CN110805023B - A special-shaped liquid nitrogen freezer, production and construction method - Google Patents

Abstract

A special-shaped liquid nitrogen freezer, a production method and a construction method are suitable for being used when shallow parts and short sections in municipal engineering are frozen, a plurality of sections of U-shaped thin freezing pipes are respectively installed in non-regular freezing holes such as long grooves, two ends of the freezing pipes are connected to form a snake-shaped freezing system, and the form that a circular freezing circulation system is formed by putting a circular liquid supply pipe into a large-diameter circular freezing pipe in a common mode in traditional construction is changed. In the construction, a long groove-shaped freezing hole is firstly constructed from the ground, the upper annular steel pipe hoop and the lower annular steel pipe hoop are used for fixing the segmented U-shaped freezing pipes respectively, the freezing pipes are ensured to be tightly attached to the stratum around the freezing hole, the cold quantity transmission effect between the freezing pipes and the stratum is improved, the liquid nitrogen freezing efficiency is improved, the vertical freezing pipes with different temperatures are symmetrically arranged, the freezing action is superposed to enable the formed freezing wall to be uniform, the outward expansion speed of the freezing wall along the length direction of the freezing hole is high, and the formed freezing wall has good stress performance.

Description

A special-shaped liquid nitrogen freezer, production and construction method

technical field

The invention relates to a liquid nitrogen freezer, a production and a construction method, and is especially suitable for a special-shaped liquid nitrogen freezer, a production and a construction method for the short-section stratum freezing construction in municipal engineering.

Background technique

In the construction of municipal engineering, it is often necessary to freeze and strengthen the stratum in a relatively short period of time to solve the technical problems encountered in the construction of underground structures in weak water-bearing strata. It has been widely used in construction. A circular freezing tube with a slightly smaller diameter is placed in the freezing hole, and then a circular liquid supply tube with a smaller diameter is placed in the freezing tube to form a freezing cycle of the circular tube. During the freezing construction, the liquid nitrogen is poured into the bottom of the freezing pipe through the liquid supply pipe, and the gas-liquid mixed state formed after the liquid nitrogen gasification flows upward along the annular space between the freezing pipe and the liquid supply pipe, and interacts with the formation around the freezing pipe. The cold energy exchange freezes the formation, and the gasified nitrogen gas is directly discharged into the atmosphere through the freezing nozzle.

The construction scope of underground works in municipal engineering is generally shallow, and the depth of the stratum that needs to be frozen is often only a few meters, and sometimes even only one to two meters. Due to the short length of the freezing tube buried in the stratum, when the traditional liquid nitrogen freezer is used for freezing, the distance of the liquid nitrogen poured into the bottom of the freezing tube flowing through the stratum after being vaporized is small, and the cooling energy exchange time between the liquid nitrogen and the surrounding stratum is short and large. Part of the liquid nitrogen has no time to vaporize and is directly discharged from the freezing tube with the nitrogen, resulting in a waste of liquid nitrogen. At the same time, due to the short length of the freezing pipe, the exchange time between liquid nitrogen and the surrounding formation is short, which will not only result in low freezing efficiency of the formation, but also cause a large temperature difference along the length of the freezing pipe, resulting in poor uniformity of the formation of the frozen wall. . The freezing pipes in the traditional liquid nitrogen freezing construction are all circular, so the shape of the freezing hole can only be circular. In order to facilitate the smooth running of the freezing pipe into the freezing hole, the diameter of the freezing hole is generally larger than that of the freezing pipe. As a result, the freezing pipe cannot be close to the stratum around the freezing hole, and the gap between the two will also affect the transfer of cold energy, which reduces the freezing efficiency of liquid nitrogen during the freezing process. Therefore, the freezing wall between the two freezing holes has high temperature and strength. The low, often called the interface in construction, is the weak link within the entire frozen wall. When the quality of the freezing pipe is large, the construction of the freezing pipe as a whole into the freezing hole requires the use of large-scale machinery such as lifting equipment, and the construction process is complicated.

In order to solve the above technical problems, a long trough-shaped liquid nitrogen freezer and a construction method are proposed. A serpentine long freezing pipe is formed by connecting a short freezing pipe around the freezing hole, and the freezing pipe is close to the stratum around the freezing hole to increase the The length of the flow path of liquid nitrogen in the formation prolongs the exchange time of liquid nitrogen and formation cold energy, improves the freezing efficiency of liquid nitrogen, and the vertical freezing pipes of different temperatures are arranged symmetrically, and the superposition of freezing effect makes the formed freezing wall uniform, and The freezing wall expands rapidly along the length direction of the freezing hole, and the formed freezing wall has good mechanical performance.

SUMMARY OF THE INVENTION

In view of the above technical problems, the present invention provides a serpentine long freezing pipe by connecting short freezing pipes around the freezing hole, and making the freezing pipe close to the formation around the freezing hole, thereby increasing the length of the flow path of liquid nitrogen in the formation, extending the The exchange time of liquid nitrogen and formation cold energy improves the freezing efficiency of liquid nitrogen, and the vertical freezing pipes of different temperatures are arranged symmetrically. The superposition of freezing effects makes the formed freezing wall uniform, and the freezing wall expands outward along the length of the freezing hole. A special-shaped liquid nitrogen freezer with high speed and good mechanical performance of the formed freezing wall, production and construction method.

In order to achieve the above technical purpose, the special-shaped liquid nitrogen freezer of the present invention includes a freezing tube, and the freezing tube is arranged in a longitudinally arranged serpentine arrangement, and the serpentine structure is a plurality of vertical freezing tubes arranged in parallel, each The two vertical freezing pipes are connected end to end through elbows. There is no liquid supply pipe in the vertical freezing pipe, but the freezing pipes are directly connected to form a liquid nitrogen circulation system. The liquid supply nozzle and the exhaust nozzle are arranged adjacent to each other. When in use, the high temperature and low temperature segments of the freezing pipe are arranged symmetrically in the freezing hole, and the length of the vertical freezing pipe is as required. The depth of the frozen potholes is the same length, and the position between the two adjacent vertical freezing pipes is adjusted as required, so that all vertical freezing pipes can be connected to the sidewall of the pit no matter what kind of pothole environment they are set in. Closely, according to actual needs, set up an enclosing structure similar to the construction pit to be frozen. The freezing pipes forming the enclosing structure are provided with an upper circumferential steel pipe hoop and a lower circumferential steel pipe hoop for wrapping and fixing all the freezing pipes.

The surrounding structure formed by the freezing pipe is cylindrical, long groove or irregular. The diameter of the freezing pipe, the arrangement spacing, and the length and width of the long groove freezing hole can be adjusted on site according to the construction needs, thereby changing the serpentine freezing pipe. The total length of the liquid nitrogen is adjusted to adjust the path length and time of the liquid nitrogen circulating in the formation.

The serpentine surrounding structure of the freezing pipe design can surround the pit to be constructed for a week, or it can continue to rotate and wind in the pit to be constructed to form a spiral structure. The orifice is arranged in the center of the spiral enclosure, or the outlet of the exhaust pipe is arranged on the periphery, and the orifice of the liquid supply pipe is arranged in the center of the encirclement.

A manufacturing method of a special-shaped liquid nitrogen freezer. First, measure the depth of the pothole to be frozen, including the different depths around the pothole, and then select the arrangement spacing between the vertical freezing pipes according to the required freezing effect, and calculate the actual freezing. The number of vertical freezing pipes required, and the corresponding length of each vertical freezing pipe is calculated according to the different depth data of the measured pit side walls, and each individual vertical freezing pipe is numbered according to the vertical freezing pipe. Pipe No. Prepare a metal pipe of corresponding length as a vertical freezing pipe. One end of the vertical freezing pipe is connected to the previous vertical freezing pipe through a U-shaped bend, and the other end is connected to the next vertical freezing pipe through a U-shaped bend. The pipes are connected and circulated in this way until the entire freezing pipe is formed, and an upper circumferential steel pipe hoop is set in the upper part of the inner ring of the freezing pipe, and a lower circumferential steel pipe hoop is set in the lower part to prevent the deformation of the surrounded frozen pipe and ensure that all vertical freezing pipes are connected with each other. The wall of the pothole is clinging.

Use a whole metal tube to start processing, and process the vertical frozen tubes in sequence according to the number and the corresponding depth data. After each vertical frozen tube is processed, bend the metal tube 180° according to the actual required spacing and continue with the next numbered one. The vertical freezing tubes are processed until all the vertical freezing tubes are processed to form serpentine frozen tubes, and then the serpentine frozen tubes are surrounded by the shape of the freezing pits as required, and the surrounded frozen tubes are enclosed. The upper part of the inner ring is provided with an upper circumferential steel pipe hoop, and the lower part is provided with a lower circumferential steel pipe hoop to prevent deformation of the enclosed frozen pipe.

A construction method of a special-shaped liquid nitrogen freezer, the steps of which are as follows:

a On the ground of the construction site, construct the freezing hole according to the design position. The section of the freezing hole is circular, slot-shaped or irregular as required, wherein the length of the long side of the slot-shaped freezing hole is determined by the length of the freezing wall and the The cycle length of the freezing tube is determined, and the width of the freezing hole is determined according to the freezing requirements;

b According to the actual on-site freezing needs, construct freezing holes, respectively connect multiple vertical freezing pipes with dual-purpose U-shaped elbows to form a U-shaped circulation system, and fix the lower ring of the two U-shaped circulation systems to both sides of the steel pipe hoop Then, go down into the freezing hole together, and make the vertical freezing pipe in close contact with the formation around the freezing hole;

c Connect the bottoms of the remaining vertical freezing pipes with elbows to form a U-shaped circulation system;

d. Lower each U-shaped circulation system into the freezing hole respectively, and fix it at the appropriate position of the lower circumferential steel pipe hoop;

e After the entire U-shaped circulation system is run into the freezing hole, the upper annular steel pipe hoop is used to open the freezing pipe at the upper part of the freezing hole, so that the freezing pipe is close to the stratum around the freezing hole, forming a ring with the shape and size of the freezing hole completely consistent. type surrounding layout;

f Connect the upper parts of the vertical freezing pipes of different U-shaped circulation systems with U-shaped elbows respectively, so that all U-shaped circulation systems in the freezing holes are connected to form a serpentine circulation system, and an adjacent liquid supply nozzle is reserved. and an exhaust port;

g The liquid nitrogen is poured into the freezing pipe from the liquid supply pipe, and the liquid nitrogen flows through the serpentine freezing pipe to exchange cold energy with the surrounding strata. process;

h From the liquid supply nozzle to the exhaust nozzle, the temperature of the freezing pipe gradually increases, and the circumferential arrangement makes the high temperature section and the low temperature section of the freezing pipe symmetrically arranged. The superposition of the two different temperature freezing pipes makes the long side direction A uniform frozen wall is formed at different cross-sectional positions on the upper surface;

i After the thickness of the frozen soil wall formed in the direction of the long side of the freezing hole meets the design requirements, the subsequent excavation and structural construction can be carried out;

j The freezing can be stopped after the excavation and structural construction are completed. After the stratum is thawed, the upper connecting elbow of the freezing circulation system is cut off, and each U-shaped circulation system is removed separately to complete the demolition of the freezing system.

Beneficial effects: Under the condition of not changing the total area of the freezing hole, by changing the flow path of the liquid nitrogen, the heat exchange time and efficiency of the liquid nitrogen in the formation are greatly prolonged, and the technical problem that the liquid nitrogen in the short freezing pipe cannot be fully gasified is solved. . The symmetrical arrangement of the high and low temperature freezing tubes and the superimposed freezing effect make the formed freezing wall uniform, which solves the problem of poor uniformity of the freezing wall formed during the freezing process of liquid nitrogen. The special-shaped freezing hole shape and the arrangement of the serpentine freezing pipe greatly improve the cooling efficiency of the freezing hole in the long-side direction, so that the frozen soil develops in a plane to both sides, and the shape and mechanical performance of the frozen soil wall formed. The requirements are consistent, and the distance between different vertical freezing pipes is small, and there is no weak interface in the frozen soil wall, which improves the mechanical performance of the frozen soil wall. As a new freezing construction method, a freezing circulation system is formed by the direct connection of the freezing pipes, which saves the liquid supply pipe, changes the flow direction and flow path of the liquid nitrogen in the formation, and prolongs the cold exchange time between the liquid nitrogen and the formation. Improves the efficiency of liquid nitrogen freezing. The freezing tube is in close contact with the stratum, which improves the cooling effect between the two, and gives full play to the advantages of liquid nitrogen and rapid cooling at low temperature.

Description of drawings

1 is a schematic structural diagram of a special-shaped liquid nitrogen freezer of the present invention.

FIG. 2 is a schematic structural diagram of the circular liquid nitrogen freezer of the present invention.

3 is a top view of the circular liquid nitrogen freezer of the present invention.

Description of drawings: 1-liquid supply nozzle, 2-exhaust nozzle, 3-freezing pipe, 4-upper circumferential steel pipe hoop, 5-lower circumferential steel pipe hoop.

Detailed ways

The following embodiments are described with reference to the accompanying drawings to illustrate specific embodiments in which the invention may be practiced.

As shown in Figure 1, the special-shaped liquid nitrogen freezer of the present invention includes a freezing tube 3, and the freezing tube is arranged as a longitudinally arranged serpentine arrangement structure, and the serpentine structure is a plurality of vertical freezing tubes arranged in parallel, Every two vertical freezing pipes are connected end-to-end through elbows. There is no liquid supply pipe in the vertical freezing pipe, but the freezing pipe 3 is directly connected to form a liquid nitrogen circulation system. The two terminals are set in the same direction, respectively There are liquid supply nozzle 1 and exhaust nozzle 2, the liquid supply nozzle 1 and the exhaust nozzle 2 are arranged adjacent to each other, the high temperature section and the low temperature section are arranged symmetrically in the freezing hole, and the length of the vertical freezing pipe is as required. The depth of the frozen potholes is the same length, and the position between the two adjacent vertical freezing pipes is adjusted as required, so that all vertical freezing pipes can be connected to the sidewall of the pit no matter what kind of pothole environment they are set in. Closely, according to actual needs, set up a surrounding structure similar to the construction pit to be frozen. The freezing pipe 3 forming the surrounding structure is provided with an upper circumferential steel pipe hoop 4 and a lower circumferential steel pipe hoop 5 for wrapping and fixing all the freezing pipes.

As shown in Figures 2 and 3, the surrounding structure formed by the freezing pipe 3 is cylindrical, long groove or irregular. The diameter of the freezing pipe, the arrangement spacing, and the length and width parameters of the long groove freezing hole can be determined according to the construction needs. On-site adjustment, thereby changing the total length of the serpentine freezing tube, adjusts the path length and time of the liquid nitrogen circulating in the formation.

The serpentine surrounding structure designed by the freezing pipe 3 can surround the pothole to be constructed for a week, or it can continue to rotate and wind in the pit to be constructed to form a spiral structure. The gas pipe port 2 is arranged in the center of the spiral surround, or the exhaust pipe port 2 is arranged on the periphery, and the liquid supply pipe port 1 is arranged in the surround center.

A manufacturing method of a special-shaped liquid nitrogen freezer, the steps of which are: firstly measure the depth of the pothole to be frozen, including the different depths around the pothole, and then select the arrangement spacing between the vertical freezing pipes according to the required freezing effect, Calculate the number of vertical freezing pipes required for actual freezing, and calculate the corresponding length of each vertical freezing pipe according to the different unknown depth data of the measured pit side walls, and number each individual vertical freezing pipe. , according to the vertical freezing pipe number, prepare a metal pipe of corresponding length as a vertical freezing pipe. One end of the vertical freezing pipe is connected with the previous vertical freezing pipe through a U-shaped elbow, and the other end is connected with the next vertical freezing pipe. The pipes are connected by a U-shaped elbow, and the cycle is repeated until the entire frozen pipe 3 is formed, and an upper circumferential steel pipe hoop 4 is set in the upper part of the inner ring of the frozen pipe 3, and a lower circumferential steel pipe hoop 5 is set in the lower part to prevent the frozen pipe after being surrounded. 3 Deform and ensure that all vertical freezing pipes are in close contact with the wall of the pothole.

Use a whole metal tube to start processing, and process the vertical frozen tubes in sequence according to the number and the corresponding depth data. After each vertical frozen tube is processed, bend the metal tube 180° according to the actual required spacing and continue with the next numbered one. The vertical freezing tubes are processed until all the vertical freezing tubes are processed to form the serpentine frozen tubes 3, and then the serpentine frozen tubes 3 are surrounded by the shape of the freezing pits as required, and after the surrounding An upper circumferential steel pipe hoop 4 is arranged in the upper part of the inner ring of the freezing pipe 3, and a lower circumferential steel pipe hoop 5 is arranged in the lower part to prevent the frozen pipe 3 from being deformed after being surrounded.

A kind of construction method of different liquid nitrogen freezer, its steps are as follows:

a On the ground of the construction site, construct the freezing hole according to the design position. The section of the freezing hole is circular, slot-shaped or irregular as required, wherein the length of the long side of the slot-shaped freezing hole is determined by the length of the freezing wall and the The cycle length of the freezing tube is determined, and the width of the freezing hole is determined according to the freezing requirements;

b According to the actual on-site freezing needs, construct freezing holes, respectively connect multiple vertical freezing pipes with dual-purpose U-shaped elbows to form a U-shaped circulation system, and connect the lower parts of the two U-shaped circulation systems to both sides of the steel pipe hoop 5 After fixing, go down into the freezing hole together, and make the vertical freezing pipe closely contact with the formation around the freezing hole;

c Connect the bottoms of the remaining vertical freezing pipes with elbows to form a U-shaped circulation system;

d Put each U-shaped circulation system into the freezing hole respectively, and fix it at the appropriate position of the lower circumferential steel pipe hoop 5;

e After the entire U-shaped circulation system is run into the freezing hole, the upper circumferential steel pipe hoop 4 is used to open the freezing pipe at the upper part of the freezing hole, so that the freezing pipe is close to the stratum around the freezing hole, and the shape and size of the freezing hole are completely consistent. Annular encircling arrangement;

f Connect the upper parts of the vertical freezing pipes of different U-shaped circulation systems with U-shaped elbows respectively, so that all U-shaped circulation systems in the freezing holes are connected to form a serpentine circulation system, and an adjacent liquid supply nozzle is reserved. 1 and an exhaust port 2;

g Liquid nitrogen is poured into the freezing pipe 3 from the liquid supply pipe port 1, and the liquid nitrogen flows through the serpentine freezing pipe to exchange cold energy with the surrounding strata. After absorbing heat, it is gradually gasified and discharged from the exhaust pipe port 2. system, complete the freezing process;

h From the liquid supply pipe port 1 to the exhaust pipe port 2, the temperature of the freezing pipe 3 gradually increases, and the circumferential arrangement makes the high temperature section and the low temperature section of the freezing pipe symmetrically arranged. Uniform frozen walls are formed at different cross-sectional positions in the long-side direction;

i After the thickness of the frozen soil wall formed in the direction of the long side of the freezing hole meets the design requirements, the subsequent excavation and structural construction can be carried out;

j The freezing can be stopped after the excavation and structural construction are completed. After the stratum is thawed, the upper connecting elbow of the freezing circulation system is cut off, and each U-shaped circulation system is removed separately to complete the demolition of the freezing system.

Further, in the construction method, the size of the upper and lower steel pipe collars can be adjusted at any time according to the size of the freezing hole, so that the freezing pipe is closely attached to the stratum outside the freezing hole. The size of the freezing hole is the same as that commonly used at present, and the diameter is φ108~180mm. The construction of the freezing hole can be carried out by using the commonly used drilling rig, and the current construction equipment and method of the freezing hole do not need to be changed. Considering the matching relationship with the freezing hole, the freezing pipe can be processed by a steel pipe with a diameter of φ18~48mm or a hose of other materials. The steel pipe hoop is made of threaded steel bars with a diameter of φ3~10mm. The size of the lower circumferential steel pipe hoop is generally slightly smaller than that of the freezing hole, which is convenient for entering the freezing hole, while the size of the upper steel pipe hoop is slightly larger than that of the freezing hole, which is convenient for subsequent freezing. The tube is propped open so that the frozen tube is snug against the formation around the freezing hole.

Further, the construction method is characterized in that the upper and lower steel pipe hoop can be processed separately, and by adjusting the size of the upper and lower steel pipe hoop, the arrangement circle diameter of the upper freezing pipe is large, and the arrangement circle diameter of the lower freezing pipe is small, thereby forming a The vertical frustum-shaped freezing wall realizes differential freezing at different depths.

Further, the construction method is characterized in that the shape of the steel pipe hoop can be adjusted in time according to the shape of the formed freezing hole, and an annular frozen pipe arrangement form consistent with its shape can be formed in a single freezing hole, so that the freezing hole arrangement parameters can be optimized, Improve freezing hole utilization efficiency. The freezing holes and freezing pipes in the traditional freezing are all circular, and the frozen soil spreads at the same speed in the surrounding. In the new construction method, the existing drilling equipment can be used to drill through multiple freezing holes together. An oval or rectangular slot-shaped freezing hole is formed. After a circle of freezing pipes is placed in the freezing hole, the frozen soil in the long-side direction expands rapidly, and the freezing wall required by the design can be formed in a relatively short time. Moreover, according to the difference of freezing efficiency of freezing holes of different shapes, it can be used to adjust the arrangement parameters of freezing holes and optimize the freezing design.

Further, the construction method is characterized in that the lower annular steel pipe hoop is located outside the freezing pipe during construction, which is convenient for entering the freezing hole, and the upper steel pipe hoop is located inside the freezing pipe, which is convenient for adjusting the contact effect between the freezing pipe and the formation. When the upper frozen pipe can not be close to the stratum around the freezing hole, measures such as moving the steel pipe hoop down, filling the steel pipe hoop with spacers, and replacing the large-diameter pipe hoop can be used to adjust the ring diameter of the upper arrangement of the freezing pipe to ensure freezing. The effect of the contact between the tube and the formation.

Further, the construction method is characterized in that the freezing pipe used in the construction can be a steel pipe with a higher strength, or a part of a hose with a lower strength can be used, and the strength of the freezing wall is used to maintain the stability of the freezing hose itself. sex. The first batch of freezing pipes that go into the freezing hole needs to be made of steel pipe, which is convenient for fixing with the steel pipe hoop, and the supporting steel pipe hoop is lowered into the freezing hole. Freeze inside the hole and connect to form a circulatory system.

Further, the construction method is characterized in that, when removing the freezing system, the upper part of the freezing circulation system can be disconnected first, and the single U-shaped circulation system can be removed respectively. Because only one U-shaped circulation system is pulled out each time, it is light in weight, low in resistance, does not need to use lifting equipment, and the construction organization is simple.

Example:

In the construction of a municipal project, the shallow weak water-bearing stratum needs to be frozen by liquid nitrogen for stratum improvement and reinforcement. The traditional freezing design needs to arrange 10 freezing holes along the reinforcement length. The diameter of the freezing holes is φ127mm and the spacing is 1m. However, according to the traditional design, the liquid nitrogen is not fully vaporized in the 1m-long freezing tube, resulting in waste of liquid nitrogen and the formation of frozen walls. uneven. If different freezing tubes are connected in series to form a freezing system, the amount of liquid nitrogen in the initial freezing tube is much larger than the amount of liquid nitrogen in the subsequent freezing tube, and even there is only low-temperature nitrogen in the final freezing tube, and the freezing effect outside the different freezing tubes The difference is large, and even the freezing wall cannot be formed at the last freezing pipe position, and since the distance between the freezing holes reaches 1m, the temperature of the frozen soil gradually increases as it moves away from the freezing pipe, and at the interface between the two freezing pipes , the temperature of the frozen soil is the highest and the strength is the lowest, which is the weak link in the entire frozen wall and becomes the interface of the frozen wall.

Using the special-shaped liquid nitrogen freezer and construction method of the invention, a continuous freezing cycle is formed in a single freezing tank, the low temperature transfer efficiency of liquid nitrogen is improved, and the problems of insufficient liquid nitrogen gasification and uneven freezing wall can be better solved. Improve the effect of liquid nitrogen freezing. The main construction process is described as follows:

a The vertical freezing holes are constructed from the ground according to the design position, and 3 circular freezing holes are penetrated to form a long slot-shaped freezing hole, the slot width is 127mm, the length is 3m, and the vertical depth is 1m;

b Referring to the size of the long groove-shaped freezing hole, use 5mm thick threaded steel bar to process the lower circumferential steel pipe hoop, and the shape and size of the steel pipe hoop are consistent with the long groove-shaped freezing hole;

c Connect the bottoms of two pairs of steel pipes with a length of 1m and a diameter of φ40mm with elbows of the same diameter to form two U-shaped circulation systems. After fixing the lower ring of the two U-shaped circulation systems to both ends of the steel pipe hoop, they are lowered into the freezing hole together, so that the freezing pipe is in close contact with the formation around the long groove-shaped freezing hole;

d Connect the bottoms of the remaining freezing pipes with elbows of the same diameter on the ground to form a U-shaped freezing pipe circulation system;

e Put each U-shaped circulation system into the freezing hole separately, and fix it at the appropriate position of the lower circumferential steel pipe hoop;

f After all the U-shaped circulation systems are put into the long-groove freezing hole, use steel pipe hoop on the upper part of the freezing hole to open all the freezing pipes, so that the upper freezing pipe is close to the stratum around the long-groove freezing hole, forming the same shape as the long groove-shaped freezing hole. Freeze the annular arrangement of hole shape and size exactly the same;

g Connect the upper parts of the freezing pipes of different U-shaped circulation systems with elbows of the same diameter, so that all U-shaped freezing pipes in each long slot-shaped freezing hole are cyclically connected to form a whole circulation system, and a liquid supply nozzle is reserved. And an exhaust pipe port for liquid nitrogen to be injected and vaporized nitrogen to be discharged;

h Continue to construct the other 2 long slot-shaped freezing holes. The size and shape of the freezing hole, the size and shape of the freezing pipe, the placement and connection method of the freezing pipe, etc. are carried out according to the above steps, and an overall freezing is formed in each freezing hole respectively. circulatory system;

i Fill the liquid nitrogen from the liquid supply pipe opening in each freezing hole respectively, the liquid nitrogen gasifies during the process of flowing through the freezing pipe, and exchanges cold energy with the surrounding formation in time, and discharges the freezing circulation system from the exhaust pipe opening, Complete the freezing and cooling process. During the freezing process, the length of liquid nitrogen flowing through the stratum is 20 times that of the traditional freezing pipe construction, which greatly prolongs the exchange time of cold energy between liquid nitrogen and the stratum, and increases the exchange of cold energy. The long trough-shaped freezing hole shape makes the frozen soil develop more uniformly to both sides, and the development speed is faster, and it is easy to form the frozen wall of the cuboid required for maintenance. At the same time, the temperature of liquid nitrogen increases gradually during the process of flowing through the freezing tube, but the high-temperature freezing tube and the low-temperature freezing tube in the circulation system are arranged symmetrically, that is, in the long slot-shaped freezing hole, along the freezing tube wall on the liquid supply tube side The temperature is gradually increased, and the temperature of the freezing pipe wall along the exhaust pipe side is gradually decreased, so different high temperature freezing pipes and low temperature freezing pipes are combined into a row, and the high and low temperature freezing pipes can complement each other and freeze, so that the formation of The frozen wall is more uniform;

j After the thickness, depth, length and other parameters of the formed frozen wall meet the design requirements, the subsequent excavation and structural construction shall be carried out;

k After the construction of the structure is completed, stop freezing. After the stratum is thawed, the upper connecting part of the circulation system is divided, and each U-shaped freezing cycle is removed separately to complete the demolition of the freezing system. Large lifting equipment is not required during the construction process.

Claims (6)

1. A special-shaped liquid nitrogen freezer, comprising a freezing tube (3), characterized in that: the freezing tube is arranged as a longitudinally arranged serpentine arrangement, and the serpentine structure is a plurality of vertical freezing tubes arranged in parallel , every two vertical freezing pipes are connected end-to-end through elbows, no liquid supply pipe is set in the vertical freezing pipe, but the freezing pipe (3) is directly connected to form a liquid nitrogen circulation system, and the two terminals are set in the same There are liquid supply nozzles (1) and exhaust nozzles (2) respectively, and the liquid supply nozzles (1) and the exhaust nozzles (2) are arranged adjacent to each other, so that the high temperature of the freezing pipe (3) is kept in use. Sections and low-temperature sections are arranged symmetrically in the freezing hole, the length of the vertical freezing pipe is the same as the depth of the pit to be frozen, and the position between the two adjacent vertical freezing pipes is adjusted as required, so that all vertical freezing pipes are No matter what kind of pothole environment the freezing pipe is installed in, it can be closely attached to the side wall of the pothole. According to the actual needs, a surrounding structure similar to that of the pit to be frozen is set up, and the freezing pipe (3) forming the surrounding structure is installed up and down. There are an upper circumferential steel pipe hoop (4) and a lower circumferential steel pipe hoop (5) that wrap and fix all the frozen pipes. 2. The special-shaped liquid nitrogen freezer according to claim 1, characterized in that: the surrounding structure formed by the freezing pipe (3) is cylindrical, long groove or irregular, and the freezing pipe diameter, arrangement spacing, long groove The length and width of the serpentine freezing hole can be adjusted on-site according to the construction needs, thereby changing the total length of the serpentine freezing pipe and adjusting the path length and time of the liquid nitrogen circulating in the formation. 3. The special-shaped liquid nitrogen freezer according to claim 1, characterized in that: the serpentine surrounding structure designed by the freezing pipe (3) can surround the pit to be constructed for a week, or can be inside the pit to be constructed. Continue to rotate and wind to form a spiral structure, set the liquid supply nozzle (1) on the periphery and the exhaust nozzle (2) in the center of the spiral surround, or set the exhaust nozzle (2) on the periphery and the liquid supply pipe as required. The mouth (1) is set at the center of the enclosure. 4. a kind of manufacture method of using the described special-shaped liquid nitrogen freezer of claim 1, it is characterized in that: first measure the pit depth that needs construction freezing, comprise the different depths of pothole one week, then select vertical according to required freezing effect The arrangement spacing between the freezing pipes, calculate the number of vertical freezing pipes required for actual freezing, and calculate the corresponding length of each vertical freezing pipe according to the measured depth data of the side walls of the pit, and calculate the length of each vertical freezing pipe. Separate vertical freezing pipe number, prepare a metal pipe of corresponding length as vertical freezing pipe according to the vertical freezing pipe number. Connect with the next vertical freezing pipe through a U-shaped elbow, and circulate in this way until the entire freezing pipe (3) is formed, and an upper circumferential steel pipe hoop (4) is set in the upper part of the inner ring of the freezing pipe (3), and the lower part is set The lower circumferential steel pipe hoop (5) is used to prevent the deformation of the surrounded frozen pipes (3) and ensure that all vertical frozen pipes are in close contact with the wall of the pit. 5. The manufacturing method according to claim 4, characterized in that: start processing with a whole metal pipe, and sequentially process the vertical freezing pipe according to the serial number and the corresponding depth data, after each processing a vertical freezing pipe, Bend the metal tube 180° according to the actual required spacing, and then continue processing the next numbered vertical freezing tube until all vertical freezing tubes are processed to form a serpentine frozen tube (3), and then freeze the serpentine The pipe (3) is surrounded by the shape of the freezing pit according to the need, and the upper circumferential steel pipe hoop (4) and the lower circumferential steel pipe hoop (5) are arranged in the middle and upper part of the inner ring of the surrounded frozen pipe (3). To prevent the frozen tube (3) from being deformed after being surrounded. 6. a construction method using the described special-shaped liquid nitrogen freezer of claim 1, is characterized in that the step is as follows: a On the ground of the construction site, construct the freezing hole according to the design position. The section of the freezing hole is circular, slot-shaped or irregular as required, wherein the length of the long side of the slot-shaped freezing hole is determined by the length of the freezing wall and the The cycle length of the freezing tube is determined, and the width of the freezing hole is determined according to the freezing requirements; b According to the actual on-site freezing needs, construct freezing holes, respectively connect multiple vertical freezing pipes with dual-purpose U-shaped elbows to form a U-shaped circulation system, and tie the lower parts of the two U-shaped circulation systems to the steel pipe hoop (5) After the two sides are fixed, they are lowered into the freezing hole together, and the vertical freezing pipe is in close contact with the formation around the freezing hole; c Connect the bottoms of the remaining vertical freezing pipes with elbows to form a U-shaped circulation system; d. Lower each U-shaped circulation system into the freezing hole respectively, and fix it at the appropriate position of the lower circumferential steel pipe hoop (5); e After the entire U-shaped circulation system is put into the freezing hole, the upper circumferential steel pipe hoop (4) is used to open the freezing pipe at the upper part of the freezing hole, so that the freezing pipe is close to the stratum around the freezing hole, and the shape and size of the freezing hole are completely matched. Consistent annular surrounding layout; f Connect the upper parts of the vertical freezing pipes of different U-shaped circulation systems with U-shaped elbows respectively, so that all U-shaped circulation systems in the freezing holes are connected to form a serpentine circulation system, and an adjacent liquid supply nozzle is reserved. (1) and an exhaust port (2); g Liquid nitrogen is poured into the freezing pipe (3) from the liquid supply pipe port (1), and the liquid nitrogen flows through the serpentine freezing pipe to exchange cold energy with the surrounding strata. The port (2) is discharged from the circulation system to complete the freezing process; h From the liquid supply pipe port (1) to the exhaust pipe port (2), the temperature of the freezing pipe (3) gradually increases, and the circumferential arrangement makes the high temperature section and the low temperature section of the freezing pipe symmetrically arranged, and the two different temperature The superposition of the freezing tube makes the different section positions in the longitudinal direction form a uniform freezing wall; i After the thickness of the frozen soil wall formed in the direction of the long side of the freezing hole meets the design requirements, the subsequent excavation and structural construction can be carried out; j The freezing can be stopped after the excavation and structural construction are completed. After the stratum is thawed, the upper connecting elbow of the freezing circulation system is cut off, and each U-shaped circulation system is removed separately to complete the demolition of the freezing system.

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