Water-rich thick sand layer subway station hole pile method construction precipitation method

Abstract

The invention provides a water-rich thick sand layer subway station hole-pile method construction precipitation method which comprises the following steps: (1) precipitation scheme design: determining precipitation well design parameters, designing a precipitation influence radius, designing a foundation pit precipitation total water inflow and designing the number of precipitation wells; (2) determining a dewatering structure form, installing a deep well pump in a dewatering well, and then dewatering through drainage; according to the tube well dewatering construction method, tube well dewatering is adopted, the underground water level and the water yield of a single tube well are overall stable after dewatering, the purpose of dewatering is achieved, practice proves that the dewatering scheme is reasonable, influences on surrounding buildings (structures) are small, and construction safety is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of subway tunnel construction, in particular to a method for dewatering a subway station in a water-rich thick sand layer using a hole pile method. Background Art

[0002] In order to prevent quicksand and pipe bursts during the excavation of subway foundation pits and ensure the dryness of the foundation pit during the excavation process and the construction of underground structures, it is usually necessary to lower the groundwater level to 0.5 to 1.5 meters below the base. In order to prevent collapse and control excessive surface settlement during the construction of subway tunnels, protect the normal use of adjacent buildings and underground pipelines, and ensure construction safety, water reduction and blocking treatment is generally required during the construction process. The methods for controlling the groundwater level mainly include water interception and precipitation. The two methods can be used alone or in combination. Both methods have their own advantages and disadvantages. The cost of using precipitation may be lower than that of water interception. Precipitation can improve the stability of slopes and surrounding rocks, but precipitation lasts for a long time. If precipitation cannot be used due to complex geological conditions or restrictions on construction conditions, only water interception and seepage isolation treatment can be carried out. Summary of the invention

[0003] The technical problem solved by the present invention is to provide a method for dewatering a subway station in a water-rich thick sand layer by the pile method, so as to solve the problems raised in the above-mentioned background technology.

[0004] The technical problem solved by the present invention is achieved by adopting the following technical scheme: a method for dewatering a subway station in a water-rich thick sand layer by using a pile method, comprising:

[0005] (1) Design of dewatering scheme, including: determination of dewatering well design parameters, dewatering influence radius design, total water inflow design of foundation pit dewatering, and dewatering well quantity design;

[0006] (2) Determine the precipitation structure form, install a deep well pump in the precipitation well and then drain the water;

[0007] (3) Pipe well dewatering construction, which includes the following steps

[0008] Step (1) measuring and setting out the well positions, and setting out the well positions according to the auxiliary channels and the designed plan layout of the dewatering well positions;

[0009] Step (2) drilling, after determining the location of the precipitation well, pipeline detection is carried out, first by manual excavation, and then by using a manual Luoyang shovel to perform pipeline detection;

[0010] Step (3) Install the drilling rig. The rig should be installed horizontally and stably, with the drill rod, drill bit and the center of the hole forming a vertical line.

[0011] Step (4) drilling into a hole;

[0012] Step (5) lowering the pipe well;

[0013] Step (6) Install the pump and conduct a test pumping. After the well construction is completed, the submersible pump should be lowered in time, the drainage pipes should be laid, the cables should be connected, etc. Once the pumping and drainage systems are installed, pumping can begin 10 days before excavation of the vertical shaft and horizontal channel.

[0014] Furthermore, the calculation formula of the precipitation impact radius of the precipitation impact radius design is as follows:

[0015]

[0016] Where R is the precipitation impact radius; S w is the water level drop of the precipitation well, m; K is the permeability coefficient of the aquifer, m / day; H is the thickness of the phreatic aquifer.

[0017] Furthermore, the calculation formula for the total water inflow of foundation pit dewatering designed is as follows:

[0018]

[0019] Where Q is the total water inflow from foundation pit dewatering, m 3 / day; S d is the designed drawdown of groundwater level in foundation pit, m; r0 is the equivalent radius of foundation pit, m.

[0020] Furthermore, the calculation formula for the number of precipitation wells required for the precipitation well quantity design is as follows:

[0021]

[0022] Where q is the design flow rate of a single well, m / day; n is the number of precipitation wells.

[0023] Furthermore, the drainage well has a diameter of 800mm, a depth of 40m, a spacing of 8m, and a center distance of 3m from the structure edge line, arranged along the periphery of the proposed building (structure). The pipe well uses a 400mm sandless concrete pipe with a porosity of 25% to 30%. The filter pipe is wrapped with a layer of 80-mesh nylon mesh. The filter material uses 3-7mm gravel to fill the outer periphery of the pipe well, and the bottom of the hole is sealed with a bottom support.

[0024] Furthermore, the deep well pump is a submersible pump with a pumping capacity of 45m / h and a head greater than 45m.

[0025] Furthermore, the precipitation well drainage adopts the method of burying drainage pipes in the ground groove of 600mm×900mm (width×depth), with a pipe diameter of 150mm. In order to prevent the drainage pipes from being crushed by passing vehicles on the road, the drainage pipes on site are buried at a depth of not less than 20cm. After the burial is completed, the ground is restored with concrete and asphalt; the groundwater pumped out from the pipe wells inside and outside the site is collected into the tertiary sedimentation tank through the drainage pipe, and after purification, it is collected into the municipal rainwater pipe network for discharge.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The tunnel pile method for subway station dewatering in the water-rich thick sand layer in this area adopted pipe well dewatering. After dewatering, the groundwater level and the water output of a single pipe well were generally stable, achieving the purpose of dewatering. Practice has proved that the dewatering scheme is reasonable and provides a reference for tunnel pile method dewatering construction in similar water-rich thick sandy strata.

[0028] (2) The construction process of pipe well dewatering includes measuring and placing the well site, exploring the borehole, installing the drilling rig, drilling the hole, lowering the pipe well, and installing the pump for trial pumping. The pipe well dewatering process must be strictly followed, and quality and safety must be strictly controlled at every link.

[0029] (3) The monitoring results show that the dewatering scheme of ground pipe well dewatering supplemented by open drainage can achieve a good effect of pumping out water and stopping water, and has little impact on surrounding buildings (structures), ensuring construction safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the pipe well drainage pipe of the present invention.

[0031] Figure 2 It is the underground water level variation curve of the vertical shaft of the present invention.

[0032] Figure 3 This is a curve diagram for monitoring the surface settlement of the vertical shaft of the present invention.

[0033] Figure 4 This is a gas pipeline surface subsidence monitoring curve diagram of the present invention.

[0034] Figure 5 It is a monitoring curve diagram of ground settlement of surrounding buildings according to the present invention.

[0035] Figure 6 It is a schematic diagram of the single-day settlement deformation of the vertical shaft of the present invention.

[0036] Figure 7 It is a schematic diagram of the daily settlement deformation of the gas pipeline of the present invention.

[0037] Figure 8 It is a schematic diagram of the single-day settlement deformation of surrounding buildings according to the present invention. DETAILED DESCRIPTION

[0038] In order to make the technical means for realizing the present invention, the creative features, the objectives and effects to be achieved easy to understand, the present invention is further explained below in conjunction with specific diagrams. In the description of the present invention, it should be noted that, unless otherwise clearly stipulated and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense. For example, it can be a fixed connection or a detachable connection, or an integral connection can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be internal communication between two elements.

[0039] like Figures 1 to 8 As shown in the figure, the dewatering method for the tunnel pile method of subway station in water-rich thick sand layer includes:

[0040] (1) Design of dewatering scheme, including: dewatering well design parameters, dewatering influence radius design, total water inflow design of foundation pit dewatering, and dewatering well quantity design

[0041] Design parameters of precipitation wells

[0042] According to the commonly used dewatering methods for subway projects in Xi'an and the analysis of the impact of groundwater on station construction, a ground pipe well dewatering scheme is adopted for the groundwater that affects the construction of the station, supplemented by open drainage and water stopping measures. The design parameters of the dewatering well are shown in Table 1.

[0043] Table 3.3-1 Design parameters of dewatering wells

[0044]

[0045]

[0046] Design of precipitation impact radius

[0047] The calculation formula of precipitation impact radius is as follows:

[0048]

[0049] In formula (1), R is the precipitation influence radius;

[0050] S w is the depth of water level drop in the precipitation well, m;

[0051] K is the permeability coefficient of the aquifer, m / day;

[0052] H is the thickness of the unconfined aquifer.

[0053] According to the formula, the precipitation impact radius of the project is 849.706m.

[0054] Design of total water inflow from foundation pit dewatering

[0055] The calculation formula for the total water inflow from foundation pit dewatering is as follows:

[0056]

[0057] In formula (2), Q is the total water inflow of foundation pit dewatering, m 3 / sky;

[0058] S d is the design drawdown of the groundwater level in the foundation pit, m;

[0059] r0 is the equivalent radius of the foundation pit, m.

[0060] Design of number of precipitation wells

[0061] The formula for calculating the number of precipitation wells required is as follows:

[0062]

[0063] In formula (3), q is the design flow rate of a single well, m / day;

[0064] n is the number of precipitation wells.

[0065] According to the above calculations, a total of 84 precipitation wells are arranged on site to meet precipitation needs, and 16 water level observation holes are set up around the site, and the depth of the observation holes is not less than 3m below the design water level.

[0066] Precipitation structure

[0067] Precipitation well

[0068] The diameter of the precipitation well is 800mm, the depth is 40m, the spacing is 8m, the center of the precipitation well is 3m away from the structure edge, and it is arranged along the periphery of the proposed building (structure). The pipe well uses a 400mm sandless concrete pipe with a porosity of 25% to 30%. The filter pipe is wrapped with a layer of 80-mesh nylon mesh. The filter material is 3-7mm gravel filled into the outer periphery of the pipe well, and the bottom of the hole is sealed with a bottom support.

[0069] Deep well pump

[0070] A deep well pump is a water-lifting machine that is directly connected to a motor and a water pump and works in the water. It is suitable for extracting groundwater from deep wells. The biggest feature of a deep well pump is that the motor and the pump are made into one piece. It is a pump that is immersed in a groundwater well to suck and transport water. It is widely used in farmland irrigation and drainage, industrial and mining enterprises, urban water supply and drainage, and sewage treatment. Since the motor is also submerged in water, the structural requirements for the motor are more special than those for general motors. The structural forms of the motor are divided into four types: dry type, semi-dry type, oil-filled type, and wet type.

[0071] This project uses a submersible pump with a pumping capacity of 45m / h and a head greater than 45m.

[0072] drain

[0073] In order to prevent the drainage ditch from leaking during the drainage process and affecting the construction, the drainage wells are buried in the ground with a groove of 600mm×900mm (width×depth), and the pipe diameter is 150mm. In order to prevent the drainage pipes from being crushed by vehicles passing by on the road, the depth of the drainage pipes on site is not less than 20cm. After the burial, the ground is restored with concrete and asphalt. The groundwater pumped from the pipe wells inside and outside the site is collected into the three-level sedimentation tank through the drainage pipes, and after purification, it is collected into the municipal rainwater pipe network for drainage. Figure 1 shown.

[0074] Construction technology of pipe well dewatering

[0075] (1) Survey and lay out the well locations. The well locations are laid out according to the auxiliary channels and the designed plan layout of the drainage well locations.

[0076] (2) Exploration hole. After the location of the precipitation well is determined, pipeline detection is carried out. First, 2m of manual excavation is carried out, and then 6m of pipeline detection is carried out using a manual Luoyang shovel. The total detection depth is 8m.

[0077] (3) Install the drilling rig. The machine should be installed horizontally and stably, with the drill rod, drill bit and the center of the hole forming a vertical line.

[0078] (4) Drilling. The diameter of the drainage well hole is 800mm. When the drilling construction reaches the designed depth of 40m, it is advisable to drill 0.3-0.5m more. The sand layer in this project is mainly located at 6.1-20.3m and 33-37.8m below the ground. During drilling, observation should be strengthened and 0.5%-0.8% drilling fluid should be added as required to increase the viscosity of the mud (the method of measuring the viscosity of the mud is to measure the viscosity of the solution to about 28s using an engineering funnel).

[0079] (5) Pipe well. Before lowering the pipe, ensure that the thickness of the sediment at the bottom of the well is no more than 20 cm before lowering the filter pipe. The pipe well connection must be firm and vertical, and tied with 4 bamboo strips and No. 10 double iron wire; the inner wall of the pipe mouth should not be misaligned, and a layer of 80-mesh nylon net should be wrapped around the outside of the pipe well to prevent the surrounding soil from entering the precipitation well.

[0080] (6) Install the pump and test pumping. After the well construction is completed, the submersible pump should be put in in time, the drainage pipes should be laid, the cables should be connected, etc. Once the pumping and drainage systems are installed, pumping can begin 10 days before the excavation of the vertical shaft and horizontal channel.

[0081] The monitoring contents include ground subsidence, groundwater level, pipeline monitoring, and above the pipeline; from the vertical shaft groundwater level change curve, it can be seen that with the progress of the precipitation project, the groundwater levels of the three vertical shafts gradually decreased and finally tended to stabilize, indicating that the precipitation scheme can better meet the requirements of engineering precipitation and achieve good precipitation effects.

[0082] From the deformation monitoring curve of each monitoring point, it can be seen from the ground subsidence monitoring curve of the vertical shaft, gas pipeline and surrounding buildings that during the construction of the precipitation project, the buildings around the foundation pit, underground pipelines, etc. were not affected by the precipitation construction and were always in a relatively stable state.

[0083] from Figure 3-8 It can be seen that during the monitoring period, the maximum daily settlement of the shaft was 1.6mm, and the maximum daily settlement of the surrounding buildings was 1mm, both within the warning range of daily settlement ±3mm; the maximum daily settlement of the gas pipeline was 1.2mm, which did not exceed the limit of daily deformation of no more than 2mm. This shows that the precipitation scheme can effectively control the settlement and deformation of surrounding buildings (structures) while meeting the precipitation requirements, thereby ensuring construction safety.

[0084] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for dewatering a subway station in a water-rich thick sand layer by means of a pile method, characterized in that: include: (1) Design of dewatering scheme, including: determination of dewatering well design parameters, dewatering influence radius design, total water inflow design of foundation pit dewatering, and dewatering well quantity design; (2) Determine the precipitation structure form, install a deep well pump in the precipitation well and then drain the water; (3) Pipe well dewatering construction, which includes the following steps Step (1) measuring and setting out the well positions, and setting out the well positions according to the auxiliary channels and the designed plan layout of the dewatering well positions; Step (2) drilling, after determining the location of the precipitation well, pipeline detection is carried out, first by manual excavation, and then by using a manual Luoyang shovel to perform pipeline detection; Step (3) Install the drilling rig. The rig should be installed horizontally and stably, with the drill rod, drill bit and the center of the hole forming a vertical line. Step (4) drilling into a hole; Step (5) lowering the pipe well; Step (6) Install the pump and conduct a test pumping. After the well construction is completed, the submersible pump should be lowered in time, the drainage pipes should be laid, the cables should be connected, etc. Once the pumping and drainage systems are installed, pumping can begin 10 days before excavation of the vertical shaft and horizontal channel.

2. The method for dewatering a subway station in a water-rich thick sand layer by using a pile method according to claim 1, characterized in that: The calculation formula of the precipitation influence radius of the precipitation influence radius design is as follows: Where R is the precipitation impact radius; S w is the water level drop of the precipitation well, m; K is the permeability coefficient of the aquifer, m / day; H is the thickness of the phreatic aquifer.

3. The method for dewatering a subway station in a water-rich thick sand layer by using a pile method according to claim 1, characterized in that: The calculation formula for the total water inflow of foundation pit dewatering designed is as follows: Where Q is the total water inflow from foundation pit dewatering, m 3 / day; S d is the designed drawdown of groundwater level in foundation pit, m; r0 is the equivalent radius of foundation pit, m.

4. The method for dewatering a subway station in a water-rich thick sand layer by using a pile method according to claim 1, characterized in that: The calculation formula for the number of precipitation wells required for the precipitation well quantity design is as follows: Where q is the design flow rate of a single well, m / day; n is the number of precipitation wells.

5. The method for dewatering a subway station in a water-rich thick sand layer by using a pile method according to claim 1, characterized in that: The drainage well has a diameter of 800mm, a depth of 40m, a spacing of 8m, and a center of the drainage well is 3m away from the structural edge line, and is arranged along the periphery of the proposed building (structure); the pipe well adopts a medium 400mm sandless concrete pipe with a porosity of 25% to 30%. The filter pipe is wrapped with a layer of 80-mesh nylon mesh. The filter material is 3 to 7mm gravel filled into the outer periphery of the pipe well, and the bottom of the hole is sealed with a bottom support.

6. The method for dewatering a subway station in a water-rich thick sand layer by using a pile method according to claim 1, characterized in that: The deep well pump is a submersible pump with a pumping capacity of 45m / h and a head greater than 45m.

7. The method for dewatering a subway station in a water-rich thick sand layer by using a pile method according to claim 1, characterized in that: The drainage of the precipitation well adopts the method of burying drainage pipes in the ground groove of 600mm×900mm (width×depth), with a pipe diameter of 150mm. In order to prevent the drainage pipes from being crushed by passing vehicles on the road, the drainage pipes on site are buried at a depth of not less than 20cm. After the burial is completed, the ground is restored with concrete and asphalt; the groundwater pumped out from the pipe wells inside and outside the site is collected into the tertiary sedimentation tank through the drainage pipe, and after purification, it is collected into the municipal rainwater pipe network for discharge.

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