Saline freezing method open caisson micro-disturbance sinking construction method

Abstract

The invention relates to a brine freezing method open caisson micro-disturbance sinking construction method. The method comprises the following steps that firstly, a site is leveled, an ammonia circulation system is installed, a cushion layer is laid, blade feet are assembled and widened, a concrete structure is poured, and a bottom section open caisson is manufactured and completed; uniformly drilling holes in the widened blade foot; after the concrete structure of the bottom section open caisson is hardened, primary sinking is conducted, and the cushion layer is pulled out; when the lower layer is a soil layer with poor properties, vertically or obliquely extending a freezing pipe, penetrating through the drill hole in the blade foot and extending the length of the freezing pipe, and after the freezing pipe is mounted in place, sealing a gap between the freezing pipe and a pipe orifice of the drill hole by adopting an anti-seepage material; then continuously supplying cold energy to the freezing pipe to gradually freeze the stratum; after freezing of a lower-layer soil body is completed in advance, soil is evenly excavated until the bottom section open caisson sinks; according to the method, waterproof reinforcement can be conducted when the soft stratum open caisson sinks, intermittent local area freezing is achieved, and the method has the advantages of being environmentally friendly, economical and efficient.

Description

Technical Field

[0001] The present invention relates to the technical field of open caisson sinking construction, and particularly relates to a construction method for slightly disturbing the sinking of an open caisson by the brine freezing method. Background Art

[0002] The open caisson method is simple in technology, has few construction equipment, less earth excavation, and has little impact on adjacent buildings. The finally obtained foundation has a deep burial depth and good stability. Compared with spread foundations, pile foundations, diaphragm walls, etc., it has the characteristics of better integrity, rigidity, stability, and seismic resistance, has a large bearing surface, and can bear large vertical and horizontal loads. It is a relatively safe and reliable construction process.

[0003] Its process is to first fabricate the bottom section of the open caisson on the ground surface, and then continuously excavate soil from the well under the enclosure of the well wall, so that the open caisson gradually sinks under its own weight. After reaching the predetermined design elevation, bottom sealing is carried out, and finally the internal structure is constructed. At present, it has been widely applied to municipal construction projects, such as the foundations of bridges, chimneys, water towers, and deep well structures such as pump houses and underground oil depots, as well as the working wells of shield tunneling and pipe jacking.

[0004] However, open caisson construction often faces problems such as soil instability and excessive inclination of the well wall, making it difficult to sink stably, which is particularly obvious in complex strata with soft upper layers and hard lower layers and high water content. In severe cases, sand gushing and ground collapse may even occur. When it is impossible to construct peripheral retaining piles and pumping wells during construction due to narrow construction sites and strict drainage prohibition, it is even more difficult to operate.

[0005] With the increasing construction of underground space projects, the artificial frozen soil wall retaining structure is widely used in underground space projects due to its strong adaptability to complex hydrogeological conditions, flexible freezing construction methods, uniform and complete frozen walls, high reliability, high strength, simple equipment, and good technical and economic effects. Especially in the construction of soft and water-bearing strata and engineering emergency rescue in special situations, it is a support technology with good development prospects.

[0006] The traditional artificial freezing method is to use artificial refrigeration to install freezing pipes filled with low-temperature refrigerant (brine or liquid nitrogen) in the soil. Through heat and mass exchange, the water in the soil layer is cooled, and finally frozen into ice and cemented with the soil to convert the original soil into frozen soil with high strength and water isolation, forming a frozen soil wall according to the designed contour to resist soil pressure and isolate groundwater, so as to play a role in temporary reinforcement. After the internal lining construction is completed, natural thawing or forced thawing is carried out to restore the soil layer to its original state. According to different freezing forms, the freezing method can be divided into vertical freezing, inclined freezing, and horizontal freezing. According to different ways of cooling the formation, it can also be divided into direct freezing (liquid nitrogen freezing) and indirect freezing (brine freezing). Summary of the Invention

[0007] Based on the above description, the present invention provides a construction method for the slightly disturbed sinking of a caisson by the brine freezing method, so as to solve the problem of waterproof reinforcement during the sinking of a caisson in soft strata, realize intermittent local area freezing, and have the characteristics of environmental protection, economy and high efficiency.

[0008] The technical solution of the present invention to solve the above technical problems is as follows: A construction method for the slightly disturbed sinking of a caisson by the brine freezing method, including the following steps:

[0009] S1. Construction preparation: First, level the site, install the ammonia circulation system, and complete the system pressure test and vacuum sealing performance test; at the same time, lay the cushion layer, assemble and widen the cutting edge, pour the concrete structure, complete the bottom section of the caisson, and evenly drill holes on the widened cutting edge;

[0010] S2. Freezing construction: After the concrete structure of the bottom section of the caisson hardens, conduct the initial sinking and extract the cushion layer; when encountering a soil layer with poor properties in the lower layer, vertically or obliquely insert the freezing pipe through the holes on the cutting edge and extend its length. After the freezing pipe is installed in place, use anti-leakage materials to seal the gap between the freezing pipe and the hole mouth of the drilling; then continuously supply cold energy to the freezing pipe to gradually freeze the formation;

[0011] S3. Caisson construction: After the lower layer of soil is frozen in advance, start to evenly excavate the soil in sequence from the center to both sides of the well wall by the excavation machinery until the bottom section of the caisson sinks to completion;

[0012] S4. Caisson structure construction: After the concrete structure of the upper section of the well wall hardens, pour the lower section of the well wall, repeat steps S2 and S3 until the caisson sinks to the design elevation, clean the foundation, roughen the cutting edge, backfill, and complete the bottom sealing treatment of the caisson; then carry out the construction of the internal partition walls, beam plates, and top plates in the well, complete the upper structure and auxiliary facilities operations, and backfill;

[0013] S5. Soil layer thawing: When it is necessary to remove the freezing pipe, use an air compressor to drain the brine in the pipe, and then quickly pull out the freezing pipe using mobile equipment, and backfill and grout with the pre-buried grouting pipe.

[0014] On the basis of the above technical solution, the present invention can also be improved as follows.

[0015] Further, before pouring the concrete structure, bind and weld the steel bars and install the formwork as a support. After acceptance, pour the concrete structure to form the bottom section of the caisson; evenly drill holes on the widened cutting edge through a drilling rig.

[0016] Further, the ammonia circulation system includes a condenser, a compressor, and an evaporator. The ammonia circulation system is connected to a cooling water circulation system and a brine circulation system. The cooling water circulation system includes a fresh water pump and a cooling tower. The brine circulation system includes a brine tank and a brine pump.

[0017] Further, after the initial settlement of the bottom section of the open caisson, when the soil properties below are good, excavation is carried out from the middle of the bottom section of the open caisson to both sides of the well wall until the bottom section of the open caisson has sunk completely.

[0018] Further, the freezing pipe is of a U-shaped structure. The freezing pipe includes a water inlet and a water outlet, and the water inlet and the water outlet are arranged flush. The freezing pipe is inserted obliquely along the vertical direction of the bottom section of the open caisson by no more than 20°.

[0019] Further, after the freezing pipe is installed in place, a water pressure leakage test is carried out. After it is confirmed to be qualified, it is sealed with anti-seepage materials. Cooling capacity is continuously supplied to the water inlet by a freezing equipment system. The freezing equipment system is debugged and pre-run before cooling supply. After it is correct, it is then operated to gradually freeze the formation.

[0020] Further, when carrying out the backfilling process, sand and concrete are used, steel bars are tied, and the bottom slab is poured to complete the bottom sealing treatment of the open caisson.

[0021] Further, during the excavation process, the construction condition of the well wall is observed and corrected in time. When the freezing pipe is not removed, natural thawing is adopted.

[0022] Further, when the freezing pipe needs to be removed, forced thawing is adopted by the method of melting with hot brine.

[0023] Further, the bottom section of the open caisson is of a hollow structure. The lower part of the bottom section of the open caisson is provided with a cutting edge. The cutting edge is of an inverted right-angled triangle structure. A convex structure is arranged on the inner side of the bottom section of the open caisson at the connection of the cutting edge. A drilling hole into which the freezing pipe can be inserted is arranged on the convex structure.

[0024] Compared with the prior art, the technical solution of the present application has the following beneficial technical effects:

[0025] 1. Compared with the traditional freezing curtain, it takes less time and has higher construction efficiency: The common artificial freezing method is to insert freezing pipes outside the designed open caisson range. After a long freezing period, a waterproof curtain is constructed to reinforce and seal the surrounding soil. During the freezing period, the brine temperature, system parameters, etc. are monitored, and it is calculated whether the freezing curtain has intersected, and whether the vertical frozen soil wall has reached the designed thickness and strength. After it is confirmed to be correct, the relevant construction of the open caisson is carried out, which has the disadvantage of taking a long time; while the freezing range required by this construction method is only the soil below the cutting edge. After freezing is completed in a local area, the soil can be excavated to make the well wall sink.

[0026] 2. Compared with the processes such as row-pile support and well drainage, by setting the bottom-section caisson and the freezing pipes thereon, this construction method can not only achieve local reinforcement of the soil layer, but also isolate the connection between the construction area and groundwater, providing a safer and more reliable working environment for caisson construction.

[0027] 3. Mature technology and flexible layout: For caisson construction under narrow construction sites, the drilling equipment adopted in this construction method can be flexibly selected, and the freezing equipment site can also be flexibly arranged.

[0028] 4. Can selectively freeze the soil mass at each stage according to soil layer conditions, environmentally friendly and efficient: When encountering a soil layer with poor properties in the lower layer, extend the freezing pipes to the specified design length to pre-freeze the soil mass in this area; when the soil mass below is firm and stable, it is possible to choose not to extend the freezing pipes to avoid excessive energy consumption, and it saves time and effort.

[0029] 5. Can choose vertical freezing or inclined freezing according to specific soil layer properties and excavation equipment conditions, flexible and adjustable: When the soil layer is relatively hard or the performance of the excavation equipment is poor, the soil layer excavation is difficult, and inclined freezing can be selected, that is, on the caisson blade footrest, the freezing pipes are inserted obliquely towards the outside of the well wall to avoid the difficulty of excavating the soil mass near the blade foot inside the well wall, causing unnecessary waste of excavation time and loss of equipment funds. Brief Description of the Drawings

[0030] Figure 1 Schematic diagram of the caisson wall structure of a construction method for slightly disturbed sinking of a caisson by the brine freezing method provided by an embodiment of the present invention;

[0031] Figure 2 Schematic diagram of the structure when the freezing pipes are inserted to the first depth in the freezing process provided by an embodiment of the present invention;

[0032] Figure 3 Schematic diagram of the structure when the freezing pipes are inserted to the second depth in the freezing process provided by an embodiment of the present invention;

[0033] Figure 4 Plan view of the caisson wall in an embodiment of the present invention;

[0034] Figure 5 Enlarged detailed view of the insertion angle of the freezing pipes in an embodiment of the present invention;

[0035] Figure 6 Flow chart of the freezing cycle system in an embodiment of the present invention;

[0036] In the drawings, the list of components represented by each reference numeral is as follows:

[0037] 1. Well wall; 2. Cutting edge; 3. Freezing pipe; 4. Ammonia circulation system; 41. Condenser; 42. Compressor; 43. Evaporator; 5. Cooling water circulation system; 51. Clear water pump; 52. Cooling tower; 6. Brine circulation system; 61. Brine tank; 62. Brine pump. Detailed implementation manner

[0038] To facilitate the understanding of this application, the following will describe this application more comprehensively with reference to the relevant drawings. Embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of this application more thorough and comprehensive.

[0039] Unless otherwise defined, 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 this application belongs. The terms used in the description of this application herein are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0040] As used herein, the singular forms "a", "an" and "the" may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms "comprising", "including" or "having" and the like specify the presence of the stated features, wholes, steps, operations, components, parts or combinations thereof, but do not preclude the presence or addition of one or more other features, wholes, steps, operations, components, parts or combinations thereof.

[0041] Please refer to Figures 1-6 , the present invention provides a technical solution: a construction method for the slightly disturbed sinking of a caisson by the brine freezing method, including the following steps:

[0042] S1. Construction preparation: First, level the site, install the ammonia circulation system 4, and complete the system pressure test and vacuum sealing performance test; at the same time, lay the cushion layer, assemble and widen the cutting edge 2, pour the concrete structure, complete the production of the bottom section of the caisson, and evenly drill holes on the widened cutting edge 2.

[0043] S2. Freezing construction: After the concrete structure of the bottom section of the caisson hardens, conduct the initial sinking and extract the cushion layer; when encountering a soil layer with poor properties in the lower layer, vertically or obliquely insert the freezing pipe 3 through the drilled holes on the cutting edge 2 and extend its length. After the freezing pipe 3 is installed in place, seal the gap between the freezing pipe 3 and the drilled hole nozzle with a leak-proof material; then continuously supply cold to the freezing pipe 3 to gradually freeze the formation.

[0044] S3. Caisson construction: After the lower layer of soil is frozen in advance, start to evenly excavate the soil in sequence from the center to both sides of the well wall 1 by an excavating machine until the bottom section of the caisson sinks to completion.

[0045] S4, caisson structure construction: After the concrete structure of the previous section of the well wall 1 has hardened, the next section of the well wall 1 is poured, and steps S2 and S3 are repeated until the caisson is sunk to the designed elevation. The base is cleaned, the blade foot 2 is roughened, and backfilling is performed to complete the bottom sealing of the caisson; then, the partition walls, beams and slabs, and top slabs in the well are constructed, and the superstructure and auxiliary facilities are completed, and backfilling is performed;

[0046] S5. Thawing of the soil layer: When the frozen pipe 3 needs to be removed, the brine in the pipe is discharged using an air compressor, and then the frozen pipe 3 is quickly pulled out using a mobile device, and the pre-buried grouting pipe is backfilled with grouting.

[0047] It should be noted that the anti-seepage material here can be polymer cement, epoxy material, glass glue, super early strength slurry, asphalt waterproof material, mortar waterproofing agent etc. with water blocking and leakproof composite material. If the soil layer also included in step S2 is hard soil or a soil layer in good condition, then excavation can be carried out directly from the middle of the bottom section caisson to both sides, without inserting freezing pipe 3 for freezing. Repeating steps S2 and S3 in step S4 refers to when a section of shaft wall 1 is installed, whether freezing pipe 3 can be set according to soil conditions when pouring the next section of shaft wall 1, if the soil conditions are good, then step S3 can be directly carried out after the initial sinking of the bottom section caisson, or when the soil layer is a bad property, then after the initial sinking of the bottom section caisson, freezing pipe 3 needs to be inserted to freeze the surrounding soil before excavation construction is carried out until the bottom section caisson sinks.

[0048] This construction method only requires freezing the soil below the blade foot 2. After the freezing is completed in the local area, the soil can be excavated to sink the well wall 1. This method is time-saving and has high construction efficiency.

[0049] Please see the attached Figure 2 、 3 Before pouring the concrete structure, tie the welded steel bars and install the formwork as support. After acceptance, pour the concrete structure to form the bottom section caisson, and drill holes evenly on the widened blade foot 2 with a drill. It should be noted that the cushioning wood is laid first, the widened blade foot 2 is assembled, and then the welded steel bars are tied and the formwork is installed. After acceptance, the concrete is poured. The strength of the concrete structure must meet the construction requirements before it can be dismantled. When drilling, the setting of adjacent holes should ensure that the freezing ranges of adjacent freezing pipes 3 overlap.

[0050] Please see the attached Figure 5, the ammonia circulation system 4 includes a condenser 41, a compressor 42, and an evaporator 43. The ammonia circulation system 4 is connected to a cooling water circulation system 5 and a brine circulation system 6. The cooling water circulation system 5 includes a fresh water pump 51 and a cooling tower 52. The brine circulation system 6 includes a brine tank 61 and a brine pump 62. The ammonia circulation system 4 cools the brine in the brine tank 61 of the brine circulation system 6 and cools it to -20° to -30°. The brine pump 62 pumps out the cooled brine and flows into the water inlet on one side of the freezing pipe 3. The cooled brine absorbs the heat around the freezing pipe 3, thereby freezing the surrounding soil layer. The temperature of the brine in the cooling pipe rises after absorbing heat and comes out from the water outlet on the other side of the freezing pipe 3 under the action of the brine pump 62, and then re-enters the condenser 41 in the cooling water circulation system 5 and the ammonia circulation system 4 for cooling. At this time, the liquid ammonia in the ammonia circulation system 4 absorbs the heat of the brine under reduced pressure, and then returns to the pipeline through the compressor 42 and the evaporator 43 for repeated use. After multiple freezings, frozen soil conditions can be well formed within a certain range at the bottom of the bottom section of the caisson, which is convenient for construction; it can not only achieve local reinforcement of the soil layer, but also isolate the connection between the construction area and the groundwater, providing a safer and more reliable working environment for the caisson construction.

[0051] Further, after the initial sinking of the bottom section of the caisson, when the soil properties below are good, excavation is carried out from the middle of the bottom section of the caisson to both sides of the well wall 1 until the bottom section of the caisson is completely sunk. It should be noted that when the soil properties below are good, the freezing pipe 3 may not be inserted. That is to say, when the soil conditions of the upper soil layer are good, the excavation construction of the bottom section of the caisson can be directly carried out first. When the soil conditions of the lower layer are not good, the freezing pipe 3 is inserted to freeze the soil layer in the local area, and then the excavation construction is carried out to achieve intermittent local area freezing; that is, before excavation, the soil in each stage can be selectively frozen according to the soil layer conditions, which is environmentally friendly and efficient: when encountering a soil layer with poor properties in the lower layer, the freezing pipe 3 is extended to the specified design length to pre-freeze the soil in this area; when the soil below is firm and stable, the freezing pipe 3 can be selected not to be extended to avoid excessive energy consumption and save time and effort. The initial sinking can only be carried out after the concrete strength of the bottom section of the caisson reaches 100% of the designed strength. Before pulling out the cushion blocks and carrying out excavation, first determine whether the soil in the first layer or the lower layer needs to be locally frozen and reinforced according to the soil layer conditions in the exploration report and the analysis of the design scheme.

[0052] Please refer to the appendix Figure 4, the freezing pipe 3 is a U-shaped structure, and the freezing pipe 3 includes a water inlet and a water outlet. The water inlet is arranged flush with the water outlet, and the freezing pipe 3 is inserted along the vertical direction of the bottom section caisson at an angle of no more than 20°. It should be noted that the freezing pipe 3 and the blade foot 2 together constitute a freezing method caisson sinking micro-disturbance device. After the freezing pipe 3 is installed in place, a water pressure leakage test should be carried out. After it is confirmed to be qualified, the gap between the freezing pipe 3 and the borehole pipe mouth should be sealed; then the freezing equipment system should be debugged and tested. After it is correct, the freezing unit should be operated to continuously supply cold air to the freezing hole to gradually freeze the stratum. During the freezing period, the system operating parameters need to be observed, the freezing condition of the frozen layer should be monitored, and the freezing range and intensity should be calculated to see if they meet the design expectations. Once all of them are met, the freezing of the soil in this area is completed. According to the specific soil properties and excavation equipment conditions, vertical freezing or inclined freezing can be selected, and the freezing pipe 3 can be flexibly adjusted: when the soil layer is relatively hard or the excavation equipment has poor performance, the soil excavation is more difficult, and inclined freezing can be selected, that is, on the caisson blade foot 2 pedal, the freezing pipe 3 is inserted obliquely toward the outside of the well wall 1, and the freezing pipe 3 is attached. Figure 4 The middle arrow indicates that the angle between the pipe body and the vertical normal is between 0 and 20 degrees, so as to avoid the difficulty of excavating the soil near the blade foot 2 inside the well wall 1, resulting in unnecessary waste of excavation time and equipment capital loss. It can realize the sinking construction of the micro-disturbance caisson, which is especially suitable for unfavorable soft water-bearing strata with poor soil quality and high groundwater level.

[0053] Furthermore, after the freezing pipe 3 is installed in place, a water pressure leakage test is carried out, and after confirmation of being qualified, it is sealed with anti-leakage materials; a freezing equipment system is used to continuously supply cold energy to the water inlet. The freezing equipment system is debugged and tested before supplying cold, and is put into operation after it is correct, so that the stratum is gradually frozen.

[0054] Furthermore, during the backfill process, sand and concrete are used, steel bars are tied, and the bottom plate is poured to complete the bottom sealing of the caisson. It should be noted that during the caisson heightening, bottom sealing, interior, and superstructure construction, the next section of the caisson wall 1 is poured only when the concrete strength of the previous section reaches 70% of the design.

[0055] Furthermore, during the excavation process, the construction status of the well wall 1 is observed and corrected in time. When the frozen pipe 3 is not removed, natural thawing is adopted.

[0056] Furthermore, when the frozen pipe 3 needs to be removed, forced thawing is performed by melting it with hot brine. That is, when the soil thaws, the decision on whether to remove the frozen pipe 3 can be made based on the difficulty of the operation and the wear and tear of the frozen pipe 3. If removal is not necessary, natural thawing can be used. If removal is required, forced thawing can be performed by melting it with hot brine, using an air compressor to drain the brine from the pipe, and then quickly removing the frozen pipe 3 using a crane. The pre-buried grouting pipe can then be backfilled and grouting can be performed in a timely manner. Alternatively, the pipe can be removed and grouting can be performed after natural thawing.

[0057] Please refer to the appendix Figure 1 , the bottom-section caisson is a hollow structure. The lower part of the bottom-section caisson is provided with the cutting edge 2. The cutting edge 2 is an inverted right-angled triangle structure. At the connection of the cutting edge 2, a protruding structure is arranged towards the inner side of the bottom-section caisson. A borehole for inserting the freezing pipe 3 can be arranged on the protruding structure.

[0058] In summary, in this construction method, a drilling rig is used to drill holes on the widened cutting edge of the caisson. According to the conditions of the underlying soil layer, the vertical or inclined freezing pipe 3 is selectively installed and lowered for vertical freezing or inclined freezing to locally freeze and reinforce the waterproofing, and then the soil is excavated to realize the construction of the caisson sinking with micro-disturbance. This is especially applicable to the poor and soft water-bearing strata with poor soil quality and high groundwater level; this construction method can realize intermittent local area freezing, which can not only play the role of waterproofing and reinforcement during the caisson sinking in the soft strata, but also has the characteristics of environmental protection, economy and high efficiency.

[0059] Compared with the traditional freezing curtain, it takes less time and has higher construction efficiency: compared with the processes such as row-pile support and wellpoint dewatering, by setting the bottom-section caisson and the freezing pipe 3 thereon, this construction method can not only realize the local reinforcement of the soil layer, but also isolate the connection between the construction area and the groundwater, providing a safer and more reliable working environment for the caisson construction; moreover, the freezing range is only the soil body below the cutting edge 2. After the local area is frozen, the soil can be excavated to make the shaft wall 1 sink; for the caisson construction under the condition of a narrow construction site, the drilling equipment adopted by this construction method can be flexibly selected, and the freezing equipment site can also be flexibly arranged. When the underlying soil layer is of poor quality, the freezing pipe 3 is extended to the specified designed length to pre-freeze the soil body in this area; when the underlying soil body is firm and stable, the freezing pipe 3 can be selected not to be extended to avoid excessive energy consumption and save time and effort. When the soil layer is relatively hard or the performance of the excavation equipment is poor, and the soil excavation is difficult, inclined freezing can be selected, that is, on the tread of the cutting edge 2 of the caisson, the freezing pipe 3 is inserted obliquely towards the outside of the shaft wall 1 to avoid the difficulty of excavating the soil body near the cutting edge 2 inside the shaft wall 1, resulting in unnecessary waste of excavation time and loss of equipment funds.

[0060] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A construction method for the slightly disturbed sinking of a caisson by the brine freezing method, characterized in that, It includes the following steps: S1. Construction preparation: First, level the site, install the ammonia circulation system, and complete the system pressure test and vacuum sealing performance test; meanwhile, lay the cushion layer, assemble and widen the cutting edge, pour the concrete structure, complete the bottom section of the open caisson, and evenly drill holes on the widened cutting edge; S2. Freezing construction: After the concrete structure of the bottom section of the open caisson hardens, conduct the initial sinking and extract the cushion layer; when encountering a soil layer with poor properties in the lower layer, vertically or obliquely insert the freezing pipes through the holes on the cutting edge and extend their lengths. After the freezing pipes are installed in place, seal the gaps between the freezing pipes and the orifices of the drill holes with anti-leakage materials; then continuously supply cold to the freezing pipes to gradually freeze the formation; S3. Open caisson construction: After the lower layer of soil is pre-frozen, start evenly excavating the soil from the center to both sides of the caisson wall by an excavating machine until the bottom section of the open caisson sinks to completion; S4. Open caisson structure construction: After the concrete structure of the upper section of the caisson wall hardens, pour the next section of the caisson wall, repeat steps S2 and S3 until the open caisson sinks to the designed elevation, clean the base, roughen the cutting edge, conduct backfilling, and complete the bottom sealing treatment of the open caisson; then construct the internal partition walls, beam plates, and top plates in the caisson, complete the construction of the upper structure and auxiliary facilities, and conduct backfilling; S5. Soil layer thawing: When it is necessary to pull out the freezing pipes, use an air compressor to drain the brine in the pipes, then quickly pull out the freezing pipes using mobile equipment, and backfill and grout with embedded grouting pipes.

2. The construction method for the slightly disturbed sinking of a caisson by the brine freezing method according to claim 1, wherein, Before pouring the concrete structure, bind and weld the steel bars and install the formwork as a support. After acceptance, pour the concrete structure to form the bottom section of the open caisson; evenly drill holes on the widened cutting edge with a drilling rig.

3. The construction method for the slightly disturbed sinking of a caisson by the brine freezing method according to claim 1, characterized in that, The ammonia circulation system includes a condenser, a compressor, and an evaporator. The ammonia circulation system is connected with a cooling water circulation system and a brine circulation system. The cooling water circulation system includes a clean water pump and a cooling tower. The brine circulation system includes a brine tank and a brine pump.

4. The construction method for the slightly disturbed sinking of a caisson by the brine freezing method according to claim 1, characterized in that, After the initial sinking of the bottom section of the open caisson, when the properties of the underlying soil are good, excavate from the middle of the bottom section of the open caisson to both sides of the caisson wall until the bottom section of the open caisson sinks to completion.

5. The construction method for slightly disturbing the sinking of a caisson by the brine freezing method according to claim 1, characterized in that, The freezing pipe is of a U-shaped structure. The freezing pipe includes a water inlet and a water outlet. The water inlet and the water outlet are arranged flush. The freezing pipe is inserted obliquely along the vertical direction of the bottom section of the open caisson at an angle not exceeding 20°.

6. The construction method for the slightly disturbed sinking of a caisson by the brine freezing method according to claim 5, characterized in that, After the freezing pipes are installed in place, conduct a water pressure leakage test. After confirmation of qualification, then seal with anti-leakage materials; continuously supply cold to the water inlet using a freezing equipment system. The freezing equipment system is debugged and tested before cooling. After being error-free, then operate to gradually freeze the formation.

7. The construction method for the slightly disturbed sinking of a caisson by the brine freezing method according to claim 1, characterized in that, When conducting the backfilling process, use sand and gravel and concrete, bind the steel bars, and pour the bottom plate to complete the bottom sealing treatment of the open caisson.

8. The construction method for the slightly disturbed sinking of a caisson by the brine freezing method according to claim 1, characterized in that, During the excavation process, observe the construction condition of the caisson wall and correct the deviation in time. When the freezing pipes are not pulled out, natural thawing is adopted.

9. The construction method for the slightly disturbed sinking of a caisson by the brine freezing method according to claim 1, characterized in that, When it is necessary to pull out the freezing pipes, forced thawing is adopted by the method of melting with hot brine.

10. The construction method for the slightly disturbed sinking of a caisson by the brine freezing method according to claim 1, characterized in that, The bottom-section caisson is of a hollow structure, and a cutting edge is provided at the lower part of the bottom-section caisson. The cutting edge is of an inverted right-angled triangle structure, and a protruding structure is provided on the inner side of the bottom-section caisson at the connection of the cutting edge. A drilling hole into which the freezing pipe can be inserted is provided on the protruding structure.

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