CN116290047B - Automatic-monitoring deep foundation pit transverse connection type net-shaped precipitation construction method - Google Patents
Automatic-monitoring deep foundation pit transverse connection type net-shaped precipitation construction method Download PDFInfo
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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
Technical Field
The invention belongs to the technical field of precipitation construction, and particularly relates to a deep foundation pit transverse connection type net-shaped precipitation construction method capable of automatically monitoring.
Background
With the development of urban traffic construction in China, the construction of domestic deep foundation pits is continuously increased, and in the construction, in order to ensure the stability of underground water resources and buildings around the foundation pits, the water quantity pumped out around the foundation pits is required to be approximately the same as the recharging water quantity, so that the water level around the foundation pits is kept stable. In general, excessive dewatering of the foundation pit can cause settlement of surrounding buildings and consolidation of soil, and excessive recharging can cause surface protrusion. In precipitation and recharging construction process, there is feedback time between recharging and the precipitation, is unfavorable for soil layer pressure to maintain original equilibrium state, simultaneously, when the precipitation is too much, the soil layer settlement volume around the foundation ditch is great, is unfavorable for the stability of soil body around the foundation ditch.
In the existing precipitation construction method, precipitation recharging mainly depends on monitoring feedback around an observation well and a site, and the following problems exist: the information is lagged, when measures such as recharging are taken, the self-transmission of water in the soil body is excessively depended, and the phenomenon of too low and too high water level concentration exists near a precipitation well and a recharging well, so that the original water level fluctuation of the soil layer is too large. Therefore, a series of technical problems still exist in the deep foundation pit dewatering construction, and under the background, the invention innovatively designs a transverse connection dewatering construction method for deep foundation pit dewatering, which increases the transverse transmission of water in a soil layer, so that the water level around the foundation pit is closer to an original balance state, the stability of soil is enhanced, and meanwhile, the water level early warning can be automatically monitored, so that the whole dewatering process management is more automatic and intelligent.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a deep foundation pit transverse connection type net-shaped precipitation construction method capable of being automatically monitored, and the problem that water level concentration is too low and too high in the vicinity of a precipitation well and a recharging well caused by too dependence on self-transmission of water in a soil body during recharging in the traditional precipitation construction method is effectively solved.
The present invention achieves the above technical object by the following means.
A deep foundation pit transverse connection type net-shaped precipitation construction method capable of being automatically monitored comprises the following steps:
step 1: deep design of drawings; determining the positions and the number of each pipe well and the driving position and the angle of a transverse filtering pipeline;
step 2: measuring and placing the point positions; determining the positions of all pipe wells on a construction site, marking, determining the installation hole positions of transverse water filtering pipes 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: marking the mounting hole positions of the transverse filtering pipeline manufactured in the step 2, pumping the transverse filtering pipeline to the vicinity of a dewatering well and a recharging well, filling water sand and stone into the transverse filtering pipeline, and plugging the rear end of the transverse filtering pipeline by cement slurry;
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.
Further, 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 is lifted to 0.50m away 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 at the bottom of the hole is less than 30cm until the mud does not contain mud blocks;
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.
Further, the specific process of the step 4 is as follows:
step 4.1: aligning the special jumbolter with the well-positioned hole site marks which are paid out in the step 2, adjusting the angle, and permitting drilling after acceptance inspection;
step 4.2: reaming construction;
the method comprises the steps of controlling high-pressure cement slurry of a high-pressure rotary drill bit of a drilling machine to be sprayed outwards from a bottom drill bit and a side wing nozzle under the pressure action of a high-pressure pump, synchronously cutting soil or sand layers on the periphery in the spraying process, gradually pushing forward by the high-pressure rotary drill bit and the side wing nozzle under the power pushing until the design depth and the diameter are reached, and obtaining sleeve holes for installing a transverse water filtering pipeline;
step 4.3: manufacturing and placing a transverse filtering pipeline;
wrapping the free section of the transverse water filtering pipeline with plastic pipes, sealing the pipe orifice of the plastic pipe at the intersection with the bottom of the transverse water filtering pipeline with waterproof adhesive tape, and transporting to the site; then, limiting and fixing two ends of a transverse water filtering pipeline by adopting a special sleeve bracket with holes on a construction site, ensuring that the transverse water filtering pipeline coincides with the axis of a drill rod, embedding a foundation pit support for a certain length at the front end of the transverse water filtering pipeline, embedding sealing hemp threads between the foundation pit support and the transverse water filtering pipeline, and ensuring that the elevation H1 at the rear end of the transverse water filtering pipeline is slightly higher than the elevation H2 of the underground water level outside the foundation pit; then, a drill rod of the drilling machine enters from the rear end of the transverse water filtering pipeline and continuously drives the transverse water filtering pipeline to drill to a designed position;
step 4.4: filling water and sand stone;
when the transverse filtering water pipeline is driven to a position 80-100 mm away from the dewatering well and the recharging well filter, water is matched with the transverse filtering water pipeline 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 the transverse filtering water pipeline 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.
Further, in the step 4.1, the construction requirements of the drilling are as follows:
surrounding formations must not be disturbed while drilling;
the horizontal hole pitch error of the transverse water filtering pipeline 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 filtering pipeline and not larger than 1% of the design length of the transverse filtering pipeline, and the aperture of the drilling hole is not smaller than the design aperture of the transverse filtering pipeline.
Further, in the step 4.2, the reaming construction is 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.
Further, in the step 6, for the precipitation well in which precipitation has been stopped before the casting of the bottom plate, the well sealing measures are as follows: cutting the top of the dewatering well pipe to a bedding surface before pouring the bottom plate, tightly filling sand stone or concrete in the dewatering well pipe, and then welding and sealing the pipe orifice of the dewatering well pipe by adopting a steel plate.
Further, in the step 6, for the reserved dewatering well, the post-pouring zone of the main structure of the basement is closed and the well can be sealed after the anti-floating requirement is met, and the well sealing measures are as follows: before the bottom plate is poured, the interior of the dewatering well pipe is firstly internally sealed, namely, sand and stone are filled in the dewatering well pipe below 1.0m at the bottom of the bottom plate, and then micro-expansion concrete 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; cutting off the dewatering well pipe at the position 80mm below the top surface of the bottom plate after the inner sealing is finished, adopting a 20mm thick steel cover plate for welding and sealing, and then pouring concrete between the two inner water stop wing rings and the water stop steel plate; when the reinforcing steel bars of the bottom plate meet the dewatering well pipe, one end of the reinforcing steel bars is bent for 250mm and welded with the dewatering well pipe, and the horizontal length of the other end of the reinforcing steel bars is not less than 1m.
The invention has the following beneficial effects:
the invention creatively proposes that the transverse connection between the dewatering well and the recharging well is realized by arranging the transverse water filtering pipeline, the high-low deviation of the pipeline is controlled by deepening construction parameters, coarse sand and stone particles are filled in the range near the pipe well and the transverse water filtering pipeline, the particle size and the proportion of the sand and stone in the transverse pipeline are optimized, water is inclined to flow in the transverse pipeline, a good H-shaped dewatering recharging water circulating system is formed among the transverse water filtering pipeline, the dewatering well and the recharging well, the groundwater in the recharging well can be quickly conveyed into surrounding soil layers, and the influence of consolidation of the soil caused by the reduction of the water content in the soil is reduced; compared with the traditional precipitation recharging method, when the settlement amount of soil bodies is overlarge around the foundation pit, the transverse water filtering pipeline can rapidly and transversely transfer water, and the influence of the settlement of the soil bodies can be reduced more effectively.
In addition, the invention combines the connected netlike 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 meter is arranged in the observation well at the inner side and the outer side of the deep foundation pit, after the construction of the pipe well is finished, the water level condition can be monitored in real time, data is sent to the monitoring center for analysis processing, and the monitoring center sends a command to the recharging water pump, so that the whole precipitation process is more intelligent and automatic; when the recharging quantity exceeds a preset value, recharging is started only by stopping recharging without increasing the water pumping quantity in the dewatering well, when the dewatering well naturally pumps down the water level and the settlement quantity is observed to start to increase, the recharging is started, the device is more sensitive to transverse transmission of water, the pumping pressure of the dewatering well is reduced when recharging is overlarge, and the risk of foundation pit piping is avoided.
Drawings
FIG. 1 is a construction flow diagram;
FIG. 2 is a schematic view of a transverse filtered water piping arrangement;
FIG. 3 is a schematic view of a transverse filtered water pipe placement construction;
fig. 4 is a schematic diagram of a dewatering well seal construction.
In the figure: 1-a transverse water filtering pipeline; 2-a cannula mount; 3-a drill rod; 4-micro-expansion concrete; 5-dewatering the well pipe; 6-a bottom plate; 7-cushion layer; 8-steel cover plate; 9-inner water stop wing ring.
Detailed Description
The invention will be further described with reference to the drawings and the specific embodiments, but the scope of the invention is not limited thereto.
The invention discloses a method for constructing a deep foundation pit transversely connected net-shaped precipitation construction capable of being automatically monitored, which is shown in figure 1 and comprises the following steps:
step 1: deep design of drawings;
combining engineering geological survey data to perform integral precipitation analysis, designing the positions and the number of all pipe wells in advance, preparing a precipitation device, strictly designing the height of a receiving end of a precipitation well and the height of a transmission end of a recharging well of a transverse water filtering pipeline 1, and accurately calculating the position and the angle of the transverse water filtering pipeline 1 driven into the vicinity of the pipe well and the arrangement height of a water level sensor;
when the pipe wells are arranged in the pore submerged layer, the pressure reducing wells are adopted for all the pipe wells, when the pipe wells are longer in length and extend into other soil layers, the pressure reducing wells are arranged alternately with the mixing wells with pressure-bearing water pressure reducing and upper diving drainage, and the pressure reducing wells, the recharging wells and the observing wells in the embodiment are all arranged in the pore submerged layer and are pressure reducing wells.
Step 2: measuring and placing the point positions;
measuring well positions according to a pipe well plane layout diagram, making well position marks after the well positions are measured and laid, when ground obstacles exist at the well positions, seeking to clear the obstacles so as to facilitate subsequent well digging, and when the ground obstacles are not easy to clear or cannot be subjected to the influence of other construction conditions, taking other measures when the well positions are originally laid, and properly adjusting the well positions when necessary;
and (3) finishing the foundation pit wall, spraying anchors, and then, according to the layout of the transverse water filtering pipeline 1 and the elevation and horizontal spacing required by design, using a leveling instrument and a steel ruler to fix the hole site for installing the transverse water filtering pipeline 1, and marking.
Step 3: constructing a pipe well;
step 3.1: drilling a hole;
according to the well position mark determined in the step 2, a special drilling tool is used for drilling a hole, the diameter of the hole is 800mm, the diameter is one diameter to one end, the upper drilling adopts a light pressure slow rotation mode, the drilling pressure is 15-35 KN, the rotating speed is 20-50 rpm, the hole forming construction adopts natural slurry making in the hole, and the slurry density in the drilling process is controlled to be 1.10-1.15 g/cm 3 When lifting the drilling tool or stopping the drilling tool, the hole must be filled with slurry to prevent the hole wall from collapsing;
step 3.2: cleaning holes and changing slurry;
after drilling to the designed elevation, the drill rod 3 is lifted to 0.50m away 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 at the bottom of the hole is less than 30cm until the mud does not contain mud blocks, and the used mud is transported out of the field through a mud box for treatment;
step 3.3: setting a well pipe;
after the well pipe enters the field, firstly checking whether the gap of the well pipe filter meets the design requirement, then measuring the hole depth, and measuring and recording the well pipe one by one to ensure that the hole depth meets the subsequent installation of the well pipe;
setting a water-sensitive sensor in each 800mm interval in the dewatering well and recharging well pipe, and simultaneously setting a signal transmission device for subsequent water level measurement; arranging a water level gauge in a well pipe of a observation well on the inner side and the outer side of a deep foundation pit, and simultaneously arranging a signal transmission device; in practical application, the water level gauge sends the detected water level height data in the observation well to a monitoring center through a signal transmission device, and the monitoring center receives the transmission information and analyzes and processes the transmission information; when the water level in the observation well is higher than a preset value, sending an instruction to a wireless control switch of the recharging water pump, and stopping recharging by the recharging water pump; when the water level in the observation well is lower than a preset value, sending an instruction to a wireless control switch of the recharging water pump, and starting the recharging water pump to supplement water; if the water level in the observation well fluctuates in the set monitoring area, 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 in order to ensure that the bottom of the well pipe is firmly plugged, and after the iron plate is inspected and plugged, beginning to blow the well pipe into a corresponding hole; when the well pipe is put down, in order to ensure the centering of the well pipe position, a set of centralizers (centralizers) with diameters smaller than 5cm of the aperture are respectively arranged at the upper end and the lower end of the well pipe, the centralizers adopt trapezoid iron rings, and the trapezoid iron rings at the upper end and the lower end are staggered by 1/2 and are not on the same straight line;
step 3.4: backfilling the filter material;
after the well pipe is lowered, a drill rod 3 is lowered into the well pipe until the distance from the bottom of the hole is 0.30-0.50 m, slurry is pumped into the well pipe through the drill rod 3, slurry is gradually mixed while punching, slurry in the well pipe overflows outwards from the well pipe, slurry is returned from an annular gap formed between the well pipe and the wall of the hole, and the slurry density in the hole is gradually adjusted to 1.05g/cm 3 Sealing the upper opening of the well pipe by a choke plug, then starting a small pump volume to fill filter materials according to the structural design requirement of the well, and filling the filter materials along with the height of the filter materials until the filter materials are backfilled to a preset position;
step 3.5: flushing the well;
the air compressor is used for flushing, the flushing is carried out from the top end to the bottom end of the well pipe, the water level in the well pipe is ensured to submerge the flushing head, if the flushing head cannot be flushed by adding water, the air compressor is used for blowing out slurry on the wall of the hole and the bottom of the well pipe to sediment, and the water in the well pipe is cleaned without sand.
Step 4: constructing a transverse water filtering pipeline 1;
step 4.1: drilling construction;
a special jumbolter is selected for drilling, wherein the jumbolter adopts a hard alloy high-pressure rotary drill bit (spray head), and a plurality of nozzles are arranged on the lateral wings of the drill bit, so that a high-pressure rotary drilling process is conveniently realized; before drilling, firstly aligning a special jumbolter with the hole site marks which are well positioned by paying off in the step 2, adjusting the angle, and then permitting the drill to be started after the quality inspector is qualified;
and the drilling construction needs to meet the following construction requirements:
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 1;
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 aperture of the design of the transverse water filtering pipeline 1;
step 4.2: reaming construction;
the method comprises the steps of controlling high-pressure cement slurry of a high-pressure rotary drill bit (a spray head) of an jumbolter to be sprayed outwards from a bottom drill bit and a lateral wing nozzle under the pressure action of a high-pressure pump, cutting soil or sand layers on the periphery in the spraying process synchronously, and gradually and forwards pushing the high-pressure rotary drill bit (the spray head) and the lateral wing nozzle under the power pushing until the design depth and the diameter are reached, so that sleeve holes (namely transverse water filtering pipeline mounting holes) are obtained;
the reaming construction needs to meet the following construction requirements:
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, and reaming at least up and down to and fro for two times;
the high-pressure rotary drill bit (nozzle) should rotate uniformly, lift or sink uniformly, spray reaming from top to bottom or from bottom to top, the overlap joint length of the spray pipe lifting or sinking in sections should not be less than 100mm;
the cement paste should be uniformly mixed and used at any time, and the cement paste mixed at one time should be used up before initial setting;
step 4.3: manufacturing and placing a transverse filtering pipeline 1;
the transverse water filtering pipeline 1 is strictly fed according to the design size, a plurality of water filtering holes are formed in the surface of the transverse water filtering pipeline 1, the free section (namely the water filtering hole section) of the transverse water filtering pipeline 1 is wrapped by a plastic pipe, and the pipe orifice of the plastic pipe at the intersection with the bottom of the transverse water filtering pipeline 1 is sealed by waterproof adhesive tape; the two ends of the transverse water filtering pipeline 1 are limited and fixed by adopting a special sleeve bracket 2 with holes on a construction site, so that the axis coincidence of the transverse water filtering pipeline 1 and a drill rod 3 is ensured, the front end of the transverse water filtering pipeline 1 is embedded into a foundation pit support for a certain length, a sealing hemp thread is embedded between the foundation pit support and the transverse water filtering pipeline 1, a gap is not reserved, and the elevation H1 at the rear end of the transverse water filtering pipeline 1 is slightly higher than the elevation H2 of the underground water level outside the foundation pit;
then, a drill rod 3 of a 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, and on the basis of a differential pressure balance principle in the drilling process, because the elevation H1 of the rear end of the transverse water filtering pipeline 1 is slightly higher than the elevation H2 of the underground water level outside the foundation pit, sand outside the foundation pit cannot flow into the foundation pit due to the pore-forming construction of the transverse sleeve;
step 4.4: filling water and sand stone;
when the transverse water filtering pipeline 1 is driven to the position 80-100 mm away from the dewatering well and recharging well filters, water is matched with the transverse water filtering pipeline 1 to be filled with water sand and stones, wherein the water sand and stones use medium sand with fineness modulus of 3.0-2.3, and the average grain diameter is 0.5-0.35 mm.
Step 4.5: plugging cement paste;
the rear end of the transverse water filtering pipeline 1, namely the transverse water filtering pipeline 1 within 1500mm from the edge of the foundation pit, is plugged by cement paste so as to prevent water from flowing back into the foundation pit and affecting the construction in the subsequent foundation pit; the cement slurry adopts 42.5-grade ordinary Portland cement, the cement doping amount is 350kg/m, the cement slurry is used along with stirring and is used up before initial setting, and before grouting and plugging operation, the dilute cement slurry is firstly used for circulating a grouting system for 1-2 min, so that the smooth grouting is ensured during grouting, and after grouting and plugging of the same batch of transverse water filtering pipelines 1 are finished, grouting pipelines of the circulating grouting system are cleaned in time.
Step 5: precipitation operation;
step 5.1: observing an initial water level;
accurately measuring an initial underground water level according to a water sensitive sensor in a dewatering well and a recharging well within a week before a test, wherein the initial underground water level comprises initial pressure-bearing water levels inside and outside a foundation pit, ensuring that the initial water level is recorded when data observed in the first time and the second time are basically the same, or taking the average value of the data observed in the first time and the second time as the initial water level; in addition, the initial value of the adjacent ground settlement around the foundation pit should be measured within one week before the test;
step 5.2: pumping test;
selecting pit well points to respectively perform a drainage well and a depressurization well pumping test so as to verify the water isolation effect of the enclosure structure, checking the water yield and the permeability condition of a soil layer, analyzing and judging the dewatering effect according to the water yield data condition, and modifying and improving the scheme according to the dewatering effect; specifically, determining detailed hydrogeological data such as initial water level, permeability coefficient, influence radius and the like of a confined aquifer through a water pumping test, analyzing the water pumping test data, drawing a corresponding graph, checking scientific rationality of a precipitation scheme, further evaluating the surrounding environment through the water pumping test, adjusting the number and structure of precipitation wells according to the requirement, and deepening the precipitation scheme;
in the water pumping test process, the water level drop condition of the observation well inside and outside the foundation pit is observed, and the observation frequency is as follows: 1h, 2h, 4h, 8h, 20h, 32h and 44h … …, taking the later observation time interval as 12h or 24h according to the water level descending condition until the water level tends to be stable or descends to 1m below the substrate, and selecting 2-5 pumping wells to install water meters in the pumping test process so as to observe the change condition of the water quantity in the pumping wells, wherein the observation frequency is the same as the observation frequency of the water level of the observation well;
step 5.3: water level recovery observation;
after water pumping is finished, the water level recovery condition of the observation well inside and outside the foundation pit is observed, the water level recovery speed is analyzed, a reference is provided for the configuration of a standby power supply in the later precipitation operation process, the observation frequency is determined according to the water level recovery speed, and the observation can be performed according to 1h, 2h, 4h, 8h, 20h, 32h and 44h … … until the water level tends to be stable or the recovery is slow.
Step 6: sealing the well;
for the dewatering well with dewatering stopped before pouring the bottom plate 6, the well sealing measures are as follows:
after design approval, cutting the top of the dewatering well pipe 5 to the surface of a 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.
For the reserved pipe well, namely the reserved dewatering well, the well sealing measures are as follows:
the post-pouring belt of the basement main body structure is closed, and the well can be sealed after the anti-floating requirement is met; before pouring the bottom plate 6, the inside of the dewatering well pipe 5 is firstly internally sealed, namely, sand is 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 a water stop steel plate (reserved by a post-pouring belt); 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.
The examples are preferred embodiments of the present invention, but the present invention is not limited to the above-described embodiments, and any obvious modifications, substitutions or variations that can be made by one skilled in the art without departing from the spirit of the present invention are within the scope of the present invention.
Claims (6)
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;
the specific process of the step 4 is as follows:
step 4.1: aligning the jumbolter with the well-positioned hole site marks which are paid out in the step 2, and drilling by adjusting the angle;
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 sleeve support (2) with holes on a construction site, ensuring that the axis of the transverse water filtering pipeline (1) is coincident with that of a drill rod (3), embedding a foundation pit support for a certain length at the front end of the transverse water filtering pipeline (1), embedding sealing hemp threads between the foundation pit support and the transverse water filtering pipeline (1) and forming no gaps, 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;
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 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 in the step 4.1, the drilling construction is 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 (1);
the depth of the anchor rod drilling hole is not smaller than the design length of the transverse filtering water pipeline (1), and is not larger than 1% of the design length of the transverse filtering water pipeline (1), and the aperture of the drilling hole is not smaller than the design aperture of the transverse filtering water pipeline (1).
4. The method for automatically monitoring the cross-connection type net-shaped precipitation construction of the deep foundation pit according to claim 1, wherein in the step 4.2, the reaming construction is 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.
5. 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.
6. 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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