A method for soft foundation treatment by combining engineering pile with drainage plate and preloading
By implementing pile driving before surcharge preloading and using water guide channels and pressure transmission plates, the problem of interference of plastic drainage boards on the construction of engineering piles was solved, the foundation consolidation efficiency and construction efficiency were improved, and economical and efficient soft soil treatment was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHINA RAILWAY CONSTR GROUP CO LTD
- Filing Date
- 2023-10-30
- Publication Date
- 2026-07-31
AI Technical Summary
When constructing engineering piles on soft clay soil, plastic drainage boards are prone to shifting and twisting during the preloading process, which becomes an obstacle to the construction of engineering piles and affects the construction efficiency and effect.
Before surcharge preloading, pile driving is carried out first. Precast engineering piles with water guide channels and pressure transmission plates are used, combined with plastic drainage boards. The foundation is consolidated by monitoring with a layered settlement meter and pore water pressure gauge to avoid interference from the plastic drainage boards during pile driving.
It improves the efficiency of foundation consolidation, reduces obstacles to the construction of engineering piles, shortens the construction cycle, is economical, and does not require the addition of new equipment.
Smart Images
Figure CN117328433B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of foundation treatment and foundation engineering technology, specifically to a soft soil foundation treatment method using a combination of engineering piles and drainage boards for surcharge preloading. Background Technology
[0002] Soft clay soil strata are widely distributed in the vast coastal areas of southeastern my country. Before carrying out engineering construction activities on such soft clay soil strata, it is often necessary to improve the foundation. For example, when building houses and other ground structures on soft clay soil foundations, the conventional practice is to first reinforce the soft soil foundation and then implant the load-bearing piles required for the engineering structure. The most common and economical method for reinforcing large-area soft soil foundations is to use the drainage consolidation method with plastic drainage boards and surcharge preloading to reduce foundation settlement and improve foundation bearing capacity. However, the biggest problem with this construction method of first implementing preloading reinforcement of the foundation and then driving the engineering piles is that the plastic drainage boards implanted first become obstacles during the subsequent construction of the engineering piles. Due to the unpredictable and uncertain displacement, twisting and tilting of the plastic drainage boards after being squeezed by the soil during surcharge preloading, the possibility of the engineering piles hitting the plastic drainage boards is extremely high. Therefore, we propose a soft soil foundation treatment method that combines engineering piles and drainage boards with surcharge preloading. Summary of the Invention
[0003] The purpose of this invention is to provide a soft soil foundation treatment method that combines engineering piles and drainage boards for surcharge preloading. This method advances the engineering pile installation process, that is, it implements pile driving before the soil is preloaded and consolidated, thus avoiding the influence and constraints of the plastic drainage boards on pile driving.
[0004] To achieve the above objectives, the present invention provides the following technical solution: a method for soft soil foundation treatment using combined surcharge preloading of engineering piles and drainage boards, the specific steps of which are as follows: Determine the length of the precast piles; Clean and level the construction area; Lay a crushed stone subbase and compact it; According to the construction requirements, the layout and positioning are carried out, and the precast engineering piles are inserted into the positioning points; Plastic drainage boards are implanted into the soft soil foundation using a board insertion machine; According to the monitoring design plan or actual needs, several stratified settlement meters and pore water pressure gauges are buried in the soft soil. Place pressure transmission plates around the top of the precast engineering piles that have already been implanted; Drainage blind ditches are excavated at the surcharge preloading site. The bottom elevation of the drainage blind ditches is 10cm lower than the bottom of the lowest crushed stone cushion layer, and the slope is three per thousand. Lay a coarse sand cushion layer on the ground surface; Lay crushed stone on a coarse sand cushion layer; The earth and rock slab filling is carried out in layers, and the total thickness of the earth and rock slab filling is determined by the design load capacity. The degree of consolidation of the foundation can be obtained by using a stratified settlement meter and pore water pressure monitoring. Once the degree of consolidation of the foundation reaches the standard, the surcharge material can be unloaded and the surcharge preloading can be terminated.
[0005] Furthermore, the diameter d of the precast engineering pile is in the range of 0.6-0.9m, and multiple water guide channels are set around the precast engineering pile. The cross-section of the water guide channel is an arc greater than or equal to a semicircle, and the radius r of the arc is in the range of 0.05-0.1m.
[0006] Furthermore, the specific formula for determining the length of the precast engineering pile is as follows: (1) (2) In the formula: The length of the engineering pile; For the pile safety factor, Take 2.0; This is the design value for the pile axial force; This represents the standard value of the ultimate side friction resistance of soft soil. This represents the standard value of the ultimate side friction resistance of normal soil. Standard value of ultimate end resistance of soil at pile tip; The diameter of the pile; This refers to the length of the pile within the normal soil layer. To reinforce the thickness of the soft soil layer; The thickness of the crushed stone subbase; The thickness of the coarse sand cushion layer; The radius of the water guide channel; The number of water guide channels for the pile.
[0007] Furthermore, the cross-sectional shape of the pressure transmission plate is a square with a missing corner, and the radius Rb of the missing corner arc is determined by the radius of the precast engineering pile. Size determined: ,in, The gap between the notched corner arc of the pressure plate and the engineering pile. The range is 5-10cm.
[0008] Furthermore, the pressure plate has a side length of 1.0m, a thickness range of 0.1-0.2m, and a corner radius of 90°.
[0009] Furthermore, the thickness of the crushed stone bedding layer... The range is 5-20cm.
[0010] Furthermore, the insertion points of the plastic drainage boards are arranged in a square or quincunx pattern, and the spacing between adjacent plastic drainage boards ranges from 0.6 to 1.6 meters.
[0011] Furthermore, the insertion length of the plastic drainage board is greater than or equal to the thickness hs of the reinforced soft soil, and the plastic drainage board adjacent to the edge of the precast pile is less than or equal to 0.3m from the edge of the precast pile.
[0012] Furthermore, the thickness of the coarse sand bedding layer... The range is 10-20cm.
[0013] Furthermore, the thickness of the crushed stone laid on the coarse sand cushion layer... The range is 5-10cm.
[0014] This invention has at least the following beneficial effects: (1) This invention changes the traditional order of preloading before pile driving when reinforcing soft foundations, thus avoiding interference and obstruction from plastic drainage boards during pile driving; (2) The design of this invention is scientific and reasonable. It improves the shape of traditional precast engineering piles, adds water guide channels, solves the problem that the soil around the pile is not easy to consolidate, and reduces the inhibitory effect of the first-sinking engineering piles on the drainage and consolidation of the soil. (3) The present invention can play a role in re-compressing the driven engineering pile while preloading, which can eliminate the pile lifting caused by the soil squeezing effect during pile driving. (4) This invention does not require the addition of new equipment, shortens the construction period, and is economical; Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description
[0015] Figure 1 This is an overall schematic diagram of the soft foundation treatment method described in this invention; Figure 2 This is a cross-sectional view of the precast engineering pile of the present invention; Figure 3 This is a schematic diagram of the structure and installation of the pressure plate of the present invention.
[0016] Figure label: 1. Precast engineering piles; 2. Water diversion channel; 3. Pressure transmission plate; 4. Gap between the arc surface of the pressure transmission plate and the precast pile; 5. Gap between two adjacent pressure transmission plates; 6. Plastic drainage board; 7. Preloaded reinforced soft soil; 8. Normal soil; 9. Bottom layer of crushed stone cushion; 10. Coarse sand cushion; 11. Top layer of crushed stone cushion; 12. Stockpiled sand and gravel. Detailed Implementation
[0017] The technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.
[0018] Soft soil refers to fine-grained soil deposited in coastal areas, lakes, valleys, and riverbanks, characterized by high water content, large void ratio, high compressibility, and low shear strength. Due to its low strength and high compressibility, soft soil often presents significant challenges to engineering construction. Therefore, it is necessary to first reinforce the soft soil foundation before implanting the load-bearing piles required for the engineering structure. The traditional surcharge preloading method involves applying a load to a saturated soft soil foundation, causing pore water to be slowly discharged, reducing the pore volume, and resulting in consolidation deformation of the foundation. Simultaneously, as the excess hydrostatic pressure gradually dissipates, the effective stress gradually increases, and the foundation soil strength gradually increases until a predetermined standard is reached, at which point the load is unloaded, compacting, settling, and consolidating the foundation soil. However, the technical solution proposed in this application differs from the traditional method of first constructing surcharge preloading and then implanting engineering piles after preloading consolidation. Instead, it involves implanting precast engineering piles before surcharge preloading and then performing surcharge preloading.
[0019] Assume the thickness of the soft soil is known. Below the soft soil is normal soil, and the length of the engineering pile is... The pile diameter is d.
[0020] Please see Figure 1-3 This invention provides a technical solution: a method for soft soil foundation treatment using combined surcharge preloading of engineering piles and drainage boards, the specific steps of which are as follows: Step 1: Complete the prefabrication and transportation of engineering piles and pressure plates to the site; like Figure 1 As shown, the diameter d of the precast pile ranges from 0.6 to 0.9 m. Multiple water guide channels are set around the precast pile. The cross-section of the water guide channel is an arc greater than or equal to a semicircle, and the radius r of the arc ranges from 0.05 to 0.10 m. The water guide channels facilitate the drainage of water in the soil around the precast pile during surcharge preloading, thereby accelerating the consolidation of the soil around the pile. Furthermore, such as Figure 2 As shown, the cross-sectional shape of the pressure plate is a square with a missing corner, and the radius of the missing corner arc is... The radius of the precast engineering pile Size determined: Where 'a' is the gap between the notched arc of the pressure transmission plate and the engineering pile, and the range of 'a' is 5-10cm. The side length of the pressure transmission plate is 1.0m, the thickness ranges from 0.1-0.2m, and the angle of the notched arc of the pressure transmission plate is 90°. In use, four pressure transmission plates are used in a group. The notched arcs of the four pressure transmission plates form a complete circle and are fitted around the precast engineering pile. This facilitates the effective transfer of surcharge pressure to the soil around the precast engineering pile during surcharge preloading, and avoids the soil around the pile from being difficult to consolidate effectively due to the obstruction of the precast engineering pile. Step 2: Determine the scope of soft soil reinforcement based on the building design and construction site requirements; Based on the building plan and foundation plan, and in conjunction with the construction site layout, determine the scope of soft soil reinforcement. The scope of soft soil reinforcement should cover the plan area of the building foundation, and appropriately expand the reinforcement scope to meet the needs of foundation construction. Step 3: Determine the length of the precast piles; (1) (2) In the formula: The length of the engineering pile; For the pile safety factor, Take 2.0; This is the design value for the pile axial force; This represents the standard value of the ultimate side friction resistance of soft soil. This represents the standard value of the ultimate side friction resistance of normal soil. Standard value of ultimate end resistance of soil at pile tip; The diameter of the pile; This refers to the length of the pile within the normal soil layer. To reinforce the thickness of the soft soil layer; The thickness of the crushed stone subbase; The thickness of the coarse sand cushion layer; The radius of the water guide channel; The number of water guide channels for the pile.
[0021] Step 4: Site cleanup and leveling; Step 5: Lay and compact the crushed stone bedding layer, with a thickness of [insert thickness here]. The range is 5-20cm; Step 6: Implant precast engineering piles using static pressure or hammer driving methods; The prefabricated engineering piles according to the designed pile diameter and length are laid out and positioned according to the pile foundation design plan. For the technical solution of this application, the static pressure method is used to implant them into the soil. Static pile driving, also known as static pressure method, uses the self-weight of a special pile frame. Through pressure beams or columns, the entire self-weight, counterweight, or structural reaction force of the pile frame is hydraulically supported on the top or body of the pile using a winch pulley block or an electric oil pump. When the static pressure applied to the pile and the pile's resistance to entering the soil reach a dynamic balance, the pile gradually sinks into the foundation soil under the action of its own weight and static pressure. Step 7: Insert the plastic drainage board into the soft soil foundation using a board inserter; The plastic drainage boards are inserted in a square or quincunx pattern. The spacing between adjacent plastic drainage boards is 0.6-1.6m. The insertion length of the plastic drainage board is greater than or equal to the thickness of the reinforced soft soil. If the insertion point of the drainage board encounters an engineering pile, it should be appropriately offset to avoid it. However, plastic drainage boards must be placed in front of, behind, to the left and right of each engineering pile, and the distance between the plastic drainage board and the edge of the engineering pile should not be greater than 0.3m. Step 8: Install several stratified settlement meters and pore water pressure gauges in the soft soil according to the monitoring design plan or actual needs; The stratified settlement gauge consists of multiple single-point settlement units connected in series with PVC pipes. It is suitable for measuring the displacement between multiple layers of soil and a relatively stationary point (bedrock). It can perform long-term monitoring and automated measurement. The stratified settlement gauge is manufactured based on the principle of magnetic flux change and is widely used in roadbed settlement monitoring in engineering fields such as highways, railways, hydropower, and dams to fully understand the settlement changes of the measured roadbed. For the technical solution of this application, the CFC-40 stratified settlement gauge is preferred for settlement monitoring.
[0022] A pore water pressure gauge (also commonly known as a vibrating wire piezometer) is a sensor used to measure the pore water pressure or osmotic pressure inside a structure. Pore water pressure gauges can be classified into differential resistance type, vibrating wire type, piezoresistive type and silicon pressure type according to the instrument type. For the technical solution of this application, the vibrating wire type is mainly adopted, preferably the SZZX-FXXB type pore water pressure gauge.
[0023] Step 9: Place a pressure plate around the top of the implanted engineering pile; Step 10: At the surcharge preloading site, excavate transverse drainage ditches 15-25cm wide at intervals of 10-30m, and longitudinal drainage ditches 25-35cm wide at intervals of 50-80m. Excavate a total drainage ditch 30cm wide around the perimeter. The bottom elevation of the drainage ditches should be 10cm lower than the bottom of the lowest crushed stone cushion layer, with a slope of 0.3%. Fill the drainage ditches with fine crushed stone. Step 11: Lay a layer of coarse sand on the ground, with a thickness of [insert thickness here]. The range is 10-20cm; Step 12: Lay a layer of gravel on the coarse sand base, with a thickness of 5-10cm; Step 13: Layered filling of soil and rock slabs, the total thickness of which is determined by the design load, is the same as the traditional slab preloading method; Step 14: The degree of consolidation of the foundation can be obtained by using the results of the stratified settlement meter and pore water pressure monitoring. Once the degree of consolidation of the foundation reaches the design requirements, the surcharge material can be unloaded and the surcharge preloading can be terminated.
[0024] The specific implementation method is as follows: This implementation takes the foundation treatment project of a high-speed railway depot in Zhejiang Province as an example. The foundation area of the depot is 3200m long and 90m wide, with a shallow soft clay layer of 8m thickness. Below the soft clay is cohesive soil with good engineering properties; and the formula is known in... The length of the engineering pile; Here is the pile safety factor; here is the design value of the pile axial force. The standard value of the ultimate side friction resistance of soft clay is 1500 kN. The standard value of the ultimate side friction resistance of cohesive soil is 25 kPa. The standard value of the ultimate end resistance of the pile tip soil is 70 kPa. The pressure is 220 kPa; the pile diameter d is 0.8 m; The length of the pile within the normal soil layer; the thickness of the soft soil layer. It is 8.0m; The thickness of the crushed stone subbase; The thickness of the coarse sand cushion layer.
[0025] The first floor of the EMU depot is used for high-speed train vehicle storage and inspection lines, the second floor is used for parking, and the third floor and above are used for high-rise residential buildings. Therefore, the foundation needs to be treated and pile foundations need to be installed to meet the needs of vehicle entry and exit, vehicle storage and the construction of high-rise buildings.
[0026] The specific steps of a soft soil foundation treatment method based on a combined surcharge preloading of precast engineering piles and plastic drainage boards are as follows: S1. Complete the prefabrication and transportation of concrete engineering piles with water guide channels and pressure transmission plates to the site; S11. Precast engineering piles with water guide channels; The precast engineering piles have a diameter d = 0.8m, and the cross-section of the water guide channel is an arc greater than or equal to a semicircle with a radius r = 0.05m. There are 4 water guide channels per pile. S12, Prefabricated pressure plate; The radius of the arc of the pressure plate 'a' represents the gap between the notched corner arc of the pressure transmission plate and the engineering pile. ; Side length of the pressure plate ,thickness Furthermore, the notched corner radius of the pressure plate is 90°. S2. Determine the scope of soft soil reinforcement based on the building design and construction site requirements; S3. Determine the length of the precast piles; S31. Determine the pile diameter d; The standard diameter of the precast piles was selected as d = 0.8m; S32, Confirm ; S33, Confirm , ; S34. Determine the pile length ; S4. Leveling the construction site; S5. Lay and compact the crushed stone bedding layer; The thickness of the crushed stone cushion layer is 0.1m; S6. Implant precast concrete piles using the static pressure method; S7. Insert the plastic drainage board into the soft soil foundation using a board inserter; S8. Install a CFC-40 type stratified sedimentation meter and an SZZX-FXXB type pore water pressure gauge; S9. Place a pile pressure plate around the top of the already implanted engineering pile; S10. At the surcharge preloading site, excavate transverse drainage blind ditches with a width of 15-25cm at intervals of 10-30m, and longitudinal drainage blind ditches with a width of 25-35cm at intervals of 50-80m. Excavate a total drainage blind ditch with a width of 30cm around the perimeter. The bottom elevation of the drainage blind ditches should be 10cm lower than the bottom of the lowest crushed stone cushion layer, with a slope of 0.3%. The drainage blind ditches should be filled with fine crushed stone. S11. Lay a layer of coarse sand on the ground surface; The coarse sand cushion layer is 0.2m thick; S12. Lay a layer of crushed stone on the coarse sand cushion layer; The thickness of the crushed stone cushion layer is 0.1m; S13. Layered filling of soil and rock slabs, the total thickness of the soil and rock slabs is determined by the design load, the same as traditional slab preloading.
[0027] In summary, the soft soil foundation treatment method of this invention uses traditional mechanical construction without adding new equipment, making construction convenient. It implements pile driving before preloading and consolidating the soil, avoiding the influence and constraints of the plastic drainage board on pile driving. Furthermore, it improves the shape of traditional precast engineering piles, adds a water guide channel, solves the problem of the soil around the pile not being easily consolidated, and reduces the inhibitory effect of the pre-driven engineering piles on soil drainage and consolidation. Simultaneously, the surcharge preloading acts as a secondary pressure on the driven engineering piles, eliminating pile lifting caused by soil squeezing during pile driving, thus ensuring the soft soil foundation reinforcement effect and the bearing capacity of the engineering piles.
[0028] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.
[0029] For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances. When an element is referred to as being "assembled on," "mounted on," "fixed to," or "set on" another element, it may be directly on the other element or there may be an intermediate element present. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be an intermediate element present. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible embodiments.
[0030] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
[0031] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," 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 disclosure. 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.
Claims
1. A method for soft soil foundation treatment using combined surcharge preloading of engineering piles and drainage boards, characterized in that, The specific steps are as follows: Determine the length of the precast piles; Clean and level the construction area; Lay a crushed stone subbase and compact it; According to the construction requirements, the layout and positioning are carried out, and the precast engineering piles are inserted into the positioning points; Plastic drainage boards are implanted into the soft soil foundation using a board insertion machine; According to the monitoring design plan or actual needs, several stratified settlement meters and pore water pressure gauges are buried in the soft soil. Place pressure transmission plates around the top of the precast engineering piles that have already been implanted; Drainage blind ditches are excavated at the surcharge preloading site. The bottom elevation of the drainage blind ditches is 10cm lower than the bottom of the lowest crushed stone cushion layer, and the slope is three per thousand. Lay a coarse sand cushion layer on the ground surface; Lay crushed stone on a coarse sand cushion layer; The earth and rock slab filling is carried out in layers, and the total thickness of the earth and rock slab filling is determined by the design load capacity. The degree of consolidation of the foundation can be obtained by using the results of stratified settlement meter and pore water pressure monitoring. Once the degree of consolidation of the foundation reaches the standard, the surcharge material can be unloaded and the surcharge preloading can be terminated. The precast engineering pile diameter d ranges from 0.6 to 0.9 m. Multiple water guide channels are set around the precast engineering pile. The cross-section of the water guide channel is an arc greater than or equal to a semicircle, and the radius r of the arc ranges from 0.05 to 0.1 m. The pressure plate has a square cross-section with a missing corner, and the radius of the missing corner arc is... The radius of the precast engineering pile Size determined: Where a is the gap between the notched arc of the pressure plate and the engineering pile, and the range of a is 5-10cm.
2. The method according to claim 1, wherein the method is characterized in that: The specific formula for determining the length of precast engineering piles is as follows: （1） （2） In the formula: The length of the engineering pile; For the pile safety factor, Take 2.0; This is the design value for the pile axial force; This represents the standard value of the ultimate side friction resistance of soft soil. This represents the standard value of the ultimate side friction resistance of normal soil. Standard value of ultimate end resistance of soil at pile tip; The diameter of the pile; This refers to the length of the pile within the normal soil layer. To reinforce the thickness of the soft soil layer; The thickness of the crushed stone subbase; The thickness of the coarse sand cushion layer; The radius of the water guide channel; The number of water guide channels for the pile.
3. The method according to claim 1, characterized in that: The pressure plate has a side length of 1.0m, a thickness range of 0.1-0.2m, and a corner radius of 90°.
4. The method according to claim 1, characterized in that: The thickness of the laid stone cushion ranging from 5 to 20 cm.
5. The method according to claim 1, wherein the method is characterized in that: The plastic drainage boards are inserted at points arranged in a square or quincunx pattern, with the spacing between adjacent plastic drainage boards ranging from 0.6 to 1.6 meters.
6. The soft soil foundation treatment method using combined surcharge preloading of engineering piles and drainage boards according to claim 5, characterized in that: The insertion length of the plastic drainage board is greater than or equal to the thickness of the reinforced soft soil. Furthermore, the plastic drainage board adjacent to the edge of the precast pile should be less than or equal to 0.3m from the edge of the precast pile.
7. The method according to claim 1, wherein the method is characterized in that: The thickness of the coarse sand bedding layer The range is 10-20cm.
8. A method for soft soil foundation treatment using combined surcharge preloading of engineering piles and drainage boards according to claim 7, characterized in that: The thickness of the gravel laid on the coarse sand cushion is in the range of 5-10 cm.