A method for constructing assembled rigid piles of composite foundation

Abstract

The invention relates to a method for constructing an assembled rigid pile body of a composite foundation, and relates to the technical field of foundation pile construction in civil engineering. The rigid pile body consists of three parts from bottom to top, namely, a dense carrier at a pile end, a prefabricated hollow pile body and a prefabricated diameter expansion body. The rigid pile body can be quickly assembled during construction, and the specific construction comprises the following steps: Step 1: sinking the prefabricated hollow pile body to a set depth at a construction pile position; Step 2: using the central hole of the prefabricated hollow pile body as a channel, and tamping fillers in the channel to form a dense carrier at the pile end at the bottom end of the prefabricated hollow pile body; Step 3: placing a prefabricated diameter expansion body at the top end of the prefabricated hollow pile body. The invention has the effects of being applicable to various geological soil layers, having high work efficiency, low cost and strong bearing capacity.

Description

Technical Field

[0001] The present application relates to the technical field of civil engineering foundation pile construction, and in particular to a method for constructing an assembled rigid pile body of a composite foundation. Background Art

[0002] At present, composite foundations are widely used in construction, especially in the field of foundation treatment of construction projects. Among the commonly used composite foundation treatment methods, compaction piles made of various materials, deep mixing piles and high-pressure rotary jet piles are traditional pile foundation treatment methods that are widely used. Their advantage is that they do not require excavation and can be used to carry out pile foundation projects on the basis of the original soil. However, these pile foundation treatment methods also have limitations. For example, the treatment quality of compaction piles is uneven and the construction period is long. Deep mixing piles have high requirements on soil quality and organic matter content. High-pressure rotary jet piles have strict process control and are prone to slurry waste and environmental pollution. Moreover, the pile bodies constructed by these methods are not strong enough, so the overall bearing capacity of their composite foundations is limited.

[0003] In high-strength composite foundations, cast-in-place concrete piles are often used as reinforcements for composite foundations. At present, long spiral pressure-cast concrete technology is often used in the construction of such piles in China, such as CFG piles. However, this type of construction method uses the soil discharge method when drilling holes, which requires on-site soil cleaning and is prone to cause problems such as loose soil at the bottom of the hole and environmental pollution.

[0004] In addition, there are also cases where prefabricated piles are used as reinforcements for composite foundations, such as prestressed concrete pipe piles. Their advantage lies in their fast construction speed, especially in avoiding the shrinkage and broken piles of cast-in-place concrete pile foundations. However, in specific applications, they also have the following disadvantages: First, when encountering hard geological conditions such as gravel layers, pebble layers and weathered rock layers, the penetration ability is low, and construction is prone to being inadequate; second, the steel content of prestressed concrete pipe piles is relatively low, and the brittleness of high-strength steel wires is relatively high, and they cannot withstand large tensile and bending stresses, resulting in a low degree of matching among compressive strength, bending strength and crack resistance; third, prestressed concrete pipe piles mainly rely on pile side resistance to bear loads, and do not fully exert the end bearing function. When bearing large loads, the pile length and pile body diameter must be increased, so the production cost is relatively high.

[0005] In composite foundations, the pile-soil area replacement ratio is one of the key parameters that determine the bearing capacity. That is, the larger the surface area of ​​the piles in the composite foundation, the more piles there are, and the smaller the distance between the piles, the higher the replacement ratio, and the higher the bearing capacity of the composite foundation. However, blindly increasing the number of piles or increasing the diameter of the piles in order to improve the bearing capacity of the foundation will undoubtedly lead to adverse effects such as increased engineering workload, increased construction costs, and longer construction periods.

[0006] Against this background, in the current stage of engineering construction, prefabricated structural buildings are being vigorously promoted by the country. Compared with traditional construction methods, prefabricated structures have many advantages, such as high production efficiency, no influence from natural environment such as bad weather, controllable construction period, high factory production precision, high quality of on-site assembly, water saving, electricity saving, material saving and environmental protection. However, they also have some disadvantages, such as high cost, increased freight, size restrictions, and slightly poor earthquake resistance. However, in the field of foundation engineering, especially composite foundation piles, due to the characteristics of the project and construction conditions, there is basically no prefabricated structure.

[0007] Based on this, people hope to provide an assembled composite foundation that meets the high bearing capacity requirements and is suitable for various geological soil layers, with high work efficiency and low cost. Summary of the invention

[0008] In order to achieve an assembled composite foundation that is applicable to various geological soil layers, has high work efficiency and low cost, the present application provides an assembled rigid pile construction method for the composite foundation.

[0009] The present application provides a composite foundation assembly rigid pile construction method using the following technical solutions: A method for constructing an assembled rigid pile body of a composite foundation. The rigid pile body consists of three parts from bottom to top: a dense carrier at the pile end, a prefabricated hollow pile body, and a prefabricated expanded diameter body. The rigid pile body can be quickly assembled during construction. The specific construction includes the following steps: Step 1: Sink the prefabricated hollow pile body to the set depth at the construction pile position; Step 2: Using the central hole of the prefabricated hollow pile body as a channel, compacting the filler in the channel to form a dense carrier at the bottom end of the prefabricated hollow pile body; Step 3: Place the prefabricated expansion body on the top of the prefabricated hollow pile body.

[0010] Preferably, before the step, i.e. before the hollow pile body is sunk to the construction pile position, a bottom sealing treatment is performed on the bottom end of the prefabricated hollow pile body using a bottom sealing steel plate; A waterproof rubber pad may also be provided between the bottom sealing steel plate and the hollow pile body.

[0011] Preferably, in step 2, when performing filler tamping, the following steps are included: Step 2.1: inserting a slender weight into the prefabricated hollow pile along the channel, so that a filler and an air flow channel are formed between the slender weight and the channel; Step 2.2: feeding the cement-sand mixture along the filler and the air flow channel, and lifting a slender weight to a certain height and then dropping it to tamp the cement-sand mixture; Step 2.3: Repeat the above steps. Use a slender heavy hammer to continuously tamp the cement-sand mixture so that the soil within a certain depth and range at the lower end of the prefabricated hollow pile is reinforced and compacted, gradually forming a dense carrier at the pile end.

[0012] Preferably, in step 2 or step 2.3, the density of the carrier is tested using any of the following control standards: Control standard 1: Measure the penetration of the slender hammer for 3 to 10 hits. When the penetration value meets the design value, stop tamping. When the penetration value does not meet the design value, continue to fill the cement sand mixture and tamping until the penetration value meets the design value. Control standard two: According to geological conditions and load requirements, calculate the set filling volume of cement-sand mixture when the soil at the pile end reaches the design bearing capacity, and fill in all the cement-sand mixture in batches according to the set filling volume and complete the compaction.

[0013] Preferably, after step 2 or step 3 is completed, concrete is poured into the central hole of the prefabricated hollow pile body according to design requirements and geological conditions, or a prefabricated steel cage is first placed and then concrete is poured to improve the strength of the pile body to meet the bearing capacity requirements.

[0014] Preferably, the prefabricated diameter expansion body is a prefabricated concrete component, which is in the shape of a circular cone or a polygonal cone, and the top surface diameter is 1.5 to 4 times the diameter of the hollow pile body. A grouting hole may be left in the center of the prefabricated diameter expansion body.

[0015] Preferably, the bottom of the prefabricated enlarged body is provided with an inner recess of a certain height corresponding to the shape and diameter of the prefabricated hollow pile body, which can wrap the pile head of the hollow pile body from the outside; or the bottom of the prefabricated enlarged body is provided with an outer embedded column corresponding to the shape and diameter of the center hole of the prefabricated hollow pile body, which can be inserted into the center hole of the prefabricated hollow pile body, so that the enlarged body and the prefabricated hollow pile body are tightly embedded to improve stability.

[0016] Preferably, the hollow pile body is a precast concrete component, including a prestressed pipe pile, a precast hollow bamboo pile, or a precast hollow square pile, and the center hole thereof is circular or square.

[0017] Preferably, in step 1, the prefabricated hollow pile body is sunk into the soil at the construction pile position by using the following method or a combination of the following methods: Method 1: sinking the prefabricated hollow pile directly into the soil by hammering, vibration or static pressure; Method 2: Pre-form a pile hole in the soil by hammering, auger drilling or rotary drilling, and then place a prefabricated hollow pile in the pile hole.

[0018] In summary, the present application includes at least one of the following beneficial technical effects: 1. The hollow pile body and the expanded body in the composite foundation are prefabricated concrete components, which can be quickly assembled during construction. Compared with the pile body constructed on site, the individual quality and standard quality are significantly improved, and there will be no unqualified piles or waste piles. In addition, the construction control is simpler, and the construction speed and efficiency are more outstanding; 2. Fully combine the respective advantages of prefabricated hollow piles and dense carriers at the pile ends: cleverly use the central hole of the prefabricated hollow pile to make a dense carrier at the pile end, so that the prefabricated hollow pile is equivalent to a casing, which not only greatly improves the bearing capacity of ordinary prefabricated hollow piles, but also solves the difficulties of drilling and blocking groundwater during the construction of ordinary carrier piles, and avoids the common problems of pile body shrinkage in soft soil layers or soil layers rich in groundwater. At the same time, the advantages of prefabricated hollow piles such as simple process, fast speed, and no fear of groundwater are brought into play; 3. Significantly improve the bearing capacity of the pile and save construction costs: The dense carrier at the pile end is composed of rammed cement sand mixture, compacted soil and impact soil. The strength and modulus gradually decrease from the inside to the outside. When subjected to force, the pressure diffuses step by step during the transmission process, which is equivalent to a multi-level extended foundation. The bearing capacity of the foundation soil at the pile end is fully utilized, so that the stress borne by the pile body is diffused, reduced and reduced layer by layer, thereby significantly improving the bearing capacity of the pile. Its ultimate bearing capacity can generally be increased by more than 2 times compared with conventional prefabricated hollow piles. The better the soil properties of the bearing layer at the pile end, the greater the bearing capacity of the dense carrier at the pile end, and the higher the characteristic value of the single pile bearing capacity. Higher bearing capacity also lays the foundation for improving the pile-soil replacement rate. At the same time, the dense carrier at the pile end can be set in the shallow soil layer in the foundation. Under the condition of providing the same bearing capacity, the length and diameter of the prefabricated hollow pile can be effectively shortened, so that the overall cost of the foundation project can be reduced by more than 30%, which is more suitable for buildings or structures with large upper loads.

[0019] 4. Significantly improve the pile-soil replacement rate. It is not necessary to increase the number of reinforced piles in the foundation, nor to expand the diameter of the pile body. Simply by placing a prefabricated diameter expansion body on the top of the pile, the pile-soil replacement rate can be significantly improved. Compared with ordinary piles, the area replacement rate is increased by 2 to 4 times, achieving twice the result with half the effort. 5. Compared with ordinary composite foundations, it has a wider range of applications and can be used in various soil layers and foundation forms. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural schematic diagram of the assembled rigid pile body of the present application.

[0021] Figure 2 This is the af construction process diagram of this application.

[0022] Figure 3 This is the construction process diagram g and h of this application.

[0023] Figure 4 It is a cross-sectional view of a prefabricated expansion body.

[0024] Figure 5 It is a top view of the prefabricated expansion body.

[0025] Explanation of reference numerals: 1. prefabricated hollow pile body; 2. prefabricated enlarged body; 3. bottom steel plate; 4. waterproof rubber pad; 5. slender weight; 6. filler and air flow channel; 7. cement sand mixture; 8. compacted soil; 9. affected soil; 10. compacted carrier at the pile end; 11. grouting hole; Implementation

[0026] The following is combined with Figure 1-5 This application is described in further detail.

[0027] The present invention will be further described below by means of specific examples.

[0028] Reference Figure 1 As shown, it is a schematic diagram of the assembled rigid pile body of the composite foundation of the embodiment of the present application. In this embodiment, the rigid pile body is composed of three parts from bottom to top, namely, a dense carrier 10 at the pile end, a prefabricated hollow pile body 1 and a prefabricated enlarged diameter body 2; wherein, the hollow pile body is a prefabricated concrete component, including prestressed pipe piles, prefabricated hollow bamboo piles, and prefabricated hollow square piles, wherein the center hole is circular or square, and can be quickly assembled during the construction process; the length of the hollow pile body is 8m and the diameter is 400mm, and the prefabricated enlarged diameter body is a circular cone with a top surface diameter of 800mm.

[0029] The prefabricated enlarged body 2 is a prefabricated concrete component, which is in the shape of a circular cone or a polygonal cone, and the diameter of its top surface is 1.5 to 4 times the diameter of the hollow pile body. A grouting hole 11 can be left in the center of the prefabricated enlarged body 2. The bottom of the prefabricated enlarged body 2 is provided with an inner recessed seat of a certain height corresponding to the shape and diameter of the prefabricated hollow pile body 1, which can wrap the pile head of the hollow pile body from the outside; or the bottom of the prefabricated enlarged body 2 is provided with an outer embedded column corresponding to the shape and diameter of the center hole of the prefabricated hollow pile body 1, which can be inserted into the center hole of the prefabricated hollow pile body 1, so that the enlarged body and the prefabricated hollow pile body 1 are tightly fitted to improve stability.

[0030] Reference Figure 2-3 As shown, it is a construction process diagram of the rigid pile body disclosed in this embodiment, referring to Figure 2 As shown in FIG. 1 , first, a bottom sealing steel plate 3 is used to seal the bottom end of the prefabricated hollow pile body 1; the bottom sealing steel plate 3 and the pile end flange are fixed by electric welding to complete the bottom sealing. In addition, in order to further achieve the sealing performance of the bottom sealing, a waterproof rubber pad 4 can be arranged between the bottom sealing steel plate 3 and the prefabricated hollow pile body 1. The waterproof rubber pad 4 is used to ensure the actual waterproof effect.

[0031] Reference Figure 2 As shown in b, after the bottom sealing operation is completed, the prefabricated hollow pile body 1 is directly sunk into the soil by hammering, vibration or static pressure, or a pile hole is pre-formed in the soil by heavy hammer impact or spiral drilling or rotary drilling, and then the prefabricated hollow pile body 1 is placed in the pile hole, and the prefabricated hollow pile body 1 is sunk to the set depth at the construction pile position by a diesel pile hammer; after sinking, refer to Figure 2 As shown in c, a slender weight 5 is inserted into the prefabricated hollow pile body 1 along the channel. The diameter of the slender weight 5 is 2 mm smaller than the central hole of the prefabricated hollow pile body 1. A filler and air flow channel 6 is formed between the slender weight 5 and the channel. The slender weight 5 is lifted to directly hit the bottom steel plate 3, thereby knocking the bottom steel plate 3 away from the bottom end of the prefabricated hollow pile body 1.

[0032] Reference Figure 2 d, the cement-sand mixture 7 is fed into the filler and the air flow channel 6, and the slender weight 5 is lifted to a certain height and then dropped to tamp the cement-sand mixture 7; Figure 2 As shown in FIG. 5 , the cement-sand mixture 7 is repeatedly filled in and tamped with a slender heavy hammer 5, so that the soil at a certain depth and range at the lower end of the prefabricated hollow pile body 1 is reinforced and compacted, and a compact carrier 10 at the pile end is gradually formed. The compact carrier 10 at the pile end is composed of the filled cement-sand mixture 7, the compacted soil 8 and the influencing soil 9 from the inside to the outside.

[0033] In order to test the compacted carrier 10 at the pile end, refer to Figure 2 As shown in figure f, the penetration of the slender hammer with 3 to 10 blows is measured. When the penetration measurement value meets the design value, the tamping is stopped. When the penetration measurement value does not meet the design value, the cement sand mixture 7 is continuously filled and the tamping operation is performed until the penetration measurement value meets the design value. This is a testing method. Alternatively, according to geological conditions and load requirements, the set filling amount of the cement sand mixture 7 when the soil at the pile end reaches the design bearing capacity is calculated. According to the set filling amount, all the cement sand mixture 7 is filled in batches and tamped to measure the penetration to form a dense carrier 10 of the pile end of the composite standard.

[0034] Reference Figure 3 As shown in FIG. 6 , after the penetration measurement is completed, the slender weight 5 is raised and the prefabricated enlarged body 2 is placed on the top of the prefabricated hollow pile body 1 .

[0035] Reference Figure 3 As shown in FIG. 1 , concrete is poured into the central channel of the prefabricated hollow pile body 1 through the grouting hole 11 of the expansion body, or a prefabricated steel cage is placed first and then concrete is poured, so as to improve the strength of the pile body to meet the bearing capacity requirements and finally complete the construction of the entire rigid pile body.

[0036] Reference Figure 4 FIG. 2 is a schematic cross-sectional view of a prefabricated enlarged diameter body 2 of an embodiment of an assembled rigid pile body of the present invention.

[0037] Reference Figure 5 As shown, the prefabricated enlarged body 2 is a circular cone, and a grouting hole 11 with a diameter of 10 cm is provided in the center thereof, so that an inner recess is provided at the bottom of the prefabricated enlarged body 2. The diameter of the inner recess is equal to the diameter of the prefabricated hollow pile body 1, and can wrap and embed the pile head of the prefabricated hollow pile body 1.

[0038] The above embodiments are merely illustrative rather than restrictive, and the protection scope of the present invention cannot be limited thereto. Other different forms of changes or modifications derived from the above descriptions are still within the protection scope of the present invention.

Claims

1. A method for constructing an assembled rigid pile body of a composite foundation, characterized in that: The rigid pile body is composed of three parts from bottom to top: a compact carrier (10) at the pile end, a prefabricated hollow pile body (1) and a prefabricated expanded diameter body (2). It can be quickly assembled during construction. The specific construction includes the following steps: Step 1: sinking the prefabricated hollow pile body (1) to a set depth at the construction pile position; Step 2: using the central hole of the prefabricated hollow pile body (1) as a channel, and compacting the filler in the channel to form a dense carrier (10) at the bottom end of the prefabricated hollow pile body (1); Step 3: placing a prefabricated enlarged body (2) on the top of the prefabricated hollow pile body (1).

2. The method for constructing a composite foundation with assembled rigid piles according to claim 1, characterized in that: Before step 1, i.e. before the hollow pile body is sunk to the construction pile position, a bottom sealing treatment is performed on the bottom end of the prefabricated hollow pile body (1) using a bottom sealing steel plate (3); A waterproof rubber pad (4) may also be provided between the bottom steel plate (3) and the hollow pile body.

3. The method for constructing a composite foundation assembly-type rigid pile according to claim 1, characterized in that: In step 2, when the filler is compacted, the following steps are included: Step 2.1: inserting a slender weight (5) into the prefabricated hollow pile body (1) along the channel, so that a filler and an air flow channel (6) are formed between the slender weight (5) and the channel; Step 2.2: feeding the cement-sand mixture (7) along the filler and air flow channel (6), and lifting the slender weight (5) to a certain height and then dropping it to tamp the cement-sand mixture (7); Step 2.3: Repeat the above step 2.2, and continuously perform tamping (7) operation on the cement-sand mixture (7) by means of a slender heavy hammer (5), so that the soil within a certain depth and range at the lower end of the prefabricated hollow pile body (1) is reinforced and compacted, and gradually forms a compact carrier (10) at the pile end.

4. The method for constructing an assembled rigid pile body of a composite foundation according to claim 1 or 3, characterized in that: In step 2 or step 2.3, the compactness of the compact carrier (10) at the pile end is tested using any of the following control standards; Control standard 1: Measure the penetration of the slender hammer with 3 to 10 hits. When the penetration value meets the design value, stop tamping. When the penetration value does not meet the design value, continue to fill the cement sand mixture (7) and tamping until the penetration value meets the design value. Control standard 2: Based on geological conditions and load requirements, calculate the set filling volume of the cement-sand mixture (7) when the soil at the pile end reaches the design bearing capacity, and fill all the cement-sand mixture (7) in batches according to the set filling volume and complete the compaction.

5. The method for constructing a composite foundation assembly-type rigid pile according to claim 1, characterized in that: After step 2 or step 3 is completed, concrete is poured into the central hole of the prefabricated hollow pile body (1), or a prefabricated steel cage is first placed and then concrete is poured, according to the design requirements and geological conditions, so as to increase the strength of the pile body to meet the bearing capacity requirements.

6. The method for constructing a composite foundation assembly-type rigid pile according to claim 1, characterized in that: The prefabricated diameter expansion body (2) is a prefabricated concrete component, which is in the shape of a circular cone or a polygonal cone, and whose top surface diameter is 1.5 to 4 times the diameter of the hollow pile body. A grouting hole (9) may be left in the center of the prefabricated diameter expansion body (2).

7. A method for constructing an assembled rigid pile body of a composite foundation according to claim 1 or 6, characterized in that: The bottom of the prefabricated enlarged diameter body (2) is provided with an inner recess of a certain height corresponding to the shape and diameter of the prefabricated hollow pile body (1), which can wrap the pile head of the hollow pile body from the outside; or the bottom of the prefabricated enlarged diameter body (2) is provided with an outer embedded column corresponding to the shape and diameter of the central hole of the prefabricated hollow pile body (1), which can be inserted into the central hole of the prefabricated hollow pile body (1), so that the enlarged diameter body and the prefabricated hollow pile body (1) are tightly embedded to improve stability.

8. The method for constructing a composite foundation assembly-type rigid pile according to claim 1, characterized in that: The hollow pile body is a precast concrete component, including prestressed pipe piles, precast hollow bamboo piles, and precast hollow square piles, and the center hole is round or square.

9. The method for constructing a composite foundation assembly-type rigid pile according to claim 1, characterized in that: In step 1, the prefabricated hollow pile body (1) is sunk into the soil at the construction pile position by using the following method or a combination of the following methods: Method 1: directly sinking the prefabricated hollow pile (1) into the soil by hammering, vibrating or static pressure; Method 2: Pre-form a pile hole in the soil by hammering, drilling or rotary drilling, and then place a prefabricated hollow pile body (1) in the pile hole.

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