Foundation treatment method for improving horizontal bearing capacity of pile foundation
By adding cement grout to graded crushed stone or sand to form backfill material, the problem of insufficient horizontal bearing capacity of pile foundations is solved, achieving efficient compaction and improved lateral force resistance of pile foundations, simplifying the construction process and reducing costs.
Patent Information
- Application Number
- CN202411077202.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-07
- Publication Date
- 2026-02-10
AI Technical Summary
Existing foundation treatment methods are insufficient to effectively improve the horizontal bearing capacity of pile foundations, resulting in some buildings failing to meet design requirements and necessitating the use of complex and costly double-basement or seismic isolation schemes.
Cement slurry is added to graded crushed stone or graded sand and gravel to form backfill material. Through layered backfilling and compaction, the cement particles fill the gaps and form a bonded whole with the crushed stone or sand and gravel, thereby improving the soil compaction and lateral force resistance.
It significantly improves the horizontal bearing capacity of pile foundations, simplifies construction processes, shortens construction periods, reduces project costs, and reduces the need for complex foundation treatments.
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Figure CN121496906A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of foundation treatment, and particularly relates to a foundation treatment method for improving the horizontal bearing capacity of a pile foundation. BACKGROUND
[0002] With the continuous standardization of domestic and foreign standards, some buildings (structures) with a pile foundation type require the pile foundation to have a very high horizontal bearing capacity under certain working conditions, such as earthquakes, explosions, wind loads, and horizontal loads of equipment and pipelines. The horizontal bearing capacity of the pile foundation refers to the maximum horizontal force that the pile foundation can withstand under the action of horizontal loads. If no foundation treatment measures are taken, the horizontal bearing capacity of the pile foundation of the buildings (structures) is often difficult to meet the design requirements.
[0003] The commonly used foundation treatment measures currently include dynamic compaction and graded sand replacement, etc. After the above methods are used, the horizontal bearing capacity of the pile foundation is improved to a certain extent, but the horizontal bearing capacity of some buildings (structures) cannot meet the design requirements even after the above foundation treatment. SUMMARY
[0004] The application aims to at least solve the technical problem of effectively improving the horizontal bearing capacity of the pile foundation. To this end, the application provides a foundation treatment method for improving the horizontal bearing capacity of the pile foundation. The foundation treatment area forms an integral whole with a certain mutual adhesion, the compactness and lateral resistance of the soil around the pile foundation are improved, and thus the horizontal bearing capacity of the pile foundation is improved.
[0005] The application provides a foundation treatment method for improving the horizontal bearing capacity of the pile foundation, which comprises the following steps:
[0006] Cement slurry or cement and water is added to the graded gravel or graded sand and is stirred and mixed uniformly to form backfill material;
[0007] The backfill material is backfilled in layers in the foundation treatment area, each layer is compacted to ensure that the compaction coefficient reaches a preset value, and cement slurry is poured on the upper surface of each layer during the layer-by-layer backfilling to form a backfill layer after curing;
[0008] If the pile foundation is a precast pile, the pile foundation is pre-constructed before backfilling; if the pile foundation is a cast-in-place pile, the pile foundation is pre-constructed before backfilling or after the completion of the backfill layer.
[0009] In an optional embodiment, when the backfill material is backfilled in layers: after each layer of backfill material is laid, cement slurry is poured on the upper surface of the adjacent lower layer of backfill material before laying the upper layer of backfill material, and cement slurry is poured on the upper surface of the last layer of backfill material after the laying of the last layer of backfill material is completed.
[0010] In an optional embodiment, the compaction coefficient of each layer of backfill material after backfilling is greater than or equal to 0.90.
[0011] In an optional embodiment, the particle size of the graded gravel or the graded sandstone is less than or equal to 50 mm.
[0012] In an optional embodiment, the cement used or used to configure the cement slurry is Portland cement or ordinary Portland cement.
[0013] In an optional embodiment, the volume ratio of the cement slurry to the graded gravel or the graded sandstone before mixing is [15%, 30%].
[0014] In an optional embodiment, the volume ratio of the cement slurry to the graded gravel or the graded sandstone in the backfill is [10%, 28%].
[0015] In an optional embodiment, the volume ratio of the cement slurry poured on the upper surface of each layer of backfill to the graded gravel or the graded sandstone of the adjacent lower layer is [2%, 5%].
[0016] In an optional embodiment, the graded sandstone includes gravel, pebble, angular gravel, round gravel, gravel sand, coarse sand, medium sand, or stone chips.
[0017] In an optional embodiment, when using fine sand or stone powder to make the graded sandstone, the weight of the gravel or pebble incorporated is greater than or equal to 30% of the total weight of the graded sandstone.
[0018] In an optional embodiment, it further comprises: when the natural ground level is higher than the design value, excavating the soil in the foundation treatment area, and grading the foundation treatment area and the non-treatment area; when the natural ground level is lower than the design value, removing impurities in the foundation treatment area, and backfilling and compacting.
[0019] From the above technical solution, the beneficial effects of the present application are:
[0020] The present application adds a certain proportion of cement slurry or cement and water to the graded gravel or the graded sandstone, uniformly stirs, and then backfills and compactly rolls in layers. The cement particles can fill the gaps in the graded gravel or the graded sandstone, and at the same time, the cement can form a whole with a certain mutual adhesion with the graded gravel or the graded sandstone after solidification, greatly improving the compactness and lateral force resistance of the soil around the pile, thereby improving the horizontal bearing capacity of the pile foundation. In addition, the whole formed by the cement and the graded gravel or the graded sandstone after solidification is relatively loose compared to concrete, so that the pile foundation has a certain deformation capacity. BRIEF DESCRIPTION OF DRAWINGS
[0021] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of this application. For those skilled in the art, other embodiments and drawings can be obtained based on these drawings without creative effort.
[0022] Figure 1 A schematic diagram of an embodiment of the foundation treatment method of the present invention for improving the horizontal bearing capacity of pile foundations is shown;
[0023] Figure 2 A schematic diagram of a second embodiment of the foundation treatment method of the present invention for improving the horizontal bearing capacity of pile foundations is shown;
[0024] Figure 3 A schematic diagram of a third embodiment of the foundation treatment method of the present invention for improving the horizontal bearing capacity of pile foundations is shown;
[0025] Figure 4 A schematic diagram of a fourth embodiment of the foundation treatment method of the present invention for improving the horizontal bearing capacity of pile foundations is shown;
[0026] Figure 5 A schematic diagram of an embodiment of the structure after foundation treatment according to the present invention is shown;
[0027] Attached diagram labels: 110, pile foundation; 120, backfill layer; 130, original soil; 140, surface layer; 200, engineering structure. Detailed Implementation
[0028] 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.
[0029] It should be noted that all directional indications in the embodiments of the present invention 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 indications will also change accordingly.
[0030] In this invention, unless otherwise explicitly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.
[0031] Furthermore, in this invention, descriptions involving "first," "second," etc., 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. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed by this invention.
[0032] This application is described below with reference to the accompanying drawings and specific embodiments:
[0033] Please refer to Figure 1 and Figure 2 The first aspect of this application provides a foundation treatment method for improving the horizontal bearing capacity of pile foundations, mainly including the preparation of backfill material, backfilling in the foundation treatment area, and curing, specifically including the following steps:
[0034] S10. The pile foundation 110 is pre-constructed in the foundation treatment area. That is, the engineering piles are completed before the backfilling of the foundation treatment area is carried out with backfill material. The construction of the engineering piles adopts the existing process. It should be noted that when the pile foundation 110 is constructed first, both precast piles and cast-in-place piles can be used.
[0035] S20. Material arrival: If crushed stone, sand and cement are transported to the site in batches by truck, the crushed stone or sand should preferably be pre-graded, or it can be graded on-site. The maximum particle size of the crushed stone should not exceed 50mm. The sand should preferably be crushed stone, pebbles, angular gravel, round gravel, gravelly sand, coarse sand, medium sand or stone chips, and should not contain plant residues, garbage or other impurities.
[0036] S30. Mix cement and water thoroughly to prepare cement slurry. The cement can be silicate cement or ordinary silicate cement. The mass ratio of cement to water in the cement slurry should be [0.5, 0.7], such as 0.5, 0.6, or 0.7. When preparing the cement slurry, the water used for mixing and curing should meet the requirements for concrete mixing water and concrete curing water in the "Standard for Water Used in Concrete" (JGJ63), respectively.
[0037] S40. When adding cement grout to graded crushed stone or graded sand, it is advisable to pre-mix the graded crushed stone or graded sand with the prepared cement grout in batches before construction. The amount of cement grout used should meet the design requirements. Specifically, during pre-mixing, cement grout should be added while stirring to ensure that the graded crushed stone or graded sand and cement grout are thoroughly and evenly mixed to form backfill material. In the backfill material, cement particles can fill the gaps between the graded crushed stone or graded sand.
[0038] S50. In the foundation treatment area, the backfill material shall be backfilled in layers and compacted. Vibratory rollers, road rollers, or plate vibrators can be used for compaction. Before laying the upper layer of backfill material, a layer of cement grout shall be poured on the upper surface of the adjacent lower layer of backfill material. After the last layer of backfill material is laid, a layer of cement grout shall be poured on the upper surface of the last layer of backfill material. Since the pile foundation 110 has been pre-constructed, measures should be taken during backfilling to ensure that the backfill layer 120 and the pile foundation 110 are tightly bonded. For example, the joint area should be cleaned and compacted tightly using a plate vibrator.
[0039] S60. Curing is carried out on the treated area to form a backfill layer 120. The curing time is not less than 7 days. After the curing is completed, the foundation treatment is completed. Then, as needed, the surface layer 140 is laid. The surface layer 140 is cast-in-place concrete or other materials.
[0040] Existing foundation treatment methods improve the horizontal bearing capacity of pile foundation 110 through dynamic compaction and graded sand and gravel replacement. However, even after such foundation treatment, the horizontal bearing capacity of pile foundation 110 still fails to meet design requirements for some buildings and structures. The reason for this is that existing foundation treatment methods have limited effect on densifying the soil around pile foundation 110. Whether the soil is loose or relatively dense, the lateral force resistance of the soil around pile foundation 110 is improved to a certain extent after treatment by existing foundation treatment methods, and it is difficult to improve it further. Due to the existence of the above situation, it is necessary to adopt a double-base isolation scheme, a double-base rigid connection scheme, or a single-base isolation scheme to reduce the horizontal bearing capacity requirements of the superstructure on pile foundation 110.
[0041] This application uses cement grout mixed with graded crushed stone or graded sand to form backfill material. After mixing, the cement particles fill the gaps in the graded crushed stone or graded sand. Once the cement has hardened, it forms a cohesive whole with the graded crushed stone or graded sand, significantly improving the compaction and lateral force resistance of the soil around the pile, enhancing the compaction and lateral force resistance of the backfill layer 120, and increasing the horizontal bearing capacity of the pile foundation 110. This solves the problem of insufficient horizontal bearing capacity of the pile foundation 110 in conventional foundation treatment methods such as dynamic compaction and graded sand replacement. The cohesive structure formed by the cement and graded crushed stone or graded sand after hardening is relatively loose compared to concrete, giving the pile foundation 110 a certain degree of deformation capacity. By adopting this application, compared with the double-base seismic isolation scheme or the double-base rigid connection scheme, the construction period will be reduced by about 2 months and the engineering cost of the foundation will be reduced by about 25%; compared with the single-base seismic isolation scheme, the construction period will be reduced by about 1 month and the engineering cost of the foundation will be reduced by about 10%.
[0042] The following is a comparison table of different foundation treatment methods for a certain project. The data in this table shows that the horizontal bearing capacity of pile foundation 110 is greatly improved after the foundation treatment method of this application.
[0043] Comparison Table of Different Foundation Treatment Methods for a Certain Project
[0044]
[0045] A certain structure in a project had a high requirement for the horizontal bearing capacity of pile foundation 110. The surface layer of the area where this structure is located was replaced with 6m thick graded sand and gravel, followed by dynamic compaction with an energy of 3000 kN·m. Before the construction of the engineering piles, test piles were conducted according to relevant specifications. However, the test results did not meet the horizontal bearing capacity requirements of the single-pile-cap rigid connection scheme for pile foundation 110. Based on the data obtained from the test piles, the horizontal bearing capacity of pile foundation 110 could meet the design requirements using a double-pile-cap seismic isolation scheme, a double-pile-cap rigid connection scheme, or a single-pile-cap seismic isolation scheme. However, these schemes have disadvantages such as longer construction period and higher cost compared to the scheme proposed in this application. Therefore, a secondary foundation treatment was carried out around the test piles using graded crushed stone + cement grout filling, and test piles were conducted again. The test results fully met the design requirements. After comparison with various methods, the foundation treatment method proposed in this application was ultimately adopted for the engineering pile area.
[0046] Please refer to Figure 3In an optional embodiment, the foundation treatment method follows steps S11-S51, using the aforementioned steps S10, S20, S50, and S60. Steps S11, S21, S41, and S51 are the same as the original steps S10, S20, S50, and S60, respectively. The difference is that when preparing cement grout and backfill in the original steps S30 and S40, they are prepared simultaneously. In step S31, cement and water are added to graded crushed stone or graded sand and gravel, and mixed evenly to form backfill. Then, the backfill is backfilled in layers according to the steps. Regardless of the mixing method used, the amount of cement grout should meet the design requirements.
[0047] Please refer to Figure 4 In an optional embodiment, the foundation treatment method follows steps S12-S52, employing steps S20 to S60 as described above. Steps S12, S22, S32, S42, and S52 are the same as the original steps S20, S30, S40, S50, and S60, respectively. The difference lies in that the pile foundation 110 is constructed after the backfill layer 120 is completed. That is, the original step S10 is omitted, and step S62 is added after the last step S52: after the backfill layer 120 is completed and cured, and the foundation treatment is finished, the pile foundation 110 is constructed in the foundation treatment area. The pile foundation 110 is a cast-in-place pile, and precast piles cannot be used at this time. During construction, protective measures must be taken for the foundation formed by the backfill layer 120 to ensure that the foundation is not damaged when the engineering piles are constructed. After the pile foundation 110 is completed, the construction of the engineering structure 200 is carried out.
[0048] Please refer to Figure 5 In an optional embodiment, the foundation treatment method follows steps S13-S63, employing steps S12 to S62 as described above. Steps S13, S43, and S53 are the same as the original steps S12, S52, and S62, except that, compared to the original steps S22-S42, this step uses a zoned backfilling method.
[0049] S23. Divide the foundation treatment area into zones, and backfill each zone. First, select a zone that has not been backfilled, and construct the graded crushed stone or graded sand and gravel that has been poured into the zone according to the designated location. Add cement and water to the graded crushed stone or graded sand and gravel in the zone, mix them evenly, and form backfill material. This step is used when the site does not have the conditions for pre-mixing. Divide the foundation treatment area into multiple mixing zones, divide the zone according to the designated location, and carry out on-site mixing in batches within the foundation treatment area. Then, directly configure the backfill material in batches within the foundation treatment area.
[0050] S33. Backfill the material in layers within each zone and compact it. Then, complete the backfilling of each zone in batches. Lay the backfill material in the foundation treatment area to complete the zone backfilling, forming one layer of backfill material. Then, pour a layer of cement grout on the upper surface of this layer. Specifically, before laying the upper layer of backfill material in each zone, pour a layer of cement grout on the upper surface of the adjacent lower layer of backfill material; that is, pouring is completed before backfilling the next layer. Repeat step S33 in this layered manner until the backfilling of the entire foundation treatment area is completed, backfilling to the preset height. After the last layer of backfill material is laid, pour a layer of cement grout on the upper surface of the last layer of backfill material.
[0051] In an optional embodiment, when backfilling the backfill material in steps S50, S41, S42, or S33: the backfill material is laid in layers, and each layer is compacted and tested after completion to ensure that the compaction coefficient reaches the preset value. Before laying the upper layer of backfill material, a layer of cement grout is poured on the upper surface of the lower layer. After the last layer is laid, a layer of cement grout is poured on its upper surface. This method completes the backfilling of all layers. Using the above method, the backfill material and cement grout layer of adjacent layers can be better bonded, and the cement fills the gaps in the graded crushed stone or graded sand and gravel, making the interior of the entire backfill layer 120 more compact after solidification. During the testing, existing compaction coefficient testing methods, such as sand filling method, water filling method, or compaction test method, are used to determine the compaction coefficient of each backfill material after backfilling. In an optional embodiment, the compaction coefficient of each backfill material after backfilling is greater than or equal to 0.90, such as 0.90 or 0.95. If the compaction coefficient meets the requirements, another layer of backfill material is laid on the surface of the backfilled backfill material.
[0052] In an optional embodiment, the particle size of the graded crushed stone or graded sand is less than or equal to 50 mm, such as 10 mm, 30 mm or 50 mm. Different particles can be used for the graded crushed stone or graded sand, such as crushed stone, pebbles, angular gravel, rounded gravel, gravelly sand, coarse sand, medium sand or stone chips, but the particle size should be ensured to be within the above range. In an optional embodiment, graded crushed stone is used, with a ratio of particles less than or equal to 10 mm to particles with a diameter in the range of (10 mm, 30 mm) of [1.4, 1.6], such as 1.4, 1.5, or 1.6. Particles with a diameter less than or equal to 10 mm include coarse sand or medium sand, and particles with a diameter greater than 10 mm and less than or equal to 30 mm include pebbles. In an optional embodiment, before mixing, the volume ratio of cement slurry to graded crushed stone or graded sand is [15%, 30%], such as 15%, 22%, or 30%. In step S30 or S32 above, cement slurry is added to the graded crushed stone or graded sand, and the mixture is prepared according to the above ratio. In an optional embodiment, in the backfill material, the volume ratio of cement slurry to graded crushed stone or graded sand is [10%, 28%], that is, after preparation, the volume ratio of cement slurry to graded crushed stone or graded sand is 10%, 20%, or 28%.
[0053] In an optional embodiment, the volume ratio of the cement grout layer poured on the upper surface of each backfill layer to the graded crushed stone or graded sand and gravel laid below is [2%, 5%]. That is, in steps S50, S41, S42, or S33, after backfilling one layer of backfill, it is compacted before backfilling the next layer. The volume ratio of cement grout to graded crushed stone or graded sand and gravel in each layer of backfill is 2%, 3%, or 5%, meaning that most of the space in the backfill is graded crushed stone or graded sand and gravel, and only the gaps between the graded crushed stone or graded sand and gravel are filled with cement grout. In an optional embodiment, when the graded sand and gravel also includes fine sand or stone powder, the use of crushed stone and pebbles can play a role in density and strength, thus enhancing the horizontal bearing capacity of the treated pile foundation 110. The weight of the crushed stone or pebbles added is greater than or equal to 30% of the total weight of the graded sand and gravel, such as 30%, 33%, or 36%.
[0054] In an optional implementation, after the foundation treatment is completed, the horizontal bearing capacity of the pile foundation 110 needs to be tested. The testing method adopts the slow-maintained load method or the unidirectional multi-cycle loading method. The foundation treatment method of this application is based on existing pile foundation theory. It does not require the development of new equipment to match it. All construction work can be completed using existing equipment. It has the advantages of simple operation, quantifiable indicators, and controllable quality. Compared with other treatment methods, it can effectively ensure construction quality, shorten the construction period, and save project costs, indirectly playing a positive role in achieving energy conservation, emission reduction, and dual-carbon goals.
[0055] In an optional implementation, the method further includes: when the natural ground level is higher than the design value, excavating the soil in the foundation treatment area and sloping the foundation treatment area and the untreated area; when the natural ground level is lower than the design value, removing impurities from the foundation treatment area and backfilling and compacting. Specifically, when the natural ground level of the foundation treatment area is higher than the design requirement value, the excess portion is excavated, and the foundation treatment area and the untreated area are sloped according to the properties of the site soil to ensure slope stability; when the natural ground level of the foundation treatment area is lower than the design requirement value, vegetation, construction and domestic waste and other debris on the surface should be removed, and backfilling should be done with plain soil, 3:7 lime-soil, 2:8 lime-soil, or graded crushed stone or graded sand and gravel without organic impurities, and compacted in layers, with the compaction coefficient meeting the design requirements.
[0056] In optional implementations, before formal construction, the layout of underground pipelines, buried cables, and other concealed works should be investigated. If relocation is not possible, necessary protective measures should be taken. For example, if underground pipelines and cables cannot be relocated, the corresponding local locations should be protected by constructing walls on both sides and adding covers to form a trench, on which backfill material is then laid. Before construction, the groundwater level should also be determined. If the groundwater level is high and affects the construction of backfill layer 120, necessary dewatering measures should be taken, such as digging open ditches and sump pits, and using water pumps to lower the groundwater level before laying the backfill material. When there are ancient wells, ancient tombs, caves, old foundations, or hidden ponds below backfill layer 120, necessary treatment should be carried out, such as excavating them before backfilling. The backfill must meet the design requirements, such as layer thickness and compaction coefficient requirements, and can only be laid after passing inspection. Alternatively, protection can be carried out to avoid these areas depending on the actual situation.
[0057] In an optional implementation, according to the relevant requirements of the Technical Specification for Building Pile Foundations (JGJ94), before formal construction, the properties of the soil at the proposed site, the status of the completed foundation treatment, and the requirements for the horizontal bearing capacity of the pile foundation 110 should be comprehensively judged. Based on the situation of similar completed projects, the thickness of the replacement layer should be estimated, and a typical area should be selected to conduct a horizontal bearing capacity test of the pile foundation 110. Only when the test results meet the design requirements can the foundation treatment of the engineering pile area be used.
[0058] This application's embodiments are widely applicable to foundation treatment of buildings and structures in fields such as oil refining, chemical engineering, storage and transportation, surface engineering, unconventional and new energy where the pile foundation's horizontal bearing capacity requirements are high. It is mainly applicable to the following four situations: 1. Foundations with a surface layer of soft soil; 2. Foundations with a surface layer of non-soft soil, but where test pile results cannot meet design requirements; 3. Foundations where, after foundation treatment, test pile results still cannot meet design requirements; 4. Foundations where the proposed site has already undergone foundation treatment, but still cannot meet design requirements and require secondary treatment.
[0059] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," "optional example," or "optional implementation," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.
[0060] Furthermore, the technical solutions of the various embodiments can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed in this application.
[0061] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.
Claims
1. A foundation treatment method for improving the horizontal bearing capacity of pile foundations, characterized in that, include: Cement grout, or cement and water, is added to graded crushed stone or graded sand and gravel and mixed evenly to form backfill material. In the foundation treatment area, the backfill material is backfilled in layers, each layer is compacted to ensure that the compaction coefficient reaches the preset value. During the layered backfilling, cement grout is poured on the upper surface of each layer and cured to form a backfill layer (120). If the pile foundation (110) is a precast pile, it shall be constructed in advance before backfilling; if the pile foundation (110) is a cast-in-place pile, it shall be constructed in advance before backfilling or after the backfill layer (120) is completed.
2. The foundation treatment method for improving the horizontal bearing capacity of pile foundations according to claim 1, characterized in that, When backfilling in layers: After each layer of backfill is laid, before laying the next layer of backfill, pour a layer of cement slurry on the upper surface of the adjacent lower layer of backfill. After the last layer of backfill is laid, pour a layer of cement slurry on the upper surface of the last layer.
3. The foundation treatment method for improving the horizontal bearing capacity of pile foundations according to claim 2, characterized in that, The compaction coefficient of the backfill material in each layer after backfilling is greater than or equal to 0.
90.
4. The foundation treatment method for improving the horizontal bearing capacity of pile foundations according to claim 1, characterized in that, The particle size of the graded crushed stone or graded sand is less than or equal to 50 mm.
5. The foundation treatment method for improving the horizontal bearing capacity of pile foundations according to claim 1, wherein the cement used or the cement used to prepare the cement grout is silicate cement or ordinary silicate cement.
6. The foundation treatment method for improving the horizontal bearing capacity of pile foundations according to claim 1, characterized in that, Before mixing, the volume ratio of the cement slurry to the graded crushed stone or graded sand is [15%, 30%].
7. The foundation treatment method for improving the horizontal bearing capacity of pile foundations according to claim 6, characterized in that, In the backfill material, the volume ratio of the cement slurry to the graded crushed stone or graded sand is [10%, 28%].
8. The foundation treatment method for improving the horizontal bearing capacity of pile foundations according to claim 7, characterized in that, The volume ratio of the cement grout poured on the upper surface of each layer of backfill to the graded crushed stone or graded sand in the adjacent lower layer is [2%, 5%].
9. The foundation treatment method for improving the horizontal bearing capacity of pile foundations according to claim 1, characterized in that, The graded sand and gravel includes crushed stone, pebbles, angular gravel, rounded gravel, gravelly sand, coarse sand, medium sand, or stone chips.
10. The foundation treatment method for improving the horizontal bearing capacity of pile foundations according to claim 9, characterized in that, When using fine sand or stone powder to make graded sand and gravel, the weight of crushed stone or pebbles added shall be greater than or equal to 30% of the total weight of the graded sand and gravel.
11. The foundation treatment method for improving the horizontal bearing capacity of pile foundations according to any one of claims 1-10, characterized in that, Also includes: When the natural ground level is higher than the design value, the soil in the foundation treatment area should be excavated, and slopes should be made between the foundation treatment area and the untreated area; when the natural ground level is lower than the design value, impurities in the foundation treatment area should be removed, and backfilling and compaction should be carried out.