Construction method for a compression and uplift resistant composite foundation structure for controlling settlement

Abstract

The present invention discloses a construction method for a compression and uplift composite foundation structure for controlling settlement, which comprises the following steps: S1. Locate the positions of the uplift piles and drill holes in the original formation to the designed depth; S2. After cleaning the holes, set plain concrete piles and uplift concrete piles; S3. Conduct inspection tests on the plain concrete piles and the uplift concrete piles; S4. After the tests are qualified, lay a gravel cushion on the surface of the original formation; S5. Construct a cushion above the gravel cushion and set a water-resistant slab on the cushion; S6. Set an anchor cable pulling groove on the water-resistant slab above the uplift concrete piles. After the strength of the water-resistant slab reaches the designed strength, carry out tensioning operation on the non-bonded anchor cables. After reaching the designed prestress value, install locking devices to lock the anchor cables, and seal the ends of the anchor cables in the anchor cable pulling groove. Its advantages are that, based on the original CFG piles, the non-bonded anchor cables are connected with the compression steel plates, so that while the vertical bearing capacity is exerted, the uplift force can also play a role.

Description

Technical Field

[0001] This application belongs to the field of foundation structure construction, and specifically relates to a construction method for a compression and uplift resistant composite foundation structure for controlling settlement. Background Art

[0002] With the large-scale construction of underground spaces, buildings need to consider not only the bearing capacity of the foundation but also the anti-floating problem. The CFG composite foundation is a mature foundation treatment method, but it does not have anti-uplift performance. Anti-uplift piles or anti-floating anchor rods are often used to solve the anti-floating problem of buildings. The difficulty lies in that the CFG composite foundation needs to simultaneously exert the bearing capacity of the foundation soil and the pile body, which requires that the pile body and the building floor slab cannot be rigidly connected. When solving the anti-floating problem, anti-floating structures such as anti-uplift piles or anti-floating anchor rods need to be closely connected to the foundation slab. Currently, there is no composite foundation treatment method that simultaneously has anti-uplift and anti-floating functions. Summary of the Invention

[0003] Based on the above problems, this application provides a construction method for a composite foundation structure that simultaneously has anti-uplift and anti-floating functions. The technical solution is as follows:

[0004] A construction method for a compression and uplift resistant composite foundation structure for controlling settlement, comprising the following steps:

[0005] S1. Locate the position of the anti-uplift piles and drill holes in the original formation to the designed depth;

[0006] S2. After cleaning the holes, pour plain concrete directly into some of the holes to form plain concrete piles; install non-bonded anchor cables in the other holes, and install compression steel plates at the bottom ends of the non-bonded anchor cables, fix them with anchor fittings and then pour plain concrete to complete the pouring of the anti-uplift concrete piles;

[0007] S3. Conduct inspection tests on the plain concrete piles and the anti-uplift concrete piles;

[0008] S4. After the tests are qualified, lay a gravel cushion on the surface of the original formation;

[0009] S5. Construct a cushion above the gravel cushion and set an anti-water board on the cushion;

[0010] S6. Set an anchor cable tensioning groove on the anti-water board above the anti-uplift concrete piles. After the strength of the anti-water board reaches the designed strength, conduct tensioning operations on the non-bonded anchor cables. After reaching the designed prestress value, install locking devices to lock the anchor cables, and seal the ends of the anchor cables in the anchor cable tensioning grooves.

[0011] Preferably, the plain concrete piles and the anti-uplift concrete piles are distributed at intervals or continuously, and the proportion relationship of the anti-uplift concrete piles is determined according to the anti-buoyancy calculation.

[0012] Preferably, the crushed stone mattress is 200 - 400 mm; the cushion layer is 100 - 150 mm thick, and the anti - water board is of steel structure.

[0013] Preferably, in step S6, when the construction of the building floor slab is completed, prestress is applied in advance to the standard value of the anti - floating tensile force to realize the pre - pressing of the composite foundation, and part of the settlement caused by the building load is eliminated in advance, so as to reduce the final settlement value of the composite foundation after all the building loads are applied.

[0014] Preferably, the calculation method of the final settlement value of the composite foundation is that when the buoyancy of the groundwater is the same as the building load and the prestress application value of the anti - floating pile, the building will have no upward floating deformation.

[0015] The upward floating deformation of the building is s w

[0016]

[0017] The final settlement value of the composite foundation is s

[0018] s = s y -s w

[0019] P w The water pressure at the foundation bottom surface, s y The foundation deformation caused by the building itself, P y The additional prestress pressure at the foundation bottom surface,

[0020] z i 、z i-1 The distance from the foundation bottom surface to the bottom surface of the i - th layer of soil and the (i - 1) - th layer of soil

[0021] The average additional stress coefficient within the range from the calculation point at the foundation bottom surface to the bottom surface of the i - th layer of soil and the (i - 1) - th layer of soil;

[0022] ψ The empirical coefficient of settlement calculation, P 0 The additional pressure of the standard foundation bottom surface, Esi The compression modulus of the i - th layer of soil at the foundation bottom.

[0023] Beneficial effects

[0024] The composite foundation structure provides anti - uplift force through the friction of the pile body, and its quantity is arranged after anti - floating calculation. In terms of anti - uplift, the composite foundation structure can realize the reliable connection between the anti - water board and the pile body, so as to transfer the anti - uplift force of the CFG to the anti - water board and achieve the purpose of building anti - uplift. Brief description of the drawings

[0025] Figure 1 This is the flow chart of the present application.

[0026] Figure 2 This is a structural schematic diagram of the present application.

[0027] Figure 3 This is a top view of the distribution of plain concrete piles and anti-pulling concrete piles.

[0028] In the figure, 1. Waterproof slab; 2. Steel bars; 3. Anchor cable pulling groove; 4. Anchor cable end sealing; 5. Cushion; 6. Crushed stone mattress; 7. Anti-pulling plain concrete pile; 8. Original formation; 9. Unbonded anchor cable; 10. Compressive steel plate; 11. Anchor; 12. Plain concrete pile Specific embodiments

[0029] The following detailed descriptions are all illustrative and are intended to provide further explanations for the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present application belongs. It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application.

[0030] A construction method for a compression and anti-pulling composite foundation structure for controlling settlement includes the following steps:

[0031] S1. Locate the position of the anti-pulling piles and drill holes in the original formation to the designed depth.

[0032] S2. After cleaning the holes, pour plain concrete directly into some of the holes to form plain concrete piles; install unbonded anchor cables in the other holes, install compressive steel plates at the bottom ends of the unbonded anchor cables, fix them with anchors and then pour plain concrete to complete the pouring of the anti-pulling concrete piles; the plain concrete piles and the anti-pulling concrete piles are distributed at intervals or continuously, and the proportion relationship of the anti-pulling concrete piles is determined according to the anti-buoyancy calculation. Figure 3 This is a distribution diagram at intervals.

[0033] S3. Conduct inspection tests on the plain concrete piles 12 and the anti-pulling concrete piles 7.

[0034] S4. After the tests are qualified, lay a crushed stone mattress 6 on the surface of the original formation; the crushed stone mattress 6 is 200 - 400 mm, preferably 300 mm.

[0035] S5. Construct a cushion above the crushed stone mattress 6, and set a waterproof slab on the cushion 5. The cushion 5 has a thickness of 120 mm, and the waterproof slab 1 is a steel bar structure.

[0036] S6. Set an anchor cable pulling groove on the waterproof slab above the anti-pulling concrete piles. After the strength of the waterproof slab 1 reaches 75% of the designed strength, conduct tensioning operations on the unbonded anchor cables 9 (the unbonded anchor cables are composed of unbonded steel strands). After reaching the designed prestress value, install locking devices to lock the anchor cables, and conduct anchor cable end sealing on the anchor cable pulling groove.

[0037] In step S6, when the construction of the building floor slab is completed, prestress is applied in advance to the standard value of the anti-floating tensile force, realizing the preloading of the composite foundation, and eliminating in advance the settlement caused by part of the building load, so as to reduce the final settlement value of the composite foundation after all the building loads are applied.

[0038] The calculation method of the final settlement value of the composite foundation is that when the buoyancy of the groundwater is the same as the building load and the prestress application value of the anti-floating pile, the building will have no upward floating deformation.

[0039] The upward floating deformation of the building is s w

[0040]

[0041] The final settlement value of the composite foundation is s

[0042] s = s y -s w

[0043] P w The water pressure at the foundation bottom surface, s y The foundation deformation amount caused by the building itself, P y The additional prestress pressure at the foundation bottom surface

[0044] z i 、z i-1 The distance from the foundation bottom surface to the bottom surface of the i-th layer of soil and the (i - 1)-th layer of soil

[0045] The average additional stress coefficient within the range from the calculation point at the foundation bottom surface to the bottom surface of the i-th layer of soil and the (i - 1)-th layer of soil;

[0046] ψ Settlement calculation empirical coefficient, P 0 The additional pressure at the standard foundation bottom surface, Esi The compression modulus of the i-th layer of soil at the foundation bottom.

[0047] The anti-pulling concrete pile in the composite foundation structure is reliably connected to the compression steel plate through a flexible pressure type anti-pulling anchor rod. Due to the characteristics of high tensile strength, poor compressive strength, and flexible wall of the flexible pressure type anti-pulling non-bonded cable, when the anti-pulling concrete pile is reliably connected to the anti-water plate, the anti-pulling concrete pile and the anti-water plate are non-rigidly connected, and there is a cushion layer 5 between the anti-pulling concrete pile and the anti-water plate, and it has the same stress state as the CFG pile in terms of bearing capacity performance.

[0048] Meanwhile, to reduce the problem of large terrain of common composite foundations, after the construction of this composite foundation, when the construction of the building floor slab is completed, prestress is applied in advance to the standard value of the anti-floating tensile force, so as to realize the preloading of the composite foundation and eliminate in advance the settlement caused by part of the building load, thereby reducing the settlement value of the composite foundation after all the building loads are applied.

[0049] During the construction of the basement, the basement backfill trench can be backfilled layer by layer along with the construction of the basement. At the same time, a water control blind ditch at the bottom of the backfill trench and a water level control well are used to control the water level within the basement range, so that the groundwater level is within the allowable value of the construction conditions. Thus, the timely backfilling of the basement backfill trench is realized, and at the same time, the buoyancy effect of groundwater is utilized to achieve the purpose of reducing the settlement value of the composite foundation.

[0050] When the basement burial depth is 20 meters, the groundwater burial depth is 0 meters, the soil layer compression modulus Esi is 10 MPa, and the additional pressure P 0 at the standard foundation bottom surface is 130 kPa, the thickness of the foundation bottom soil layer is 10 meters, P y The additional prestress pressure at the foundation bottom surface is 100 kPa, and the settlement calculation empirical coefficient ψ is 1.

[0051] According to the convention, without prestressed anchor cables, the building settlement s is 13 mm;

[0052] According to the prestressed anchor cable anti-floating formula, the building self-settlement s y is 3 mm;

[0053] The foundation deformation amount s caused by groundwater w is 3 mm;

[0054] The final foundation settlement s is 0 mm.

[0055] The above are only the preferred embodiments of the present application and are not used to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A construction method for a compression and uplift resistance composite foundation structure for controlling settlement, characterized in that, it includes the following steps, S1. Locate the position of the uplift resistance piles and drill holes in the original stratum to the designed depth; S2. After cleaning the holes, pour plain concrete directly into part of the holes to form plain concrete piles; install non-bonded anchor cables in the other part of the holes, install compression steel plates at the bottom ends of the non-bonded anchor cables, fix them with anchor fittings and pour plain concrete to complete the pouring of the uplift resistance concrete piles; S3. Conduct inspection tests on the plain concrete piles and the uplift resistance concrete piles; S4. After the tests are qualified, lay a gravel cushion on the surface of the original stratum; S5. Construct a cushion above the gravel cushion and set a water-resistant slab on the cushion; S6. Set an anchor cable tensioning groove on the water-resistant slab above the uplift resistance concrete piles. After the strength of the water-resistant slab reaches the designed strength, conduct tensioning operations on the non-bonded anchor cables. After reaching the designed prestress value, install locking devices to lock the anchor cables, and seal the ends of the anchor cables for the anchor cable tensioning grooves; When the construction of the building floor slab is completed, apply prestress in advance to the standard value of the anti-floating tensile force to realize the preloading of the composite foundation, and eliminate in advance the settlement caused by part of the building load, so as to reduce the final settlement value of the composite foundation after all the building loads are loaded; The calculation method for the final settlement value of the composite foundation is that when the buoyancy of the groundwater is the same as the building load and the applied value of the prestress of the anti-floating piles, the building will have no upward deformation, The floating deformation of the building is s w and the final settlement value of the composite foundation is s s = s y -s w P w Hydrostatic pressure at the base of the foundation, s y Foundation settlement caused by the building itself, P y Additional prestressed pressure at the base of the foundation z i 、z i-1 The distance from the base of the foundation to the bottom surface of the i-th layer of soil and the bottom surface of the (i - 1)-th layer of soil The average additional stress coefficient within the range from the calculation point at the foundation bottom surface to the bottom surfaces of the i-th layer of soil and the (i - 1)-th layer of soil, ψ Empirical coefficient for settlement calculation, P 0 Additional pressure at the standard foundation base, Esi Compression modulus of the i-th layer of soil at the foundation base 2. A construction method for a compression and uplift resistance composite foundation structure for controlling settlement according to claim 1, characterized in that, the plain concrete piles and the uplift resistance concrete piles are distributed at intervals or continuously, and the proportion relationship of the uplift resistance concrete piles is determined according to the anti-buoyancy calculation.

3. A construction method for a compression and uplift resistance composite foundation structure for controlling settlement according to claim 1, characterized in that, the thickness of the gravel cushion is 200 - 400 mm; the thickness of the cushion is 100 - 150 mm, and the water-resistant slab is a steel bar structure.

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