A method for freezing a ground trench

Abstract

The present application relates to a vertical shaft freezing shaft mouth ditch construction technical field, especially to a new type freezing ditch construction method, comprising the following steps: S1, after the drilling construction is finished, the original drilling mud ditch is expanded, and the annular ditch is excavated as a freezing ditch; S2, a cushion layer is punched on the ground of the excavated freezing ditch; S3, a brick wall is built on the cushion layer of the freezing ditch; S4, a freezing pipe and a liquid collecting and distributing system are bound in the freezing ditch; S5, a steel plate is used to seal the top of the freezing ditch. The method improves the original ditch large excavation mode, discards the setting of the annular liquid collecting and distributing ring, uses a small diameter polyethylene plastic pipe to replace the original large diameter spiral welded pipe as the liquid collecting and distributing ring, in addition, the ditch cover plate adopts independent steel plates, the improved ditch not only meets the original use function, but also facilitates the inspection and maintenance of the freezer during the freezing operation.

Description

Technical Field

[0001] This invention relates to the field of construction technology for frozen wellhead trenches in vertical shafts, and more particularly to a method for constructing frozen trenches. Background Technology

[0002] The freezing method for constructing mine shafts includes three major circulation systems: brine circulation, ammonia circulation, and cooling water circulation.

[0003] As an important part of the brine circulation system, the wellhead freezing trench of the vertical shaft is the space for placing the brine collection and distribution ring at the wellhead. It is not only an important channel for brine circulation, but also plays a role in protecting the brine pipeline, freezing pipe and small monitoring instruments, and plays a vital role in the freezing construction.

[0004] The quality of trench construction directly affects the overall effectiveness and safety of the freezing method. In freezing construction, brine circulates through freezing pipes, absorbing heat from the surrounding soil to freeze it. The trench ensures smooth and efficient brine circulation, guaranteeing the freezing and cooling effect; therefore, proper trench design is essential before construction.

[0005] Trench construction is carried out after the freezing and drilling are completed. The traditional trench construction process is generally as follows: breaking the drilled soil plate—excavating a circular trench about 2 meters deep—pouring the trench bottom slab—building the inner and outer walls—cutting the freezing pipes that are more than 300mm above the bottom slab—installing the brine trunking system—and sealing the trench with a cement cover. Traditional trenches are time-consuming due to their deep excavation, wall construction, and freezing device removal. Furthermore, in shallow water strata, the trench bottom slab is prone to seepage and leakage. Therefore, the traditional process is more suitable for medium to large-sized freezing wells with deep groundwater levels, numerous freezing holes, and long freezing times. It is not suitable for small and micro-sized freezing wells. Therefore, a solution is urgently needed.

[0006] The above content is only used to help understand the technical solution of the present invention and does not represent an admission that the above content is the closest prior art. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a construction method for freezing trenches. This method improves the original large-scale excavation mode of trenches, abandons the setting of the annular liquid distribution ring, and uses small-diameter polyethylene plastic pipes to replace the original large-diameter spiral welded pipes as the liquid distribution rings. In addition, the trench cover plates are made of independent steel plates. The improved trenches not only meet the original functions, but also facilitate the inspection and maintenance of the freezer during freezing operation.

[0008] To achieve the aforementioned objective, the technical solution of the present invention is implemented as follows: a method for constructing frozen trenches, comprising the following steps:

[0009] S1. After the drilling is completed, the original drilling mud trench is enlarged and an annular trench is excavated as a freezing trench.

[0010] S2. Lay a bedding layer on the ground of the excavated freezing trench;

[0011] S3. Construct a brick wall on the bedding layer of the freezing tank;

[0012] S4. Tie the freezing pipes and liquid distribution system together inside the freezing tank;

[0013] S5. Seal the top of the freezing tank with a steel plate.

[0014] Preferably, the excavation process of the annular trench includes: expanding the existing drilled mud trench, expanding the mud trench with the freezing hole as the center, and deepening and widening the mud trench to form a freezing trench.

[0015] Preferably, in step S2, the construction process of laying a subfloor on the ground of the freezing tank includes: laying a subfloor with concrete to harden the bottom of the freezing tank, and setting a water collection pit at the bottom of the freezing tank.

[0016] Preferably, in step S3, the construction process of building a brick wall on the bedding layer of the freezing trench includes: building a trench retaining wall with a wall size of 37 on the bottom slab of the trench.

[0017] Preferably, in step S4, the process of binding and connecting the freezing tubes in the freezing tank includes:

[0018] S41. Based on the location of the freezing holes in the freezing tank, all the freezing holes are divided into two parts: inner row and outer row.

[0019] S42. The freezing holes in the inner row are shallow holes and are connected in series, with 4-5 holes per group; the freezing holes in the outer row are deep holes and are connected in series, with 2-3 holes per group.

[0020] Preferably, the process of installing the liquid distribution system in the freezing tank includes:

[0021] S43. Each freezing pipe in the inner and outer drainage holes is equipped with an inlet and an outlet; polyethylene plastic pipes are used to connect the inlet of each freezing pipe to the valves of the brine outlet of the brine main pipe outside the trench.

[0022] S44. Use polyethylene plastic pipes to connect the outlet end of each freezing pipe to each valve of the brine circuit of the brine main pipe outside the trench.

[0023] Thus, the inlet end of each freezing pipe forms a brine outlet that connects to the brine outlet main pipe outside the freezing tank, and the outlet end of the freezing pipe forms a brine loop that connects to the brine loop main pipe outside the trench.

[0024] Preferably, in step S5, the process of sealing the top of the freezing tank with a steel plate includes: using a 10mm steel plate instead of a 120mm thick cement cover plate to seal the trench, so as to ensure the safety of the freezing pipe and the supply and return liquid pipes in the trench.

[0025] The trench cover is made of independent thin steel plates. The improved trench not only meets the original function, but also facilitates the troubleshooting and handling of abnormalities in the freezer during freezing operation.

[0026] Preferably, in step S1, the freezing tank has a width of 2.0m and a depth of 0.8m.

[0027] Preferably, in step S5, to facilitate future inspection of the freezer, the steel plate and the steel plate on the adjacent freezing tank are independent of each other and do not need to be welded into one piece. Furthermore, the steel plate is sporadically welded with steel teeth to prevent the vehicle from slipping when passing through.

[0028] Preferably, the circulation depth of brine in each set of external or internal freezing holes after series connection is 200-340m.

[0029] The beneficial effects of this invention are reflected in:

[0030] (1) The method provided by this invention improves upon the original large-scale trench excavation mode, abandoning the setting of the annular liquid distribution ring and replacing the original large-diameter spiral welded pipe with a small-diameter polyethylene plastic pipe as the liquid distribution ring. In addition, the trench cover plates are made of independent steel plates. The improved trench, while meeting the original functional requirements, also facilitates the inspection and maintenance of the freezer during freezing operation, shortening the trench excavation period. At the same time, it saves construction costs, reduces the labor intensity of workers, is simple and easy to implement, improves the original working environment, and provides a better construction environment.

[0031] (2) The method provided by the present invention is not affected by the foundation of the derrick, and can be applied to small repair wells with limited space. It has a short construction period, low cost, and is not limited by the site. It can meet the construction needs and achieve the purpose of speeding up construction and saving construction costs.

[0032] (3) The method provided by the present invention can be adapted to local conditions according to the actual situation on site, and make full use of the conditions of the construction site in a limited space. It saves construction costs, improves work efficiency, improves the construction environment, and reduces labor intensity. It also takes a step further in terms of civilized construction and aesthetics, and is worth promoting and applying. Attached Figure Description

[0033] Figure 1 This is a comparative example of the construction process of a traditional vertical shaft trench structure in this invention.

[0034] Figure 2 This is a diagram of the improved vertical shaft trench structure of the present invention;

[0035] Figure 3 This is a diagram of the improved series connection method of the freezing holes according to the present invention. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example

[0037] like Figure 1-3 As shown:

[0038] This invention provides a method for constructing frozen trenches, comprising the following steps:

[0039] S1. After the drilling is completed, the original drilling mud trench is enlarged and an annular trench is excavated as a freezing trench. In the mud trench, the freezing hole is enlarged and the mud trench is deepened and widened to form a freezing trench.

[0040] In specific operations, the existing drilling mud trench is expanded to utilize the existing trench space and save the amount of original trench excavation. The specific steps are as follows: The mud trench (original size 0.9m wide × 0.5m deep) is expanded and deepened with the freezing hole as the center (excavator construction) to a width of 2.0m × depth of 0.8m.

[0041] S2. Lay a subfloor on the ground of the excavated freezing trench; use concrete to lay the subfloor and harden the bottom of the freezing trench, and set up a water collection pit at the bottom of the freezing trench.

[0042] In practice, laying a C25 concrete bedding layer to harden the bottom of the trench and setting up a water collection pit can improve the strength of the trench bottom plate and keep the trench dry.

[0043] S3. Construct brick walls on the foundation layer of the freezing trench; construct trench retaining walls with a 37mm wall thickness on the trench bottom slab. The trench walls are constructed on top of the trench bottom slab to prevent the trench sidewalls from collapsing.

[0044] S4. Bind and connect the freezing pipes and the liquid distribution system within the freezing tank; the process of binding and connecting the freezing pipes within the freezing tank includes:

[0045] S41. The freezing holes in the annular freezing tank are divided into inner ring freezing holes and outer ring freezing holes. Based on the position of the freezing holes in the freezing tank, they are divided into inner row and outer row.

[0046] S42. The freezing holes in the inner row are shallow holes and are connected in series, with 4-5 holes per group; the freezing holes in the outer row are deep holes and are connected in series, with 2-3 holes per group.

[0047] In practical applications, each freezing hole is equipped with a freezing tube, which is made of seamless steel pipe, and a liquid supply pipe is placed inside the seamless steel pipe. The specifications of the seamless steel pipe are generally φ140*5mm, and the specifications of the liquid supply pipe are generally φ75*6mm polyethylene pipe.

[0048] The opening of the freezing tube is sealed with a cover plate, and two holes are made in the cover plate. One hole is connected to the liquid supply pipe, and the other is connected to the gap between the seamless steel pipe and the liquid supply pipe. Thus, the two holes form the inlet and outlet ends used for the circulation of brine in the freezing tube.

[0049] Connect the inlet end of the polyethylene plastic tube to the inlet end of the freezing tube to form a brine outlet; connect the outlet end of the polyethylene plastic tube to the outlet end of the freezing tube to form a brine circuit.

[0050] like Figure 3 As shown, the specific series connection method is as follows: Connect the inlet end of the freezing tube at hole A to the outlet end of the freezing tube at hole A in sequence; connect the outlet end of the freezing tube at hole A to the inlet end of the freezing tube at hole B; connect the inlet end of the freezing tube at hole B to the outlet end of the freezing tube at hole B; connect the outlet end of the freezing tube at hole B to the inlet end of the freezing tube at hole C; and connect the inlet end of the freezing tube at hole C to the outlet end of the freezing tube at hole C. In actual use, adjust the number of holes in the polyethylene plastic tube series according to the position of the freezing holes (internal or external).

[0051] like Figure 3 As shown, the process of installing the liquid distribution system in the freezing tank includes:

[0052] S43. Each freezing pipe in the inner and outer drainage holes is equipped with an inlet and an outlet; polyethylene plastic pipes are used to connect the inlet of each freezing pipe to the valves of the brine outlet of the brine main pipe outside the trench.

[0053] S44. Use polyethylene plastic pipes to connect the outlet end of each freezing pipe to each valve of the brine circuit of the brine main pipe outside the trench.

[0054] Thus, the inlet end of each freezing pipe forms a brine outlet that connects to the brine outlet main pipe outside the freezing tank, and the outlet end of the freezing pipe forms a brine loop that connects to the brine loop main pipe outside the trench.

[0055] Use small-diameter polyethylene plastic pipes to replace the original large-diameter spiral welded pipe distribution rings, and connect the freezing holes in series (according to the flow requirements, the freezing circulation depth is controlled at 200-340m, and the freezing holes are generally in groups of 4-5).

[0056] Two pipelines, one connecting the inlet end and the other the outlet end of the freezing pipe in the freezing hole, are led out to the wellbore lock port and connected to the valves of the supply and return main pipes pre-welded to the end of the brine main pipe to achieve centralized external control of the flow rate.

[0057] This connection method saves on the original process by replacing the original steel pipe with a polyethylene plastic pipe for liquid distribution ring, thus saving costs and trench space.

[0058] S5. Seal the top of the freezing tank with a steel plate. Use a 10mm steel plate instead of a 120mm thick cement cover plate to seal the trench, so as to ensure the safety of the freezing pipes and the supply and return liquid pipes inside the trench.

[0059] After the trench construction is completed, in the past, a 120mm thick cement cover plate was used to seal the trench according to its dimensions. In order to facilitate construction and future maintenance, this patent uses a 10mm steel plate for sealing.

[0060] In practice, the size of the steel plate is selected according to the size of the annular trench. The steel plate is generally about 1.2m long, 2.4m wide, and 10mm thick. Before laying the steel plate, steel teeth are welded sporadically on top of it to increase the friction of the steel plate and prevent slippage. The steel plate is laid manually along the annular trench, and each steel plate is independent and does not need to be welded together.

[0061] The construction method provided by this invention has certain advantages over traditional freezing trench construction methods:

[0062] 1. Comparison of trench excavation

[0063] Traditional frozen trench excavation involves large excavation dimensions (2.5m depth, 3m width), extensive masonry work, and the installation of large-diameter liquid distribution rings (273mm diameter steel pipes) within the trench. The structure is complex, the workload is large, and the construction period is generally 7 days.

[0064] This construction method expands the existing mud trenches by only utilizing existing drilled trenches, greatly reducing the amount of trench excavation and masonry work, and saving 50% of the construction time.

[0065] 2. Comparison of liquid collection and distribution systems

[0066] Traditional fluid distribution systems consist of a wellhead fluid distribution ring installed in the main brine inlet and outlet pipes. Fluid enters and exits from the freezing hole and flows through the fluid distribution ring to the main brine inlet and outlet pipes to form a circulation system. The system takes 2 days to install.

[0067] This construction method eliminates the need for a distribution ring, allowing the inlet and outlet of the freezing hole to directly connect to the main brine supply and return pipes to form a circulation system. This can save 50% of the construction time and reduce the need for a distribution ring.

[0068] 3. Comparison of trench structures

[0069] Traditional trench structures use 120mm precast concrete slabs or cast-in-place structures for the top slab, which are formed in one piece. Personnel need to enter the trench from the outside to carry out maintenance work.

[0070] This construction method uses steel plates for sealing, and the steel plates can be opened directly for later maintenance. It also saves on precast concrete cover plates, and the steel plates can be recycled after use.

[0071] Benefit Analysis

[0072] 1. Economic benefits

[0073] Compared with the traditional sealing construction method, the economic benefits of the method provided by this invention are mainly reflected in the construction period and construction cost.

[0074] The specific calculations are shown in the table below:

[0075] Economic Benefit Comparison Table

[0076]

[0077]

[0078] Summary and Analysis:

[0079] The construction method provided by this invention is an improvement and optimization of the traditional freezing trench construction method. It innovates the trenching method for freezing shallow holes in small-diameter wells in freezing projects, achieving less trenching and masonry, and simplifying the liquid collection and distribution system. At the same time, it meets the requirements of saving construction time and cost, and has the effect of wide application and promotion.

[0080] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for constructing frozen trenches, characterized in that, Includes the following steps: S1. After the drilling is completed, the original drilling mud trench is enlarged and an annular trench is excavated as a freezing trench. S2. Lay a bedding layer on the ground of the excavated freezing trench; S3. Construct a brick wall on the bedding layer of the freezing tank; S4. Tie the freezing pipes and liquid distribution system together inside the freezing tank. The process of binding and connecting the freezing tubes in the freezing tank includes: S41. Based on the location of the freezing holes in the freezing tank, all the freezing holes are divided into two parts: inner row and outer row. S42. The freezing holes in the inner row are shallow holes and are connected in series, with 4-5 holes per group; the freezing holes in the outer row are deep holes and are connected in series, with 2-3 holes per group. The process of installing a liquid distribution system in a freezing tank includes: S43. Each freezing pipe in the inner and outer drainage holes is equipped with an inlet end and an outlet end; each freezing pipe inlet end is connected to the valve of the brine outlet of the brine main pipe outside the trench using polyethylene plastic pipe, and the ring distribution ring is abandoned. The original large-diameter spiral welded pipe is replaced by a small-diameter polyethylene plastic pipe as the distribution ring. S44. Use polyethylene plastic pipes to connect the outlet end of each freezing pipe to each valve of the brine circuit of the brine trunk line outside the trench. S5. The top of the freezing trench is sealed with a steel plate. The process of sealing the top of the freezing trench with a steel plate includes: replacing the 120mm thick cement cover plate with a 10mm steel plate to seal the trench. The trench cover plates are made of independent steel plates. The improved trench not only meets the original function, but also facilitates the inspection and maintenance of the freezer during freezing operation and shortens the trench excavation period. An improvement on the original large-scale trench excavation method has been made for small repair wells where space is limited.

2. The method for constructing a frozen trench according to claim 1, characterized in that, In step S1, the excavation process of the annular trench includes: expanding the existing drilled mud trench, expanding the mud trench with the freezing hole as the center, and deepening and widening the mud trench to form a freezing trench.

3. The method for constructing a frozen trench according to claim 1, characterized in that, In step S2, the construction process of laying a subfloor on the ground of the freezing tank includes: laying a subfloor with concrete to harden the bottom of the freezing tank, and setting up a water collection pit at the bottom of the freezing tank.

4. The method for constructing a frozen trench according to claim 1, characterized in that, In step S3, the construction process of building a brick wall on the foundation of the freezing trench includes: building a trench retaining wall with a wall size of 37 on the bottom slab of the trench.

5. A method for constructing frozen trenches according to claim 2, characterized in that, In step S1, the freezing tank has a width of 2.0m and a depth of 0.8m.

6. The method for constructing a frozen trench according to claim 1, characterized in that, In step S5, the steel plate is independent of the steel plate on the adjacent freezing tank, and the steel plate is sporadically welded with steel toothed bars above the steel plate.

7. A method for constructing frozen trenches according to claim 1, characterized in that, The circulation depth of brine in each set of external or internal freezing holes after series connection is 200-340m.

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