CN116290047A - A horizontally connected net-like dewatering construction method for deep foundation pits that can be automatically monitored - Google Patents

Abstract

The invention provides a deep foundation pit transverse connection type net-shaped dewatering construction method capable of being automatically monitored, which is improved in the traditional deep foundation pit dewatering method, a transverse water filtering pipeline is driven into a dewatering well and a range near a recharging well, coarse sand and stones are filled in the range near the pipe well and the transverse water filtering pipeline, water flows in the transverse pipeline, a good H-shaped dewatering recharging water circulation system is formed between the underground water and the dewatering well as between the underground water filtering pipeline and the recharging well, groundwater in the recharging well can be quickly conveyed into surrounding soil layers, the influence of consolidation of soil caused by the reduction of water content in the soil is reduced, and the stability of the soil is increased. In addition, the invention combines the connected net-shaped precipitation with the intelligent monitoring system, a plurality of water-sensitive sensors are arranged in the precipitation well and the recharging well water filter, a water level gauge is arranged in the observation well at the inner side and the outer side of the deep foundation pit, the water level condition is monitored in real time, and data is sent to a monitoring center for analysis and treatment, and the precipitation recharging control is carried out.

Description

A horizontally connected net-like dewatering construction method for deep foundation pits that can be automatically monitored

technical field

The invention belongs to the technical field of dewatering construction, and in particular relates to a horizontally connected mesh dewatering construction method for deep foundation pits that can be automatically monitored.

Background technique

With the development of my country's urban transportation construction, the construction of deep foundation pits in China continues to increase. In order to ensure the stability of groundwater resources and buildings around the foundation pit during construction, the amount of water pumped out around the foundation pit must be approximately the same as the amount of recharged water, so that the foundation pit The surrounding water level remains stable. Usually, excessive precipitation in the foundation pit will cause the settlement of the surrounding buildings and the consolidation of the soil, while excessive recharge will cause the surface to bulge. In the process of dewatering and recharging construction, there is a feedback time between recharging and dewatering, which is not conducive to maintaining the original balance of soil pressure. At the same time, when there is too much precipitation, the settlement of the soil around the foundation pit is large, which is not conducive to Soil stability.

In the existing precipitation construction methods, the precipitation recharge mainly depends on the monitoring feedback from the observation wells and surrounding sites, and there are the following problems: information lags, and too much dependence on the self-transmission of water in the soil when taking measures such as recharge, Near the dewatering well and the reinjection well, there is a phenomenon of too low and too high water level concentration, which makes the original water level of the soil layer fluctuate too much. Therefore, there are still a series of technical problems to be solved in the deep foundation pit dewatering construction. In this context, the present invention innovatively designs a horizontal connection dewatering construction method for deep foundation pit dewatering, which increases the water in the soil layer. The horizontal transmission makes the water level around the foundation pit closer to the original equilibrium state, enhances the stability of the soil, and can also automatically monitor the water level for early warning, making the management of the entire precipitation process more automated and intelligent.

Contents of the invention

Aiming at the deficiencies in the prior art, the present invention provides a horizontally connected network dewatering construction method for deep foundation pits that can be automatically monitored, which effectively solves the problem of the traditional dewatering construction method that relies too much on water in the soil when recharging. The concentration of water level is too low and too high near the precipitation well and the reinjection well caused by the self-transmission in the body.

The present invention achieves the above-mentioned technical purpose through the following technical means.

A method for automatic monitoring of deep foundation pit horizontally connected network dewatering construction method, including the following process:

Step 1: Deepen the design of the drawing; determine the position and quantity of each tube well, the position and angle of the horizontal water filter pipe;

Step 2: Measure and release the position; determine the position of each tube well on the construction site and mark it, determine the installation hole position of the horizontal water filter pipe on the construction site and mark it;

Step 3: According to the tube well position mark done in step 2, construct the hole for installing the well tube, install a water-sensitive sensor or a water level gauge in the well tube, and install a signal transmission device at the same time, and the signal transmission device is connected to the external monitoring center; Then use an iron plate to block the bottom of the well pipe, then lower the well pipe, backfill the filter material, and finally wash the well;

Step 4: According to the installation hole mark of the horizontal water filtration pipe made in step 2, drive the horizontal water filtration pipe to the vicinity of the dewatering well and the reinjection well, fill the horizontal water filtration pipe with water and sand, and then fill it with water in the horizontal water filtration pipe. The back end of the water pipe is sealed with cement slurry;

Step 5: Carry out the precipitation operation test, judge the precipitation effect, and carry out in-depth design of the precipitation construction plan;

Step 6: Seal the well.

Further, the specific process of the step 3 is:

Step 3.1: Drill into the hole;

According to the position mark of the tube well, use special drilling tools to drill the hole, the diameter of the hole is 800mm, one diameter to the bottom, the hole construction adopts natural slurry in the hole, and the mud density is controlled at 1.10 ~ 1.15g/cm ³ during the drilling process;

Step 3.2: cleaning the hole and changing the slurry;

After drilling to the design elevation, lift the drill pipe to 0.50m from the bottom of the hole before lifting the drill, punch the hole to remove impurities in the hole, and at the same time gradually adjust the mud density in the hole to 1.10g/cm ³ , the bottom of the hole The silt is less than 30cm, until there is no mud in the mud;

Step 3.3: downhole pipe;

First install a water-sensitive sensor at intervals of 800mm in the well pipes of dewatering wells and reinjection wells, and install signal transmission devices at the same time; install water level gauges in the well pipes of observation wells inside and outside deep foundation pits, and install signal transmission devices at the same time; The water level data transmitted by the signal transmission device is analyzed and processed. When the water level in the observation well is higher than the preset value, an instruction is sent to the wireless control switch of the recharging water pump, and the recharging water pump stops recharging; when the groundwater level around the deep foundation pit is low When it is at the preset value, send an instruction to the wireless control switch of the recharge pump, and the recharge pump starts to replenish water; otherwise, continue to monitor the groundwater level and recharge water volume inside and outside the deep foundation pit; then use an iron plate to seal the bottom of the well pipe, And the length of the lower plugging iron plate is not less than 6mm. After the plugging is completed, start running the well pipe into the corresponding hole;

Step 3.4: backfill filter material;

Step 3.5: Wash the wells.

Further, the specific process of step 4 is:

Step 4.1: Align the special bolter with the hole mark that has been set out and positioned in step 2, adjust the angle, and allow drilling after passing the acceptance;

Step 4.2: Reaming construction;

The high-pressure cement slurry that controls the high-pressure rotary drill bit of the drilling rig is sprayed outward from the bottom drill bit and the flank nozzles under the pressure of the high-pressure pump. During the spraying process, the surrounding soil or sand layer is cut synchronously. Push it forward gradually until it reaches the design depth and diameter, and obtain the casing hole for installing the horizontal water filter pipe;

Step 4.3: Fabrication and placement of horizontal water filtration pipes;

Wrap the free section of the horizontal water filtration pipeline with a plastic pipe, seal the mouth of the plastic pipe at the intersection with the bottom of the horizontal water filtration pipeline with waterproof tape, and transport it to the site; The two ends are limited and fixed to ensure that the horizontal filter pipe coincides with the axis of the drill pipe, and the front end of the horizontal filter pipe is embedded in the foundation pit support for a certain length, and the sealing hemp silk is embedded between the foundation pit support and the horizontal filter pipe. There is no gap, and ensure that the elevation H1 of the rear end of the horizontal filtering pipe is slightly higher than the elevation H2 of the groundwater level outside the foundation pit; location;

Step 4.4: Water and gravel filling;

After the horizontal water filtration pipe is drilled to a position 80-100mm away from the dewatering well and the filter of the recharge well, the matching water is poured into the horizontal water filtration pipe through high pressure to fill with water and sand. The fineness modulus of water sand is 3.0 Medium sand between ～2.3, with an average particle size of 0.5～0.35mm;

Step 4.5: cement slurry plugging;

Use cement slurry to block the horizontal water filter pipe within 1500mm from the edge of the foundation pit to prevent water from flowing back into the foundation pit; the cement slurry is made of 42.5 grade ordinary Portland cement, and the cement content is 350kg/m.

Further, the construction requirements of the borehole are as follows:

Do not disturb the surrounding strata when drilling;

The hole spacing error in the horizontal direction of the horizontal water filtering pipeline is not greater than 50mm, the error of the hole spacing in the vertical direction is not greater than 100mm, and the deviation at the bottom of the drilling hole is not greater than 3% of the diameter of the horizontal water filtering pipeline;

The depth of the bolt hole shall not be less than the design length of the horizontal water filter pipe, nor greater than 1% of the design length of the horizontal water filter pipe, and the diameter of the drilled hole shall not be less than the design aperture of the horizontal water filter pipe.

Further, the reaming construction requirements are as follows:

The hole expansion pressure of rotary spraying is 20-25MPa, and the lifting speed of rotary spraying is 10-15cm/min;

The raw material of the cement slurry used for hole reaming is sandstone with a fineness modulus of 3.7-3.1, a particle size greater than 0.5mm in the content of more than 50% of the total weight, and an average particle size of 1mm-0.5mm;

The length of the high-pressure pipe connecting the high-pressure injection pump and the rock bolter to transport the high-pressure injection liquid is not more than 50 meters;

Use the cement slurry reaming process, at least up and down reaming twice;

The high-pressure rotary drill bit of the drilling rig rotates evenly, lifts or sinks evenly, and performs high-pressure jet reaming from top to bottom or from bottom to top. The overlapping length of the jet tube for segmental lifting or sinking is not less than 100mm.

Further, in step 6, for the dewatering wells whose dewatering has been stopped before the bottom plate is poured, the well closure measures are as follows: before pouring the bottom plate, the top of the well pipe of the dewatering well is cut to the cushion surface, and the well pipe of the dewatering well is filled with sand or concrete dense, and then use steel plates to weld and seal the well pipe mouth of the dewatering well.

Further, in the step 6, for the reserved dewatering well, the post-casting belt of the main structure of the basement is closed and the well can be closed after meeting the anti-floating requirements. That is, fill the well pipe of the dewatering well below 1.0m at the bottom of the bottom plate with sand and gravel, and then pour micro-expanded concrete with a strength level higher than that of the bottom plate to 80mm below the top surface of the bottom plate of the foundation; after the internal sealing is completed, the well pipe of the dewatering well Cut off at 80mm below the top surface of the bottom plate, weld and seal it with a 20mm thick steel cover plate, and then pour concrete between the two inner water-stop rings and the water-stop steel plate; when the bottom plate steel bar meets the well pipe of the dewatering well, one end of it bends 250mm It is welded with the well pipe of the precipitation well, and the horizontal length of the other end is not less than 1m.

The present invention has following beneficial effect:

The present invention creatively proposes to realize the horizontal connection between the dewatering well and the reinjection well by setting horizontal water filtering pipes, control the high and low position deviation of the pipes by deepening the construction parameters, and fill the area near the pipe well and the horizontal water filtering pipes with coarse sand Optimize the particle size and ratio of sand and stone in the horizontal pipes, let the water flow in the horizontal pipes, and form a good "H" shape precipitation and recharge water cycle among the horizontal filter pipes, dewatering wells, and recharge wells The system can quickly transport the groundwater in the recharge well to the surrounding soil layer, reducing the impact of soil consolidation due to the reduction of water content in the soil; compared with the traditional precipitation recharge method, the settlement of the soil around the foundation pit When the amount is too large, the horizontal water filter pipe can quickly transfer water horizontally, which can more effectively reduce the impact of soil settlement.

In addition, the present invention combines the connected network dewatering with the intelligent monitoring system, and sets multiple water-sensitive sensors in the water filters of the dewatering wells and recharge wells, and sets water level gauges in the observation wells inside and outside the deep foundation pit. , can monitor the water level in real time, and send the data to the monitoring center for analysis and processing, and the monitoring center will issue instructions to the recharge water pump, making the whole precipitation process more intelligent and automatic; when the recharge amount exceeds the preset value, only need There is no need to increase the pumping volume in the dewatering well to stop recharging. When the water level of the dewatering well is naturally pumped down and the settlement begins to increase, the recharging will start. This setting is more sensitive to the lateral transfer of water and reduces When it is large, the pumping pressure of the dewatering well increases, and the risk of foundation pit surge is avoided.

Description of drawings

Figure 1 is a construction flow chart;

Figure 2 is a schematic diagram of the layout of the horizontal water filtering pipeline;

Figure 3 is a schematic diagram of the installation of the horizontal water filter pipeline;

Figure 4 is a schematic diagram of the closure construction of the dewatering well.

In the figure: 1-horizontal water filter pipe; 2-casing support; 3-drill pipe; 4-micro-expansion concrete; - Inner stop hydrofoil ring.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited thereto.

The automatic monitoring deep foundation pit horizontally connected mesh dewatering construction method of the present invention is shown in Figure 1, including the following process:

Step 1: Deepen the design of drawings;

Combined with engineering geological survey data, conduct overall precipitation analysis, design the location and quantity of each tube well in advance, prepare precipitation devices, strictly design the height of the receiving end of the horizontal water filtration pipeline 1 and the height of the transmitting end of the reinjection well, and accurately calculate the horizontal The position and angle of the water filter pipe 1 driven into the tube well, and the arrangement height of the water level sensor;

Among them, when the tube wells are set in the porous submerged layer, each tube well adopts a relief well; when the length of the tube well is longer and extends to other soil layers, each tube well adopts a relief well with both confined water decompression and the upper part. The mixed wells for diving and drying are arranged interspersedly. The dewatering wells, reinjection wells and observation wells in this embodiment are all set in the pore submerged layer, all of which are decompression wells.

Step 2: measuring and releasing points;

Measure the well position according to the layout plan of the tube well, and mark the well position after the completion of the well position measurement. If it is not easy to remove the debris or it is impossible to drill the well at the original well location due to other construction conditions, other measures should be taken, and the well location can be adjusted appropriately if necessary;

The wall of the foundation pit shall be trimmed and sprayed with anchors, and then according to the layout drawing of the horizontal water filtering pipeline 1 and the elevation and horizontal spacing required by the design, the hole position for the subsequent installation of the horizontal water filtering pipeline 1 shall be determined with a level gauge and a steel ruler, and then made. Good mark.

Step 3: tube well construction;

Step 3.1: Drill into the hole;

According to the well position mark determined in step 2, use special drilling tools to drill the hole, the diameter of the hole is 800mm, one diameter to the bottom, the upper part is drilled with light pressure and slow rotation, the drilling pressure is 15 ~ 35KN, and the speed is 20 ~ 50rpm, natural slurry in the hole is used in the hole forming construction, and the mud density is controlled at 1.10~1.15g/cm ³ during the drilling process. When the drilling tool is lifted or shut down, the hole must be filled with mud to prevent the hole wall from collapsing;

Step 3.2: cleaning the hole and changing the slurry;

After drilling to the design elevation, lift the drill pipe 3 to 0.50m from the bottom of the hole before lifting the drill, punch the hole to remove debris in the hole, and at the same time gradually adjust the mud density in the hole to 1.10g/cm ³ , the hole The bottom sedimentation is less than 30cm, until there is no mud in the mud, and the used mud is transported out of the site through the mud box for treatment;

Step 3.3: downhole pipe;

After the well pipe enters the site, first check whether the gap of the well pipe filter meets the design requirements, then measure the hole depth, and measure and record the well pipe one by one to ensure that the hole depth meets the subsequent installation of the well pipe;

Then install a water-sensitive sensor every 800mm in the well pipe of the dewatering well and the reinjection well, and install a signal transmission device at the same time for subsequent water level measurement; set a water level gauge in the well pipe of the observation well inside and outside the deep foundation pit, and install a signal Transmission device; in practical application, the water level gauge sends the detected water level data in the observation well to the monitoring center through the signal transmission device, and the monitoring center receives the transmission signal and analyzes and processes it; when the water level in the observation well is higher than the preset value, it sends an instruction to the wireless control switch of the recharging water pump, and the recharging water pump stops recharging; when the water level in the observation well is lower than the preset value, an instruction is sent to the wireless control switch of the recharging water pump, and the recharging water pump starts to replenish water; If there is fluctuation in the fixed monitoring area, continue to monitor the groundwater level and recharge water volume inside and outside the deep foundation pit;

Then use the iron plate to seal the bottom of the well pipe. In order to ensure the reliable sealing of the bottom of the well pipe, the length of the lower sealing iron plate should not be less than 6mm. In order to ensure that the well pipe is centered, a set of centralizers (straighteners) with a diameter less than 5cm in diameter are installed at the upper and lower ends of the well pipe. The centralizer adopts trapezoidal iron rings. on the same line;

Step 3.4: backfill filter material;

After the well pipe is lowered, the drill pipe 3 is run into the well pipe to 0.30m~0.50m from the bottom of the hole, and the mud is pumped into the well pipe through the drill pipe 3, and the slurry is gradually mixed while punching, so that the mud in the well pipe The well pipe overflows from the inside to the outside, and the slurry is returned in the annular gap formed between the well pipe and the hole wall, so that the mud density in the hole is gradually adjusted to 1.05g/cm ³ , the upper opening of the well pipe is sealed with a sealing head, and then a small pump is turned on Fill in the filter material according to the structural design requirements of the well, and measure the height of the filter material as it fills, until the filter material is backfilled to the predetermined position;

Step 3.5: washing the well;

Use an air compressor to wash the well. The well washing should be carried out from the top to the bottom of the well pipe to ensure that the water level in the well pipe should submerge the well cleaning head. The bottom settles until the water in the well pipe is clear and free of sand.

Step 4: Construction of the horizontal water filter pipeline 1;

Step 4.1: drilling construction;

Use a special rock bolt rig for drilling. Among them, the rock bolt rig uses a cemented carbide high-pressure rotary drill bit (nozzle head), and multiple nozzles are set on the side of the drill bit to facilitate the realization of high-pressure rotary drilling technology; Align the hole position marks that have been set out and positioned in step 2, adjust the angle, and then allow the drilling after the quality inspector passes the inspection;

And drilling construction must meet the following construction requirements:

Do not disturb the surrounding strata when drilling;

The hole spacing error in the horizontal direction of the horizontal water filtering pipeline 1 is not greater than 50mm, the hole spacing error in the vertical direction is not greater than 100mm, and the deviation at the bottom of the borehole is not greater than 3% of the diameter of the horizontal water filtering pipeline;

The depth of the bolt hole should not be less than the design length of the horizontal water filtering pipeline 1, nor should it be greater than 1% of the design length of the horizontal water filtering pipeline 1, and the borehole diameter should not be less than the designed aperture of the horizontal water filtering pipeline 1;

Step 4.2: Reaming construction;

The high-pressure cement slurry that controls the high-pressure rotary drill bit (sprinkler) of the rock bolter is sprayed outward from the bottom drill bit and the side nozzles under the pressure of the high-pressure pump. During the spraying process, the surrounding soil or sand layer is simultaneously cut, and the high-pressure rotation The drill bit (sprinkler head) and the side wing nozzles are gradually pushed forward under the driving force until they reach the design depth and diameter, and the casing hole (ie, the horizontal water filter pipe installation hole) is obtained;

The above-mentioned reaming construction shall meet the following construction requirements:

The hole expansion pressure of rotary spraying is 20-25MPa, and the lifting speed of rotary spraying is 10-15cm/min;

The raw material of the cement slurry used for hole reaming is sandstone with a fineness modulus of 3.7-3.1, a particle size greater than 0.5mm in the content of more than 50% of the total weight, and an average particle size of 1mm-0.5mm;

The length of the high-pressure pipe connecting the high-pressure injection pump and the bolter to transport the high-pressure injection liquid should not be greater than 50 meters;

When using the cement slurry reaming process, the reaming should be done at least twice up and down;

The high-pressure rotary drill bit (spray head) should rotate evenly, lift or sink evenly, carry out high-pressure jet reaming from top to bottom or from bottom to top, and the overlapping length of the jet tube's segmental lifting or sinking should not be less than 100mm;

The cement slurry should be mixed evenly and used as it is mixed, and the cement slurry mixed at one time should be used up before the initial setting;

Step 4.3: Fabrication and placement of the horizontal water filtration pipeline 1;

The horizontal water filtering pipe 1 is blanked strictly according to the design size, and its surface is provided with a number of water filtering holes. The mouth of the plastic pipe is sealed with waterproof tape; at the construction site, a special perforated casing bracket 2 is used to limit and fix the two ends of the horizontal water filter pipe 1 to ensure that the axis of the horizontal water filter pipe 1 coincides with the axis of the drill pipe 3, and the horizontal The front end of the water filter pipe 1 is embedded in the foundation pit support for a certain length, and there is no gap between the foundation pit support and the horizontal water filter pipe 1, and the rear end elevation H1 of the horizontal water filter pipe 1 is slightly higher than that of the foundation pit. Outside groundwater level elevation H2;

Then the drill pipe 3 of the drilling rig enters from the rear end of the horizontal water filtering pipe 1, and continuously drives the horizontal water filtering pipe 1 to drill into the designed position. During the drilling process, based on the principle of differential pressure balance, due to The end elevation H1 is slightly higher than the groundwater level H2 outside the foundation pit, so the sand outside the foundation pit will not flow into the foundation pit due to the construction of horizontal casing holes;

Step 4.4: Water and gravel filling;

After the horizontal water filter pipe 1 is drilled to a position 80-100 mm away from the dewatering well and the filter of the reinjection well, the matching water is poured into the horizontal water filter pipe 1 through high pressure to fill with water and sand. The medium sand with a modulus between 3.0 and 2.3 has an average particle size of 0.5 to 0.35 mm.

Step 4.5: cement slurry plugging;

At the rear end of the horizontal water filter pipe 1, that is, cement slurry is used to block the horizontal water filter pipe 1 within 1500mm from the edge of the foundation pit to prevent water from flowing back into the foundation pit and affect the subsequent construction in the foundation pit; The slurry is made of 42.5 grade ordinary Portland cement, and the amount of cement added is 350kg/m. The cement slurry should be used as it is stirred and used up before initial setting. Circulating grouting system for 1 to 2 minutes to ensure that the grout is unblocked during grouting. After the same batch of horizontal filter pipes 1 are grouted and blocked, the grouting pipes of the circulating grouting system should be cleaned in time.

Step 5: Precipitation operation;

Step 5.1: Observing the initial water level;

Within one week before the test, the initial groundwater level was accurately measured according to the water-sensitive sensors in the dewatering well and the reinjection well, including the initial confined water level inside and outside the foundation pit, and the observations were made 1 or 2 times a day. If it is the same, record it as the initial water level, or take the average value of the two observation data as the initial water level; in addition, within one week before the test, the initial value of the adjacent ground settlement around the foundation pit should also be measured;

Step 5.2: pumping test;

Select the well points of the foundation pit to carry out the pumping test of the draining well and the decompression well respectively to verify the water-proof effect of the enclosure structure, check the water output and the permeability of the soil layer, and analyze and judge the effect of precipitation according to the data of the water output. Based on this, the scheme is modified and improved; specifically, detailed hydrogeological data such as the initial water level, permeability coefficient, and influence radius of the confined aquifer are determined through the pumping test, and the pumping test data is analyzed and corresponding curves are drawn. Test the scientific rationality of the precipitation plan, further evaluate the surrounding environment through pumping tests, adjust the number and structure of precipitation wells as needed, and carry out in-depth design of the precipitation plan;

During the pumping test, observe the water level drop of the observation well inside and outside the foundation pit. The observation frequency is as follows: 1h, 2h, 4h, 8h, 20h, 32h, 44h... The later observation time interval is taken as 12h or 12h according to the water level drop. 24h, until the water level tends to be stable or drops to 1m below the basement. During the pumping test, select 2 to 5 pumping wells to install water meters to observe the changes in the water volume in the pumping wells. The frequency of observation is the same as that of the observation wells;

Step 5.3: Water level recovery observation;

After pumping, observe the recovery of the water level of the observation well inside and outside the foundation pit, analyze the recovery speed of the water level, and provide reference for the backup power configuration during the later dewatering operation. 20h, 32h, 44h... until the water level stabilizes or recovers slowly.

Step 6: sealing the well;

For the dewatering wells that have stopped dewatering before the bottom plate 6 is poured, the well closure measures are:

After the design is approved, the top of the well pipe 5 of the dewatering well is cut to the surface of the cushion layer 7 before the bottom plate 6 is poured, and the well pipe 5 of the dewatering well is filled with sand or concrete, and then the mouth of the well pipe 5 of the dewatering well is welded and closed with a steel plate .

For reserved tube wells, i.e. reserved dewatering wells, the well closure measures are as follows:

After the main structure of the basement is closed, the well can only be closed after the anti-floating requirements are met; before the floor 6 is poured, the inside of the well pipe 5 of the dewatering well is internally sealed, that is, the well pipe 5 of the dewatering well below 1.0m below the bottom of the bottom plate 6 is used Fill with sand and gravel, and then pour micro-expansion concrete 4 with a strength level higher than that of the bottom slab to 80mm below the top surface of the foundation bottom slab 6; after the internal sealing is completed, the well pipe 5 of the dewatering well is cut off at 80mm below the top surface of the bottom slab 6, And use 20mm thick steel cover plate 8 to weld and seal, and then pour concrete between the two inner water-stop rings 9 and the water-stop steel plate (reserved for post-pouring belt); 250mm is welded with the well pipe 5 of the dewatering well, and the horizontal length of the other end is not less than 1m.

The described embodiment is a preferred implementation of the present invention, but the present invention is not limited to the above-mentioned implementation, without departing from the essence of the present invention, any obvious improvement, replacement or modification that those skilled in the art can make Modifications all belong to the protection scope of the present invention.

Claims (7)

1. The deep foundation pit transverse connection type net-shaped precipitation construction method capable of being automatically monitored is characterized by comprising the following steps of:

step 1: deep design of drawings; determining the positions and the number of all the pipe wells and the driving positions and angles of the transverse water filtering pipes (1);

step 2: measuring and placing the point positions; determining the positions of all pipe wells on a construction site and marking, and determining the mounting hole positions of a transverse water filtering pipeline (1) on the construction site and marking;

step 3: constructing a hole for installing a well pipe according to the pipe well position mark manufactured in the step 2, arranging a water sensitive sensor or a water level gauge in the well pipe, and simultaneously arranging a signal transmission device which is connected with an external monitoring center; then plugging the bottom of the well pipe by using an iron plate, then lowering the well pipe, backfilling filter materials, and finally flushing the well;

step 4: according to the mark of the mounting hole position of the transverse water filtering pipeline (1) manufactured in the step 2, the transverse water filtering pipeline (1) is driven to the vicinity of a dewatering well and a recharging well, water and sand are filled into the transverse water filtering pipeline (1), and then the rear end of the transverse water filtering pipeline (1) is plugged by cement paste;

step 5: performing a precipitation operation test, judging the precipitation effect, and performing deepening design on a precipitation construction scheme;

step 6: and (5) sealing the well.

2. The method for automatically monitoring the cross-connection type net-shaped precipitation construction of the deep foundation pit according to claim 1, wherein the specific process of the step 3 is as follows:

step 3.1: drilling a hole;

drilling a hole by using a special drilling tool according to the position mark of the pipe well, wherein the diameter of the hole is 800mm, the diameter is equal to the bottom, the hole is formed by adopting natural slurry in the hole, and the slurry density is controlled to be 1.10-1.15 g/cm in the drilling process ³ ；

Step 3.2: cleaning holes and changing slurry;

after drilling to the designed elevation, the drill rod (3) is lifted to 0.50m from the bottom of the hole before lifting the drill, punching is carried out to remove sundries in the hole, and meanwhile, the slurry density in the hole is adjusted to 1.10g/cm step by step ³ The sediment of the hole bottom is less than 30cm until mud blocks are not contained in the mud;

step 3.3: setting a well pipe;

firstly, arranging a water-sensitive sensor in each of a dewatering well and a recharging well pipe at an interval of 800mm, simultaneously arranging a signal transmission device, arranging a water level gauge in a well pipe of a deep foundation pit inside and outside observation well, and simultaneously arranging the signal transmission device; the monitoring center receives the water level data transmitted by the signal transmission device and analyzes and processes the water level data, and when the water level in the observation well is higher than a preset value, an instruction is sent to a wireless control switch of the recharging water pump, and the recharging water pump stops recharging; when the underground water level around the deep foundation pit is lower than a preset value, sending an instruction to a wireless control switch of a recharging water pump, and starting the recharging water pump to supplement water; otherwise, continuously monitoring the underground water level and the recharging water quantity inside and outside the deep foundation pit; then, plugging the bottom of the well pipe by using an iron plate, wherein the length of the iron plate plugged at the lower part is not less than 6mm, and after plugging is completed, beginning to blow the well pipe into a corresponding hole;

step 3.4: backfilling the filter material;

step 3.5: and (5) flushing the well.

3. The method for automatically monitoring the cross-connection type net-shaped precipitation construction of the deep foundation pit according to claim 1, wherein the specific process of the step 4 is as follows:

step 4.1: aiming the special jumbolter at the well-positioned hole site marks which are paid out in the step 2, and adjusting the angle to drill;

step 4.2: reaming construction;

the high-pressure cement slurry of the high-pressure rotary drill bit of the drilling machine is controlled to be sprayed outwards from the bottom drill bit and the side wing nozzles under the pressure action of the high-pressure pump, soil or sand layers on the periphery are cut synchronously in the spraying process, and the high-pressure rotary drill bit and the side wing nozzles are pushed forward gradually under the power pushing until reaching the designed depth and diameter, so that a sleeve hole for installing a transverse water filtering pipeline (1) is obtained;

step 4.3: manufacturing and placing a transverse filtering pipeline (1);

wrapping the free section of the transverse water filtering pipeline (1) by a plastic pipe, sealing the pipe orifice of the plastic pipe at the intersection with the bottom of the transverse water filtering pipeline (1) by a waterproof adhesive tape, and transporting to the site; then, limiting and fixing two ends of a transverse water filtering pipeline (1) by adopting a special sleeve bracket (2) with holes on a construction site, ensuring that the axis of the transverse water filtering pipeline (1) coincides with that of a drill rod (3), embedding the front end of the transverse water filtering pipeline (1) into a foundation pit support for a certain length, embedding sealing hemp threads between the foundation pit support and the transverse water filtering pipeline (1) and ensuring that the elevation of the rear end of the transverse water filtering pipeline (1) is higher than that of the underground water level outside the foundation pit; then, a drill rod (3) of the drilling machine enters from the rear end of the transverse water filtering pipeline (1) and continuously drives the transverse water filtering pipeline (1) to drill to a designed position;

step 4.4: filling water and sand stone;

when the transverse filtering water pipeline (1) is driven to a position 80-100 mm away from the dewatering well and recharging well filters, water is matched with the transverse filtering water pipeline (1) to be filled with water sand, wherein the water sand is middle sand with fineness modulus of 3.0-2.3 and average grain diameter of 0.5-0.35 mm;

step 4.5: plugging cement paste;

cement slurry is adopted to block a transverse water filtering pipeline (1) within 1500mm from the edge of the foundation pit, so that water is prevented from flowing into the foundation pit; the cement slurry adopts 42.5-grade ordinary Portland cement, and the cement mixing amount is 350kg/m.

4. The automatic monitoring deep foundation pit transverse connection type net-shaped precipitation construction method according to claim 3, wherein the drilling construction requirements are as follows:

surrounding formations must not be disturbed while drilling;

the horizontal hole pitch error of the transverse water filtering pipeline (1) is not more than 50mm, the vertical hole pitch error is not more than 100mm, and the deflection size of the bottom of the drilled hole is not more than 3% of the diameter of the transverse water filtering pipeline;

the depth of the anchor rod drilling hole is not smaller than the design length of the transverse water filtering pipeline (1), and is not larger than 1% of the design length of the transverse water filtering pipeline (1), and the aperture of the drilling hole is not smaller than the design aperture of the transverse water filtering pipeline (1).

5. The automatic monitoring deep foundation pit transverse connection type net-shaped precipitation construction method according to claim 3, wherein the reaming construction requirements are as follows:

the pressure of the rotary jet reaming is 20-25 MPa, and the lifting speed of the rotary jet reaming is 10-15 cm/min;

coarse sand with fineness modulus of 3.7-3.1, particle content greater than 0.5mm and particle size of more than 50% of total weight and average particle size of 1-0.5 mm is adopted as cement slurry raw material for reaming;

the length of a high-pressure pipe for conveying high-pressure injection liquid, which is connected with the high-pressure injection pump and the jumbolter, is not more than 50 meters;

adopting a cement slurry reaming process to ream at least twice in a reciprocating way;

the high-pressure rotary drill bit of the drilling machine uniformly rotates, uniformly lifts or sinks, performs high-pressure jet reaming from top to bottom or from bottom to top, and the lap joint length of the jet pipe section lifting or sinking is not less than 100mm.

6. The method for constructing the cross-connection type net-shaped dewatering of the deep foundation pit capable of being automatically monitored according to claim 1, wherein in the step 6, for the dewatering well in which the dewatering is stopped before the bottom plate (6) is poured, the well sealing measures are as follows: cutting the top of the dewatering well pipe (5) to the surface of the cushion layer (7) before pouring the bottom plate (6), tightly filling sand stone or concrete in the dewatering well pipe (5), and then welding and sealing the pipe orifice of the dewatering well pipe (5) by adopting a steel plate.

7. The method for automatically monitoring the cross-connection type net-shaped dewatering construction of the deep foundation pit according to claim 1, wherein in the step 6, for the reserved dewatering well, the post-pouring zone of the main structure of the basement is closed and the rear side meeting the anti-floating requirement can be sealed, and the well sealing measures are as follows: before the bottom plate (6) is poured, the interior of the dewatering well pipe (5) is firstly sealed, namely sand and stone are filled in the dewatering well pipe (5) below 1.0m at the bottom of the bottom plate (6), and then micro-expansion concrete (4) with a strength level higher than that of the bottom plate concrete is poured to a position 80mm below the top surface of the foundation bottom plate (6); after the inner sealing is finished, the dewatering well pipe (5) is cut off at the position 80mm below the top surface of the bottom plate (6), a 20mm thick steel cover plate (8) is adopted for welding and sealing, and then concrete is poured between the two inner water stop wing rings (9) and the water stop steel plate; when the bottom plate steel bar meets the dewatering well pipe (5), one end of the bottom plate steel bar is bent for 250mm and welded with the dewatering well pipe (5), and the horizontal length of the other end is not less than 1m.

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