CN115262603B - Urban underground construction freezing and water-resisting method without influence on earth surface - Google Patents
Urban underground construction freezing and water-resisting method without influence on earth surface Download PDFInfo
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- CN115262603B CN115262603B CN202210572184.3A CN202210572184A CN115262603B CN 115262603 B CN115262603 B CN 115262603B CN 202210572184 A CN202210572184 A CN 202210572184A CN 115262603 B CN115262603 B CN 115262603B
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D19/00—Keeping dry foundation sites or other areas in the ground
- E02D19/06—Restraining of underground water
- E02D19/12—Restraining of underground water by damming or interrupting the passage of underground water
- E02D19/14—Restraining of underground water by damming or interrupting the passage of underground water by freezing the soil
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Abstract
The invention relates to the waterproof technical field of tunnels, adit or other underground caverns, and discloses a method for freezing and insulating underground construction in cities without influence on the earth surface. According to the invention, on the premise of not lowering the water level, the part of the multi-layer underground building, which is higher than the underground water level line, is firstly excavated, and then the refrigerating system is arranged underground in a suspended manner, so that the multi-layer underground building is not required to be detached from the ground, the noise generated in the freezing process can not influence the ground, the length of the refrigerating brine pipe is shortened, and the loss of refrigerating capacity is reduced. The refrigerating unit is arranged on the floor of the underground layer and is separated from the frozen stratum, so that the refrigerating unit is prevented from shaking due to the change of the volume of the stratum. Through separating for a plurality of cabins with frozen soil curtain, every cabin is frozen alone, is tested loudly and is excavated, avoids bringing the heavy load that appears suddenly for urban power network, and the cabin of leaking simultaneously can not influence other cabins.
Description
Technical Field
The invention relates to the technical field of water prevention of tunnels, adits or other underground caverns, in particular to a method for freezing and water isolation in urban underground construction without affecting the earth surface.
Background
With the development of cities, the surface area of the ground is more and more unable to meet the demand, so a large amount of municipal infrastructure is buried underground, including subways and various municipal pipelines, and correspondingly more underground caverns need to be excavated.
Most underground caverns, such as subway tunnels or underground pipelines, can be constructed by adopting a pipe jacking construction mode or a shield construction mode, and the two construction modes have no requirements on precipitation in the excavation process (namely, the underground water level is reduced to the position below the underground cavern), and can even be carried out at the bottom of a river or even at the bottom of the sea. However, for underground caverns such as subway stations, which cannot be constructed by a pipe-jacking method or a shield method but can be constructed by a more traditional underground excavation method (such as a sheet pile method), the precipitation work of the working surface before excavation is very important.
The traditional method for lowering the water level of the underground cavern is to pump a plurality of water lowering wells from the ground to finish the water level lowering before the excavation, but two problems are brought, one is that the number of the water lowering wells to be dug is very large, generally hundreds of wells are required to be dug uniformly on the underground cavern to be excavated, and buildings which can obstruct the pumping of the water lowering wells are arranged on the ground surface, so that the construction and removal cost is increased, and the method is unacceptable for a large city with high removal cost; it is two that it can consume a large amount of groundwater resources to draw water, and the new phase project of beijing subway No. 19 line north taiping zhuang station that this application relates to is the example, need draw water about 3850 ten thousand tons, and this causes ground subsides very easily, and the water waste is serious simultaneously, and must shut down in the precipitation weather (do not allow to municipal drainage pipe way drainage in the precipitation weather).
For mine and foundation pit construction, a freezing and water stopping mode exists, namely, soil containing water is frozen to form a frozen soil curtain, so that seepage of underground water is blocked. However, when the method is used for the facility working hours of the subway stations in cities, the method also has various problems:
1. the refrigerating unit occupies a large area, and the problem of high removal cost also exists when the refrigerating unit is applied in cities;
2. the refrigerating unit has high power and belongs to suddenly appearing electric equipment, and the power supply for the refrigerating unit is difficult to be ensured on the premise of not influencing the urban power supply;
3. the noise is large in the refrigeration process, and the noise is generated in 24 hours.
For multi-storey underground buildings, the middle slab is usually used to refer to the non-sub-floor, and the bottom slab is used to refer to the sub-floor. Because the thickness and the waterproof requirement of the two are different greatly, the middle plate only needs enough bearing capacity and does not need to resist the pressure of the stratum and prevent water.
Disclosure of Invention
The invention provides a freezing and water isolating method for urban underground construction without influence on the ground surface.
The technical problem to be solved is that: when underground buildings which cannot be constructed by a shield/pipe jacking method are constructed in cities, a series of problems can be caused no matter a dewatering well is dug for dewatering or water is frozen for stopping.
In order to solve the technical problem, the invention adopts the following technical scheme: a freezing and water-resisting method for underground construction in city without influence on earth surface is used for the construction of multi-layer underground buildings including subway stations, a freezing system is adopted to freeze water-containing soil into frozen soil curtain to block the seepage of underground water, the freezing system comprises a freezing unit for producing frozen salt water, a freezer inserted in the water-containing soil and used for freezing the water-containing soil into frozen soil curtain, and a heat dissipation device for dissipating heat for the freezing unit; the freezing and water-resisting method is used for the construction of a multi-layer underground building with the middle plate of the first layer higher than the underground water line, and comprises the following steps:
the method comprises the following steps: under the premise of not lowering the water level of the stratum, excavating earthwork of the part of the multi-layer underground building above an underground water line, and constructing an envelope above the underground water line and a middle plate of a first layer, wherein a cavity between the middle plate of the first layer and the underground water line is marked as a pipe distribution cavity;
step two: building a pipe distribution pilot tunnel, wherein the pipe distribution pilot tunnel surrounds the multi-layer underground building in a plane for one circle, is higher than an underground water line at the bottom and is close to the edge of a middle plate at the first layer at the top and is used for providing a construction space;
step three: vertically downwards punching holes from the pipe distribution cavity and the pipe distribution guide hole, installing freezers for forming frozen soil curtains in the holes, and installing a freezing unit on the middle plate of the first layer and communicating with the freezers;
the frozen soil curtain wraps the part of the multi-layer underground building below the underground water line, and comprises a frozen soil enclosing wall arranged around the multi-layer underground building for one circle and a frozen soil bottom plate lower than the multi-layer underground building;
the freezer used for forming the frozen soil bottom plate is marked as a bottom plate device, and the freezer used for forming the frozen soil enclosing wall is marked as an enclosing wall device; the upper end of the bottom plate device is lower than the bottom plate of the multi-layer underground building and is uniformly distributed in the frozen soil bottom plate; the upper end of the wall enclosing device is higher than the underground water level line, the lower end of the wall enclosing device is flush with the lower end of the bottom plate device, and the wall enclosing device is uniformly distributed in the frozen soil wall;
step four: starting a refrigerating unit to freeze to form a frozen soil curtain;
step five: under the conditions that the refrigerating unit and the freezer are kept operating and the temperature of the frozen soil curtain is lower than the melting point of water, earthwork of the rest part of the multi-layer underground building is excavated, an enclosure structure and a middle plate of the rest part are built, then the refrigerating unit is closed, the freezer is removed, and a bottom plate of the multi-layer underground building is built.
Furthermore, a leakage inspection well for measuring whether the frozen soil curtain leaks water is also excavated in the pipe distribution cavity, and the bottom of the leakage inspection well is higher than the frozen soil bottom plate and lower than the bottom plate of the multi-layer underground building;
step four, checking leakage after the frozen soil curtain is frozen, and entering step five after the frozen soil curtain is not leaked;
the leakage detection method comprises the following steps: pumping water in the leakage inspection well, and if the water level in the leakage inspection well is not changed after the water pumping is stopped, indicating that the frozen soil curtain does not leak; if the water level in the leakage well rises after the water pumping is stopped, the frozen soil curtain is proved to have leakage, at the moment, the thickened frozen soil curtain is continuously frozen, and the leakage of the frozen soil curtain is repaired until the frozen soil curtain is not leaked.
Furthermore, the frozen soil curtain also comprises frozen soil isolation walls, the frozen soil isolation walls divide the frozen soil curtain into a plurality of mutually independent cabins, the upper ends of the frozen soil isolation walls are flush with the top of the frozen soil enclosing wall, and the lower ends of the frozen soil isolation walls are connected with the frozen soil bottom plate into a whole;
the freezer used for forming the frozen soil isolation wall is marked as an isolation wall, the upper end of the isolation wall is flush with the upper end of the wall enclosing device, and the lower end of the isolation wall is flush with the lower end of the bottom plate device;
and in the third step, the isolation wall devices are arranged in the pipe distribution cavity and are uniformly distributed in the frozen soil isolation wall.
Furthermore, in the third step, the refrigerating units corresponding to the freezers of the cabins are mutually independent and are not mutually mixed; in two adjacent cabins frozen successively, a frozen earth isolation wall between the two cabins belongs to a cabin frozen first, and an isolation wall device in the frozen earth isolation wall is connected with a refrigerating unit corresponding to the cabin frozen first;
and step four, freezing the frozen soil curtains of the cabins one by one, checking leakage of the cabin after the frozen soil curtain of each cabin is frozen, reducing the power of a refrigerating unit corresponding to a freezer of the cabin after leakage is avoided, keeping the frozen soil curtain of the cabin at a constant temperature, and then performing step five on the cabin and simultaneously starting freezing the frozen soil curtain of the next cabin.
Further, in the fourth step, whether the frozen soil curtain is frozen is judged by adopting the following method:
temperature sensors are uniformly distributed in the frozen soil curtain, the temperature sensors are arranged in the area where the frozen soil curtain is located before freezing begins, and a distance of at least half a meter is reserved between the temperature sensors and the nearest freezer;
setting the thickness and the average temperature which are required to be reached by the frozen soil curtain when the frozen soil curtain is frozen, carrying out temperature field simulation on the stratum by adopting finite element software, solving the temperature field change condition of the area where the frozen soil curtain is located in the freezing process, obtaining the temperature of the point position where each temperature measuring sensor is located when the thickness and the average temperature of the frozen soil curtain reach set values according to the temperature field change condition, and recording the temperature as threshold temperature;
when the temperature measured by each temperature measuring sensor is not higher than the threshold temperature, the frozen soil curtain is frozen, and leakage inspection can be started.
Further, in the fifth step, the freezer is dismantled in the following way: cutting off the portion of the freezer that is higher than the lower surface of the floor of the multi-story underground building.
Further, a buffer layer which is 4-6 meters thick and used for preventing deformation and temperature change of the frozen soil bottom plate from influencing construction of the multi-layer underground building is reserved between the bottom plate of the multi-layer underground building and the frozen soil bottom plate, the thickness of the frozen soil enclosing wall and the thickness of the frozen soil isolation wall are not less than two meters, and the thickness of the frozen soil bottom plate is not less than two times of the thickness of the frozen soil enclosing wall.
Further, the refrigerating unit is a water-cooled unit, the heat dissipation device is a cooling tower, and the cooling tower is arranged in an area without obstacles above the ground of the multi-layer underground building.
Furthermore, in the refrigeration system, a frozen brine outlet of the refrigeration unit is communicated with a brine tank, an outlet of the brine tank is communicated with a liquid distribution ring which is respectively communicated with inlets of all freezers along a pipeline with a brine pump, an outlet of each freezer is respectively communicated with a liquid collection ring, and the liquid collection rings are communicated with the frozen brine inlet of the refrigeration unit; the cooling water outlet of the refrigerating unit is communicated with the top of the cooling water tower along a pipeline, the outlet of the cooling water tower is communicated with the clear water tank, and the outlet of the clear water tank is communicated with the cooling water inlet of the refrigerating unit along a pipeline with a clear water pump.
Furthermore, the frozen brine is a calcium chloride solution, the pipelines through which the frozen brine flows are all heat-preservation pipes, and the brine tank is a heat-preservation container.
Compared with the prior art, the urban underground construction freezing and water-resisting method without influence on the earth surface has the following beneficial effects:
according to the invention, on the premise of not carrying out precipitation (the prior art requires that precipitation is carried out first and then excavation is carried out), the part of the multilayer underground building, which is higher than the underground water level line, is excavated firstly, the pipe distribution pilot tunnel is excavated around the multilayer underground building for one circle, then the refrigerating unit is installed in the excavated underground cavern (the part of the refrigerating unit, which is not placed in the pilot tunnel), the installation of the freezers is completed below the refrigerating unit and in the pipe distribution pilot tunnel, the removal work on the ground surface is not needed, the noise generated in the freezing process can not influence the ground, the length of the frozen brine pipe is shortened, and the loss of cooling capacity is reduced.
In the invention, the refrigerating unit is arranged on the middle plate of the first floor (the middle plate is equivalent to a floor slab in a building, and the middle plate is equivalent to the refrigerating unit is arranged on the floor slab of the underground floor), is equivalent to suspended erection and is separated from a frozen stratum, so that the phenomenon that the refrigerating unit shakes due to the large volume change of the frozen stratum (the volume of water shrinks in the cooling process and expands in the freezing process) is avoided, and the refrigerating unit is kept stable in the operation process (a large number of motors exist in the refrigerating unit, and the motors can be seriously damaged if the motors are installed unstably).
According to the invention, the frozen soil curtain is divided into a plurality of cabins, and each cabin is independently frozen and excavated instead of being frozen at one time and then being excavated, so that sudden heavy load on an urban power grid caused by freezing at one time is avoided, and the construction progress is accelerated (the excavation in the cabin can be carried out every time one cabin is frozen, and the whole frozen soil curtain does not need to be frozen.
According to the invention, the frozen soil curtain is divided into the plurality of cabins, leakage is independently checked in each cabin, the cabin which leaks water cannot influence other cabins, if some cabin leaks water, only the cabin needs to be subjected to leakage repairing, the whole frozen soil curtain does not need to be subjected to leakage repairing, the difficulty and the workload of leakage repairing are reduced, and meanwhile, the safety degree during excavation is obviously improved.
According to the method, a finite element method is adopted in advance to simulate a temperature field, the threshold temperature of each temperature measuring point is obtained when the thickness and the average temperature of the frozen soil curtain meet requirements, the thickness and the average temperature of the frozen soil curtain can be judged to meet the requirements when the actual temperature of the temperature measuring points is lower than the threshold temperature, the thickness of the frozen soil curtain does not need to be measured (the thickness of the frozen soil curtain is difficult to measure), the number of the temperature measuring points can also be reduced (the average temperature does not need to be obtained by using the measured temperature), the freezing end point is judged quickly and accurately, and the phenomenon that the frozen end point passes through the head or does not reach the standard is avoided.
In the invention, a water-cooled refrigerating unit is adopted, and a heat dissipation device (cooling water towers are used, the number is small, the occupied area is small, and clear water pipes do not need to be insulated and can be far away from the refrigerating unit) of the refrigerating unit is placed on the ground in an obstacle-free area (namely, the heat dissipation device does not need to be detached), so that the difficulty in heat dissipation caused by the fact that the refrigerating unit is located in an underground cavern is avoided.
Drawings
FIG. 1 is a schematic cross-sectional view of a multi-storey underground building constructed using the present invention;
FIG. 2 is a schematic diagram showing the relative positions of the refrigerating unit and the piping guide hole;
FIG. 3 is a top view of a frozen soil curtain;
FIG. 4 is a schematic diagram of a refrigeration system;
in the figure, 11-a refrigerating unit, 12-a freezer, 13-a heat dissipation device, 21-a frozen soil enclosing wall, 22-a frozen soil bottom plate, 23-a frozen soil isolation wall, 3-an underground water line, 4-a building envelope, 5-a middle plate, 6-a pipe distribution guide hole and 7-a pipe distribution cavity.
Detailed Description
As shown in fig. 1 to 4, a freezing and water-insulating method for underground construction in a city without influence on the ground surface is used for the construction of multi-story underground buildings including subway stations, and a freezing system is used to freeze water-containing soil into frozen soil curtains to block seepage of groundwater, and includes a freezing unit 11 for producing frozen brine, a freezer 12 inserted into the water-containing soil and used to freeze the water-containing soil into frozen soil curtains, and a heat sink 13 for dissipating heat from the freezing unit 11. These are all mature complete sets on the market, and can be purchased freely directly according to the needs.
The method in the application has use limitation, because the application needs to dig out the space for installing the refrigerating unit 11 and the space for constructing the freezer 12 on the premise of not lowering the water, and the refrigerating unit 11 also needs to be installed on the middle plate 5 of the first floor of the underground building to avoid stratum interference. It is required that the underground construction is a multi-story underground construction and the middle plate 5 of the first story is higher than the ground water line 23, which is required to be clarified in the underground hydrological exploration before construction. The building envelope 4 herein refers to various lining for resisting earth pressure, and is constructed while excavating, and the same is applied below.
The multi-layer underground building in the embodiment is a subway station, the construction is carried out by adopting a sheet pile method, and the attached vertical shaft and the attached transverse channel are also isolated by adopting the freezing water isolation method in the application.
The freezing water-resisting method comprises the following steps:
the method comprises the following steps: on the premise of not lowering the water level of the stratum, excavating earthwork of the part of the multi-layer underground building above the underground water level line 23, building the enclosure structure 4 above the underground water level line 23 and the middle plate 5 of the first layer, and marking a cavity between the middle plate 5 of the first layer and the underground water level line 23 as a pipe distribution cavity 7.
Step two: building a pipe distribution pilot tunnel 6, as shown in fig. 2, the pipe distribution pilot tunnel 6 is a pilot tunnel which surrounds the multi-layer underground building for a circle in a plane, is higher than the underground water line 23 at the bottom and is close to the edge of the middle plate 5 at the top of the first layer and is used for providing a construction space;
the pipe distribution guide hole 6 is used for forming a frozen soil enclosing wall 21, and the space of the pipe distribution guide hole is not too large enough to put down the drilling equipment and the freezer 12. The freezer 12 is preferably of a flexible type to facilitate turning. The pipe distribution guide hole 6 and the pipe distribution cavity 7 generally need to have the height of more than 3 meters.
Step three: vertically drilling holes downwards from the pipe distribution cavity 7 and the pipe distribution guide hole 6, installing freezers 12 for forming frozen soil curtains in the holes, installing a freezing unit 11 on the middle plate 5 on the first layer, and communicating the freezers 12 through pipelines;
the frozen soil curtain wraps the part of the multi-layer underground building below the underground water line 23, and comprises a frozen soil enclosing wall 21 arranged around the multi-layer underground building for one circle and a frozen soil bottom plate 22 lower than the multi-layer underground building; the frozen earth curtain is not a full enclosure structure, but is semi-enclosed, with no cover on top.
The freezer 12 for forming the frozen soil floor 22 is referred to as a floor device, and the freezer 12 for forming the frozen soil enclosure 21 is referred to as an enclosure device; the upper end of the bottom plate device is lower than the bottom plate of the multi-layer underground building and is uniformly distributed in the frozen soil bottom plate 22; the upper end of the wall enclosing device is higher than the underground water level line 23, the lower end of the wall enclosing device is flush with the lower end of the bottom plate device, and the wall enclosing device is uniformly distributed in the frozen soil enclosing wall 21;
if there is a certain space in the pipe distribution guide 6 after the freezer 12 is installed, a part of the freezer unit 11 can be placed in the pipe distribution guide 6, thereby further shortening the length of the brine pipe between the freezer unit 11 and the wall enclosing device.
Step four: the freezer unit 11 is started to start freezing to form a frozen earth curtain.
Step five: under the conditions that the refrigerating unit 11 and the freezer 12 are kept running and the temperature of the frozen soil curtain is lower than the melting point of water, the earthwork of the rest part of the multi-layer underground building is excavated, the building envelope 4 and the middle plate 5 of the rest part are built, then the refrigerating unit 11 is closed, the freezer 12 is removed, and then the bottom plate of the multi-layer underground building is built.
A leakage detection well for measuring whether the frozen soil curtain leaks water is also excavated in the pipe distribution cavity 7, and the bottom of the leakage detection well is higher than the frozen soil bottom plate 22 and lower than the bottom plate of the multi-layer underground building;
in the fourth step, checking leakage after the frozen soil curtain is frozen, and entering the fifth step after the frozen soil curtain is not leaked;
the leakage detection method comprises the following steps: pumping water in the leakage detecting well, and if the water level in the leakage detecting well is unchanged after the water pumping is stopped, indicating that the frozen soil curtain does not leak; if the water level in the leakage well rises after the water pumping is stopped, the frozen soil curtain is proved to have leakage, at the moment, the thickened frozen soil curtain is continuously frozen, and the leakage of the frozen soil curtain is repaired until the frozen soil curtain is not leaked.
After the frozen soil curtain is not leaked, underground water outside the frozen soil curtain cannot seep into the frozen soil curtain, the amount of the underground water inside the frozen soil curtain is small, the frozen soil curtain can be quickly pumped out by using a leakage inspection well, and the influence is small even if the frozen soil curtain is not pumped out.
As shown in fig. 2-3, the frozen soil curtain further comprises a frozen soil separating wall 23, the frozen soil separating wall 23 divides the frozen soil curtain into a plurality of mutually independent cabins, the upper end of the frozen soil separating wall 23 is flush with the top of the frozen soil enclosing wall 21, and the lower end of the frozen soil separating wall is connected with the frozen soil bottom plate 22 into a whole;
the freezer 12 for forming the frozen soil isolation wall 23 is marked as an isolation wall device, the upper end of the isolation wall device is flush with the upper end of the wall device, and the lower end of the isolation wall device is flush with the lower end of the bottom plate device;
in the third step, the isolation wall devices are arranged in the pipe distribution cavity 7 and are uniformly distributed in the frozen soil isolation wall 23.
In the third step, the refrigerating units 11 corresponding to the freezers 12 of each cabin are mutually independent and are not mixed; in two adjacent cabins which are frozen successively, the frozen soil isolation wall 23 between the two cabins belongs to the cabin which is frozen firstly, and the isolation wall device in the frozen soil isolation wall 23 is connected with the refrigerating unit 11 corresponding to the cabin which is frozen firstly; thus, the water leakage gap formed by the cabin frozen firstly is avoided.
And step four, freezing the frozen soil curtains of the cabins one by one, checking leakage of each cabin after freezing of the frozen soil curtain of each cabin is finished, reducing the power of the refrigerating unit 11 corresponding to the freezer 12 of the cabin after leakage is avoided, keeping the frozen soil curtain of the cabin at a constant temperature, and then performing step five on the cabin and simultaneously starting freezing of the frozen soil curtain of the next cabin.
In the fourth step, whether the frozen soil curtain is frozen is judged by adopting the following method:
temperature sensors are uniformly distributed in the frozen soil curtain, the temperature sensors are arranged in the area of the frozen soil curtain before the freezing starts, and a distance of at least half a meter is reserved between the temperature sensors and the nearest freezer 12;
setting the thickness and the average temperature which are required to be reached by the frozen soil curtain when the frozen soil curtain is frozen, carrying out temperature field simulation on the stratum by adopting finite element software, solving the temperature field change condition of the area where the frozen soil curtain is located in the freezing process, obtaining the temperature of the point position where each temperature measuring sensor is located when the thickness and the average temperature of the frozen soil curtain reach set values according to the temperature field change condition, and recording the temperature as threshold temperature;
the temperature measured by each temperature measuring sensor corresponds to a specific thickness and average temperature of the frozen soil curtain, and the lower the temperature measured by the temperature measuring sensor is, the thicker the frozen soil curtain is and the lower the average temperature is, and when the temperature measured by each temperature measuring sensor is not higher than the threshold temperature, the frozen soil curtain is completely frozen, and leakage checking can be started. Here, the freezing end point of each chamber is also separately determined.
In the fifth step, the freezer 12 is removed in the following manner: the portion of the freezer 12 higher than the lower surface of the floor of the multi-story underground building is cut off.
A buffer layer with the thickness of 4-6 meters is left between the bottom plate and the frozen soil bottom plate 22 of the multi-layer underground building and is used for preventing the deformation and the temperature change of the frozen soil bottom plate 22 from influencing the construction of the multi-layer underground building, the thickness of the frozen soil enclosing wall 21 and the thickness of the frozen soil isolation wall 23 are not less than two meters, and the thickness of the frozen soil bottom plate 22 is not less than two times of the thickness of the frozen soil enclosing wall 21. The frozen earth bottom plate 22 is subject to greater formation pressure and is therefore thicker. In this embodiment, the thickness of the frozen soil enclosing wall 21 and the frozen soil isolation wall 23 is 2.2 m, and the thickness of the frozen soil bottom plate 22 is 5 m.
The refrigerating unit 11 is a water-cooled unit, and the heat sink 13 is a cooling tower disposed in an unobstructed area above the ground of the multi-story underground structure.
As shown in fig. 4, in the freezing system, the outlet of the freezing brine of the freezing unit 11 is communicated with a brine tank, the outlet of the brine tank is communicated with a liquid distribution ring which is respectively communicated with the inlet of each freezer 12 along a pipeline with a brine pump, the outlet of each freezer 12 is respectively communicated with a liquid collecting ring, and the liquid collecting ring is communicated with the inlet of the freezing brine of the freezing unit 11; the cooling water outlet of the refrigerating unit 11 is communicated with the top of the cooling water tower along a pipeline, the outlet of the cooling water tower is communicated with the clear water tank, and the outlet of the clear water tank is communicated with the cooling water inlet of the refrigerating unit 11 along a pipeline with a clear water pump. Refrigeration systems of this construction are readily available on the market and will not be described in detail here.
The frozen brine is a calcium chloride solution, pipelines through which the frozen brine flows are all heat preservation pipes, and the brine tank is a heat preservation container. The heat preservation pipe can only reduce the loss of cold energy when the frozen brine flows to a certain extent, and the most fundamental way is to shorten the length of the pipeline as much as possible.
The above-mentioned embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solution of the present invention by those skilled in the art should fall within the protection scope defined by the claims of the present invention without departing from the spirit of the present invention.
Claims (8)
1. A freezing and water-resisting method for underground construction in city without influence on earth surface is used for the construction of multi-layer underground buildings including subway stations, a freezing system is adopted to freeze water-bearing soil into frozen soil curtain to block the seepage of underground water, the freezing system comprises a freezing unit (11) for producing frozen salt water, a freezer (12) inserted into the water-bearing soil and used for freezing the water-bearing soil into frozen soil curtain, and a heat dissipation device (13) for dissipating heat for the freezing unit (11); the method is characterized in that: the freezing and water-resisting method is used for the construction of a multi-layer underground building with a middle plate (5) of a first layer higher than an underground water line (23), and comprises the following steps:
the method comprises the following steps: on the premise of not lowering the water level of the stratum, excavating earthwork of a part of the multi-layer underground building above an underground water line (23), and constructing an envelope (4) above the underground water line (23) and a middle plate (5) of a first layer, wherein a cavity between the middle plate (5) of the first layer and the underground water line (23) is marked as a pipe distribution cavity (7);
step two: building a pipe distribution pilot tunnel (6), wherein the pipe distribution pilot tunnel (6) surrounds the multi-layer underground building for a circle in a plane, is higher than an underground water line (23) at the bottom and is close to the edge of a middle plate (5) at the top of the first layer and is used for providing a construction space;
step three: a hole is vertically drilled downwards from the pipe distribution cavity (7) and the pipe distribution guide hole (6), freezers (12) for forming frozen soil curtains are installed in the holes, and a freezing unit (11) is installed on the middle plate (5) on the first layer and is communicated with the freezers (12);
the frozen soil curtain wraps the part of the multi-layer underground building below an underground water line (23), and comprises a frozen soil enclosing wall (21) arranged around the multi-layer underground building for one circle and a frozen soil bottom plate (22) lower than the multi-layer underground building;
the freezer (12) for forming the frozen soil bottom plate (22) is marked as a bottom plate device, and the freezer (12) for forming the frozen soil enclosing wall (21) is marked as an enclosing wall device; the upper end of the bottom plate device is lower than the bottom plate of the multi-layer underground building and is uniformly distributed in the frozen soil bottom plate (22); the upper end of the wall enclosing device is higher than the underground water line (23), the lower end of the wall enclosing device is flush with the lower end of the bottom plate device, and the wall enclosing device is uniformly distributed in the frozen soil enclosing wall (21);
step four: starting the refrigerating unit (11) to freeze to form a frozen soil curtain;
step five: under the conditions that the refrigerating unit (11) and the freezer (12) are kept in operation and the temperature of a frozen soil curtain is lower than the melting point of water, excavating earthwork of the rest part of the multi-layer underground building, building an enclosure structure (4) and a middle plate (5) of the rest part, closing the refrigerating unit (11), removing the freezer (12) and building a bottom plate of the multi-layer underground building;
in the fourth step, whether the frozen soil curtain is frozen is judged by adopting the following method:
temperature sensors are uniformly distributed in the frozen soil curtain, the temperature sensors are arranged in the area where the frozen soil curtain is located before freezing begins, and a distance of at least half a meter is reserved between the temperature sensors and the nearest freezer (12);
setting the thickness and the average temperature which are required to be reached by the frozen soil curtain when the frozen soil curtain is frozen, carrying out temperature field simulation on the stratum by adopting finite element software, solving the temperature field change condition of the area where the frozen soil curtain is located in the freezing process, obtaining the temperature of the point position where each temperature measuring sensor is located when the thickness and the average temperature of the frozen soil curtain reach set values according to the temperature field change condition, and recording the temperature as threshold temperature;
when the temperature measured by each temperature measuring sensor is not higher than the threshold temperature, the frozen soil curtain is frozen, and leakage inspection can be started;
the refrigerating unit (11) is a water-cooled unit, the heat dissipation device (13) is a cooling tower, and the cooling tower is arranged in an obstacle-free area above the multi-layer underground building on the ground.
2. The method for freezing and water isolating in the underground construction of the city without influence on the earth surface according to claim 1, which is characterized in that: a leakage inspection well for measuring whether the frozen soil curtain leaks water is further excavated in the pipe distribution cavity (7), and the bottom of the leakage inspection well is higher than the frozen soil bottom plate (22) and lower than the bottom plate of the multi-layer underground building;
in the fourth step, checking leakage after the frozen soil curtain is frozen, and entering the fifth step after the frozen soil curtain is not leaked;
the leakage detection method comprises the following steps: pumping water in the leakage detecting well, and if the water level in the leakage detecting well is unchanged after the water pumping is stopped, indicating that the frozen soil curtain does not leak; if the water level in the inspection leakage well rises after water pumping is stopped, the frozen soil curtain is indicated to have leakage, at the moment, the thickened frozen soil curtain is continuously frozen, and leakage is mended on the frozen soil curtain until the frozen soil curtain does not leak.
3. The method for freezing and water isolating in the underground construction of the city without influence on the earth surface as claimed in claim 2, wherein: the frozen soil curtain also comprises frozen soil isolation walls (23), the frozen soil isolation walls (23) divide the frozen soil curtain into a plurality of mutually independent cabins, the upper ends of the frozen soil isolation walls (23) are flush with the top of the frozen soil enclosing wall (21), and the lower ends of the frozen soil isolation walls are connected with the frozen soil bottom plate (22) into a whole;
a freezer (12) for forming a frozen soil isolation wall (23) is marked as an isolation wall device, the upper end of the isolation wall device is flush with the upper end of the wall device, and the lower end of the isolation wall device is flush with the lower end of the bottom plate device;
in the third step, the isolation wall devices are arranged in the pipe distribution cavity (7) and are uniformly distributed in the frozen soil isolation wall (23).
4. The method for freezing and water isolating in the underground construction of the city without influence on the earth surface according to claim 3, wherein the method comprises the following steps: in the third step, the refrigerating units (11) corresponding to the freezers (12) of all the cabins are mutually independent and are not mixed; in two adjacent cabins which are frozen successively, a frozen earth isolation wall (23) between the two cabins belongs to the cabin which is frozen first, and an isolation wall device in the frozen earth isolation wall (23) is connected with a refrigerating unit (11) corresponding to the cabin which is frozen first;
and in the fourth step, freezing the frozen soil curtains of all the cabins one by one, checking leakage of each cabin after freezing of the frozen soil curtain of each cabin is finished, reducing the power of a refrigerating unit (11) corresponding to a freezer (12) of the cabin after leakage is avoided, keeping the frozen soil curtain of the cabin at a constant temperature, and then, performing the fifth step on the cabin and simultaneously starting freezing of the frozen soil curtain of the next cabin.
5. The method for freezing and water isolating in the underground construction of the city without influence on the earth surface according to claim 1, which is characterized in that: in the fifth step, the freezer (12) is dismantled in the following way: the portion of the freezer (12) above the lower surface of the floor of the multi-story underground building is cut off.
6. The method for freezing and water isolating in the underground construction of the city without influence on the earth surface according to claim 3, wherein the method comprises the following steps: the buffer layer is arranged between the bottom plate and the frozen soil bottom plate (22) of the multi-layer underground building, is 4-6 meters thick and is used for preventing deformation and temperature change of the frozen soil bottom plate (22) from influencing construction of the multi-layer underground building, the thickness of the frozen soil enclosing wall (21) and the thickness of the frozen soil isolation wall (23) are not less than two meters, and the thickness of the frozen soil bottom plate (22) is not less than two times of the thickness of the frozen soil enclosing wall (21).
7. The method for freezing and water isolating in the underground construction of the city without influence on the earth surface according to claim 1, which is characterized in that: in the freezing system, a frozen brine outlet of a freezing unit (11) is communicated with a brine tank, an outlet of the brine tank is communicated with a liquid distribution ring which is respectively communicated with inlets of freezers (12) along a pipeline with a brine pump, outlets of the freezers (12) are respectively communicated with a liquid collection ring, and the liquid collection ring is communicated with a frozen brine inlet of the freezing unit (11); the cooling water outlet of the refrigerating unit (11) is communicated with the top of the cooling water tower along a pipeline, the outlet of the cooling water tower is communicated with the clear water tank, and the outlet of the clear water tank is communicated with the cooling water inlet of the refrigerating unit (11) along a pipeline with a clear water pump.
8. The method of claim 7, wherein the method comprises the following steps: the frozen brine is a calcium chloride solution, pipelines through which the frozen brine flows are all heat preservation pipes, and the brine tank is a heat preservation container.
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| RU2170810C2 (en) * | 1999-05-13 | 2001-07-20 | ОАО "Газпром" | Method of thaw prevention of wellbore region in permafrost zone |
| CN107524459A (en) * | 2016-12-26 | 2017-12-29 | 北京城建集团有限责任公司 | A kind of Underground Subway Station vertical shaft and transverse passage-way freeze water sealing structure and method |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP6563343B2 (en) * | 2016-01-19 | 2019-08-21 | 東京電力ホールディングス株式会社 | Frozen soil impermeable walls |
| CN105908765B (en) * | 2016-06-16 | 2018-11-30 | 中铁工程设计咨询集团有限公司 | For protecting the open trench tunnel water sealing structure and construction method of groundwater environment |
| CN106401618A (en) * | 2016-09-30 | 2017-02-15 | 北京城建集团有限责任公司 | Basin-shaped freezing water-stop system for water-enriched sandy gravel stratum deep-buried metro station |
| CN108797641A (en) * | 2018-07-20 | 2018-11-13 | 中铁十八局集团有限公司 | A kind of structure and its construction method of Underground Subway Station construction period full station sealing |
| CN110685697A (en) * | 2019-09-28 | 2020-01-14 | 中铁九局集团第四工程有限公司 | Freezing construction method and freezing system for connection channel |
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Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| RU2170810C2 (en) * | 1999-05-13 | 2001-07-20 | ОАО "Газпром" | Method of thaw prevention of wellbore region in permafrost zone |
| CN107524459A (en) * | 2016-12-26 | 2017-12-29 | 北京城建集团有限责任公司 | A kind of Underground Subway Station vertical shaft and transverse passage-way freeze water sealing structure and method |
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