A method of treating a coral sand foundation

Abstract

The application relates to the technical field of geotechnical engineering, in particular to a coral sand foundation treatment method. The method comprises the following steps: S1, uniformly mixing coral sand and waste tire rubber particles according to a mass ratio of (85-95):(5-15), and adding 2%-5% of coral micro powder in the coral sand to obtain a composite backfill material; S2, filling the composite backfill material in a preset thickness in a foundation area to be treated, and then sequentially performing vibration rolling and static pressure rolling operations; S3, repeating the step S2 until the filling reaches the design height and the density requirement; when the mass ratio is (90-95):(5-10), the vibration rolling is performed 3-4 times; when the mass ratio is (85-90):(10-15), the vibration rolling is performed 4-6 times. According to the scheme, the waste tire rubber particles and the coral micro powder are used to optimize the gradation of the coral sand, the vibration and static pressure combined process is used, the problems of easy crushing of the aggregate and uneven compaction in the backfill process can be solved, the bearing capacity of the foundation can be improved, and excellent engineering benefits and environmental protection values are achieved.

Description

Technical Field

[0001] This application relates to the field of geotechnical engineering technology, and in particular to a method for treating coral sand foundations. Background Technology

[0002] Coral sand is mainly formed by the accumulation of coral, shellfish, and other marine organism debris through marine processes. It is characterized by a wide gradation, high permeability, and brittleness, resulting in unique engineering properties for coral sand foundations. Current technologies commonly use vibro-compaction or dynamic compaction. While vibro-compaction is effective for deep foundations, it struggles to ensure the compaction of shallow foundations, and the high energy input during construction can easily lead to excessive fragmentation of coral sand particles, causing gradation deterioration. Dynamic compaction is highly effective for shallow foundations, but its energy decays rapidly, limiting the treatment depth, and it also faces the problem of particle fragmentation due to high-energy impacts. Summary of the Invention

[0003] To overcome the problems existing in related technologies, this application provides a method for treating coral sand foundations. By optimizing the gradation of coral sand with waste tire rubber particles and coral powder, and combining it with a specific vibration and static pressure combination process, this method can solve the problems of easy aggregate breakage and uneven compaction during backfilling, and improve the bearing capacity of the foundation, thus achieving both excellent engineering benefits and environmental protection value.

[0004] This application provides a method for treating coral sand foundations, including the following steps: S1. Mix coral sand and waste tire rubber particles at a mass ratio of (85~95):(5~15) evenly, and add coral micro powder accounting for 2%~5% of the mass of the coral sand to obtain composite backfill. S2. The composite backfill material is laid in the foundation area to be treated with a preset thickness, and then vibratory compaction and static compaction are carried out in sequence. S3. Repeat step S2 until the filling reaches the design height and density requirements; When the mass ratio is (90~95):(5~10), the number of vibration compaction cycles is 3~4 times; when the mass ratio is (85~90):(10~15), the number of vibration compaction cycles is 4~6 times.

[0005] In some embodiments, when the median particle size ratio of the waste tire rubber particles to the coral sand is 0.8 to 1.2, the vibration frequency of the vibratory roller is 28 to 32 Hz, the rolling speed is 2 to 4 km / h, and the working mass of the vibratory roller is 18t to 22t.

[0006] In some embodiments, the compaction speed of the static compaction is controlled at 1.5~2.5 km / h, and the working mass of the static compaction roller is 15~25t.

[0007] In some embodiments, the coral sand has a particle size of 0.075~10mm, with a median particle size greater than 0.25mm.

[0008] In some embodiments, the coral micropowder has a particle size of less than 0.075 mm, a specific surface area of ​​0.8~1.2 m2 / g, and a calcium carbonate content of more than 90%.

[0009] In some embodiments, the particle size of the waste tire rubber particles ranges from 0.5 to 5 mm.

[0010] In some embodiments, the moisture content of the composite backfill material is 8% to 15%.

[0011] In some embodiments, the preset thickness is 200~500mm.

[0012] Compared with existing technologies, the coral sand foundation treatment method provided in this application has the following advantages: (1) This application introduces waste tire rubber particles to optimize the gradation of coral sand. The low elastic modulus of waste tire rubber particles and the high stiffness of coral sand form a modulus complementary effect. At the same time, the filling of the inter-particle interface gaps and the calcareous cementing effect of coral micro powder can improve the defects of high compressibility and easy breakage of pure coral sand backfill, and enhance the bearing capacity of the foundation. It can also realize the high added value resource utilization of bulk industrial solid waste, and has both engineering safety and environmental sustainability.

[0013] (2) This application addresses the brittle and fragile engineering characteristics of coral sand by adopting a combined construction process of vibration followed by static compaction to balance the contradiction between compaction energy input and particle integrity protection. This avoids the problem of excessive particle breakage and gradation deterioration caused by a single dynamic compaction or impact rolling process. It can ensure the stability of coral sand particle gradation and enable the backfill to achieve the high density required by the design.

[0014] (3) This application controls the corresponding number of vibration compaction by the mass ratio of coral sand and waste tire rubber particles. Under different material ratios, it can prevent post-work settlement caused by underpressure and avoid energy waste and equipment wear caused by overpressure. Detailed Implementation

[0015] The technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0016] This application provides a method for treating coral sand foundations, including the following steps: S1. Mix coral sand and waste tire rubber particles at a mass ratio of (85~95):(5~15) evenly, and add coral micro powder accounting for 2%~5% of the mass of the coral sand to obtain composite backfill. S2. The composite backfill material is laid in the foundation area to be treated with a preset thickness, and then vibratory compaction and static compaction are carried out in sequence. S3. Repeat step S2 until the filling reaches the design height and density requirements; When the mass ratio of the coral sand to the waste tire rubber particles is (90~95):(5~10), the number of vibration compaction cycles is 3~4. When the mass ratio of the coral sand to the waste tire rubber particles is (85~90):(10~15), the number of vibration compaction cycles is 4~6.

[0017] In step S1, the coral sand described in this application is preferably obtained locally to save on material transportation costs for offshore engineering projects. The collected coral sand raw materials are screened using a vibrating screen to remove impurities and obtain target graded coral sand with a preset particle size range of 0.075mm to 10mm.

[0018] Subsequently, gradation testing is conducted to ensure that the content of particles with a median particle size (d50) greater than 0.25 mm is not less than 50%, thus guaranteeing the gradation continuity and skeleton strength of the backfill aggregate. In practice, different median particle sizes can be flexibly selected according to the engineering design load and foundation treatment requirements. Typical but non-limiting median particle sizes include 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, and 9 mm. After passing the test, this graded coral sand can be used as backfill aggregate.

[0019] During the screening process of coral sand, fine particles with a diameter less than 0.075 mm are collected simultaneously, and the specific surface area and calcium carbonate content of this batch of material are sampled and tested. If the test results show that the specific surface area of ​​the current batch of material is between 0.8 and 1.2 m², the sample is considered complete. 2 If the content of coral sand is within the range of / g and the calcium carbonate content is greater than 90%, it will be used as coral micro powder for future use. If the coral sand material does not meet the standard, it will be transferred to another site for disposal.

[0020] Waste tire rubber granules can be obtained directly through external purchase, or they can be obtained by grading and crushing using multi-stage mechanical cutting equipment (such as tire shredders, crushers, and cutters) and then screening.

[0021] When using an external purchasing method, the irregularity (shape factor), particle size distribution (d50 and d90), and surface roughness can be considered. For irregularity, a multi-faceted, needle-like particle shape with high flaky content is preferred. This irregular shape structure, when mixed with coral sand, can form a complex spatial interlocking structure. This configuration increases the frictional resistance between particles and, under load, provides multi-point, multi-faceted elastic buffer protection for the surrounding coral sand particles using the angular parts, effectively dispersing stress concentration and inhibiting brittle breakage of the coral sand. The particle size distribution determines the overall gradation continuity of the backfill material, with d50 (median particle size) being the core factor controlling the gradation. The d50 particle size ratio of the waste tire rubber particles to the coral sand should preferably be controlled between 0.5 and 2.0, with a preferred embodiment being 0.8 to 1.2. Within this particle size ratio range, waste tire rubber particles can fully play their role in skeleton filling or reinforcement. They will not expand the coral sand skeleton due to excessive particle size, resulting in a void, nor will they lose their unique elastic damping effect due to excessive particle size, thus ensuring the uniformity and stability of the coral sand foundation.

[0022] This application utilizes a twin-shaft horizontal screw mixer for dry mixing of coral sand and waste tire rubber granules. By controlling the mixing speed and feeding rate, materials with significantly different densities are uniformly dispersed macroscopically and microscopically in three-dimensional space. Simultaneously, before mixing, the initial moisture content of the waste tire rubber granules, coral sand, and coral powder must be sampled and tested separately. Then, based on the designed proportions and initial moisture contents of each component, moisture content conversion and water replenishment calculations are performed. When the initial moisture content of the composite backfill is lower than the design lower limit (8%), the metering water spray system located at the feed end of the screw mixer is activated, preferably using atomizing nozzles to spray the corresponding amount of atomized water onto the mixture, controlling the moisture content of the composite backfill within the range of 8% to 15%, thereby providing a suitable liquid phase environment for subsequent vibratory compaction and ensuring compaction efficiency and density. The specific mass ratio of coral sand to waste tire rubber granules can be (85~95):(5~15). When the rubber content is below 5%, its buffering effect on coral sand is not significant; when the rubber content is above 15%, it will significantly increase the difficulty and cost of compaction.

[0023] Furthermore, due to the difference in particle size distribution between coral sand and waste tire rubber particles, a large number of interfacial voids inevitably form at the microscopic scale. Even after high-intensity vibration and static pressure combined operation, these microscopic local voids are difficult to completely eliminate. To fill these interfacial gaps and avoid interfacial stress concentration or bonding failure due to porosity defects, a calculated amount of coral micropowder is added to the coral sand before mixing with the waste tire rubber particles. The coral micropowder has a particle size of less than 0.075 mm and a preferred specific surface area of ​​0.8~1.2 m². 2The coral powder content is 90% or higher than 90%. During subsequent vibratory compaction, the coral powder fills the interfacial gaps between the waste tire rubber particles and the coral sand. Under the combined action of moisture and high-frequency vibration, the calcium carbonate components on the surface of the coral powder and coral sand dissolve and recrystallize, forming a dense calcareous cementitious layer in situ at the particle contact points to enhance the structural strength of the composite foundation. In specific implementation, the amount of coral powder is adaptively adjusted according to the particle size distribution of the coral sand. For example, when the median particle size (d50) of the coral sand is in the range of 3mm to 10mm (i.e., relatively coarse particles), the number of voids between particles is relatively small, but the size of each void is relatively large. At this time, the amount of coral powder is controlled at 2% to 3% of the coral sand mass, focusing on targeted filling of large pores; when the median particle size (d50) of the coral sand is in the range of 0.25mm to 3mm (i.e., relatively fine particles), the number of voids between particles is large and the connectivity is good, requiring more fine material to fill them. At this point, the amount of coral micro powder should be increased to 3% to 5% of the coral sand mass to ensure that the micropores are fully filled and to achieve continuity and densification of the gradation.

[0024] In step S2, this application employs a layered filling process to lay the coral sand foundation. The preset thickness of each layer is set to 200mm~500mm, and the specific thickness can be dynamically adjusted according to the engineering design load and the results of on-site compaction tests. The specific laying process is as follows: (1) First, a vibratory roller with a working mass of 18t~22t is used for vibratory compaction. When the d50 particle size ratio of waste tire rubber particles to coral sand is 0.8~1.2, the frequency of vibratory compaction is precisely controlled at 28Hz~32Hz, and the compaction speed is controlled at 2km / h~4km / h. At the same time, when the mass ratio is (90~95):(5~10), the number of vibratory compaction cycles is set to 3~4 times; when the mass ratio is (85~90):(10~15), due to the increase in rubber content leading to increased damping, it is necessary to increase the compaction work, and the number of vibratory compaction cycles is set to 4~6 times.

[0025] Furthermore, to improve compaction efficiency, the vibratory roller preferably employs a composite vibration mode combining vertical and horizontal vibration, with the vertical vibration frequency ranging from 25Hz to 35Hz and the horizontal vibration frequency from 20Hz to 25Hz. This mode can apply dynamic loads to the material in multiple directions, effectively promoting aggregate rearrangement and improving the uniformity of compaction.

[0026] Furthermore, vibratory compaction can be carried out using a combination of weak vibration followed by strong vibration, with 1-2 passes of weak vibration and 2-4 passes of strong vibration. The excitation force of the weak vibration is typically controlled at 40%-60% of the roller's rated excitation force, while the excitation force of the strong vibration is controlled at 80%-100% of the rated excitation force. This energy gradient setting avoids the problem of coral sand breakage caused by initial high energy, and utilizes the elastic hysteresis characteristics of waste tire rubber particles to promote the filling and bonding of coral microparticles through repeated inter-particle movement during the strong vibration stage, achieving effective interlocking of flexible and rigid particles.

[0027] (2) After the vibration compaction is completed, a static compaction operation is carried out by a static compaction roller with a working mass of 15t~25t. The compaction speed of the static compaction can be set to 1.5km / h~2.5km / h, and the number of compaction times can be set to 2~4 times.

[0028] (3) After static compaction, the current fill layer is tested for quality by standard penetration test or static cone penetration test to test the bearing capacity and relative density of the foundation. If the standard penetration blow count and relative density meet the preset requirements (e.g., relative density Dr≥75% or standard penetration blow count N≥15 blows), the next layer is filled.

[0029] Correspondingly, if any indicator fails to meet the standard, an additional vibration compaction and static compaction treatment will be applied to that layer until the test indicators meet the standard.

[0030] In step S3, after the current layer is filled and tested, the cyclic construction process is executed until the filling reaches the design height and density requirements.

[0031] This application utilizes a combined vibration and static pressure processing technology, establishing a matching relationship between material parameters and process parameters. When the particle size ratio of the rubber mortar (d50,r / d50,s) is 0.8~1.2, controlling the vibration compaction frequency to 28Hz~32Hz and the static pressure load to 18t~22t allows the composite backfill material to achieve optimal compaction. For every 5% increase in rubber content, the number of vibration compactions increases by one. This matching relationship ensures that the design compaction requirements are met under different rubber content conditions, avoiding energy waste caused by excessive compaction or insufficient compaction leading to substandard compaction. Vibration compaction can achieve a relative compaction of 70%~75%, which can be further increased to 80%~85% by subsequent static pressure compaction. Simultaneously, this application fully utilizes waste tire rubber particles as backfill material and coral micropowder, which is homologous to coral sand, as an interface modifier, achieving full utilization of local island and reef materials. This reduces the demand for natural sand and gravel materials, resulting in significant environmental, economic, and social benefits.

[0032] To facilitate a further understanding of this application, the solutions described below are further described in conjunction with embodiments. Those skilled in the art will understand that the examples described in this application are only a portion of the examples, and any other suitable specific examples are within the scope of this application.

[0033] The physical and mechanical performance tests of the embodiments and comparative examples in this application were all conducted in accordance with current national standards. Foundation bearing capacity and relative density: measured in accordance with the Technical Specification for Foundation Treatment of Buildings JGJ79-2012; Compression modulus: determined by consolidation test in accordance with GB / T 50123-2019 "Standard for Geotechnical Testing Methods".

[0034] Example 1 A ground treatment project for the runway foundation of an island airport, covering an area of ​​approximately 50,000 square meters. 2 The treatment depth is 2.0m. The foundation soil is dredged coral sand with an initial void ratio of about 1.2, a relative density of about 45%, a bearing capacity characteristic value of about 120kPa, and a compression modulus of 10MPa.

[0035] The specific steps for foundation treatment using the method described in this application are as follows: (1) Material preparation Coral sand: taken from the engineering site, screened by a vibrating screener to obtain a particle size range of 0.075mm~10mm, with a median particle size d50,s=1.2mm.

[0036] Coral micropowder: Coral micropowder with a particle size <0.075mm is collected simultaneously during the sieving of coral sand. According to relevant standards, its specific surface area is 1.0 m². 2 / g, calcium carbonate content 95%, to be stored for future use.

[0037] Waste tire rubber pellets: Waste tires are subjected to primary crushing using a tire shredder, crusher, and cutting and pulverizing machine to produce pellets with a particle size range of 1mm to 3mm, with a median particle size d50,r=1.35mm and a particle size ratio d50,r / d50,s=1.125.

[0038] Mixing and moisture content control: The initial moisture content of each component was sampled and tested. Coral micro powder accounting for 3% of the mass of coral sand was added to the coral sand. Coral sand and waste tire rubber particles were fed into a twin-shaft horizontal screw mixer at a mass ratio of 90:10. Water was precisely added through the metering spray system at the feed end to control the moisture content of the composite backfill to 12% and mix evenly.

[0039] (2) Layered filling The composite backfill material is laid in layers on the foundation area to be treated, with each layer having a loose thickness of 35cm.

[0040] (3) Vibratory compaction A vibratory roller with a working mass of 18t was used for compaction. Based on the mortar particle size ratio d50,r / d50,s=1.125, the vibration frequency was controlled at 30Hz, and the compaction speed at 3km / h. Based on a rubber content of 10%, the number of vibration compaction passes was controlled to 4. During vibration operation, a combination of one weak vibration and three strong vibrations was used, simultaneously activating a composite vibration mode.

[0041] (4) Static compaction After vibratory compaction, a 20t three-wheeled roller is used for static compaction at a speed of 2km / h, and the roller is compacted 3 times.

[0042] (5) Quality inspection According to GB 50007-2011 and JTG 3430-2020, the standard penetration test was used, and the standard penetration blow count N=18 blows was measured. The relative density Dr was calculated to be 82%, which meets the design requirements (N≥15 blows, Dr≥75%). The current compacted layer thickness is recorded as 30.0 cm.

[0043] (6) Cyclic construction Calculate the loose paving coefficient, loose paving coefficient = loose paving thickness / compacted thickness = 1.17, then correct the loose paving thickness of layers 2 to 6 to 39.7cm, repeat steps (2) to (5), and finally the cumulative compacted thickness reaches 200.1cm.

[0044] After treatment, the characteristic value of the foundation bearing capacity reached 250 kPa, which is 108% higher than before treatment, and the compression modulus reached 25 MPa.

[0045] Example 2 Foundation treatment project for a wharf site on an island reef, with a treatment area of ​​approximately 20,000 m². 2 The treatment depth is 6m. The original foundation soil is dredged coral sand with an initial void ratio of about 1.35, a relative density of about 40%, and a bearing capacity characteristic value of 100kPa.

[0046] The specific steps for foundation treatment using the method described in this application are as follows: (1) Material preparation Coral sand: taken from the engineering site, screened by a vibrating screener to obtain a particle size range of 0.075mm~10mm, with a median particle size d50,s=1.5mm.

[0047] Coral micropowder: Coral micropowder with a particle size <0.075mm was collected simultaneously during the sieving of coral sand. Sampling was conducted to determine the specific surface area and calcium carbonate content of the coral micropowder. The test results showed that its specific surface area was 1.1 m². 2 / g, calcium carbonate content 93%, to be stored for future use.

[0048] Waste tire rubber pellets: Waste tires are primary crushed using a tire shredder, crusher, and cutting and pulverizing machine to produce waste tire rubber pellets with a particle size range of 0.5mm to 4mm, with a median particle size d50,r=1.35mm and a particle size ratio d50,r / d50,s=0.9.

[0049] Mixing and moisture content control: The initial moisture content of each component was sampled and tested. Then, 4% coral micro powder was added to the coral sand by mass. The coral sand and waste tire rubber particles were fed into a twin-shaft horizontal screw mixer at a mass ratio of 88:12. Water was precisely added through the metering spray system at the feed end to control the moisture content of the composite backfill to 11% and mix evenly.

[0050] (2) Layered filling.

[0051] The composite backfill material is laid in layers on the foundation area to be treated, with each layer having a loose thickness of 50cm.

[0052] (3) Vibratory compaction A vibratory roller with a working mass of 20t was used for compaction. Based on the mortar particle size ratio d50,r / d50,s=0.9, the vibration frequency was controlled at 28Hz, and the compaction speed was 2.5km / h. Given a rubber content of 12%, the number of vibration compaction cycles was controlled to be 5. During vibration operation, a combination of 2 weak vibrations and 3 strong vibrations was used, and a composite vibration mode was simultaneously activated during compaction.

[0053] (4) Static compaction After vibratory compaction, a 25t three-wheeled roller is used for static compaction at a speed of 2km / h, for a total of 4 passes.

[0054] (5) Quality inspection The static cone penetration test was used to test the cone tip resistance qc=12MPa and the relative density Dr=80%, which met the design requirements. The current compacted layer thickness was recorded as 43.9cm.

[0055] (6) Cyclic construction Calculate the loose paving coefficient, loose paving coefficient = loose paving thickness / compacted thickness = 1.14, then correct the loose paving thickness of layers 2 to 13 to 48.8cm, repeat steps (2) to (5), and finally the cumulative compacted thickness reaches 600.1cm.

[0056] After treatment, the characteristic value of the foundation bearing capacity reached 250 kPa, which is 150% higher than before treatment; the post-construction settlement was controlled within the design allowable range.

[0057] Five temporary verification zones were divided in the runway foundation of an island airport in Example 1, with each zone having an area of ​​100m². 2 Verification tests were conducted.

[0058] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that Comparative Example 1 uses pure coral sand for backfilling, without adding waste tire rubber particles or coral powder. After treatment, the load-bearing capacity is 150 kPa, Dr = 70%, and the compression modulus is 15 MPa.

[0059] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that Comparative Example 2 only underwent vibratory compaction, without static compaction. After treatment, the bearing capacity was 135 kPa, Dr = 66%, and the compression modulus was 13 MPa.

[0060] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that Comparative Example 3 only underwent static compaction, without vibratory compaction. After treatment, the bearing capacity was 125 kPa, Dr = 60%, and the compression modulus was 11 MPa.

[0061] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that Comparative Example 4 did not incorporate coral micropowder. After treatment, the load-bearing capacity was 220 kPa, Dr = 80%, and the compressive modulus was 22 MPa.

[0062] Comparative Example 5 The difference between Comparative Example 5 and Example 1 is that Comparative Example 5 has a vibration frequency of 25Hz, a static load of 15t, and is vibratory compacted only 3 times. After treatment, the bearing capacity is 210kPa, Dr=75%, and the compression modulus is 21MPa.

[0063] Compared with Comparative Example 1, Example 1 of this application, after adding waste tire rubber particles and coral powder, has an increased foundation bearing capacity of about 66%, an increase in relative density of 12 percentage points, and an increase in compression modulus of 66%.

[0064] Compared with Comparative Examples 2 and 3, Example 1 adopts a combined treatment of vibration and static pressure, which increases the bearing capacity of the foundation by 85% and 100% respectively, and the relative density by 16 percentage points and 22 percentage points respectively, verifying the technical advantages of the combined treatment process.

[0065] Compared with Comparative Example 4, in Example 1 of this application, the bearing capacity of the foundation increased by about 14% and the compression modulus increased by about 14% after coral micropowder was incorporated.

[0066] Compared with Comparative Example 5, Example 1 of this application, after adopting material-process parameter matching control, increased the foundation bearing capacity by about 19% and the relative density by 5 percentage points.

[0067] In summary, this application can improve the bearing capacity of coral sand foundations by optimizing the gradation of waste tire rubber particles and coral sand, adjusting the interface and cementing effect of coral micropowder, and scientifically matching material parameters and process parameters.

[0068] The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for treating coral sand foundations, characterized in that, Includes the following steps: S1. Mix coral sand and waste tire rubber particles at a mass ratio of (85~95):(5~15) evenly, and add coral micro powder accounting for 2%~5% of the mass of the coral sand to obtain composite refill material. S2. The composite backfill material is laid in the foundation area to be treated with a preset thickness, and then vibratory compaction and static compaction are carried out in sequence. S3. Repeat step S2 until the filling reaches the design height and density requirements; When the mass ratio is (90~95):(5~10), the number of vibration compaction cycles is 3~4 times; when the mass ratio is (85~90):(10~15), the number of vibration compaction cycles is 4~6 times.

2. The method for treating coral sand foundations according to claim 1, characterized in that, When the median particle size ratio of the waste tire rubber particles to the coral sand is 0.8 to 1.2, the vibration frequency of the vibratory roller is 28 to 32 Hz, the rolling speed is 2 to 4 km / h, and the working mass of the vibratory roller is 18t to 22t.

3. The method for treating coral sand foundations according to claim 1, characterized in that, The compaction speed of the static compaction is controlled at 1.5~2.5km / h, and the working mass of the static compaction roller is 15~25t.

4. The method for treating coral sand foundations according to claim 1, characterized in that, The coral sand has a particle size of 0.075~10mm, with a median particle size greater than 0.25mm.

5. The method for treating coral sand foundations according to claim 1, characterized in that, The coral micropowder has a particle size of less than 0.075 mm and a specific surface area of ​​0.8~1.2 m². 2 / g, and the calcium carbonate content is greater than 90%.

6. The method for treating coral sand foundations according to claim 1, characterized in that, The particle size range of the waste tire rubber particles is 0.5~5mm.

7. The method for treating coral sand foundations according to claim 1, characterized in that, The moisture content of the composite backfill material is 8%~15%.

8. The method for treating coral sand foundations according to claim 1, characterized in that, The preset thickness is 200~500mm.