CN110805023B - Special-shaped liquid nitrogen freezer and production and construction method - Google Patents
Special-shaped liquid nitrogen freezer and production and construction method Download PDFInfo
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- CN110805023B CN110805023B CN201911058355.5A CN201911058355A CN110805023B CN 110805023 B CN110805023 B CN 110805023B CN 201911058355 A CN201911058355 A CN 201911058355A CN 110805023 B CN110805023 B CN 110805023B
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- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 title claims abstract description 167
- 239000007788 liquid Substances 0.000 title claims abstract description 114
- 229910052757 nitrogen Inorganic materials 0.000 title claims abstract description 83
- 238000010276 construction Methods 0.000 title claims abstract description 63
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 10
- 230000008014 freezing Effects 0.000 claims abstract description 457
- 238000007710 freezing Methods 0.000 claims abstract description 457
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 63
- 239000010959 steel Substances 0.000 claims abstract description 63
- 230000000694 effects Effects 0.000 claims abstract description 11
- 238000000034 method Methods 0.000 claims description 23
- 230000008569 process Effects 0.000 claims description 16
- 239000002689 soil Substances 0.000 claims description 13
- 238000013461 design Methods 0.000 claims description 11
- 238000012545 processing Methods 0.000 claims description 10
- 239000002184 metal Substances 0.000 claims description 9
- 238000009412 basement excavation Methods 0.000 claims description 8
- 230000001788 irregular Effects 0.000 claims description 6
- 241000270295 Serpentes Species 0.000 claims description 4
- 238000005452 bending Methods 0.000 claims description 3
- 230000015572 biosynthetic process Effects 0.000 claims description 3
- 238000004804 winding Methods 0.000 claims description 3
- 206010066054 Dysmorphism Diseases 0.000 claims 1
- 230000009471 action Effects 0.000 abstract description 4
- 230000005540 biological transmission Effects 0.000 abstract description 4
- 230000002035 prolonged effect Effects 0.000 description 4
- WYTGDNHDOZPMIW-RCBQFDQVSA-N alstonine Natural products C1=CC2=C3C=CC=CC3=NC2=C2N1C[C@H]1[C@H](C)OC=C(C(=O)OC)[C@H]1C2 WYTGDNHDOZPMIW-RCBQFDQVSA-N 0.000 description 3
- 238000007599 discharging Methods 0.000 description 3
- 230000008520 organization Effects 0.000 description 3
- 230000008901 benefit Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000005553 drilling Methods 0.000 description 2
- 238000012423 maintenance Methods 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 238000002309 gasification Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 238000005057 refrigeration Methods 0.000 description 1
- 230000002787 reinforcement Effects 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D3/00—Improving or preserving soil or rock, e.g. preserving permafrost soil
- E02D3/11—Improving or preserving soil or rock, e.g. preserving permafrost soil by thermal, electrical or electro-chemical means
- E02D3/115—Improving or preserving soil or rock, e.g. preserving permafrost soil by thermal, electrical or electro-chemical means by freezing
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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
Technical Field
The invention relates to a liquid nitrogen freezer, a production method and a construction method, in particular to a special-shaped liquid nitrogen freezer which is suitable for short-section stratum freezing construction with small depth in municipal engineering, and a production method and a construction method.
Background
In municipal engineering construction, stratum freezing, strengthening and improving are often required within a short time to solve the technical problem encountered when underground structure construction is carried out in a weak water-containing stratum, and liquid nitrogen freezing is used as an efficient and rapid freezing method and is widely applied to stratum improvement construction. A round freezing pipe with a slightly smaller diameter is put into the freezing hole, and a round liquid supply pipe with a smaller diameter is put into the freezing pipe, so that the freezing cycle of the round pipe is formed. During freezing construction, liquid nitrogen is filled into the bottom of the freezing pipe through the liquid supply pipe, a gas-liquid mixed state formed after the liquid nitrogen is gasified flows upwards along an annular space between the freezing pipe and the liquid supply pipe and exchanges cold energy with a stratum around the freezing pipe to freeze the stratum, and the gasified nitrogen is directly discharged into the atmosphere through the freezing pipe opening.
Underground works in municipal works are generally shallow in construction range, and the depth of a stratum needing to be frozen is usually only a few meters, sometimes even only one to two meters. Because the length of the freezing pipe embedded in the stratum is short, when the traditional liquid nitrogen freezer is used for freezing, the distance of the liquid nitrogen filled into the bottom of the freezing pipe flowing through the stratum after being gasified is small, the cold energy exchange time between the liquid nitrogen and the surrounding stratum is short, most of the liquid nitrogen is not gasified and is directly discharged out of the freezing pipe along with the nitrogen, and the waste of the liquid nitrogen is caused. Meanwhile, the length of the freezing pipe is short, and the time for exchanging the cold energy of the liquid nitrogen and the cold energy of the surrounding stratum is short, so that the freezing efficiency of the stratum is not high, and the temperature difference along the length direction of the freezing pipe is large, so that the uniformity of the formed freezing wall is poor. The freezing pipes in the traditional liquid nitrogen freezing construction are all round, so the shape of the freezing holes can only be round, in order to conveniently and smoothly put the freezing pipes into the freezing holes, the diameter of the freezing holes is generally larger than that of the freezing pipes, the freezing pipes cannot be tightly attached to the stratum around the freezing holes, the cold quantity transmission can be influenced by gaps between the freezing pipes and the stratum, the freezing efficiency of liquid nitrogen in the freezing process is reduced, the temperature of the freezing wall between the two freezing holes is high, the strength is low, the freezing pipe is often called as an interface in the construction, and the weak link in the whole freezing wall is formed. When the mass of the freezing pipe is large, large-scale machinery such as hoisting equipment is needed for the construction of integrally putting the freezing pipe into the freezing hole, and the construction process is complicated in organization.
In order to solve the technical problems, a long groove-shaped liquid nitrogen freezer and a construction method are provided, short freezing pipes are connected around a freezing hole to form a snake-shaped long freezing pipe, the freezing pipes are tightly attached to the stratum around the freezing hole, the length of a flow path of liquid nitrogen in the stratum is increased, the time of exchanging cold energy of the liquid nitrogen and the stratum is prolonged, the freezing efficiency of the liquid nitrogen is improved, 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 in the length direction of the freezing hole is high, and the formed freezing wall is good in stress performance.
Disclosure of Invention
The invention aims at the technical problems and provides a special-shaped liquid nitrogen freezer which is formed by connecting short freezing pipes around a freezing hole to form a snake-shaped long freezing pipe, enables the freezing pipes to be tightly attached to the stratum around the freezing hole, increases the length of a flow path of liquid nitrogen in the stratum, prolongs the time of exchanging cold energy of the liquid nitrogen and the stratum, improves the freezing efficiency of the liquid nitrogen, is symmetrically arranged with vertical freezing pipes with different temperatures, and ensures that the formed freezing wall is uniform due to the superposition of freezing actions, and the outward expansion speed of the freezing wall along the length direction of the freezing hole is high, so that the formed freezing wall has good stress performance, and a production and construction method thereof.
In order to achieve the technical purpose, the special-shaped liquid nitrogen freezer comprises freezing pipes, wherein the freezing pipes are arranged in a longitudinally-arranged snake-shaped arrangement structure, the snake-shaped structure is formed by arranging a plurality of vertical freezing pipes in parallel, every two vertical freezing pipes are connected end to end through a bent pipe, a liquid supply pipe is not arranged in each vertical freezing pipe, the freezing pipes are directly connected to form a liquid nitrogen circulating system, two terminals are arranged in the same direction and are respectively provided with a liquid supply pipe opening and an exhaust pipe opening, the liquid supply pipe openings and the exhaust pipe openings are adjacently arranged, when the special-shaped liquid nitrogen freezer is used, high-temperature sections and low-temperature sections of the freezing pipes are symmetrically arranged in the freezing holes, the length of each vertical freezing pipe is equal to the depth of a pit to be frozen, and the positions of the two adjacent vertical freezing pipes are adjusted according to needs, so that all the vertical freezing pipes can be tightly attached to the, an enclosing structure similar to the pit to be frozen in construction is arranged according to actual needs, and an upper annular steel pipe hoop and a lower annular steel pipe hoop which wrap and fix all the freezing pipes are arranged above and below the freezing pipes forming the enclosing structure.
The enclosed structure formed by the freezing pipes is cylindrical, long groove-shaped or irregular, the diameter, the arrangement distance and the length and the width of the long groove-shaped freezing holes of the freezing pipes can be adjusted on site according to construction requirements, so that the total length of the snake-shaped freezing pipes is changed, and the path length and the time of liquid nitrogen circulating in the stratum are adjusted.
The snakelike structure of encircleing of freezing the design of pipe can be from beginning to end will treat to be under construction the pothole in enclose a week, also can continue rotatory winding formation helical structure in treating the construction pothole, will supply the liquid pipe mouth to set up peripherally as required, the exhaust pipe mouth sets up at the spiral and surrounds the center, perhaps sets up the exhaust pipe mouth peripherally, supplies the liquid pipe mouth to set up at and surrounds the center.
A method for manufacturing a special-shaped liquid nitrogen freezer includes measuring the depth of a pit to be frozen, including different depths around the pit, then the arrangement space between the vertical freezing pipes is selected according to the required freezing effect, the number of the vertical freezing pipes required by the actual freezing is calculated, and calculates the length corresponding to each vertical freezing pipe according to the measured different depth data of the side wall of the pot hole, and numbers each single vertical freezing pipe, preparing metal pipes with corresponding lengths as vertical freezing pipes according to the serial numbers of the vertical freezing pipes, connecting one end of each vertical freezing pipe with the last vertical freezing pipe through a U-shaped bent pipe, connecting the other end of each vertical freezing pipe with the next vertical freezing pipe through a U-shaped bent pipe, circulating the steps until the whole freezing pipe is formed, and an upper annular steel pipe hoop is arranged at the middle upper part of the inner ring of the freezing pipe, and a lower annular steel pipe hoop is arranged at the lower part of the inner ring of the freezing pipe so as to prevent the surrounded freezing pipe from deforming and ensure that all vertical freezing pipes are tightly attached to the wall of the pit.
The method comprises the steps of starting processing by using a whole metal pipe, sequentially processing vertical freezing pipes according to numbers and corresponding depth data, after each vertical freezing pipe is processed, bending the metal pipe for 180 degrees according to actual needs, and then processing the vertical freezing pipe of the next number until all the vertical freezing pipes are processed to form the freezing pipes in a snake-shaped arrangement, then surrounding the freezing pipes in the snake-shaped arrangement according to the shape of a freezing pot hole to be constructed, arranging an upper annular steel pipe hoop at the middle upper part of an inner ring of the surrounded freezing pipe, and arranging a lower annular steel pipe hoop at the lower part to prevent the surrounded freezing pipe from deforming.
A construction method of a special-shaped liquid nitrogen freezer comprises the following steps:
a, constructing a freezing hole on the ground of a construction site according to a designed position, wherein the section of the freezing hole is round, long groove-shaped or irregular as required, the length of the long side of the long groove-shaped freezing hole is determined by the length of a freezing wall and the cycle length of a freezing pipe, and the width of the freezing hole is determined according to the freezing requirement;
b, constructing freezing holes according to actual on-site freezing requirements, connecting the plurality of vertical freezing pipes in pairs by using U-shaped bent pipes to form U-shaped circulating systems, fixing the lower parts of the two U-shaped circulating systems to the two sides of the steel pipe hoop, putting the two U-shaped circulating systems into the freezing holes together, and enabling the vertical freezing pipes to be in close contact with stratums around the freezing holes;
c, connecting the bottoms of the other vertical freezing pipes by using elbows in pairs to respectively form a U-shaped circulating system;
d, respectively putting each U-shaped circulating system into the freezing hole, and clamping the U-shaped circulating systems at proper positions of the annular steel pipe hoop at the lower part for fixing;
e, after all the U-shaped circulating systems are put into the freezing holes, the freezing pipes are propped open at the upper parts of the freezing holes by using upper annular steel pipe hoops, so that the freezing pipes are tightly attached to the stratums around the freezing holes to form an annular surrounding arrangement mode which is completely consistent with the shapes and the sizes of the freezing holes;
f, respectively connecting the upper parts of the vertical freezing pipes of different U-shaped circulating systems by using U-shaped bent pipes, so that all the U-shaped circulating systems in the freezing holes are connected to form a coiled pipe circulating system, and reserving one adjacent liquid supply pipe opening and one adjacent exhaust pipe opening;
filling liquid nitrogen into the freezing pipe from the liquid supply pipe orifice, wherein cold energy exchange is generated between the process that the liquid nitrogen flows through the serpentine freezing pipe and the surrounding stratum, the liquid nitrogen is gradually gasified after absorbing heat and is discharged from the circulating system from the gas exhaust pipe orifice to finish the freezing process;
h, gradually raising the temperature of the freezing pipes from the liquid supply pipe orifice to the exhaust pipe orifice, symmetrically arranging the high-temperature section and the low-temperature section of the freezing pipes in an annular arrangement mode, and forming uniform freezing walls at different cross section positions in the long edge direction under the superposition effect of the two freezing pipes with different temperatures;
i, after the thickness of the frozen soil wall formed in the long side direction of the frozen hole meets the design requirement, subsequent excavation and structural construction can be carried out;
and j, stopping freezing after the excavation and the structure construction are finished, removing the connecting elbow at the upper part of the freezing circulating system after the stratum is unfrozen, and removing each U-shaped circulating system to finish the detaching work of the freezing system.
Has the advantages that: under the condition of not changing the total area of the freezing holes, the heat exchange time and efficiency of the liquid nitrogen in the stratum are greatly prolonged by changing the flow path of the liquid nitrogen, 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-low temperature freezing pipes and the overlapping freezing action enable the formed freezing wall to be uniform, and the problem of poor uniformity of the formed freezing wall in the liquid nitrogen freezing process is solved. The special-shaped freezing hole shape and the arrangement form of the snake-shaped freezing pipes greatly improve the cold transmission efficiency in the long edge direction of the freezing hole, so that the frozen soil develops towards two sides in a plane, the shape of the formed frozen soil wall is consistent with the stress performance requirement, the distance between different vertical freezing pipes is small, a weak interface cannot appear in the frozen soil wall, and the stress performance of the frozen soil wall is improved. As a new freezing construction method, a freezing circulation system is formed by directly connecting freezing pipes, so that liquid supply pipes are saved, the flowing direction and the flowing path of liquid nitrogen in the stratum are changed, the cold exchange time of the liquid nitrogen and the stratum is prolonged, and the freezing efficiency of the liquid nitrogen is improved. The freezing pipes are in close contact with the stratum, the cold exchange effect between the freezing pipes and the stratum is improved, the advantage of liquid nitrogen low-temperature quick refrigeration is fully exerted, the freezing pipes in the freezing holes are constructed in a segmented mode, large-scale hoisting equipment is not needed, and the construction organization is simple.
Drawings
FIG. 1 is a schematic structural diagram of the special-shaped liquid nitrogen freezer of the present invention.
FIG. 2 is a schematic diagram of the structure of the circular liquid nitrogen freezer of the present invention.
FIG. 3 is a top view of the circular liquid nitrogen freezer of the present invention.
Description of the drawings: 1-a liquid supply pipe orifice, 2-an exhaust pipe orifice, 3-a freezing pipe, 4-an upper annular steel pipe hoop and 5-a lower annular steel pipe hoop.
Detailed Description
The following description of the embodiments refers to the accompanying drawings for illustrating the specific embodiments in which the invention may be practiced.
As shown in figure 1, the special-shaped liquid nitrogen freezer comprises freezing pipes 3, wherein the freezing pipes are arranged in a longitudinally-arranged snake-shaped arrangement structure, the snake-shaped structure is formed by arranging a plurality of vertical freezing pipes in parallel, every two vertical freezing pipes are connected end to end through a bent pipe, a liquid supply pipe is not arranged in each vertical freezing pipe, the freezing pipes 3 are directly connected to form a liquid nitrogen circulating system, two terminals are arranged in the same direction and are respectively provided with a liquid supply pipe opening 1 and an exhaust pipe opening 2, the liquid supply pipe opening 1 and the exhaust pipe opening 2 are adjacently arranged, a high-temperature section and a low-temperature section are symmetrically arranged in the freezing holes, the length of each vertical freezing pipe is equal to the depth of a pit to be frozen, and the position between every two adjacent vertical freezing pipes is adjusted according to needs, so that all the vertical freezing pipes can be tightly attached to the side wall of the pit no matter what kind, the freezing pipe 3 forming the surrounding structure is provided with an upper annular steel pipe hoop 4 and a lower annular steel pipe hoop 5 which wrap and fix all the freezing pipes.
As shown in fig. 2 and 3, the surrounding structure formed by the freezing pipes 3 is cylindrical, long groove-shaped or irregular, the diameter, the arrangement distance, the length and the width parameters of the long groove-shaped freezing holes of the freezing pipes can be adjusted on site according to the construction requirement, so that the total length of the serpentine freezing pipes is changed, and the path length and the time of the liquid nitrogen circulating in the stratum are adjusted.
The snakelike surrounding structure that freezes pipe 3 design can be around in will treating the construction pot hole end to end, also can continue rotatory winding formation helical structure in treating the construction pot hole, will supply the liquid pipe orifice 1 to set up peripherally as required, exhaust pipe orifice 2 sets up at the spiral and surrounds the center, perhaps sets up exhaust pipe orifice 2 peripherally, supply liquid pipe orifice 1 to surround the center.
A method for manufacturing a special-shaped liquid nitrogen freezer comprises the following steps: firstly, measuring the depth of the pit needing to be constructed and frozen, including different depths of the whole circle of the pit, then selecting the arrangement distance between the vertical freezing pipes according to the required freezing effect, calculating the number of the vertical freezing pipes required by actual freezing, and calculates the length corresponding to each vertical freezing pipe according to the different unknown depth data of the measured side wall of the pot hole, and numbers each single vertical freezing pipe, preparing metal pipes with corresponding lengths as vertical freezing pipes according to the serial numbers of the vertical freezing pipes, connecting one end of each vertical freezing pipe with the last vertical freezing pipe through a U-shaped bent pipe, connecting the other end of each vertical freezing pipe with the next vertical freezing pipe through a U-shaped bent pipe, circulating the steps until the whole freezing pipe 3 is formed, and an upper annular steel pipe hoop 4 is arranged at the middle upper part of the inner ring of the freezing pipe 3, and a lower annular steel pipe hoop 5 is arranged at the lower part of the inner ring to prevent the surrounded freezing pipe 3 from deforming and ensure that all vertical freezing pipes are tightly attached to the wall of the pot hole.
The method comprises the steps of starting processing by using a whole metal pipe, sequentially processing vertical freezing pipes according to numbers and corresponding depth data, after each vertical freezing pipe is processed, bending the metal pipe by 180 degrees according to actual needs, and then processing the vertical freezing pipe of the next number until all the vertical freezing pipes are processed to form the freezing pipes 3 arranged in a snake shape, then surrounding the freezing pipes 3 arranged in the snake shape according to the shape of a freezing pot hole to be constructed, arranging an upper annular steel pipe hoop 4 at the middle upper part of an inner ring of the surrounded freezing pipe 3, and arranging a lower annular steel pipe hoop 5 at the lower part to prevent the surrounded freezing pipe 3 from deforming.
A construction method of a different liquid nitrogen freezer comprises the following steps:
a, constructing a freezing hole on the ground of a construction site according to a designed position, wherein the section of the freezing hole is round, long groove-shaped or irregular as required, the length of the long side of the long groove-shaped freezing hole is determined by the length of a freezing wall and the cycle length of a freezing pipe, and the width of the freezing hole is determined according to the freezing requirement;
b, constructing freezing holes according to actual on-site freezing requirements, connecting the plurality of vertical freezing pipes in pairs by using U-shaped bent pipes to form U-shaped circulating systems, fixing the lower parts of the two U-shaped circulating systems to two sides of the steel pipe hoop 5, putting the lower parts of the two U-shaped circulating systems into the freezing holes together, and enabling the vertical freezing pipes to be in close contact with stratums around the freezing holes;
c, connecting the bottoms of the other vertical freezing pipes by using elbows in pairs to respectively form a U-shaped circulating system;
d, respectively putting each U-shaped circulating system into the freezing hole, and clamping the U-shaped circulating systems at proper positions of the annular steel pipe hoop 5 at the lower part for fixing;
e, after all the U-shaped circulating systems are put into the freezing holes, the freezing pipes are propped open at the upper parts of the freezing holes by using the upper ring towards the steel pipe hoops 4, so that the freezing pipes are tightly attached to the stratums around the freezing holes to form a ring-shaped surrounding arrangement mode which is completely consistent with the shapes and the sizes of the freezing holes;
f, respectively connecting the upper parts of the vertical freezing pipes of different U-shaped circulating systems by using U-shaped bent pipes, so that all the U-shaped circulating systems in the freezing holes are connected to form a coiled pipe circulating system, and reserving a liquid supply pipe opening 1 and an exhaust pipe opening 2 which are adjacent;
injecting liquid nitrogen into the freezing pipe 3 from the liquid supply pipe orifice 1, exchanging cold energy with surrounding strata in the process that the liquid nitrogen flows through the serpentine freezing pipe, gradually gasifying the liquid nitrogen after absorbing heat, and discharging the liquid nitrogen out of the circulating system from the exhaust pipe orifice 2 to finish the freezing process;
h, gradually raising the temperature of the freezing pipes 3 from the liquid supply pipe orifice 1 to the exhaust pipe orifice 2, symmetrically arranging the high-temperature section and the low-temperature section of the freezing pipes in an annular arrangement mode, and forming uniform freezing walls at different cross section positions in the long edge direction under the superposition effect of the two freezing pipes with different temperatures;
i, after the thickness of the frozen soil wall formed in the long side direction of the frozen hole meets the design requirement, subsequent excavation and structural construction can be carried out;
and j, stopping freezing after the excavation and the structure construction are finished, removing the connecting elbow at the upper part of the freezing circulating system after the stratum is unfrozen, and removing each U-shaped circulating system to finish the detaching work of the freezing system.
Furthermore, in the construction method, the sizes of the upper steel pipe hoop and the lower steel pipe hoop can be adjusted at any time according to the size of the formed freezing hole, so that the freezing pipe is tightly attached to the stratum outside the freezing hole. The size of the freezing hole is the same as the current common size, the diameter is phi 108-180 mm, the current common drilling machine is selected to carry out the construction of the freezing hole, and the current construction equipment and method of the freezing hole do not need to be changed. Considering the matching relation with the freezing hole, the freezing pipe can be processed by a steel pipe with the diameter phi of 18-48 mm or a hose made of other materials. The steel pipe hoop is processed on site by adopting a twisted steel bar with the diameter phi of 3-10 mm, the size of the lower annular steel pipe hoop is generally smaller than that of the freezing hole, the steel pipe hoop is convenient to put into the freezing hole, and the size of the upper steel pipe hoop is larger than that of the freezing hole, so that the subsequent freezing pipe is conveniently propped open, and the freezing pipe is tightly attached to the stratum around the freezing hole.
Furthermore, the construction method is characterized in that an upper steel pipe hoop and a lower steel pipe hoop can be respectively processed, the arrangement ring diameter of the upper freezing pipe is large, the arrangement ring diameter of the lower freezing pipe is small by adjusting the size of the upper steel pipe hoop and the size of the lower steel pipe hoop, so that a vertical frustum-shaped freezing wall is formed, and different freezing at different depths is realized.
Furthermore, 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 freezing hole, and an annular freezing pipe arrangement form consistent with the shape of the steel pipe hoop is formed in a single freezing hole, so that the arrangement parameters of the freezing hole can be optimized, and the utilization efficiency of the freezing hole is improved. The freezing holes and the freezing pipes in the traditional freezing process are circular, the diffusion speed of frozen soil to the periphery is the same during freezing, in the new construction method, a plurality of freezing holes can be combined and drilled through by utilizing the existing drilling equipment to form oval or rectangular groove-shaped freezing holes, after a circle of freezing pipes are put into the freezing holes at home, the expansion speed of the frozen soil in the long edge direction is high, and the frozen wall required by design can be formed in a short time. And the arrangement parameters of the freezing holes can be adjusted according to the difference of the freezing efficiency of the freezing holes with different shapes, so that the freezing design is optimized.
Furthermore, the construction method is characterized in that the lower annular steel pipe hoop is positioned outside the freezing pipe during construction to facilitate entering the freezing hole, and the upper steel pipe hoop is positioned inside the freezing pipe to facilitate adjusting the contact effect of the freezing pipe and the stratum. When the upper freezing pipe cannot be tightly attached to the stratum around the freezing hole, measures such as downwards moving the steel pipe hoop, filling the cushion blocks on the periphery of the steel pipe hoop, replacing the large-diameter pipe hoop and the like can be taken to adjust the upper arrangement ring diameter of the freezing pipe and ensure the contact effect of the freezing pipe and the stratum.
Further, the construction method is characterized in that the freezing pipe used in the construction can be a steel pipe with high strength, or a hose with low strength can be partially used, and the stability of the freezing hose itself is maintained by the strength of the freezing wall. The first freezing pipe which is put into the freezing hole needs to adopt a steel pipe, so that the steel pipe is convenient to fix with a steel pipe hoop, the steel pipe hoop is supported to be put into the freezing hole, and other U-shaped circulating systems can also adopt a hose to be fixed on the steel pipe hoop, are put into the freezing hole together and form a circulating system after being connected.
Furthermore, the construction method is characterized in that when the freezing system is dismantled, the upper part of the freezing circulating system can be disconnected, and the single U-shaped circulating system can be dismantled respectively. Because only 1U-shaped circulating system is pulled out each time, the weight is light, the resistance is small, hoisting equipment is not needed, and the construction organization is simple.
Example (b):
in certain municipal engineering construction, a shallow weak water-containing stratum needs to be improved and reinforced by adopting liquid nitrogen freezing, the freezing depth is 1m, the freezing length is 10m, and a frozen wall with the thickness of 2m is formed to provide maintenance functions needed by underground structure excavation and construction. The traditional freezing design needs to arrange 10 freezing holes along the length direction of the reinforcement, the diameter phi of the freezing holes is 127mm, the distance between the freezing holes is 1m, however, according to the traditional design, liquid nitrogen is not sufficiently gasified in a freezing pipe with the length of 1m, liquid nitrogen waste is caused, and the formed freezing wall is not uniform. If different freezing pipes are connected in series to form a freezing system, the amount of liquid nitrogen in the starting freezing pipe is far larger than that of liquid nitrogen connected into the freezing pipe at the back, even the last freezing pipe is only filled with low-temperature nitrogen, the difference of freezing effects of the different freezing pipes is large, even the position of the last freezing pipe cannot form a freezing wall, and as the distance between freezing holes reaches 1m, the temperature of the frozen soil gradually rises along with the distance from the freezing pipes, and on the interface between the two freezing pipes, the temperature of the frozen soil is the highest, the strength is the lowest, and the frozen soil is a weak link in the whole freezing wall and becomes the interface of the freezing wall.
By utilizing the special-shaped liquid nitrogen freezer and the construction method, continuous freezing circulation is formed in a single freezing tank, the low-temperature transmission efficiency of liquid nitrogen is improved, the problems of insufficient gasification and uneven freezing wall of the liquid nitrogen can be solved better, and the freezing effect of the liquid nitrogen is improved. The main construction process is described as follows:
a, constructing vertical freezing holes from the ground according to a designed position, and penetrating 3 round freezing holes to form 1 long-groove-shaped freezing hole, wherein the groove width is 127mm, the length is 3m, and the vertical depth is 1 m;
b, processing a lower annular steel pipe hoop by using a deformed steel bar with the diameter of 5mm according to the size of the formed long groove-shaped freezing hole, wherein the shape and the size of the steel pipe hoop are consistent with those of the long groove-shaped freezing hole;
c, respectively connecting the bottoms of two pairs of steel pipes with the length of 1m and the diameter of phi 40mm by using bent pipes with the same diameter to form 2U-shaped circulating systems. Fixing the lower parts of the 2U-shaped circulating systems to two ends of a steel pipe hoop, and then putting the steel pipe hoop into a freezing hole together to enable the freezing pipe to be in close contact with the stratum around the long groove-shaped freezing hole;
d, connecting the bottoms of the other freezing pipes in pairs by using elbows with the same diameter on the ground to respectively form a U-shaped freezing pipe circulating system;
e, respectively putting each U-shaped circulating system into the freezing hole, and clamping the U-shaped circulating systems at proper positions of the annular steel pipe hoop at the lower part for fixing;
f, after all the U-shaped circulating systems are put into the elongated slot-shaped freezing holes, opening all the freezing pipes at the upper parts of the freezing holes by using steel pipe hoops, and enabling the upper freezing pipes to be tightly attached to the surrounding strata of the elongated slot-shaped freezing holes to form an annular arrangement mode completely consistent with the shape and the size of the elongated slot-shaped freezing holes;
g, respectively connecting the upper parts of the freezing pipes of different U-shaped circulating systems by using bent pipes with the same diameter, circularly connecting all the U-shaped freezing pipes in each long groove-shaped freezing hole to form an integral circulating system, reserving a liquid supply pipe opening and an exhaust pipe opening, and discharging nitrogen gas after liquid supply nitrogen is filled and gasified;
h, other 2 long groove-shaped freezing holes are continuously constructed, the size and the shape of the freezing holes, the size and the shape of the freezing pipes, the placing and connecting modes of the freezing pipes and the like are constructed according to the steps, and an integral freezing circulation system is formed in each freezing hole;
and i, respectively filling liquid nitrogen from the liquid supply pipe orifice in each freezing hole, gasifying the liquid nitrogen in the process of flowing through the freezing pipe, generating cold energy exchange with the surrounding stratum in time, and discharging the liquid nitrogen out of the freezing circulation system from the exhaust pipe orifice to finish the freezing and refrigerating process. In the freezing process, the length of the liquid nitrogen flowing through the stratum is 20 times that in the traditional freezing pipe construction, so that the cold energy exchange time of the liquid nitrogen and the stratum is greatly prolonged, and the cold energy exchange quantity is increased. The shape of the long-groove-shaped freezing hole enables the frozen soil to develop more uniformly towards two sides, the development speed is higher, and a cuboid freezing wall required by maintenance is easy to form. Meanwhile, the temperature of the liquid nitrogen gradually rises in the process of flowing through the freezing pipes, but the high-temperature freezing pipes and the low-temperature freezing pipes in the circulating system are symmetrically arranged, namely the temperature of the freezing pipe wall along the liquid supply pipe side is gradually increased and the temperature of the freezing pipe wall along the exhaust pipe side is gradually decreased in the long groove-shaped freezing holes, so that different high-temperature freezing pipes and low-temperature freezing pipes are combined into a row, and the high-temperature freezing pipes and the low-temperature freezing pipes can be mutually complemented and frozen to form a more uniform freezing wall;
j, after the parameters such as the thickness, the depth, the length and the like of the formed frozen wall meet the design requirements, performing subsequent excavation and structural construction;
and after the construction of the k structure is finished, the freezing is stopped, after the stratum is unfrozen, the connecting part at the upper part of the circulating system is cut off, each U-shaped freezing cycle is pulled out respectively, the dismantling work of the freezing system is finished, and large-scale hoisting equipment is not needed in the construction process.
Claims (6)
1. The utility model provides a dysmorphism liquid nitrogen freezer, includes freezing pipe (3), its characterized in that: the freezing pipes are arranged into a vertically arranged snake-shaped arrangement structure, the snake-shaped structure is formed by arranging a plurality of vertical freezing pipes in parallel, every two vertical freezing pipes are connected end to end through a bent pipe, a liquid supply pipe is not arranged in each vertical freezing pipe, the freezing pipes (3) are directly connected to form a liquid nitrogen circulating system, two terminals are arranged in the same direction and are respectively provided with a liquid supply pipe opening (1) and an exhaust pipe opening (2), the liquid supply pipe openings (1) and the exhaust pipe openings (2) are adjacently arranged, when the freezing pipes are used, high-temperature sections and low-temperature sections of the freezing pipes (3) are symmetrically arranged in the freezing holes, the length of each vertical freezing pipe is as long as the depth of a pit to be frozen, the position between every two adjacent vertical freezing pipes is adjusted as required, all the vertical freezing pipes can be tightly attached to the side wall of the pit no matter what kind of pit is arranged, an enclosing structure similar to a pit to be frozen and, the upper part and the lower part of the freezing pipe (3) forming the surrounding structure are respectively provided with an upper annular steel pipe hoop (4) and a lower annular steel pipe hoop (5) which wrap and fix all the freezing pipes.
2. The contoured liquid nitrogen freezer of claim 1, wherein: the surrounding structure formed by the freezing pipes (3) is cylindrical, long groove-shaped or irregular, the diameter, the arrangement distance and the length and the width of the long groove-shaped freezing holes of the freezing pipes can be adjusted on site according to construction requirements, so that the total length of the snake-shaped freezing pipes is changed, and the path length and the time of liquid nitrogen circulating in the stratum are adjusted.
3. The contoured liquid nitrogen freezer of claim 1, wherein: the snakelike structure of encircleing that freezes pipe (3) design can be the head and the tail will wait to be under construction in the pot hole enclose a week, also can continue rotatory winding formation helical structure in waiting to be under construction the pot hole, will supply liquid pipe mouth (1) to set up peripherally as required, exhaust pipe mouth (2) set up at the spiral and surround the center, perhaps set up exhaust pipe mouth (2) peripherally, supply liquid pipe mouth (1) and surround the center.
4. A method of manufacturing a shaped liquid nitrogen freezer using the liquid nitrogen freezer of claim 1, comprising: firstly, measuring the depth of the pit needing to be constructed and frozen, including different depths of the whole circle of the pit, then selecting the arrangement distance between the vertical freezing pipes according to the required freezing effect, calculating the number of the vertical freezing pipes required by actual freezing, and calculates the length corresponding to each vertical freezing pipe according to the measured different depth data of the side wall of the pot hole, and numbers each single vertical freezing pipe, preparing metal pipes with corresponding lengths as vertical freezing pipes according to the serial numbers of the vertical freezing pipes, connecting one end of each vertical freezing pipe with the previous vertical freezing pipe through a U-shaped bent pipe, connecting the other end of each vertical freezing pipe with the next vertical freezing pipe through a U-shaped bent pipe, circulating the steps until the whole freezing pipe (3) is formed, and an upper annular steel pipe hoop (4) is arranged at the middle upper part of the inner ring of the freezing pipe (3), and a lower annular steel pipe hoop (5) is arranged at the lower part of the inner ring of the freezing pipe (3) to prevent the surrounded freezing pipe (3) from deforming and ensure that all vertical freezing pipes are tightly attached to the wall of the pot hole.
5. The manufacturing method according to claim 4, characterized in that: the method comprises the steps of starting processing by using a whole metal pipe, sequentially processing vertical freezing pipes according to numbers and corresponding depth data, after each vertical freezing pipe is processed, bending the metal pipe by 180 degrees according to actual needs, and then processing the vertical freezing pipe of the next number until all the vertical freezing pipes are processed to form the freezing pipes (3) arranged in a snake shape, then surrounding the freezing pipes (3) arranged in the snake shape according to the shape of a freezing pot hole required to be constructed, arranging an upper annular steel pipe hoop (4) at the middle upper part of an inner ring of the surrounded freezing pipe (3), and arranging a lower annular steel pipe hoop (5) at the lower part to prevent the surrounded freezing pipe (3) from deforming.
6. A construction method using the special-shaped liquid nitrogen freezer of claim 1 is characterized by comprising the following steps:
a, constructing a freezing hole on the ground of a construction site according to a designed position, wherein the section of the freezing hole is round, long groove-shaped or irregular as required, the length of the long side of the long groove-shaped freezing hole is determined by the length of a freezing wall and the cycle length of a freezing pipe, and the width of the freezing hole is determined according to the freezing requirement;
b, constructing freezing holes according to actual on-site freezing requirements, connecting the plurality of vertical freezing pipes in pairs by using U-shaped bent pipes to form U-shaped circulating systems, fixing the lower parts of the two U-shaped circulating systems to two sides of a steel pipe hoop (5), and putting the two U-shaped circulating systems into the freezing holes together to enable the vertical freezing pipes to be in close contact with stratums around the freezing holes;
c, connecting the bottoms of the other vertical freezing pipes by using elbows in pairs to respectively form a U-shaped circulating system;
d, respectively putting each U-shaped circulating system into the freezing hole, and clamping the U-shaped circulating systems at proper positions of the annular steel pipe hoop (5) at the lower part for fixing;
e, after all the U-shaped circulating systems are put into the freezing holes, the freezing pipes are propped open at the upper parts of the freezing holes by using upper annular steel pipe hoops (4), so that the freezing pipes are tightly attached to the stratums around the freezing holes to form an annular surrounding arrangement mode which is completely consistent with the shapes and the sizes of the freezing holes;
f, respectively connecting the upper parts of the vertical freezing pipes of different U-shaped circulating systems by using U-shaped bent pipes, so that all the U-shaped circulating systems in the freezing holes are connected to form a coiled pipe circulating system, and reserving one adjacent liquid supply pipe opening (1) and one adjacent exhaust pipe opening (2);
injecting liquid nitrogen into the freezing pipe (3) from the liquid supply pipe orifice (1), wherein the liquid nitrogen is subjected to cold energy exchange with surrounding strata in the process of flowing through the snake-shaped freezing pipe, gradually gasified after absorbing heat and discharged out of the circulating system from the exhaust pipe orifice (2) to finish the freezing process;
h, from the liquid supply pipe orifice (1) to the exhaust pipe orifice (2), the temperature of the freezing pipe (3) is gradually raised, the high-temperature section and the low-temperature section of the freezing pipe are symmetrically arranged in the circumferential arrangement mode, and the freezing pipes with different temperatures are superposed to form uniform freezing walls at different section positions in the long edge direction;
i, after the thickness of the frozen soil wall formed in the long side direction of the frozen hole meets the design requirement, subsequent excavation and structural construction can be carried out;
and j, stopping freezing after the excavation and the structure construction are finished, removing the connecting elbow at the upper part of the freezing circulating system after the stratum is unfrozen, and removing each U-shaped circulating system to finish the detaching work of the freezing system.
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| CN105698582B (en) * | 2016-01-28 | 2017-10-10 | 中国人民解放军后勤工程学院 | Improve the preset energy ball geothermal heat exchanger of heat transfer efficiency |
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