A composite plate for adjusting deformation of a top of an end-bearing rigid pile composite foundation

Abstract

The present application relates to a kind of end bearing rigid pile composite foundation pile top deformation adjustment composite board, belong to foundation engineering technical field, be located in the pile top of rigid pile, including upper steel cover plate, lower steel backing plate, stiffening hoop and the variable strength foam concrete board tightened by stiffening hoop, wherein upper steel cover plate and lower steel backing plate are movably embedded in stiffening hoop, and upper steel cover plate and lower steel backing plate are located at the two sides of variable strength foam concrete board respectively, and three constitute sandwich structure.The present application is arranged by composite board in the position of rigid pile top, when the stress of rigid pile top exceeds design bearing capacity characteristic value, different strength foam concrete board yields in turn, subsequent deformation is generated to continue to coordinate pile soil settlement, different from the current pile top adjusting device only relying on stiffness control method, the present application can change single stiffness control into first stiffness then strength control, increase the tolerance of composite foundation to settlement deformation, greatly improve the operability of end bearing rigid pile composite foundation engineering practice.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of foundation engineering, in particular to a pile top deformation adjustment composite plate for end-bearing rigid pile composite foundation. BACKGROUND

[0002] The rigid pile composite foundation generally adopts friction pile, when the pile end bearing layer is medium weathered rock layer, the end-bearing rigid pile cannot penetrate into the ground like the friction pile to coordinate the pile soil deformation, and can only rely on the upper cushion layer to adjust the deformation, but the adjustment capacity of the cushion layer is limited, and when the soil settlement between piles is large, the cushion layer has the problem of insufficient adjustment capacity.

[0003] The existing pile top deformation adjustment device mainly sets the adjustment stiffness according to the bearing and deformation needs, but once installed, the stiffness cannot be adjusted, and the reasonable application greatly depends on the accuracy of the design calculation settlement, and when the actual settlement is significantly greater than the design settlement, the pile and soil internal force sharing will have a large difference from the design.

[0004] The existing pile top stiffness adjustment device mainly produces vertical deformation through the crushing of internal materials or the buckling of steel structures, and the preparation process is relatively complex and the manufacturing cost is relatively high, and multiple adjustment devices often need to be connected in parallel to meet the bearing capacity requirements in engineering applications.

[0005] In the patents with the authorization announcement numbers CN203716139U and CN204343279U, a flexible pile cushion rigid pile composite foundation is proposed, the flexible pile cushion adopts an extruded plate, the natural foundation soil is caused to sink by an amount equivalent to the compressible deformation amount of the pile cap through the adjustment of the flexible pile cushion, and the bearing capacity of the natural foundation soil is improved by more than 20%, but the compressive strength of the extruded plate can only reach 900KPa, the yield strength is low, and the needs of the pressure bearing capacity of the rigid pile top of the high-rise building cannot be met, in addition, the stiffness of the extruded plate is zero after yielding, the stiffness of the rigid pile system produces a sudden change before and after yielding, and a large settlement difference is easily caused under the action of a small difference load near the yield point load, thereby causing a large additional internal force of the raft due to uneven settlement. SUMMARY

[0006] To solve the adverse effects of the pile soil settlement difference, the present application designs a pile top deformation adjustment composite plate for end-bearing rigid pile composite foundation, the composite plate is arranged at the position of the rigid pile top, when the stress of the rigid pile top exceeds the design bearing capacity characteristic value, the foam concrete plates with different strengths yield in turn to produce subsequent deformation to continue to coordinate the pile soil settlement, unlike the current pile top adjustment device which only relies on the stiffness control method, the present application can change the single stiffness control into the first stiffness and then strength control, increases the tolerance of the composite foundation to the settlement deformation, and greatly improves the operability of the end-bearing rigid pile composite foundation engineering practice.

[0007] The technical problem of the present application is solved by the following technical solution: a pile top deformation adjustment composite plate for an end bearing rigid pile composite foundation, provided on the pile top of a rigid pile, comprising an upper steel cover plate, a lower steel base plate, a stiffening hoop, and a variable strength foam concrete plate clamped by the stiffening hoop, wherein the upper steel cover plate and the lower steel base plate are movably embedded in the stiffening hoop, and the upper steel cover plate and the lower steel base plate are respectively located on both sides of the variable strength foam concrete plate, and the three constitute a sandwich structure.

[0008] In some embodiments, the diameter of the composite plate is the same as the diameter of the rigid pile.

[0009] In some embodiments, the upper steel cover plate and the lower steel base plate are adhered to the variable strength foam concrete plate by cement paste.

[0010] A preparation method of a pile top deformation adjustment composite plate for an end bearing rigid pile composite foundation, comprising the following steps:

[0011] S1. preparing an upper steel cover plate, a lower steel base plate, and a stiffening hoop;

[0012] S2. preparing foam by a physical or chemical method, and then mixing the foam into a mixed slurry composed of cement paste, admixture, and additive, which has been stirred uniformly, pouring and solidifying to form a foam concrete plate containing a large number of uniformly closed pores;

[0013] S3. layering pouring according to the method of S2, pouring upwards after the lower foam concrete plate has been cured for 2-3 days, and changing the strength of each layer of foam concrete plate by changing the amount of cement paste or the bubble rate of foam during preparation, so as to form a multi-layer variable strength foam concrete plate;

[0014] S4. adhering the upper steel cover plate and the lower steel base plate to the upper and lower surfaces of the variable strength foam concrete plate respectively, embedding the whole structure into the stiffening hoop after the three are adhered together, and tightening the stiffening hoop, so as to form a composite plate.

[0015] In some embodiments, the thickness of the upper steel cover plate and the lower steel base plate is 2-3 mm, and the wall thickness of the stiffening hoop is 1-5 mm.

[0016] In some embodiments, the thickness of each layer of the multi-layer variable strength foam concrete plate is equal, and the total thickness is 30-60 mm.

[0017] In some embodiments, the composite plate has three-stage stress characteristics of an elastic stage, a yield platform stage, and a densification stage, wherein the strain of the yield platform stage reaches 0.5-0.6.

[0018] In some embodiments, the variable strength foam concrete plate is 3-4 layers, and each layer is 10-15 mm thick.

[0019] In some embodiments, the design strength of the foam concrete plate is 1-5 MPa, the design elastic compression modulus of the foam is 230-1200 MPa, the minimum strength of the foam concrete plate can be taken as the characteristic value of the bearing capacity of the rigid pile, and the ratio of the design strength of each layer of the foam concrete plate is 1:1.15:1.3 or 1:1.15:1.3:1.45.

[0020] In summary, the present application has the following advantages:

[0021] 1. The compressive strength of the traditional high polymer material foam plate is 100-900 KPa, and the yield strength is low, which cannot meet the needs of the compressive bearing capacity of the rigid pile of high-rise buildings. The yield strength of the foam concrete plate constrained by the stiffening hoop according to the present application can be configured according to the design needs, and a higher strength can be achieved, which can meet the requirements of the pile top pressure of the rigid pile of high-rise buildings.

[0022] 2. The foam concrete in the composite plate is poured by the method of layered pouring, and the variable strength of the foam concrete is realized by changing the cement dosage and bubble rate of each layer of foam concrete. When the stress on the top of the rigid pile exceeds the minimum strength of the variable strength composite plate, the foam concrete of different strengths buckles in turn, and subsequent deformation is generated to continue to coordinate the deformation of the pile and soil. The subsequent deformation stiffness is determined by the strength ladder configuration of the multi-layer foam concrete and the plastic soil deformation amount corresponding to each layer of foam, which can be artificially controlled according to the design needs, and has strong operability.

[0023] 3. The present application changes the single stiffness control of the traditional pile top adjusting device into the control of strength and stiffness by setting the composite plate on the top of the pile, increases the tolerance of the rigid pile composite foundation to the settlement deformation, and improves the operability of the end-bearing rigid pile composite foundation engineering practice.

[0024] 4. The materials contained in the whole adjusting device are common building materials, and the cost is very low, and the construction is convenient, so it has great engineering application development prospect. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 It is a structure schematic view of a variable deformation adjusting composite plate on the top of an end-bearing rigid pile composite foundation.

[0026] Marked in the figure: 1, composite plate; 2, upper steel cover plate; 3, lower steel base plate; 4, stiffening hoop; 5, variable strength foam concrete plate.

[0027] Figure 2 It is a structure schematic view of an embodiment of the composite plate in the end-bearing rigid pile composite foundation.

[0028] Marked in the figure: 1, composite board; 6, rigid pile; 7, soil between piles; 8, bedrock; 9, cushion layer; 10, raft foundation;

[0029] Figure 3 The stress-strain measured curve of the foam concrete board with a hoop constraint strength of 0.8 MPa;

[0030] Figure 4 The stress-strain measured curve of the composite board composed of two kinds of strength foam concrete;

[0031] Figure 5 The load-total settlement test comparison curve of the two groups of rigid pile composite foundations in the second embodiment of the application;

[0032] Figure 6 The load-pile top stress test comparison curve of the two groups of rigid pile composite foundations in the second embodiment of the application;

[0033] Figure 7 The load-soil between piles stress test comparison curve of the two groups of rigid pile composite foundations in the second embodiment of the application;

[0034] Figure 8 The method schematic diagram for keeping the mixing ratio of the foam concrete unchanged, increasing the steel content of the stiffening hoop (increasing the constraint) through layering, and realizing the strength improvement of the foam concrete through the stiffening hoop change. DETAILED DESCRIPTION

[0035] The embodiments of the application are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar notations represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are intended to explain the application, and cannot be understood as a limitation of the application.

[0036] In the description of the application, it should be understood that the terms "length", "width", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the application and simplifying the description, and therefore cannot be understood as indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the application.

[0037] In addition, the terms "first", "second", "third", etc. are used only for descriptive purposes and should not be construed as implying or suggesting relative importance or an implied order of precedence of the features so indicated. Thus, features having "first", "second", "third" designations can include one or more of such features, either explicitly or implicitly.

[0038] In the present application, unless specifically and particularly defined otherwise, the terms "mounting", "connecting", "connecting", "fixing" and the like should be interpreted broadly, for example, can be fixed connection, or detachable connection, or integrated; can be mechanical connection, or electrical connection; can be directly connected, or indirectly connected through an intermediate medium, can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0039] As shown in Figure 1 and Figure 2 A top deformation adjusting composite plate of an end-bearing rigid pile composite foundation, provided on the top of a rigid pile, comprises an upper steel cover plate, a lower steel base plate, a stiffening hoop, and a variable strength foam concrete plate clamped by the stiffening hoop, wherein the upper steel cover plate and the lower steel base plate are movably embedded in the stiffening hoop, and the upper steel cover plate and the lower steel base plate are respectively located on both sides of the variable strength foam concrete plate, and the three form a sandwich structure.

[0040] In some embodiments, the diameter of the composite plate is the same as the diameter of the rigid pile.

[0041] In some embodiments, the upper steel cover plate and the lower steel base plate are adhered to the variable strength foam concrete plate by cement paste.

[0042] A preparation method of a top deformation adjusting composite plate of an end-bearing rigid pile composite foundation, comprising the following steps:

[0043] S1. Preparing an upper steel cover plate, a lower steel base plate, and a stiffening hoop;

[0044] S2. Preparing foam by physical or chemical methods, and then mixing the foam into a mixed slurry composed of cement paste, admixture, and additive, which has been stirred uniformly, pouring and solidifying to form a foam concrete plate containing a large number of uniformly closed pores;

[0045] S3. Layered pouring according to the method of S2, pouring upwards after 2-3 days of final setting of the lower foam concrete plate, and changing the strength of each layer of foam concrete plate by changing the amount of cement paste or the bubble rate of foam during preparation of each layer of foam concrete plate, so as to form a variable strength foam concrete plate with a multi-layer structure;

[0046] S4. The upper steel cover plate and the lower steel base plate are respectively bonded on the upper and lower surfaces of the variable strength foam concrete plate, and after the three are bonded into an integrated structure, the integrated structure is embedded into the stiffening hoop, and the stiffening hoop is tightened, so as to form the composite plate.

[0047] In some embodiments, the thickness of the upper steel cover plate and the lower steel base plate is 2mm-3mm, and the wall thickness of the stiffening hoop is 1mm-5mm.

[0048] In some embodiments, the thickness of each layer of the variable strength foam concrete plate of the multi-layer structure is equal, and the total thickness is 30mm-60mm.

[0049] In some embodiments, the composite plate has three-stage stress characteristics of an elastic stage, a yield platform stage and a densification stage, wherein the strain of the yield platform stage reaches 0.5-0.6.

[0050] In some embodiments, the variable strength foam concrete plate is 3-4 layers, and the thickness of each layer is 10mm-15mm.

[0051] In some embodiments, the design strength of the foam concrete plate is 1MPa-5MPa, the design elastic compression modulus of the foam is 230MPa-1200MPa, the minimum strength of the foam concrete plate can be valued according to the characteristic value of the bearing capacity of the rigid pile, and the ratio of the design strengths of the foam concrete plates of each layer is 1:1.15:1.3 or 1:1.15:1.3:1.45.

[0052] Through the above technical solutions:

[0053] Embodiment 1:

[0054] The indoor model test of the rigid pile was carried out in the structure laboratory of Nanchang University, and two groups of stress tests of the rigid pile composite foundation were carried out, one group was a pure cushion adjustment rigid pile composite foundation, and the other group was a cushion plus composite plate to adjust the rigid pile composite foundation, the test box size was 1.10m*0.83m*1.05m(length*width*height), the model pile used a diameter of 300mm round pile, the cushion thickness was 12cm, the composite plate was a composite plate composed of 0.7MPa and 1.2MPa two strength foam concrete plates, the diameter of the composite plate was the same as the diameter of the pile, Figure 4 The stress-strain curve of the composite plate test of the embodiment of the application; Figure 5 The load-total settlement test comparison curve of the rigid pile composite foundation of the embodiment of the application, Figure 6 The load-pile top stress test comparison curve of the rigid pile composite foundation of the embodiment of the application, Figure 7 The load-pile top stress test comparison curve of the rigid pile composite foundation of the embodiment of the application, it can be seen from the test results that when the pile top stress of the rigid pile exceeds the yield strength of the composite plate, the composite plate can play a good effect on adjusting the pile top stress.

[0055] Example 2

[0056] A 20-story high-rise building adopts a raft foundation, the standard value of the load transmitted by the upper structure to the raft is 300KPa, the characteristic value of the bearing capacity of the natural foundation is 200kpa, a rigid pile composite foundation is adopted, the pile-soil stress ratio is 10, the characteristic value of the bearing capacity of the rigid pile top is 2MPa, a rigid pile with a diameter of 500 is adopted, the thickness of the cushion layer at the top of the pile is 250mm according to the specification, since the pile end is in a medium weathered rock layer, the deformation of the pile end is very small, the adjustment capacity of the cushion layer is insufficient, and it is also worried that there will be post-construction settlement after the building is completed, the top of the pile is adjusted by the composite board of the application, the composite board has a diameter of 500mm, the stiffening hoop is a single cavity hoop surrounded by a steel plate, the composite board is poured in three layers, the thickness of each layer of foam concrete is 10mm, and the strength is 2MPa, 2.2MPa and 2.4MPa respectively, and the corresponding mix proportions of the different strength foam concretes in each layer are as follows:

[0057]

[0058]

[0059] Since the plastic strain rate of each layer of foam concrete can reach more than 0.5, each layer of foam concrete board with a thickness of 10mm can produce a deformation of 5mm after yielding, and the three layers of foam concrete boards can produce a total deformation capacity of 15mm, so even if the actual settlement is greater than the design settlement by 15mm, the stress at the top of the pile increases from 2MPa to 2.4MPa, and the pile-soil deformation coordination can be realized.

[0060] Example 3

[0061] The difference between example 2 and example 3 is that the foam concrete does not change the strength by changing the cement content and bubble rate, but gradually increases the strength of the foam concrete by changing the configuration of the stiffening steel hoop, the outer ring thickness of the stiffening hoop is 3mm, and the inner partition plate thickness is 2mm, as shown in Figure 8 The uppermost layer of foam concrete adopts a single cavity steel hoop, the middle layer of foam concrete adopts a 4-cavity steel hoop, and the lowermost layer of foam concrete adopts an 8-cavity steel hoop, and the increase of the yield strength of the layered foam concrete is realized by changing the steel content of the foam concrete.

[0062] This specific embodiment is only an explanation of the application, and is not a limitation of the application, and those skilled in the art can make modifications to the embodiment without creative contribution after reading the specification, but as long as it is within the scope of the claims of the application, it is protected by the patent law.

Claims

1. A composite plate for adjusting deformation of a pile top of an end-bearing rigid pile composite foundation, provided at a pile top of a rigid pile, characterized in that: The composite board comprises an upper steel cover plate, a lower steel base plate, a stiffening hoop and a variable strength foam concrete board fastened by the stiffening hoop, wherein the upper steel cover plate and the lower steel base plate are movably embedded in the stiffening hoop, and the upper steel cover plate and the lower steel base plate are respectively located on two sides of the variable strength foam concrete board, and the three constitute a sandwich structure. A preparation method of a pile top deformation adjusting composite board of an end-bearing rigid pile composite foundation, comprising the following steps: S1. preparing an upper steel cover plate, a lower steel base plate and a stiffening hoop; S2. preparing foam by a physical or chemical method, mixing the foam into a mixed slurry composed of cement slurry, admixture and additive, and pouring and solidifying to form a foam concrete board containing a large number of uniformly closed pores; S3. layer-by-layer pouring according to the method of S2, pouring upward after 2-3 days of final setting of the lower foam concrete board, and changing the strength of each layer of foam concrete board by changing the amount of cement slurry or the bubble rate of foam during preparation of each layer of foam concrete board, so as to form a multi-layer variable strength foam concrete board; S4. bonding the upper steel cover plate and the lower steel base plate to the upper and lower surfaces of the variable strength foam concrete board respectively, embedding the whole structure into the stiffening hoop after bonding the three into one, and tightening the stiffening hoop, so as to form a composite board.

2. The composite pile top deformation adjusting plate of an end-bearing rigid pile composite foundation according to claim 1, characterized in that: The diameter of the composite board is the same as the diameter of the rigid pile.

3. The composite pile top deformation adjusting plate of an end-bearing rigid pile composite foundation according to claim 1, characterized in that: The upper steel cover plate and the lower steel base plate are bonded to the variable strength foam concrete board by cement slurry.

4. The composite pile top deformation adjusting plate of an end-bearing rigid pile composite foundation according to claim 1, characterized in that: The thickness of the upper steel cover plate and the lower steel base plate is 2-3 mm, and the wall thickness of the stiffening hoop is 1-5 mm.

5. The composite pile top deformation adjusting plate of an end-bearing rigid pile composite foundation according to claim 1, characterized in that: The thickness of each layer of the multi-layer variable strength foam concrete board is equal, and the total thickness is 30-60 mm.

6. The composite pile top deformation adjusting plate of an end-bearing rigid pile composite foundation according to claim 1, characterized in that: The composite board has three-stage stress characteristics of an elastic stage, a yield platform stage and a densification stage, wherein the strain of the yield platform stage reaches 0.5-0.

6.

7. The composite pile top deformation adjusting plate of an end-bearing rigid pile composite foundation according to claim 5, characterized in that: The variable strength foam concrete board has 3-4 layers, and each layer has a thickness of 10-15 mm.

8. The composite pile top deformation adjusting plate of an end-bearing rigid pile composite foundation according to claim 7, characterized in that: The design strength of the foam concrete board is 1-5 MPa, the design elastic compression modulus of the foam is 230-1200 MPa, the minimum strength of the foam concrete board is determined according to the characteristic value of the bearing capacity of the rigid pile, and the ratio of the design strengths of the layers of foam concrete board is 1:1.15:1.3 or 1:1.15:1.3:1.45.

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