of combined pre-compaction and humidified dynamic compaction for disordered high fill sites as described in claim 2, characterized in that: In step 103), the resistivity data of the target area is measured using a Winner device, with an isolation coefficient of 1 to 10 during the measurement.

5. The construction method for combined pre-compaction and humidified dynamic compaction of disordered high fill sites as described in claim 2, characterized in that: The specific method for determining the distribution range and depth of cracks and cavities in the fill of the target area based on the resistivity profile is as follows: the average value of the resistivity measurement of the fill in the area without cracks and cavities is set as the resistivity threshold. On the resistivity profile of each detected area, a closed area with a resistivity value greater than the resistivity threshold is searched. When there is a closed area with a resistivity value greater than the resistivity threshold, this closed area is the undetermined layer of cracks and cavities in the detected area. When there is no closed area with a resistivity value greater than the resistivity threshold, there are no cracks or cavities in the detected area.

6. The construction method of combined pre-compaction and humidification dynamic compaction for disordered high fill sites as described in claim 2, characterized in that: The method for inspecting the crack and cavity areas in step 106) of step 105) is as follows: Drilling and static cone penetration tests are conducted on the crack and cavity areas. The drilling and static cone penetration tests are conducted within the filling body. The maximum depth of the drilling and static cone penetration tests must penetrate the top surface of the original foundation and enter the original foundation, and exceed the effective detection depth of the high-density electrical resistivity tomography. When a sudden drop of the drill or a uniform drop of the drilling mud occurs in the hole during the drilling process, and the static cone penetration resistance at the adjacent position and the target depth is reduced to the target range value, then there is a crack or cavity development at that location. Otherwise, there is no crack or cavity development.

7. The construction method for combined pre-compaction and humidified dynamic compaction of disordered high fill sites as described in claim 1, characterized in that: The method for determining the humidification parameters of the target site after pre-compaction in step 301) is as follows: Before construction, take undisturbed soil samples from the target site after pre-compaction, with a sampling interval of 0.5m to 1.0m, and determine the natural moisture content of the soil at different depths below the compaction surface. w 0. Maximum dry density ρ d and optimum moisture content w op The weighted average of the natural water content of the soil at different depths below the ramming surface was calculated using the thickness-weighted method. w .

8. The construction method for combined pre-compaction and humidification dynamic compaction of disordered high fill sites as described in claim 7, characterized in that: The method for determining the wetting depth of the target site after pre-compaction (302) is as follows: based on the natural moisture content of the soil in step 301). w 0. Determine the wetting depth within the required reinforcement depth range. The determination method is: when the natural moisture content of the soil... w When the soil moisture content is below 8%, the soil needs to be moistened; when the natural moisture content of the soil is... w When the moisture content is below 10%, the soil needs to be moistened to the optimum moisture content.

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