Sinking Control Method for Active Control Caisson Construction

Abstract

The invention discloses a sinking control method for actively controlled caisson construction, comprising the following steps: step 1: integrating a sinking coefficient Kst and a sinking stability coefficient Kst,s into an actively controlled sinking coefficient Kc; step 2: symmetrically partitioning a well bottom soil (103), excavating each area of ​​the symmetrical partitions asymmetrically, and applying an uneven lifting force F to the caisson (100) during the asymmetrical partition excavation, so that the actively controlled sinking coefficient Kc always approaches 1.0 infinitely during the sinking construction process of the caisson (100). The invention can solve the problems of caisson tilting, sudden sinking, over-sinking, significant impact of caisson construction on surrounding strata, and slow construction progress in the prior art.

Description

Technical Field

[0001] The invention relates to a caisson construction method, in particular to a sinking control method for actively controlled caisson construction. Background Art

[0002] Based on relevant engineering experience, functional requirements, and construction conditions, the following construction methods can be used for vertical shaft construction: open cut, traditional caisson, and VSM. The traditional caisson construction process involves first creating a shaft-like structure on the surface. Then, protected by the shaft walls, soil is continuously excavated from within the shaft, allowing the caisson to gradually sink under its own weight and overhead loads. This process continues until the designed elevation is reached, at which point the bottom is sealed.

[0003] Since traditional caisson construction methods generally rely on passive sinking by deadweight, the switch between stable and sinking states is mainly achieved by excavation. Due to the unevenness of excavation and the conversion of static-dynamic friction on the outside, the sinking of traditional caissons is relatively rough and difficult to control. Traditional caisson construction methods have the following technical problems:

[0004] 1. The construction is difficult. It is difficult to correct the tilt of the well body due to the passive sinking method of excavation.

[0005] 2. Sudden sinking and over-sinking are prone to occur, posing certain construction safety hazards.

[0006] 3. The construction depth should not be too large, as it will have a greater impact on the settlement of the surrounding strata and slow down the construction progress.

[0007] Therefore, it is necessary to provide a sinking control method for actively controlled caisson construction, which can solve the above-mentioned technical problems existing in the prior art. Summary of the Invention

[0008] The purpose of the present invention is to provide a sinking control method for actively controlled caisson construction, which can solve the above-mentioned technical problems existing in the prior art.

[0009] The present invention is achieved in that:

[0010] A sinking control method for actively controlled caisson construction comprises the following steps:

[0011] Step 1: Integrate the sinking coefficient Kst and the sinking stability coefficient Kst,s into the active control sinking coefficient Kc;

[0012] Step 2: Divide the soil at the bottom of the well into symmetrical partitions, perform asymmetrical excavation on each area of ​​the symmetrical partitions, and apply uneven lifting pressure F to the caisson during the asymmetrical partition excavation, so that the active control sinking coefficient Kc always approaches 1.0 infinitely during the sinking construction process of the caisson.

[0013] The calculation formula of the sinking coefficient Kst is:

[0014] Kst=(Gk-Fw) / Tf Formula (1)

[0015] Where Gk is the deadweight of the caisson, Fw is the buoyancy of the caisson, and Tf is the lateral friction resistance of the caisson. The lateral friction resistance Tf is the sum of the soil friction resistance Tf1 and the mud jacket friction resistance Tf2.

[0016] The calculation formula of the sinking stability coefficient Kst,s is:

[0017] Kst,s=(Gk-Fw) / (Tf+R1+R2) Formula (2)

[0018] Among them, R1 is the foundation bearing capacity of the blade foot of the caisson, and R2 is the foundation bearing capacity of the cross beam of the caisson.

[0019] The calculation formula of the active control sink coefficient Kc is:

[0020] Kc=(Gk-Fw+F) / (Tf+R1+R2) Formula (3)

[0021] Among them, F is the lifting force, that is, the lifting force or pressing force applied by the lifting equipment on the caisson.

[0022] The symmetrical partitions include the inner circle area on the side of the cross beam and the outer circle area on the side of the cross beam, as well as the inner circle area on the bottom of the cross beam and the outer circle area on the bottom of the cross beam; the order of excavation of the asymmetrical partitions is: first excavate the area on the side of the cross beam, and then excavate the area at the bottom of the cross beam.

[0023] When excavating the area on the side of the cross beam, the inner circle area on the side of the cross beam is excavated first, and then the outer circle area on the side of the cross beam is excavated; when excavating the area at the bottom of the cross beam, the inner circle area at the bottom of the cross beam is excavated first, and then the outer circle area at the bottom of the cross beam is excavated.

[0024] The inner circle area of ​​the side of the cross beam is divided into a first area, a second area, a third area and a fourth area by the cross beam. The first area is diagonally arranged with the second area, and the third area is diagonally arranged with the fourth area. The excavation order of the inner circle area of ​​the side of the cross beam is: first area → second area → third area → fourth area, and the excavation order of each area is from inside to outside.

[0025] The outer circle area on the side of the cross beam is divided into the fifth area, the sixth area, the seventh area and the eighth area by the cross beam. The fifth area is diagonally arranged with the sixth area, and the seventh area is diagonally arranged with the eighth area. The excavation order of the outer circle area on the side of the cross beam is: the fifth area → the sixth area → the seventh area → the eighth area, and the excavation order of each area is from the inside to the outside.

[0026] The inner circle area of ​​the bottom of the cross beam includes the ninth area A, the tenth area B, the eleventh area C and the twelfth area D. The ninth area A is located between the first area and the third area of ​​the inner circle area of ​​the side of the cross beam, the tenth area B is located between the second area and the fourth area of ​​the inner circle area of ​​the side of the cross beam, the eleventh area C is located between the second area and the third area, and the twelfth area D is located between the first area and the fourth area; the excavation order of the inner circle area of ​​the bottom of the cross beam is the ninth area A→the tenth area B→the eleventh area C→the twelfth area D, and the excavation order of each area is from the inside to the outside.

[0027] The outer circle area of ​​the bottom of the cross beam includes the thirteenth area E, the fourteenth area F, the fifteenth area G and the sixteenth area H. The thirteenth area E is located between the fifth area and the seventh area of ​​the outer circle area of ​​the side of the cross beam, the fourteenth area F is located between the sixth area and the eighth area of ​​the outer circle area of ​​the side of the cross beam, the fifteenth area G is located between the sixth area and the seventh area, and the sixteenth area H is located between the fifth area and the eighth area; the excavation order of the inner circle area of ​​the bottom of the cross beam is the thirteenth area E→the fourteenth area F→the fifteenth area G→the sixteenth area H, and the excavation order of each area is from the inside to the outside.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. Since the present invention integrates the sinking coefficient and the sinking stability coefficient into an active control sinking coefficient, it can be determined by the active control sinking coefficient whether the caisson is in a stable sinking state or a stopped sinking state under the current lifting pressure. The change of the lifting pressure under different working conditions is used to make the active control sinking coefficient always infinitely close to 1.0, that is, to ensure that the caisson is in a dynamic micro-balance state. It has good active control ability during the caisson construction process, reduces the impact of settlement on the surrounding strata, and is conducive to improving the construction progress.

[0030] 2. The present invention performs symmetrical zoning and asymmetric small-advance zoning excavation on the well body soil, and applies uneven lifting pressure in the excavation area during the asymmetric zoning excavation, so that the active control sinking coefficient is always infinitely close to 1.0, that is, the caisson is ensured to be in a dynamic micro-balance state, realizing the dynamic correction function, effectively preventing sudden sinking, over-sinking, etc. during the sinking process, and is conducive to improving construction safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the stress state during the caisson construction process in the sinking control method of the active control type caisson construction of the present invention;

[0032] Figure 2 It is a schematic diagram of the symmetrical partitioning of the soil at the bottom of the well in the sinking control method of the active control type caisson construction of the present invention.

[0033] In the figure, 100 caisson, 101 blade foot, 102 cross beam, 103 soil at the bottom of the well, 1 first area, 2 second area, 3 third area, 4 fourth area, 5 fifth area, 6 sixth area, 7 seventh area, 8 eighth area, A ninth area, B tenth area, C eleventh area, D twelfth area, E thirteenth area, F fourteenth area, G fifteenth area, H sixteenth area. DETAILED DESCRIPTION

[0034] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0035] Please see the attached Figure 1 and attached Figure 2 A sinking control method for actively controlled caisson construction comprises the following steps:

[0036] Step 1: Integrate the sink coefficient Kst and the sink stability coefficient Kst,s into the active control sink coefficient Kc.

[0037] Please see the attached Figure 1 , the calculation formula of the sinking coefficient Kst is:

[0038] Kst=(Gk-Fw) / Tf Formula (1)

[0039] Wherein, Gk is the deadweight of the caisson 100, Fw is the buoyancy force on the caisson 100, and Tf is the side friction resistance on the caisson 100.

[0040] Gk can be calculated based on the number and weight of the segments in the caisson 100, Fw can be calculated based on the sinking depth of the caisson 100 using a buoyancy formula, and Tf can be detected by a sensor.

[0041] The lateral friction resistance Tf is the sum of the soil friction resistance Tf1 and the mud jacket friction resistance Tf2.

[0042] The calculation formula of the sinking stability coefficient Kst,s is:

[0043] Kst,s=(Gk-Fw) / (Tf+R1+R2) Formula (2)

[0044] Wherein, R1 is the foundation bearing capacity of the blade foot 101 of the caisson 100 , and R2 is the foundation bearing capacity of the cross beam 102 of the caisson 100 . R2 can be detected by a sensor.

[0045] The calculation formula of the active control sink coefficient Kc is:

[0046] Kc=(Gk-Fw+F) / (Tf+R1+R2) Formula (3)

[0047] Wherein, F is the lifting force, that is, the lifting force or the pressing force applied by the lifting equipment to the caisson 100, the lifting force acts in an upward direction, and the pressing force acts in a downward direction.

[0048] The active control sinking coefficient Kc can be used to determine whether the caisson 100 sinks stably under the current lifting pressure F. The magnitude and direction of the lifting pressure F can be adjusted accordingly through the calculation of formula (3), so that the active control sinking coefficient Kc is infinitely close to 1.0, that is, the sum of the downward sinking force and the sum of the upward anti-sinking force on the caisson 100 are close to equal, so that the caisson 100 is always in a dynamic micro-balanced state.

[0049] To fully estimate the magnitude of the lifting force F for equipment and structural design development, the foundation bearing capacity R1 of blade foot 101 is corrected per meter of water depth according to the "Code for Design of Highway Bridge and Culvert Foundations and Substructures" to achieve a more realistic foundation bearing capacity R1 of blade foot 101. The correction process for the foundation bearing capacity R1 of blade foot 101 is carried out in accordance with the "Code for Design of Highway Bridge and Culvert Foundations and Substructures" and will not be detailed here.

[0050] The mud friction resistance Tf2 is linked to the sinking state of the caisson 100. The sinking state includes a stable sinking state and a stopped sinking state. In each sinking state, the active control sinking coefficient Kc is always infinitely close to 1.0. As to whether the soil is excavated under the cross beam 102, the mud friction resistance Tf2, the active control sinking coefficient Kc and the lifting force F under various sinking states are analyzed, and the lifting force, i.e., the pressing force and the lifting force capacity requirements of the lifting equipment are calculated, i.e., the maximum lifting force and the maximum pressing force under various sinking states. The outward bending condition of the blade foot 101 is verified according to the calculated maximum pressing force to ensure that when the lifting equipment applies the maximum pressing force to the caisson 100, the foundation bearing capacity R1 of the blade foot 101 meets the design requirements.

[0051] Please see the attached Figure 2Step 2: divide the bottom soil 103 into symmetrical partitions, perform asymmetrical partition excavation on each area of ​​the symmetrical partitions, and apply uneven lifting pressure F to the caisson 100 during the asymmetrical partition excavation, so that the active control sinking coefficient Kc always approaches 1.0 infinitely during the sinking construction process of the caisson 100.

[0052] During soil excavation, the side friction resistance Tf, the foundation bearing capacity R1 of the blade foot 101, and the foundation bearing capacity R2 of the cross beam change. The deadweight Gk of the caisson 100 and the buoyancy Fw it experiences remain unchanged. The lifting force F can be calculated using the active control sinking coefficient Kc≈1.0. By applying uneven lifting force F to the excavated and non-excavated areas of the caisson 100 to adapt to soil excavation under any operating conditions, the active control sinking coefficient Kc is kept close to 1.0, thus maintaining the dynamic microbalance of the caisson 100 and preventing tilting, sudden sinking, and oversinking.

[0053] The symmetrical partitions include the inner circle area and the outer circle area on the side of the cross beam 102, as well as the inner circle area and the outer circle area on the bottom of the cross beam 102; the order of excavation of the asymmetrical partitions is: first excavate the area on the side of the cross beam 102, and then excavate the area at the bottom of the cross beam 102.

[0054] When excavating the area on the side of the cross beam 102, the inner circle area on the side of the cross beam is excavated first, and then the outer circle area on the side of the cross beam is excavated; when excavating the area at the bottom of the cross beam 102, the inner circle area at the bottom of the cross beam is excavated first, and then the outer circle area at the bottom of the cross beam is excavated.

[0055] The foundation bearing capacity R2 at the bottom of the cross beam 102 has a greater impact on the sinking state of the caisson 100 than the side friction resistance Tf, so the bottom area of ​​the cross beam is excavated later than the side area of ​​the cross beam; and the outer circle area can reduce the side friction resistance Tf of the blade foot 101 more than the inner circle area, so the outer circle area is excavated later than the inner circle area.

[0056] The inner circle area of ​​the side of the cross beam is divided into a first area 1, a second area 2, a third area 3 and a fourth area 4 by the cross beam 102. The first area 1 is diagonally arranged with the second area 2, and the third area 3 is diagonally arranged with the fourth area 4. The excavation order of the inner circle area of ​​the side of the cross beam is: first area 1 → second area 2 → third area 3 → fourth area 4. The excavation order of each area is from the inside to the outside, that is, from the center of the cross beam 102 to the edge of the cross beam 102.

[0057] The first area 1, the second area 2, the third area 3 and the fourth area 4 are excavated in a diagonally asymmetric manner and excavated from the inside to the outside with a small advance, thereby ensuring the stable sinking state of the caisson 100.

[0058] The outer circle area of ​​the side of the cross beam is divided into a fifth area 5, a sixth area 6, a seventh area 7 and an eighth area 8 by the cross beam 102. The fifth area 5 and the sixth area 6 are diagonally arranged, and the seventh area 7 and the eighth area 8 are diagonally arranged; the excavation order of the outer circle area of ​​the side of the cross beam is: the fifth area 5 → the sixth area 6 → the seventh area 7 → the eighth area 8, and the excavation order of each area is from the inside to the outside, that is, from the position close to the center of the cross beam 102 to the edge of the cross beam 102.

[0059] The fifth area 5, the sixth area 6, the seventh area 7 and the eighth area 8 are excavated in a diagonally asymmetric manner, and are excavated from the inside to the outside with a small advance, which ensures that the caisson 100 sinks steadily.

[0060] The inner circle area of ​​the bottom of the cross beam includes the ninth area A, the tenth area B, the eleventh area C and the twelfth area D. The ninth area A is located between the first area 1 and the third area 3, the tenth area B is located between the second area 2 and the fourth area 4, the eleventh area C is located between the second area 2 and the third area 3, and the twelfth area D is located between the first area 1 and the fourth area 4; the excavation order of the inner circle area of ​​the bottom of the cross beam is the ninth area A→the tenth area B→the eleventh area C→the twelfth area D, and the excavation order of each area is from the inside to the outside, that is, from the center of the cross beam 102 to the edge of the cross beam 102.

[0061] The ninth area A, the tenth area B, the eleventh area C and the twelfth area D are excavated in an asymmetrical manner and with a small advance from the inside to the outside, ensuring the stable sinking state of the caisson 100.

[0062] The outer circle area of ​​the bottom of the cross beam includes the thirteenth area E, the fourteenth area F, the fifteenth area G and the sixteenth area H. The thirteenth area E is located between the fifth area 5 and the seventh area 7, the fourteenth area F is located between the sixth area 6 and the eighth area 8, the fifteenth area G is located between the sixth area 6 and the seventh area 7, and the sixteenth area H is located between the fifth area 5 and the eighth area 8; the excavation order of the inner circle area of ​​the bottom of the cross beam is the thirteenth area E→the fourteenth area F→the fifteenth area G→the sixteenth area H, and the excavation order of each area is from the inside to the outside, that is, from the position close to the center of the cross beam 102 to the edge of the cross beam 102.

[0063] The thirteenth area E, the fourteenth area F, the fifteenth area G and the sixteenth area H are excavated in an asymmetrical manner and excavated from the inside to the outside with a small advance, thereby ensuring the stable sinking state of the caisson 100.

[0064] By excavating 16 areas of soil under the cross beam in sequence, the ratio of the soil area at the bottom of the cross beam 102 to the soil area at the bottom of the blade foot 101 can be changed, thereby changing the ratio of the foundation bearing capacity R2 of the cross beam 102 to the end bearing capacity (R1+R2), that is, the end resistance of the caisson. By controlling the excavation range under the cross beam 102, the size and distribution of the end resistance of the caisson can be effectively adjusted. Combined with the lifting pressure F and the side friction resistance Tf applied to the caisson 100 by the pressure-lifting equipment, the dynamic micro-balance of the caisson 100 is ensured, and the "brake" function of stopping the sinking state of the caisson 100 during the sinking process and the "steering wheel" function of correcting the deviation in the stable sinking state are realized.

[0065] When excavating the bottom soil 103, a 40cm small-footprint excavation mode is adopted, which improves construction safety and stability. Through the symmetrical partitioning of the bottom soil 103 and the small-footprint excavation mode, the caisson 100 is always in a dynamic micro-balance state, which not only ensures that the lifting pressure is not excessively amplified, but also ensures the smooth and stable sinking of the caisson 100. At the same time, through the asymmetric partitioning of the bottom soil 103 and combined with formula (3), the pressure-raising equipment is used to apply uneven lifting pressure F to the excavation area and non-excavation area of ​​the caisson 100, so that the active control sinking coefficient is always infinitely close to 1.0, maintaining the dynamic micro-balance state of the caisson 100, preventing the caisson 100 from tilting and other problems, thereby avoiding sudden sinking, over-sinking and other situations. During the sinking construction process of the caisson 100, the automatic monitoring system installed in the well body is used to realize the dynamic correction function.

[0066] The above are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A sinking control method for actively controlled caisson construction, characterized by: The following steps are involved: Step 1: Integrate the sinking coefficient Kst and the sinking stability coefficient Kst,s into the active control sinking coefficient Kc; Step 2: symmetrically partitioning the soil at the bottom of the well (103), performing asymmetrical partition excavation on each area of ​​the symmetrical partition, and applying uneven lifting pressure F to the caisson (100) during the asymmetrical partition excavation, so that the active control sinking coefficient Kc always approaches 1.0 infinitely during the sinking construction process of the caisson (100); The calculation formula of the sinking coefficient Kst is: Kst=(Gk-Fw) / Tf Formula (1) The calculation formula of the sinking stability coefficient Kst,s is: Kst,s=(Gk-Fw) / (Tf+R1+R2) Formula (2) The calculation formula of the active control sink coefficient Kc is: Kc=(Gk-Fw+F) / (Tf+R1+R2) Formula (3) Wherein, Gk is the deadweight of the caisson (100), Fw is the buoyancy force on the caisson (100), Tf is the lateral friction force on the caisson (100), and the lateral friction force Tf is the sum of the soil friction force Tf1 and the mud jacket friction force Tf2; R1 is the foundation bearing capacity of the blade foot (101) of the caisson (100), and R2 is the foundation bearing capacity of the cross beam (102) of the caisson (100); and F is the lifting force, i.e., the pulling force or pressing force applied by the lifting and pressing equipment on the caisson (100).

2. The sinking control method for actively controlled caisson construction according to claim 1 is characterized by: The symmetrical partitions include an inner ring area on the side of the cross beam and an outer ring area on the side of the cross beam (102), and an inner ring area on the bottom of the cross beam and an outer ring area on the bottom of the cross beam (102); the order of excavation of the asymmetrical partitions is: first excavate the area on the side of the cross beam (102), and then excavate the area on the bottom of the cross beam (102).

3. The sinking control method for active control type caisson construction according to claim 2 is characterized in that: When excavating the area on the side of the cross beam (102), the inner circle area on the side of the cross beam is excavated first, and then the outer circle area on the side of the cross beam is excavated; when excavating the area at the bottom of the cross beam (102), the inner circle area at the bottom of the cross beam is excavated first, and then the outer circle area at the bottom of the cross beam is excavated.

4. The sinking control method for actively controlled caisson construction according to claim 3 is characterized by: The inner ring area of ​​the cross beam side is divided into a first area (1), a second area (2), a third area (3) and a fourth area (4) by the cross beam (102), the first area (1) and the second area (2) are arranged diagonally, and the third area (3) and the fourth area (4) are arranged diagonally; the excavation order of the inner ring area of ​​the cross beam side is: the first area (1) → the second area (2) → the third area (3) → the fourth area (4), and the excavation order of each area is from the inside to the outside.

5. The sinking control method for actively controlled caisson construction according to claim 3 is characterized by: The outer ring area of ​​the cross beam side is divided into a fifth area (5), a sixth area (6), a seventh area (7) and an eighth area (8) by the cross beam (102), the fifth area (5) and the sixth area (6) are arranged diagonally, and the seventh area (7) and the eighth area (8) are arranged diagonally; the excavation order of the outer ring area of ​​the cross beam side is: the fifth area (5) → the sixth area (6) → the seventh area (7) → the eighth area (8), and the excavation order of each area is from the inside to the outside.

6. The sinking control method for actively controlled caisson construction according to claim 4 is characterized by: The inner circle area at the bottom of the cross beam includes a ninth area A, a tenth area B, an eleventh area C and a twelfth area D. The ninth area A is located between the first area (1) and the third area (3) of the inner circle area on the side of the cross beam, the tenth area B is located between the second area (2) and the fourth area (4) of the inner circle area on the side of the cross beam, the eleventh area C is located between the second area (2) and the third area (3), and the twelfth area D is located between the first area (1) and the fourth area (4); the excavation order of the inner circle area at the bottom of the cross beam is the ninth area A→the tenth area B→the eleventh area C→the twelfth area D, and the excavation order of each area is from the inside to the outside.

7. The sinking control method for actively controlled caisson construction according to claim 5 is characterized by: The outer ring area of ​​the bottom of the cross beam includes the thirteenth area E, the fourteenth area F, the fifteenth area G and the sixteenth area H. The thirteenth area E is located between the fifth area (5) and the seventh area (7) of the outer ring area of ​​the side of the cross beam, the fourteenth area F is located between the sixth area (6) and the eighth area (8) of the outer ring area of ​​the side of the cross beam, the fifteenth area G is located between the sixth area (6) and the seventh area (7), and the sixteenth area H is located between the fifth area (5) and the eighth area (8); the excavation order of the inner ring area of ​​the bottom of the cross beam is the thirteenth area E→the fourteenth area F→the fifteenth area G→the sixteenth area H, and the excavation order of each area is from the inside to the outside.

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