Pile-pier composite foundation construction method

Abstract

This invention discloses a pile-pier composite foundation construction method, comprising: determining the construction area for dynamic compaction foundation treatment based on a site survey report; determining the number of settlement-reducing piles based on the requirements of the superstructure; determining the layout of dynamic compaction replacement points and settlement-reducing piles based on the location of the structural column foundations; constructing and testing the dynamic compaction replacement piers based on the layout of the dynamic compaction replacement points; constructing and testing the settlement-reducing piles based on the layout of the settlement-reducing piles; and constructing the structural column foundations after passing the tests. This method fully utilizes the advantages of dynamic compaction, dynamic compaction replacement, and settlement-reducing piles, enabling the rapid and efficient formation of dynamic compaction replacement piers with high foundation bearing capacity on deep fill foundations. Settlement-reducing piles are then driven into the dynamic compaction replacement piers to further reduce settlement. It is intuitive, reliable, and convenient to construct, significantly shortening the construction period, reducing costs, and offering energy conservation, emission reduction, and high social benefits, ensuring smooth project construction.

Description

Technical Field

[0001] This invention relates to the field of pile-pier composite foundation technology, and more specifically, to a pile-pier composite foundation construction method. Background Technology

[0002] With socio-economic development, land resources are becoming increasingly scarce. The Western Development Strategy has alleviated this scarcity through land reclamation projects involving mountain clearing and backfilling. As peak-shaving and valley-filling land reclamation projects increase, backfill foundation treatment technology is developing rapidly. The dynamic compaction method, due to its economic, fast, and efficient advantages, is being widely adopted in coastal areas of my country.

[0003] In dynamic compaction construction, the depth of compaction treatment is limited by construction capacity due to the increasing complexity of site fill thickness and geological conditions. Simultaneously, with economic and technological advancements, design requirements for foundation bearing capacity and settlement are constantly increasing. Simple dynamic compaction treatment of fill cannot reach the required depth or meet design requirements. How to effectively control settlement while utilizing the economic and efficient advantages of dynamic compaction in deep fill foundation treatment remains a challenge. This invention presents a pile-pier composite foundation method, using site dynamic compaction and dynamic compaction replacement piers to improve bearing capacity, and settlement-reducing piles to control foundation settlement, achieving both increased fill bearing capacity and controlled foundation settlement. Therefore, it is necessary to propose a pile-pier composite foundation method to at least partially solve the problems existing in the prior art. Summary of the Invention

[0004] The summary section introduces a series of simplified concepts, which will be further explained in detail in the detailed description section. The summary section of this invention is not intended to limit the key features and essential technical features of the claimed technical solution, nor is it intended to determine the scope of protection of the claimed technical solution.

[0005] To at least partially solve the above problems, the present invention provides a pile-pier composite foundation construction method, comprising:

[0006] S100. Determine the construction area for dynamic compaction foundation treatment based on the survey report, and determine the number of settlement reduction piles based on the requirements of the superstructure.

[0007] S200. Based on the location of the structural column foundation, determine the layout of the dynamic compaction replacement points and the layout of the settlement reduction piles.

[0008] S300. Based on the layout of the dynamic compaction replacement points, carry out the construction and testing of the dynamic compaction replacement piers;

[0009] S400. Based on the layout of the settlement reduction piles, carry out the construction and testing of the settlement reduction piles;

[0010] S500, after passing the inspection, proceed with the construction of the structural column foundation.

[0011] Preferably, in step S100, the construction area for dynamic compaction foundation treatment is determined based on the fill thickness in the survey report.

[0012] Preferably, in step S100, the backfill soil after dynamic compaction is calculated based on the treatment depth, bearing capacity and compression modulus according to the requirements of the superstructure, and the number of dynamic compaction replacement piers and settlement reduction piles is determined according to the design requirements.

[0013] Preferably, in step S200, determining the arrangement of the dynamic compaction replacement points based on the location of the structural column foundation includes:

[0014] Based on the location of the structural column foundation, determine the location of the dynamic compaction replacement point;

[0015] Based on the dimensions of the structural column foundation, select a dynamic compaction replacement point at the center of the structural column foundation, or select multiple dynamic compaction replacement points symmetrically arranged along the central axis of the structural column foundation.

[0016] Preferably, in step S200, determining the arrangement of the settlement reduction piles includes: arranging at least two settlement reduction piles in a symmetrical manner according to the shape of the structural column foundation and the arrangement of the dynamic compaction replacement points.

[0017] Preferably, in step S300, the construction of the dynamic compaction replacement pier, based on the arrangement of the dynamic compaction replacement points, includes:

[0018] The construction location of the dynamic compaction replacement pier is determined based on the layout of the dynamic compaction replacement points;

[0019] The construction of the dynamic compaction replacement pier was carried out using a flat hammer or a column hammer, and the length and density of the dynamic compaction replacement pier met the design requirements.

[0020] The fill materials used in the construction of the dynamic compaction replacement pier include: crushed stone, quarried stone, concrete blocks, and hard coarse-grained materials such as coal gangue.

[0021] The dynamic compaction replacement pier body includes: the pier base solid body formed by construction close to the bearing layer, and the dynamic compaction replacement dense pier body formed by construction on the upper part of the pier base solid body.

[0022] Preferably, in S300, the detection of the dynamic compaction replacement pier includes: using dynamic penetration testing and drilling to detect the formed dynamic compaction replacement pier, determining the length, density and treatment effect of the dynamic compaction replacement pier, and determining the bearing capacity of the foundation after dynamic compaction and the compression modulus of the dynamic compaction replacement pier.

[0023] Preferably, in step S400, the construction of the settlement reduction piles, based on their arrangement, includes:

[0024] Based on the arrangement of the settlement reduction piles, the settlement reduction piles are constructed at the locations of the formed dynamic compaction replacement piers.

[0025] Among them, the construction of the settlement reduction pile is carried out by inserting steel pipe piles into the pre-formed hole and filling the steel pipe piles with crushed stone for grouting to form the settlement reduction pile, or by using precast piles to form the settlement reduction pile, or by using cast-in-place piles to form the settlement reduction pile.

[0026] The lower part of the settlement reduction pile is combined with the reinforcement body under the pier, and the depth of the settlement reduction pile needs to reach the bearing layer below the fill soil.

[0027] Preferably, in step S400, the detection of the settlement reduction piles includes:

[0028] The integrity of the pile body and the bearing capacity of each individual pile were tested in accordance with the testing and acceptance methods for rigid pile composite foundations.

[0029] The testing requirements for grouting-formed settling piles are as follows: the settling piles should be tested only after the grouting strength meets the design strength.

[0030] Preferably, during the construction of the settlement reduction piles, a detection device is used to monitor the piles in real time, and the radial offset of the piles is adjusted based on the detection results; specifically including:

[0031] The coordinates of multiple detection points on the circumference of the cross section at the top height of the pile and at least two different heights are obtained by the detection device in the vertical direction.

[0032] The detection points on the circumference of each cross section are processed to remove outliers, and the detection points on the circumference of the cross section after removing outliers are fitted to obtain the center coordinates of the fitted curve of the circumference of the cross section. The fitted curve is either circular or elliptical.

[0033] The offset and height difference of the center coordinates of the fitted curve at different heights and the center coordinates of the fitted curve at the top height in the horizontal plane were calculated respectively, and the construction of the pile was adjusted accordingly.

[0034] Compared with the prior art, the present invention has at least the following beneficial effects:

[0035] The pile-pier composite foundation construction method described in this invention fully utilizes the advantages of three processes: dynamic compaction, dynamic compaction replacement, and settlement reduction piles. It can quickly and efficiently form dynamic compaction replacement piers with high foundation bearing capacity on deep fill foundations. Settlement reduction piles are then driven into the dynamic compaction replacement piers to further reduce settlement. This method is intuitive, reliable, and convenient to construct, which can greatly shorten the construction period, reduce costs, and has energy-saving and emission-reduction benefits, as well as high social benefits. Ensuring smooth project construction is a key feature of this method.

[0036] The pile-pier composite foundation construction method of the present invention, other advantages, objectives and features of the present invention will be partly apparent from the following description, and partly understood by those skilled in the art through study and practice of the present invention. Attached Figure Description

[0037] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0038] Figure 1 This is a flowchart of the pile-pier composite foundation construction method described in this invention;

[0039] Figure 2 This is a schematic diagram of the structure of the composite foundation formed by dynamic compaction and dynamic compaction replacement of the pier body and the settlement reduction piles in the pile-pier composite foundation construction method described in this invention.

[0040] Figure 3 In the pile-pier composite foundation construction method described in this invention Figure 2 A partially enlarged structural diagram;

[0041] Figure 4 This is a schematic diagram showing the tilting of a pile during the inspection of the piles constructed in the pile-pier composite foundation method described in this invention (the portion of the pile below ground level is not shown). Detailed Implementation

[0042] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments, so that those skilled in the art can implement it based on the description.

[0043] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0044] A structural column is a vertical main structural member in a building (superstructure) that supports the weight of the objects above it.

[0045] Structural column foundations are load-bearing components that are in contact with the ground at the bottom of a building. Their function is to transfer the load of the upper part of the building to the ground. Therefore, the ground must be firm, stable and reliable. The structural components below ground level of an engineering structure are used to transfer the load of the upper structure to the ground. They are an important part of houses, bridges, docks and other structures.

[0046] Isolated foundations, also known as independent foundations or column foundations, are commonly used when the superstructure of a building is a frame structure or a single-story frame structure. Square or rectangular isolated foundations are often used, and their forms include stepped and conical. Isolated foundations under structural columns are the most common and economical type of structural column foundation. They are suitable for columns with a column spacing of 4-12m, small and uniform loads, uniform site conditions, and a certain degree of adaptability to uneven settlement. The materials used depend on the column material and the size of the load, and commonly include brick, concrete, and reinforced concrete.

[0047] The technical challenges of deep fill foundation treatment include: ① The need for fill treatment to ensure sufficient treatment depth and bearing capacity to meet the requirements of the subsequent superstructure; ② The subsequent independent foundations are sensitive to settlement, and due to the characteristics of dynamic compaction and dynamic compaction replacement processes, the foundations cannot be treated to the bottom or the calculated settlement after treatment cannot meet the design requirements; ③ After the dynamic compaction replacement piers are formed, it makes the construction of subsequent settlement reduction piles difficult, and ordinary pile foundation construction cannot reach the predetermined depth.

[0048] This invention solves the technical difficulties in the treatment of deep fill foundations and makes full use of the advantages of both dynamic compaction replacement and settlement reduction pile construction techniques.

[0049] like Figures 1-4 As shown, the present invention provides a pile-pier composite foundation construction method, comprising:

[0050] S100. Determine the construction area for dynamic compaction foundation treatment based on the survey report, and determine the number of settling reduction piles 2 according to the requirements of the superstructure.

[0051] S200. Based on the location of the structural column foundation 4, determine the layout of the dynamic compaction replacement points and the layout of the settlement reduction piles 2.

[0052] S300. Based on the layout of the dynamic compaction replacement points, carry out the construction and testing of dynamic compaction replacement pier 1;

[0053] S400. Based on the arrangement of the settlement reduction piles 2, carry out the construction and testing of the settlement reduction piles 2;

[0054] After passing the S500 inspection, proceed with the construction of the structural column foundation 4.

[0055] The working principle of the above technical solution is as follows: Based on the borehole profile provided in the survey report, the construction area requiring dynamic compaction foundation treatment is determined. The energy level of dynamic compaction replacement is determined according to the thickness of the fill. The number of settlement reduction piles 2 is determined according to the requirements of the superstructure. Based on engineering experience and the location of the structural column foundation 4, the layout of the dynamic compaction replacement points and the layout of the settlement reduction piles 2 are determined. First, the fill is dynamically compacted in the construction area. Then, the construction and testing of the dynamic compaction replacement pier 1 and the construction and testing of the settlement reduction piles 2 are carried out in sequence. After the construction and testing results of the dynamic compaction replacement pier 1 and the settlement reduction piles 2 are qualified, a pile cap 5 is set on the top of the settlement reduction piles 2. Then, a cushion layer 6 is set on the pile cap 5. Then, the construction of the structural column foundation 4 is carried out according to the general independent foundation construction process.

[0056] Here is an example of an engineering application:

[0057] The project is located in a new energy industrial park in a mountainous city in southwest my country. The backfill soil layer on the site is relatively thick, with the deepest layer reaching more than 20m. Below the backfill soil is basically bedrock (bearing layer 3). The original design plan was to use pile foundation (a deep foundation consisting of piles and pile caps connecting the pile tops, or a single pile foundation consisting of columns and pile foundations, referred to as pile foundation). Later, the pile-pier composite foundation construction method described in this invention was adopted, which saved 60% of the cost and 50% of the construction period compared with the original design plan.

[0058] The successful implementation process of this construction method is as follows: During the implementation of this project, due to the large thickness of the backfill soil, reaching a maximum of over 20m, dynamic compaction and dynamic compaction replacement tests were conducted using energy levels of 18000kN·m to 25000kN·m. The replacement depth was found to be approximately 18 to 20m. For some backfill soil with a thickness less than 18 to 20m, it was assumed that the dynamic compaction replacement pier 1 had reached the bottom (close to the bearing layer 3). However, for backfill soil thicker than 18 to 20m, some backfill soil remained unreinforced. Considering the potential for excessive foundation settlement due to settlement of the unreinforced backfill soil, settlement reduction piles were constructed to form a pile-pier composite foundation method, thereby reducing post-construction settlement. The specific construction steps of this method are as follows:

[0059] ①Based on the survey report, the construction area for dynamic compaction foundation treatment was determined;

[0060] ②Based on engineering experience and superstructure requirements, the number of settlement reduction piles is determined through calculation;

[0061] ③ Determine the layout of the dynamic compaction replacement points based on the location of the structural column foundation 4;

[0062] ④ Determine the layout of the settlement reduction piles based on the location of the structural column foundation 4 and the arrangement of the dynamic compaction replacement points;

[0063] ⑤ Carry out the construction of dynamic compaction replacement pier 1 to form dynamic compaction replacement pier 1;

[0064] ⑥ Conduct inspection and acceptance of the dynamic compaction replacement pier 1;

[0065] ⑦ Carry out the construction of the settlement reduction piles to ensure that the settlement reduction piles penetrate into the bedrock 3;

[0066] ⑧ Carry out the construction of pile cap 5 and the acceptance of the settlement reduction pile;

[0067] ⑨ Carry out the construction of the structural column foundation 4.

[0068] The beneficial effects of the above technical solution are as follows: The original intention of this invention is to provide a fast, efficient, intuitive, and reliable method for foundation treatment in deep fill soil areas where there are high requirements for bearing capacity and settlement. This method can fully utilize the advantages of three processes: dynamic compaction, dynamic compaction replacement, and settlement reduction piles. It can quickly and efficiently form a dynamic compaction replacement pier 1 with high foundation bearing capacity on the dynamic compaction foundation of deep fill soil areas. Settlement reduction piles are then driven into the dynamic compaction replacement pier 1 to reduce settlement. The method is intuitive, reliable, and convenient to construct, which can greatly shorten the construction period, reduce costs, save energy and reduce emissions, and has high social benefits. Ensuring smooth construction of the project is also a key feature of this method.

[0069] In one embodiment, in step S100, the construction area for the site dynamic compaction foundation treatment is determined based on the fill thickness in the survey report.

[0070] The working principle and beneficial effects of the above technical solution are as follows: Based on the borehole profile provided in the survey report, the thickness of the fill can be determined, thereby identifying the construction area that requires site dynamic compaction treatment, and determining the energy level of dynamic compaction replacement according to the fill thickness. This construction method can be adopted for areas with thick fill, where dynamic compaction replacement is feasible, but where there are many limitations on pile foundation construction and where pile formation efficiency and economy are not advantageous.

[0071] In one embodiment, in S100, according to the requirements of the superstructure, the backfill soil after the site is subjected to dynamic compaction is calculated based on the treatment depth, bearing capacity and compression modulus, and the number of dynamic compaction replacement piers 1 and settlement reduction piles 2 are determined according to the design requirements.

[0072] The design requires that the superstructure load be borne jointly by the rigid pile foundation and the ground foundation. The number n of the settlement reduction piles 2 is determined by the following formula:

[0073]

[0074] The foundation settlement calculation shall be performed in accordance with 5.3.5 of the "Code for Design of Building Foundations" (GB50007-2011), where p0 is taken as p 0spk The calculated S ≤ [S];

[0075] In the formula: u p Let be the perimeter (m) of settlement pile 2;

[0076] q si Let be the characteristic value (kPa) of the side resistance of the i-th layer of soil around the settlement pile 2, i = 1, 2, ..., m, determined according to the investigation report or experience of the foundation after dynamic compaction;

[0077] l pi Let be the thickness (m) of the i-th soil layer within the length of settlement pile 2;

[0078] α p The end resistance utilization coefficient of settlement pile 2 is determined according to specifications or experience;

[0079] q p The characteristic value (kPa) of the end resistance of the settlement pile 2 is determined according to the investigation report or experience of the post-compacted foundation.

[0080] N represents the axial force (kN) in the structural column foundation.

[0081] R a The characteristic value of the bearing capacity of a single pile (kN);

[0082] A p The area at the pile tip (㎡);

[0083] p 0spk To satisfy the additional pressure (kPa) shared by the composite foundation in the deformation calculation (S≤[S]), if the condition is not met, the number of settlement piles 2 n is increased;

[0084] l p and b p These are the length and width dimensions (m) of the pile cap 5;

[0085] l and b are the length and width dimensions (m) of the structural column foundation 4, respectively;

[0086] S represents the settlement (m) of the structural column foundation 4.

[0087] [S] represents the maximum settlement (m) specified in the design or specifications.

[0088] The working principle and beneficial effects of the above technical solution are as follows: When the foundation bearing capacity meets the requirements of the superstructure, the treated fill is calculated based on the treatment depth, bearing capacity, and empirical values ​​of the compression modulus according to settlement control. The number of dynamic compaction replacement piers 1 and settlement reduction piles 2 is determined according to the design requirements to ensure that the resulting composite foundation meets the settlement design requirements. The number n of settlement reduction piles 2 is determined using the above calculation method. The number of dynamic compaction replacement piers 1 is mainly based on the load size, the size of the structural column foundation 4, and the geological conditions. Larger loads require larger structural column foundation 4 dimensions, necessitating the arrangement of 2 or 4 replacement points under the structural column foundation 4. Generally, one replacement point is arranged under each structural column foundation 4. If the geological conditions indicate deep soft soil, a column hammer dynamic compaction replacement is generally used. If the area of ​​the column hammer replacement pier is small (2-4 square meters), there may be more dynamic compaction replacement points. If the geological conditions are good and the energy level is high, a flat hammer dynamic compaction replacement is generally used. If the area of ​​the flat hammer replacement pier is large (5-10 square meters), there will be relatively fewer dynamic compaction replacement points.

[0089] In one embodiment, in step S200, determining the arrangement of the dynamic compaction replacement points based on the location of the structural column foundation 4 includes:

[0090] Based on the location of structural column foundation 4, the location of the dynamic compaction replacement point is determined;

[0091] Based on the dimensions of the structural column foundation 4, a dynamic compaction replacement point can be arranged at the center of the structural column foundation 4, or multiple dynamic compaction replacement points can be arranged symmetrically along the central axis of the structural column foundation 4.

[0092] The working principle and beneficial effects of the above technical solution are as follows: The location of the structural column foundation 4 is determined by the superstructure (building) and is known. Therefore, the arrangement of the dynamic compaction replacement points is determined based on the location, size, and shape of the structural column foundation 4. The arrangement of the dynamic compaction replacement points is determined based on the superstructure load and the shape and size of the foundation. For small-sized, regularly shaped structural column foundations 4, one dynamic compaction replacement point can be arranged at the center of the structural column foundation 4. For larger-sized structural column foundations 4, multiple dynamic compaction replacement points can be arranged in an axially symmetrical manner to ensure uniform stress distribution under the structural column foundation 4. For example, two (even numbers) dynamic compaction replacement points can be symmetrically arranged (even numbers) or four dynamic compaction replacement points can be evenly arranged under a larger-sized structural column foundation 4 so that the structural column foundation 4 can evenly transfer the stress of the superstructure to the dynamic compaction replacement pier 1, thereby uniformly bearing the load of the superstructure.

[0093] In one embodiment, in step S200, determining the arrangement of the settlement reduction piles 2 includes: arranging at least two settlement reduction piles 2 in a symmetrical manner according to the shape of the structural column foundation 4 and the arrangement of the dynamic compaction replacement points.

[0094] The working principle and beneficial effects of the above technical solution are as follows: the settlement reduction piles 2 are arranged symmetrically at the center and / or axis. The settlement reduction piles 2 can be precast piles or cast-in-place piles. The top pile of the settlement reduction piles 2 is generally equipped with a pile cap 5. According to the shape and size of the structural column foundation 4 and the arrangement of the dynamic compaction replacement points, more than two settlement reduction piles 2 are arranged symmetrically. The settlement reduction piles 2 are arranged on the outside or edge of the dynamic compaction replacement points to ensure that the settlement reduction effect of the settlement reduction piles 2 is fully utilized.

[0095] In one embodiment, in step S300, the construction of the dynamic compaction replacement pier 1, based on the arrangement of the dynamic compaction replacement points, includes:

[0096] Based on the layout of the dynamic compaction replacement points, the construction location of dynamic compaction replacement pier 1 is determined;

[0097] The construction of pier 1 was carried out by dynamic compaction using a flat hammer or a column hammer;

[0098] Among them, the fill materials used in the construction of the dynamic compaction replacement pier 1 include: crushed stone, quarried stone, concrete blocks and hard coarse materials such as coal gangue.

[0099] The dynamic compaction replacement pier 1 includes: a pier base reinforcement body 120 formed by construction near the bearing layer 3, and a dynamic compaction replacement dense pier 110 formed on the upper part of the pier base reinforcement body 120.

[0100] The working principle and beneficial effects of the above technical solution: The dynamic compaction replacement pier 1 includes: a pier under-reinforcement body 120 formed close to the bearing layer 3, and a dynamic compaction replacement dense pier 110 formed on the upper part of the pier under-reinforcement body 120. The radial dimension of the pier under-reinforcement body 120 is greater than the radial dimension of the dynamic compaction replacement dense pier 110.

[0101] The soil layer that directly bears the foundation load is called bearing layer 3, which can be bedrock;

[0102] Based on the requirements of the superstructure, foundation size, geological conditions, environmental requirements, fill material supply, and construction equipment capacity at the construction site, either flat hammer dynamic compaction or column hammer dynamic compaction can be used for replacement. Flat hammers with a diameter of 2-3m are used, while column hammers with a diameter of 1-2m are used to form a dynamic compaction replacement pier 1 of a certain depth. The fill material used in the construction of the dynamic compaction replacement pier 1 should be hard coarse-grained materials, including crushed stone, quarried stone, mountain stone, concrete blocks, coal gangue, and other hard coarse-grained materials that are not easy to crush. Plant roots, silt, domestic waste, etc. must not be mixed in. This ensures the bearing capacity and deformation resistance of the formed dynamic compaction replacement pier 1.

[0103] In one embodiment, the detection of the dynamic compaction replacement pier 1 in S300 includes: using dynamic penetration and drilling to detect the dynamic compaction replacement pier 1 formed by dynamic compaction of the site, determining the depth and treatment effect of the dynamic compaction replacement pier 1, and determining the bearing capacity of the foundation after dynamic compaction and the compression modulus of the dynamic compaction replacement pier 1.

[0104] The working principle and beneficial effects of the above technical solution are as follows: By combining dynamic penetration testing with drilling, and also by combining plate load testing, the dynamic compaction replacement pier 1 under the structural column foundation 4 can be tested to determine the depth, range and treatment effect (foundation bearing capacity) of the dynamic compaction replacement pier 1, and to determine the foundation bearing capacity after dynamic compaction and the compression modulus of the dynamic compaction replacement pier 1, etc., to provide a basis for subsequent settlement calculation.

[0105] Dynamic penetration testing can perform the following tests: provide the bearing capacity and deformation modulus (compression modulus) of shallow foundations; check the compaction degree of the dynamic compaction replacement pier 1; check whether there is an underlying soft layer in the foundation (i.e. whether there is still some backfill soil under the dynamic compaction replacement pier 1 that has not been reinforced, which can determine the depth of the dynamic compaction replacement pier 1).

[0106] Drilling is a mechanical engineering technique that uses deep drilling to obtain a profile of the strata and collect physical samples to provide information on the compaction degree, depth, and other information of the dynamic compaction replacement pier 1.

[0107] The plate load test is an in-situ test in which loads are applied in stages to a rigid bearing plate of a certain size, and the deformation of the dynamic compaction replacement pier 1 under pressure is observed under each load level to detect the bearing capacity of the foundation.

[0108] In one embodiment, in step S400, the construction of the settlement reduction piles 2, based on their arrangement, includes:

[0109] According to the arrangement of the settlement reduction piles 2, the settlement reduction piles 2 are constructed at the formed dynamic compaction replacement pier 1.

[0110] Among them, the construction of the settlement reduction pile 2 is carried out by inserting a steel pipe pile into the pre-formed hole and filling the steel pipe pile with crushed stone for grouting to form the settlement reduction pile 2, or by using a precast pile to form the settlement reduction pile 2, or by using a cast-in-place pile to form the settlement reduction pile 2.

[0111] The lower part of the settling pile 2 is combined with the pier reinforcement 120, and the depth of the settling pile 2 needs to reach the bearing layer 3 below the fill soil.

[0112] The working principle and beneficial effects of the above technical solution are as follows: the settlement reduction pile 2 is constructed at the formed dynamic compaction replacement pier 1. The settlement reduction pile 2 is constructed at the outside or edge of the dynamic compaction replacement pier 1 within the reinforcement range of the dynamic compaction replacement pier 1.

[0113] The settling reduction pile 2 can be formed in the following three ways:

[0114] The first method involves using a rotary drill to pre-drill holes. The pre-drilled holes pass through the backfill treated on the outside of the compacted pier body 110 and the solidified body 120 under the pier from top to bottom, reaching the bearing layer 3. Then, steel pipe piles are inserted into the pre-drilled holes and filled with crushed stone and grout. Once the grout strength meets the requirements, the settlement reduction pile 2 is formed. The casing can be pulled out after the steel pipe piles are inserted into the pre-drilled holes and before grouting.

[0115] The second method is to use precast piles, which are pre-formed concrete precast piles. Then, by arranging the settlement reduction piles 2, the piles are driven by hammering, so that the precast piles pass through the backfill treated on the outside of the compacted pier body 110 and the solidified body 120 under the pier to the bearing layer 3. The casing needs to be pulled out before the pile is driven to ensure that the bottom of the settlement reduction pile 2 is inserted into the bearing layer 3 below the backfill.

[0116] The third type is cast-in-place piles, which are piles made by drilling in place and then pouring in concrete or reinforced concrete. Common types include bored cast-in-place piles, which are made by drilling in place using augers, submersible drilling rigs, etc., and then pouring in concrete. During construction, there is no vibration or soil displacement, but the settlement of the pile is slightly larger. Dredged cast-in-place piles are made by driving a steel pipe with a reinforced concrete pile shoe (pile tip) or a flap-type pile shoe into the soil using a hammer or vibration, and then pouring in concrete while simultaneously pulling out the pipe to form a pile.

[0117] After the settlement reduction pile 2 is constructed, its lower part passes through the reinforcement 120 under the pier and is combined with it. Furthermore, the bottom end of the settlement reduction pile 2 is combined with the bearing layer 3 below the fill soil to better achieve the purpose of preventing foundation settlement.

[0118] In one embodiment, the detection of the settlement reduction pile 2 in step S400 includes:

[0119] The integrity of the pile body and the bearing capacity of a single pile 2 were tested in accordance with the testing and acceptance method for rigid pile composite foundation.

[0120] The testing requirements for the grouting-formed settling pile 2 are as follows: the settling pile 2 should be tested only after the grouting strength meets the design strength.

[0121] The working principle and beneficial effects of the above technical solution are as follows: After the settlement reduction pile 2 is constructed, its integrity and single pile bearing capacity should be tested as rigid piles to meet the pre-design requirements. For piles with grouting, the grouting strength should meet the design strength before testing. After the test is qualified, a pile cap 5 should be installed on the top of the settlement reduction pile 2.

[0122] In one embodiment, during the construction of the settlement reduction pile 2, a detection device is used to monitor the pile in real time, and the radial offset of the pile is adjusted based on the detection results; specifically including:

[0123] Step 1: Using a detection device, measure the coordinates P of multiple detection points on the circumference of the cross-section at the top height of the pile and at least two different heights in the vertical direction. ij (x ij ,y ij ,z ij To obtain;

[0124] Step 2: Process the detection points on the circumference of each cross section, remove outliers, and fit the detection points on the circumference of the cross section after removing outliers to obtain the center coordinates of the fitting curve of the circumference of the cross section. The fitting curve is either circular or elliptical.

[0125] The outliers were removed using the following method:

[0126] Calculate the average vertical height of multiple detection points on the same cross-section circumference.

[0127]

[0128] Calculate the difference Δz between the j-th detection point on the circumference of this cross section and the average value. j :

[0129]

[0130] Determine the difference Δz j Detection points that do not meet the preset difference value are considered abnormal detection points and are removed.

[0131] Step 3: Calculate the offset and height difference of the center coordinates of the fitted curve at different heights and the center coordinates of the fitted curve at the top height in the horizontal plane, and adjust the construction of the pile accordingly.

[0132] In step 2, the center coordinates of the fitted curve are corrected using the following method:

[0133] The point where the line connecting the detection point on the cross-sectional circumference after removing outliers and the center coordinate point of the fitted curve intersects the fitted curve is the error point. The difference between the detection point and the corresponding error point is calculated and denoted as the deviation value e.

[0134] The detection points are processed using the following formula:

[0135]

[0136] ε represents the processing result, and μ represents the processing standard value. When ε = 1, it indicates that the corresponding detection point is normal. When ε = 0, it indicates that the corresponding detection point is abnormal, and the abnormal detection point needs to be removed.

[0137] The remaining detection points after removing the abnormal detection points are fitted again to obtain the center coordinates of the corrected fitted curve.

[0138] It needs to be explained that μ, the standard value for processing, is interpreted as the standard error of the detection. It is a numerical standard for measuring the accuracy of the detection, also known as the root mean square error. It is the square root of the ratio of the square of the deviation between the detected value and the true value to the number of detection points n. Its magnitude reflects the accuracy of the set of detected values.

[0139] The working principle and beneficial effects of the above technical solution: Establish a three-dimensional coordinate system for the detection device, P ij (x ij ,y ij ,z ij Let x be the three-dimensional coordinates of the j-th detection point on the circumference of the cross-section at the i-th detection height. ij y ij and z ij Let P be the x, y, and z coordinates of the j-th detection point at the i-th detection height. The number of detection heights is not limited to three; this example uses three heights. The possible values ​​are i = 1, 2, 3, j = 1, 2, ..., n. 1j Let P be the coordinates of the detection point on the circumference of the cross-section at the top height of the pile. 2j The coordinates of the detection point on the circumference of the cross-section at the midpoint height of the pile are taken as P. 3j The coordinates of the detection point on the circumference of the cross section at the lowest point of the pile exposed on the ground at the current moment are taken. Then, the detection point is processed (this is the first processing of the detection point, that is, correcting the measurement error of its z-axis) to remove outliers, that is, remove points with large detection errors. The remaining detection points are fitted using the least squares method to obtain the center coordinates of the fitted closed curve of the cross section circumference. Then, the second processing method of the detection points is used to correct the center coordinates of the fitted curve (this is the second processing of the detection point, that is, correcting the measurement errors of its x and y axes). In this way, a more accurate corrected fitted curve center coordinate can be obtained. Then, the three-dimensional center coordinates of the cross section circumference at the three heights are k1(x1,y1,z1), k2(x2,y2,z2), and k3(x3,y3,z3). The offset and height difference of the fitted curve center coordinates at different heights and the fitted curve center coordinates at the top height in the horizontal plane are calculated respectively. Then, the inclination degree τ of the pile during the pile construction process can be calculated by the following formula:

[0140]

[0141] The angle at which the pile is inserted into the pre-drilled hole is adjusted by the degree of inclination.

[0142] By conducting real-time monitoring of the piles under construction using the above method, the piles can be kept vertical during insertion, preventing them from tilting into the pre-drilled holes and affecting the bearing capacity and anti-settlement effect of the resulting settlement reduction pile 2. The piles mentioned here can be steel pipe piles in the first type of settlement reduction pile 2, precast piles in the second type of settlement reduction pile 2, or steel pipes with reinforced concrete pile shoes (pile tips) or flap-type pile shoes in the third type of settlement reduction pile 2, to ensure that the resulting settlement reduction pile 2 has good verticality and can effectively combine with the bearing layer 3 to achieve better bearing capacity and anti-settlement effect. Moreover, compared with the prior art, this embodiment can more accurately detect the tilt degree of the pile during the construction process, thereby improving the accuracy of its adjustment and further ensuring the formation quality of the settlement reduction pile 2.

[0143] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "depth," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0144] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to 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.

[0145] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. Other modifications can be easily made by those skilled in the art. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A pile-pier composite foundation construction method, characterized in that, include: S100. Determine the construction area for the site dynamic compaction foundation treatment based on the survey report, and determine the number of settlement reduction piles (2) based on the requirements of the superstructure. S200. Based on the location of the structural column foundation (4), determine the arrangement of the dynamic compaction replacement points and the arrangement of the settlement reduction piles (2); S300. Based on the layout of the dynamic compaction replacement points, carry out the construction and testing of the dynamic compaction replacement pier (1); S400. Based on the arrangement of the settlement reduction piles (2), carry out the construction and testing of the settlement reduction piles (2); S500, after passing the inspection, proceed with the construction of the structural column foundation (4); In S300, the construction of the dynamic compaction replacement pier (1) according to the arrangement of the dynamic compaction replacement points includes: Based on the layout of the dynamic compaction replacement points, the construction location of the dynamic compaction replacement pier (1) is determined; The construction of the dynamic compaction replacement pier (1) was carried out by using a flat hammer or a column hammer. The length and density of the dynamic compaction replacement pier (1) met the design requirements. Among them, the fill materials used in the construction of the dynamic compaction replacement pier (1) include: crushed stone, quarry stone, concrete blocks and coal gangue; The dynamic compaction replacement pier (1) includes: a pier under-reinforcement body (120) formed by construction near the bearing layer (3), and a dynamic compaction replacement dense pier (110) formed by construction on the upper part of the pier under-reinforcement body (120). In S400, the construction of the settlement reduction piles (2) according to their arrangement includes: According to the arrangement of the settlement reduction piles (2), the settlement reduction piles (2) are constructed at the formed dynamic compaction replacement pier (1); Among them, the construction of the settling pile (2) is carried out by inserting steel pipe piles into the pre-formed hole and filling the steel pipe piles with crushed stone for grouting to form the settling pile (2), or by using precast piles to form the settling pile (2), or by using cast-in-place piles to form the settling pile (2). The lower part of the settling pile (2) is combined with the pier reinforcement body (120), and the depth of the settling pile (2) needs to reach the bearing layer (3) below the fill soil.

2. The pile-pier composite foundation construction method according to claim 1, characterized in that, In S100, the construction area for dynamic compaction foundation treatment is determined based on the fill thickness in the survey report.

3. The pile-pier composite foundation construction method according to claim 1, characterized in that, In S100, according to the requirements of the superstructure, the backfill soil after the site is subjected to dynamic compaction is calculated based on the treatment depth, bearing capacity and compression modulus, and the number of dynamic compaction replacement piers (1) and settling piles (2) is determined according to the design requirements.

4. The pile-pier composite foundation construction method according to claim 1, characterized in that, In S200, the arrangement of the dynamic compaction replacement points is determined according to the location of the structural column foundation (4), including: Based on the location of the structural column foundation (4), determine the location of the dynamic compaction replacement point; Based on the dimensions of the structural column foundation (4), a dynamic compaction replacement point is selected at the center of the structural column foundation (4), or multiple dynamic compaction replacement points are selected symmetrically arranged along the central axis of the structural column foundation (4).

5. The pile-pier composite foundation construction method according to claim 4, characterized in that, In S200, the arrangement of the settlement reduction piles (2) is determined, including: according to the shape of the structural column foundation (4) and the arrangement of the dynamic compaction replacement points, at least two settlement reduction piles (2) are arranged in a symmetrical manner.

6. The pile-pier composite foundation construction method according to claim 1, characterized in that, In the S300, the detection of the dynamic compaction replacement pier (1) includes: using dynamic penetration and drilling to detect the formed dynamic compaction replacement pier (1), determining the length, density and treatment effect of the dynamic compaction replacement pier (1), and determining the bearing capacity of the foundation after dynamic compaction and the compression modulus of the dynamic compaction replacement pier (1).

7. The pile-pier composite foundation construction method according to claim 1, characterized in that, In S400, the testing of the settlement reduction pile (2) includes: The integrity of the pile body and the bearing capacity of a single pile (2) were tested in accordance with the testing and acceptance method for rigid pile composite foundation. The testing requirements for the grouting-formed settling pile (2) are as follows: the settling pile (2) shall be tested after the grouting strength meets the design strength.

8. The pile-pier composite foundation construction method according to claim 1, characterized in that, During the construction of the settlement reduction piles (2), the piles are monitored in real time using a detection device, and the radial offset of the piles is adjusted based on the detection results; specifically including: The coordinates of multiple detection points on the circumference of the cross section at the top height of the pile and at least two different heights are obtained by the detection device in the vertical direction. The detection points on the circumference of each cross section are processed to remove outliers, and the detection points on the circumference of the cross section after removing outliers are fitted to obtain the center coordinates of the fitted curve of the circumference of the cross section. The fitted curve is either circular or elliptical. The offset and height difference of the center coordinates of the fitted curve at different heights and the center coordinates of the fitted curve at the top height in the horizontal plane were calculated respectively, and the construction of the pile was adjusted accordingly.

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