Open caisson sinking control method

Abstract

The invention relates to the technical field of beam bridge construction foundations, in particular to an open caisson sinking control method which comprises the following steps that actual conditions of all soil layers, including the maximum value and the minimum value of the friction angle and the cohesive force in the soil layers, are obtained through geological exploration tests, and an open caisson sinking finite element model is established according to the actual conditions of the soil layers and the actual conditions of an open caisson; for each soil layer, a first critical sinking state and a second critical sinking state of the open caisson are obtained; and soil taking construction is conducted according to the first critical sinking state, the inclination angle and the sinking amount of the open caisson are measured on site after the open caisson sinks, the optimal critical sinking state is found, and under the optimal critical sinking state, soil taking construction continues till the open caisson sinks and passes through the current soil layer. According to the open caisson sinking control method, the technical problems of unstable sinking, poor safety performance, slow sinking and low efficiency in the open caisson sinking process are solved.

Description

Technical Field

[0001] The invention relates to the technical field of beam bridge construction foundation, and in particular to a caisson sinking control method. Background Art

[0002] At present, caisson foundation is a common foundation form, which is widely used in large-span bridge foundations. As the span of the bridge increases and the load increases, the foundation scale increases sharply, and the difficulty of controlling the sinking of the caisson foundation increases. During the sinking construction of the caisson, the posture must be kept stable, and unfavorable situations such as sudden sinking and tilting should be avoided.

[0003] In the related art, the traditional caisson sinking control method is that the caisson mainly relies on taking soil from the wellbore to make it sink. In the actual sinking process, once the caisson tilts, whichever side tilts more, more soil is taken from the other side in the following period of time to guide the caisson to tilt to the other side; in this way, one side tilts and soil is taken from the other side, and adjustments are made repeatedly to achieve the purpose of keeping the caisson vertical as much as possible.

[0004] However, this method of repeatedly adjusting the tilt during the sinking process makes the entire sinking process unstable and has poor safety performance. It requires constant monitoring to prevent excessive tilting accidents. At the same time, the sinking is slow and inefficient. Summary of the invention

[0005] The present application provides a caisson sinking control method to solve the technical problems of unstable sinking, poor safety performance, slow sinking and low efficiency during the caisson sinking process.

[0006] The present application provides a method for controlling sinking of a caisson, comprising the following steps: The geological survey test obtains the actual conditions of each soil layer, including the maximum and minimum values ​​of the friction angle and cohesion within the soil layer, and a finite element model of the caisson sinking is established based on the actual conditions of the soil layer and the caisson; For each soil layer, based on the finite element model, the first critical sinking state of the caisson is obtained according to the minimum value of the internal friction angle and cohesion of the soil layer; the second critical sinking state of the caisson is obtained according to the maximum value of the internal friction angle and cohesion of the soil layer; Soil excavation is carried out according to the first critical sinking state. After the caisson sinks, the inclination angle and the amount of sinking are measured on site. If both are within the respective set threshold ranges, the first critical sinking state is determined to be optimal. Otherwise, the soil excavation state between the first critical sinking state and the second critical sinking state is refined until the inclination angle and the amount of sinking are within the respective set threshold ranges, at which time the corresponding critical sinking state is optimal. Under the optimal critical sinking state, soil excavation is continued until the caisson sinks through the current soil layer.

[0007] On the basis of the above technical solution, in one embodiment, for multiple soil layers, a first critical sinking state and a second critical sinking state corresponding to the caisson in each soil layer are obtained, and an optimal critical sinking state of the caisson in each soil layer is obtained between the first critical sinking state and the second critical sinking state; The caisson maintains the optimal critical sinking state in each soil layer, and soil is taken from each soil layer in turn starting from the first soil layer until the caisson sinks to the bottom.

[0008] Based on the above technical solution, in one embodiment, the step of determining whether the tilt angle and the sinking amount are both within respective set threshold ranges includes: The threshold range of the tilt angle is less than or equal to a preset tilt angle value; The sinking amount is greater than or equal to a preset sinking value.

[0009] On the basis of the above technical solution, in one embodiment, the outer side walls of the caisson are divided into a number of wellbores by a number of partition walls; in the process of obtaining the first critical sinking state, obtaining the second critical sinking state, performing actual soil excavation construction according to the first critical sinking state, or maintaining the optimal critical sinking state to continue soil excavation construction, soil excavation is carried out according to the principle of excavating the middle first and then the surroundings, and first the wellbore and then the blind area.

[0010] Based on the above technical solution, in one embodiment, the soil taking principle also includes symmetrical soil taking with the caisson axis as the center.

[0011] Based on the above technical solution, in one embodiment, the critical sinking state represents the remaining soil layer morphology in which the caisson is vertical and has a sinking depth greater than a set depth.

[0012] Based on the above technical solution, in one embodiment, the refining of the soil extraction state between the first critical subsidence state and the second critical subsidence state includes: Gradually approaching the first critical subsidence state to the second critical subsidence state, and in the process, priority is given to expanding the excavation area and secondly to expanding the depth.

[0013] On the basis of the above technical solution, in one embodiment, when the cross section of the caisson is circular, the refinement of the soil extraction state between the first critical sinking state and the second critical sinking state comprises: Gradually approach the second critical sinking state from the first critical sinking state, take the axis of the caisson as the center, maintain a circular excavation area, and excavate soil according to the principle of excavating soil from the middle then the surroundings, and from the wellbore first then the blind area.

[0014] On the basis of the above technical solution, in one embodiment, when the cross section of the caisson is square, the refinement of the soil taking state between the first critical sinking state and the second critical sinking state comprises: Gradually approach the second critical sinking state from the first critical sinking state, take the axis of the caisson as the center, maintain a square excavation area, and excavate soil according to the principle of excavating soil from the middle then the surroundings, and from the wellbore first then the blind area.

[0015] On the basis of the above technical solution, in one embodiment, when an unexpected situation occurs and the inclination angle of the caisson exceeds the set threshold range, the inclination correction is first performed. After the correction is completed, the optimal critical sinking state is re-obtained, and the optimal critical sinking state is continued, and soil is taken until the caisson sinks through the current soil layer.

[0016] The beneficial effects brought by the technical solution provided by the embodiment of the present application include at least: 1. The caisson sinking control method of the present application simplifies the finite element model of the caisson sinking and the complex soil layer mixed with the maximum value and the minimum value of the soil layer parameter into a soil layer with a single soil layer parameter, and performs simplification twice to obtain a first critical sinking state corresponding to the minimum value of the internal friction angle and the cohesion and a second critical sinking state corresponding to the maximum value of the internal friction angle and the cohesion. The actual soil excavation is guided according to these two critical sinking states, and the optimal critical sinking state can be quickly obtained according to actual measurement. The remaining soil layer in the optimal critical sinking state can well support the caisson to maintain a vertical state, maintain the optimal critical sinking state, and continue soil excavation construction until it sinks through the current soil layer. The phenomenon of the caisson not sinking or sudden sinking during the sinking process can be effectively avoided. The caisson sinking control method can more accurately grasp the critical state of the caisson sinking process by combining theoretical calculation, on-site implementation and real-time measurement, to ensure that the caisson sinks steadily and controllably with good safety performance.

[0017] 2. The caisson sinking control method of the present application divides the soil layers into multiple layers according to geological survey tests, and construction is carried out layer by layer starting from the first layer. Each layer needs to obtain the optimal critical sinking state according to the first critical sinking state and the second critical sinking state, and maintain the optimal critical sinking state for repeated soil excavation construction until the caisson penetrates the current soil layer. Since the soil quality of each soil layer is different, each soil layer has a different optimal critical sinking state. The caisson sinking control method of the present application can quickly obtain the optimal critical sinking state for smooth and efficient soil excavation construction when constructing each soil layer, thereby greatly improving the efficiency of caisson sinking construction.

[0018] 3. The caisson sinking control method of the present application, whether in obtaining the first critical sinking state and obtaining the second critical sinking state, or in actual soil excavation construction, follows the principle of excavating the soil from the middle first and then the surroundings, from the wellbore first and then the blind area, which can ensure the stable vertical sinking of the caisson to the greatest extent, ensure smooth and controllable sinking and greatly improve the sinking efficiency.

[0019] 4. The caisson sinking control method of the present application can respond quickly and regain the optimal critical sinking state after correction even if an unexpected situation occurs during soil excavation and the tilt angle exceeds the set threshold range. It can also quickly recover and maintain the optimal critical sinking state. Soil excavation and construction are carried out until the caisson sinks through the current soil layer. The caisson is stable and the construction efficiency is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0021] Figure 1 A flow chart of a caisson sinking control method provided in an embodiment of the present application; Figure 2 A schematic diagram of a first critical sinking state of a soil layer provided in an embodiment of the present application; Figure 3 A schematic diagram of a second critical sinking state of a soil layer provided in an embodiment of the present application; Figure 4 A schematic diagram of an intermediate state between a first critical subsidence state and a second critical subsidence state of a soil layer provided in an embodiment of the present application. DETAILED DESCRIPTION

[0022] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0023] The present application provides a caisson sinking control method to solve the technical problems of unstable sinking, poor safety performance, slow sinking and low efficiency during the sinking process of the caisson; the present application adopts the maximum value of the soil layer parameter (φ max and c max ) and minimum value (φ min and cmin ), the critical sinking state of the caisson sinking construction is obtained, and the critical sinking state is always maintained, which can more accurately grasp the sinking state of the caisson and ensure the smooth, controllable and efficient sinking of the caisson.

[0024] like Figure 1 As shown, the present application discloses a caisson sinking control method, comprising the following steps: S1: The geological survey test obtains the actual conditions of each soil layer, including the maximum and minimum values ​​of the friction angle and cohesion within the soil layer. According to the actual conditions of the soil layer and the caisson, a finite element model of the caisson sinking is established.

[0025] Specifically, the geological survey test obtains the actual conditions of each soil layer, which includes the maximum value of the soil layer parameter φ max and c max , and the minimum value φ min and c min ; where φ max and φ min They represent the maximum and minimum internal friction angles of the soil layer, c max and c min The maximum cohesion and minimum cohesion of the soil layer are represented respectively; the finite element model of the caisson sinking is established according to the actual conditions of the soil layer and the caisson. Specifically, the actual conditions of the soil layer include the soil layer depth and soil layer parameters, and the actual conditions of the caisson include the caisson material, shape and volume.

[0026] S2: When constructing each soil layer, based on the finite element model, the first critical sinking state of the caisson is obtained according to the minimum value of the internal friction angle and cohesion of the soil layer; the second critical sinking state of the caisson is obtained according to the maximum value of the internal friction angle and cohesion of the soil layer.

[0027] Specifically, the soil layer parameter of a soil layer in the finite element model is set to φ min and c min The soil layer parameters in the finite element model of caisson sinking are adjustable. The complex soil layer mixed with the maximum and minimum soil layer parameters is simplified into a soil layer with a single minimum soil layer parameter. The scene conditions are simplified to obtain the first critical sinking state of the caisson. Among them, the critical sinking state represents the remaining soil layer morphology when the caisson is vertical and has a sinking depth greater than the set depth sinking amount (such as Figure 2 , Figure 3 or Figure 4 ). The soil layer parameters of the same soil layer in the finite element model of the caisson sinking are set to φ max and c max , obtain the second critical sinking state of the caisson. S3: Carry out soil excavation construction according to the first critical sinking state. After the caisson sinks, measure the inclination angle and the sinking amount of the caisson on site. If both are within the respective set threshold ranges, the first critical sinking state is determined to be optimal. Otherwise, refine the soil excavation state between the first critical sinking state and the second critical sinking state until the inclination angle and the sinking amount are both within the respective set threshold ranges, at which time the corresponding critical sinking state is optimal. Under the optimal critical sinking state, continue soil excavation construction until the caisson sinks through the current soil layer.

[0028] Specifically, actual soil excavation is carried out according to the first critical sinking state. When the soil layer reaches the first critical sinking state, the tilt angle and sinking amount of the caisson are measured on site after the caisson sinks to determine whether the tilt angle and sinking amount are within the respective set threshold ranges. The tilt angle and sinking amount are used to define whether it is an ideal sinking. If they are within the range, it means it is an ideal sinking, and if they are not within the range, it means it is not an ideal sinking. If so (i.e., the tilt angle and sinking amount are within the respective set threshold ranges), it means that the first critical sinking state is the optimal critical sinking state, indicating that the remaining soil layer in this state can well support the caisson without tilting, maintain the first critical sinking state, and continue soil excavation construction until it sinks through the current soil layer. If not (i.e. the inclination angle and the settlement amount are not both within the respective set threshold ranges), it means that the first critical settlement state is not the optimal critical settlement state. The soil excavation state between the first critical settlement state and the second critical settlement state is refined, and multiple actual soil excavation tests are carried out. If the soil is excavated to a certain intermediate state, the inclination angle and the settlement amount are both within the respective set threshold ranges, the intermediate state is identified as the optimal critical settlement state. The optimal critical settlement state is maintained, and soil excavation construction is continued until the caisson sinks through the current soil layer.

[0029] The caisson sinking control method of the present application simplifies the complex soil layer mixed with the maximum value and the minimum value of the soil layer parameter into a soil layer with a single soil layer parameter according to the finite element model of the caisson sinking, and performs simplification twice to obtain the first critical sinking state corresponding to the minimum value of the internal friction angle and the cohesion and the second critical sinking state corresponding to the maximum value of the internal friction angle and the cohesion. The actual soil excavation is guided according to these two critical sinking states, and the optimal critical sinking state can be quickly obtained according to actual measurement. The remaining soil layer in the optimal critical sinking state can well support the caisson to maintain a vertical state, maintain the optimal critical sinking state, and continue soil excavation construction until it sinks through the current soil layer. The phenomenon of the caisson not sinking or sudden sinking during the sinking process can be effectively avoided. The caisson sinking control method can more accurately grasp the critical state in the caisson sinking process by combining theoretical calculation, on-site implementation and real-time measurement, to ensure the steady and controllable sinking of the caisson with good safety performance.

[0030] In one embodiment, for multiple soil layers, a first critical sinking state and a second critical sinking state corresponding to the caisson in each soil layer are obtained, and an optimal critical sinking state of the caisson in each soil layer is obtained between the first critical sinking state and the second critical sinking state; The caisson maintains its own optimal critical sinking state in each soil layer, and soil excavation is carried out in each soil layer in turn starting from the first soil layer until the caisson sinks to the bottom.

[0031] Specifically, the n soil layers obtained from the geological survey test, where n is a positive integer greater than or equal to 1, each soil layer has a soil layer parameter φ max 、c max ,φ min and c min .

[0032] Caisson sinking control methods include: According to the four parameters of the first soil layer, the first critical sinking state and the second critical sinking state of the caisson in the first soil layer are obtained; actual soil excavation construction is performed to obtain the optimal critical sinking state of the caisson in the first soil layer, and the soil excavation construction is repeated while maintaining the optimal critical sinking state until the caisson penetrates the first soil layer; Continue to repeat the above steps according to the four parameters of the second to nth soil layers respectively until the caisson sinks to the bottom.

[0033] In one example, based on the four parameters of a soil layer, the first critical subsidence state is obtained as follows: Figure 2 As shown, the second critical sinking state obtained Figure 3 As shown in the figure, the optimal critical sinking state is obtained as Figure 3 shown.

[0034] The caisson sinking control method of the present application divides the soil layer into n layers according to geological survey tests, and constructs layer by layer from the first layer to the nth layer. Each layer needs to obtain the optimal critical sinking state according to the first critical sinking state and the second critical sinking state, and maintain the optimal critical sinking state for repeated soil excavation construction until the caisson penetrates the current soil layer. Since the soil quality of each soil layer is different, each soil layer has a different optimal critical sinking state. The caisson sinking control method of the present application can quickly obtain the optimal critical sinking state for smooth and efficient soil excavation construction when constructing each soil layer, thereby greatly improving the efficiency of caisson sinking construction.

[0035] In one embodiment, determining whether the tilt angle and the sinking amount are both within respective set threshold ranges includes: The threshold range of the tilt angle is less than or equal to the preset tilt angle value, in order to always ensure the verticality of the caisson; the sinking amount is greater than or equal to the preset sinking value, in order to ensure that there is sinking and it is vertical.

[0036] In one embodiment, the outer side walls of the caisson are divided into a plurality of well holes by a plurality of partition walls; In the four processes of obtaining the first critical subsidence state, obtaining the second critical subsidence state, carrying out actual soil excavation construction according to the first critical subsidence state, or maintaining the optimal critical subsidence state and continuing soil excavation construction, soil excavation is carried out according to the principle of excavating the middle first and then the surroundings, and from the wellbore first and then the blind area.

[0037] Specifically, the blind area refers to the area directly below the bottom end surface of the partition wall.

[0038] The caisson sinking control method of the present application, whether in obtaining the first critical sinking state and obtaining the second critical sinking state, or in actual soil excavation construction, follows the principle of excavating soil from the middle first and then the surroundings, from the wellbore first and then the blind area, which can ensure the stable vertical sinking of the caisson to the greatest extent, ensure smooth and controllable sinking and greatly improve the sinking efficiency.

[0039] Furthermore, the principle of soil excavation also includes symmetrical soil excavation with the axis of the caisson as the center. Symmetrical soil excavation with the axis of the caisson as the center further ensures the stability of soil excavation and the stability of the sinking of the caisson.

[0040] In one embodiment, the critical sinking state indicates that the caisson is vertical and has a residual soil layer shape with a sinking depth greater than a set depth sinking amount. It is only necessary that the residual soil layer shape of the soil layer can vertically support the caisson.

[0041] In one embodiment, refining the soil taking step between the first critical subsidence state and the second critical subsidence state comprises: It gradually approaches the second critical sinking state from the first critical sinking state, and in the process, the soil excavation area is expanded first, and then the depth is expanded. In this process, until a certain intermediate state is obtained, the inclination angle and the sinking amount of the caisson are within the respective set threshold ranges, which means that the intermediate state is the optimal critical sinking state.

[0042] In one embodiment, when the cross section of the caisson is circular, the step of refining the soil extraction state between the first critical sinking state and the second critical sinking state comprises: Gradually approach the second critical sinking state from the first critical sinking state, take the axis of the caisson as the center, maintain a circular excavation area, and excavate soil according to the principle of excavating soil from the middle then the surroundings, and from the wellbore first then the blind area.

[0043] When the cross-section of the caisson is circular, maintaining a circular excavation area can maintain the stability of the caisson.

[0044] In one embodiment, when the cross section of the caisson is square, the refinement of the soil extraction state between the first critical sinking state and the second critical sinking state includes: Gradually approach the second critical sinking state from the first critical sinking state, take the axis of the caisson as the center, maintain a square excavation area, and excavate soil according to the principle of excavating soil from the middle then the surroundings, and from the wellbore first then the blind area.

[0045] When the cross-section of the caisson is square, maintaining a square excavation area can maintain the stability of the caisson.

[0046] In one embodiment, when an unexpected situation occurs and the inclination angle of the caisson exceeds a set threshold range, the inclination correction is first performed. After the correction is completed, the optimal critical sinking state is re-acquired, and the optimal critical sinking state is continued, and soil is taken and construction is carried out until the caisson sinks through the current soil layer.

[0047] The caisson sinking control method of the present application can respond quickly and regain the optimal critical sinking state after correction even if an unexpected situation occurs during soil excavation and the tilt angle exceeds the set threshold range. It can also quickly recover and maintain the optimal critical sinking state. Soil excavation and construction are carried out until the caisson sinks through the current soil layer. The caisson is stable and the construction efficiency is high.

[0048] In the description of the present application, it should be noted that the terms "upper", "lower", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. Unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

[0049] It should be noted that, in this application, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0050] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A method for controlling sinking of a caisson, characterized in that: The following steps are involved: The geological survey test obtains the actual conditions of each soil layer, including the maximum and minimum values ​​of the friction angle and cohesion within the soil layer, and a finite element model of the caisson sinking is established based on the actual conditions of the soil layer and the caisson; For each soil layer, based on the finite element model, the first critical sinking state of the caisson is obtained according to the minimum value of the internal friction angle and cohesion of the soil layer; the second critical sinking state of the caisson is obtained according to the maximum value of the internal friction angle and cohesion of the soil layer; Soil excavation is carried out according to the first critical sinking state. After the caisson sinks, the inclination angle and the amount of sinking are measured on site. If both are within the respective set threshold ranges, the first critical sinking state is determined to be optimal. Otherwise, the soil excavation state between the first critical sinking state and the second critical sinking state is refined until the inclination angle and the amount of sinking are within the respective set threshold ranges, at which time the corresponding critical sinking state is optimal. Under the optimal critical sinking state, soil excavation is continued until the caisson sinks through the current soil layer.

2. A caisson sinking control method as claimed in claim 1, characterized in that: For multiple soil layers, the first critical sinking state and the second critical sinking state corresponding to the caisson in each soil layer are obtained, and the optimal critical sinking state of the caisson in each soil layer is obtained between the first critical sinking state and the second critical sinking state; The caisson maintains the optimal critical sinking state in each soil layer, and soil is taken from each soil layer in turn starting from the first soil layer until the caisson sinks to the bottom.

3. A caisson sinking control method as claimed in claim 1, characterized in that: The step of judging whether the tilt angle and the sinking amount are both within respective set threshold ranges includes: The threshold range of the tilt angle is less than or equal to a preset tilt angle value; The sinking amount is greater than or equal to a preset sinking value.

4. A caisson sinking control method as claimed in claim 1, characterized in that: The outer side walls of the caisson are divided into a plurality of well holes by a plurality of partition walls; In the process of obtaining the first critical subsidence state, obtaining the second critical subsidence state, carrying out actual soil excavation construction according to the first critical subsidence state, or continuing soil excavation construction while maintaining the optimal critical subsidence state, soil excavation is carried out in accordance with the principle of excavating the middle first and then the surroundings, and first the wellbore and then the blind area.

5. A caisson sinking control method as claimed in claim 4, characterized in that: The soil excavation principle also includes symmetrical soil excavation with the caisson axis as the center.

6. A caisson sinking control method as claimed in claim 1, characterized in that: The critical sinking state indicates that the caisson is vertical and has a remaining soil layer morphology with a sinking depth greater than a set depth.

7. A caisson sinking control method as claimed in claim 1, characterized in that: The step of refining the soil extraction state between the first critical subsidence state and the second critical subsidence state comprises: Gradually approaching the first critical subsidence state to the second critical subsidence state, and in the process, priority is given to expanding the excavation area and secondly to expanding the depth.

8. A caisson sinking control method as claimed in claim 7, characterized in that: When the cross section of the caisson is circular, the refinement of the soil extraction state between the first critical sinking state and the second critical sinking state includes: Gradually approach the second critical sinking state from the first critical sinking state, take the axis of the caisson as the center, maintain a circular excavation area, and excavate soil according to the principle of excavating soil from the middle then the surroundings, and from the wellbore first then the blind area.

9. A method for controlling sinking of a caisson as claimed in claim 7, characterized in that: When the cross section of the caisson is square, the refinement of the soil extraction state between the first critical sinking state and the second critical sinking state includes: Gradually approach the second critical sinking state from the first critical sinking state, take the axis of the caisson as the center, maintain a square excavation area, and excavate soil according to the principle of excavating soil from the middle then the surroundings, and from the wellbore first then the blind area.

10. A caisson sinking control method according to any one of claims 1 to 9, characterized in that: When an unexpected situation occurs, when the inclination angle of the caisson exceeds the set threshold range, the inclination correction is first performed. After the correction is completed, the optimal critical sinking state is re-obtained, and the optimal critical sinking state is continued, and soil is taken until the caisson sinks through the current soil layer.

Images