CN104831762A - Dynamic monitoring system and monitoring method of deep foundation pit confined water drawdown - Google Patents

Abstract

The invention discloses a dynamic monitoring system and a monitoring method of deep foundation pit confined water drawdown. The dynamic monitoring system comprises a monitoring well and is characterized in that a drawdown well pipe is arranged in the monitoring well; the bottom of the drawdown well pipe is provided with a filter pipe in a confined water layer area to be tested; the bottom of the filter pipe is provided with a precipitation pipe; the bottom of the precipitation pipe is sealed; a gap between the upper part of the drawdown well pipe and the hole wall of the monitoring well is filled with hole sealing clay; the gap between the lower part of the drawdown well pipe and the hole wall of the monitoring well is filled with waterstop clay; the gap between the filter pipe and the hole wall of the monitoring well as well as the gap between the precipitation pipe and the hole wall of the monitoring well is filled with gravel filter materials; the inner wall of the drawdown well pipe is longitudinally uniformly provided with a plurality of hole pressure sensors; each hole pressure sensor is respectively connected with a data acquisition instrument via a lead; the data acquisition instrument is connected with a monitoring computer; the filter pipe is communicated with an external water suction pump via a water suction pipe. The dynamic monitoring system has the advantages that confined water level drawdown can be dynamically, precisely and reliably measured, foundation pit confined water drawdown can be judged in real time, and time for a pumping well to stop working is determined.

Description

Deep foundation ditch artesian water precipitation dynamic monitoring system and monitoring method

Technical field

The present invention relates to a kind of Ground Water Pumping during Excavation Dynamic Monitoring, especially relate to a kind of deep foundation ditch artesian water precipitation dynamic monitoring system and monitoring method.

Background technology

In recent years, base pit engineering is to the large degree of depth, large area development, the problem of groundwater faced is also more and more serious, particularly the basifacial artesian water of excavation of foundation pit can cause that bottom heave, base plate are prominent the problem such as to be gushed and cause instability of foundation pit, artesian water be controlled to the key that can whole base pit engineering carry out smoothly.The stable judgment basis of foundation ditch is the jacking force that soil pressure between base plate of foundation pit to artesian aquifer top board should be greater than artesian water, that is: H γ _s>=F _sγ _wh, wherein H is to artesian aquifer top board spacing (m) at the bottom of foundation ditch, γ _sfor at the bottom of foundation ditch to the heavy (kN/m of the weighted average of the soil between artesian aquifer top board ³), h is artesian water head height, and namely static level is to the distance (m) of artesian aquifer top board, γ _wfor the severe (kN/m of water ³), Fs is safety factor (getting 1.05).On the deep-foundation pit engineering affected by artesian water, can adopt the methods such as water seal curtain partition, artesian water precipitation and back cover reinforcing, wherein precipitation method controls artesian head is the comparatively cost-effective measure of one.

In deep foundation ditch artesian water dewatering project, the good construction how reasonably arranging artesian water dewatering well and dewatering well is successful key.But, because decompression of confined water precipitation will inevitably cause soil layer around foundation ditch to produce sedimentation, drawdown is excessive must cause surface settlement excessive, and water level precipitation is too small, does not reach decompression design effect, thus still may cause the generation of Foundation Pit Pouring, instability of foundation pit accident.In order to avoid similar accident occurs, the drawdown of Measurement accuracy artesian water, direct relation excavation of foundation pit safety.

Because excavation of foundation pit is timely to water level prediction requirement, accurately, so water level measuring frequency is higher, traditional artificial lining rope amount method often causes waterlevel data deviation very large by the subjective judgement of people, there is very big potential safety hazard.Current limnograph on the market; pop one's head in larger; cost of equipment is very high; it often can tangle in well when measuring dynamic water level in dewatering well the flange drawn water on interior pipe; cause instrument damage; and once damage the equipment that just must again more renew, so it is unfavorable for measuring the water level in dewatering well.Therefore, be suggested about deep foundation ditch artesian water Rainfall Monitoring techniques and methods more in recent years, through finding prior art retrieval: application number is that " the foundation pit dewatering well measurements water level device " utility model patent of [201220002120.1] proposes a kind of foundation pit dewatering well measurements water level device, mainly comprise universal meter, 2 wires, universal meter probe, counterweight; The two ends of every wire are all connected with universal meter probe, and wherein the universal meter probe of electric wire one end is used for contacting with the water surface in well, and the universal meter of one end inserts the probe insertion of universal meter with probe in addition; 2 universal meters of one end of contacting with the water surface in well are popped one's head in and to be fixed in counterweight by insulative water-proof adhesive tape.

Application number be 201410119862.6 " a kind of foundation pit dewatering depth detection apparatus and detection method " patent of invention propose precipitation depth checkout gear and detection method, this testing fixture is made up of pore-forming pipe, detector tube and scale bar.Pore-forming pipe top cover has and is embedded with the anti-of level gauge and pounds plate, sidewall is furnished with water seepage hole, bottom is that sealed end is provided with solid conehead, and detector tube is inner at pore-forming pipe, bottom end closure, sidewall is distributed with into water aperture, its outer wrapping is every husky net, and scale bar, in detector tube, is made with light material, top is provided with rule, and bottom is provided with light hollow ball.In detector tube, scale bar rises under buoyancy, the rule of scale bar reads height of water level and namely completes water level detecting.

Application number is " in a kind of foundation pit dewatering well groundwater table surface relative elevation Simple measurement device " utility model patent of 201420100363.8, propose groundwater table surface relative elevation Simple measurement device in a kind of foundation pit dewatering well, it comprises the support being fixed on the multiple upper and lower parallel interval setting on dewatering well sidewall by support bar, an annulus is installed in the end of each support, the centres of whole annulus is arranged, a vertical hollow vertical rod vertically arranged is passed multiple annulus and can be slided at multiple annulus internal freedom and arranges, in the bottom of vertical hollow vertical rod, ball float is installed, the support bar being positioned at well head top is provided with the gauge vertically arranged, gauge and vertical hollow vertical rod are oppositely arranged, gauge is provided with relative elevation scale within the scope of precipitation depth, the top of vertical hollow vertical rod that what pointer was vertical be fixed on and level point to gauge scale place and on gauge scale reading, in lower range.

Although the artificial lining rope amount method that above-mentioned technology is more traditional has certain improvement, similar with artificial lining rope amount method in essence, the main drawdown still forecasting artesian water by artificial reading.In addition, be no matter artificial lining rope or scale bar, hollow vertical rod, when drawdown is large, flexible distortion, thus the precision of read data is surveyed in impact.

Summary of the invention

Technical problem to be solved by this invention is to provide a kind of dynamic, accurate, reliable deep foundation ditch artesian water precipitation dynamic monitoring system and the monitoring method measuring artesian water drawdown; the method can the drawdown of real-time judgment foundation ditch artesian water; determine the pumped well out-of-work time; to guarantee the sedimentation on the stable of foundation ditch and control foundation ditch periphery earth's surface, reduce foundation pit construction to the impact of environment.

The present invention solves the problems of the technologies described above adopted technical scheme:

1, a kind of deep foundation ditch artesian water precipitation dynamic monitoring system, comprise monitor well, downcast well pipe is provided with in described monitor well, the bottom of described downcast well pipe is provided with chimney filter in artesian aquifer region to be measured, the bottom of described chimney filter is provided with the sediment tube for precipitating sand, the sealed bottom of described sediment tube is arranged, sealing of hole clay is filled with between the top of described downcast well pipe and the hole wall of described monitor well, sealing clay is filled with between the bottom of described downcast well pipe and the hole wall of described monitor well, gravel filtrate is filled with between the hole wall of described chimney filter and described monitor well and between the hole wall of described sediment tube and described monitor well, the inwall of described downcast well pipe is longitudinally evenly equipped with several sensor for pore water pressures, sensor for pore water pressure described in each is respectively by wire connection data Acquisition Instrument, described data collecting instrument connects monitoring computer, described chimney filter is communicated with outside suction pump by drinking-water pipe.

Described chimney filter comprises reinforcing cage that diameter is 200mm ~ 300mm and is coated on the filter screen of described reinforcing cage periphery, and the aperture of described filter screen is 1 ~ 2mm, and the particle diameter of described gravel filtrate is 3 ~ 15mm.

The aperture of described monitor well is 550 ~ 600mm, and the diameter of described downcast well pipe is 300 ~ 450mm; The mouth of pipe of described downcast well pipe is above the ground level 0.50-1m.Infiltrate in well to prevent surface waste water.

Described sensor for pore water pressure is pore water pressure sensor, and its diameter is 1.5 ~ 12mm, and range is 100kPa ~ 500kPa.

The transmission coefficient of described sealing clay is 1.0 × 10 ^-8cm/s ~ 1.0 × 10 ^-10cm/s.

2, a deep foundation ditch artesian water precipitation dynamic monitoring method, specifically comprises the following steps:

(1) artesian water precipitation dynamic monitoring system is arranged

The inwall of downcast well pipe is longitudinally equidistantly installed several sensor for pore water pressures, the bottom of downcast well pipe is connected chimney filter and sediment tube successively, and shuts bottom sediment tube, adopt diving to bore mud off and offer monitor well, sediment tube is divided into successively from down to up in monitor well, chimney filter and downcast well pipe, and sediment tube and chimney filter are arranged in artesian aquifer region to be measured, gravel filtrate is backfilled by between the hole wall of monitor well and sediment tube and between the hole wall of monitor well and chimney filter, sealing clay is backfilled by between the hole wall of monitor well and downcast well pipe bottom, sealing of hole clay is backfilled by between the hole wall of monitor well and downcast well pipe top, each sensor for pore water pressure is wired on data collecting instrument, data collecting instrument is connected on monitoring computer, form a complete artesian water precipitation dynamic monitoring system,

(2) Dynamic Data Acquiring analysis

Extend chimney filter by drinking-water pipe, open pumping for water pump, and after stable level, time t is set to initial value 0, gather the initial pore water pressure value P of each sensor for pore water pressure _ij0, convert and obtain the degree of depth of respective aperture pressure sensor below water level, and be set to the ID value H of sensor for pore water pressure with this _ij0; Continue to draw water, water level decreasing, gathers t, the pore water pressure force value P of each sensor for pore water pressure _ijt, convert and obtain the depth value H of t respective aperture pressure sensor _ijt; By the depth value H of t sensor for pore water pressure _ijtdeduct the ID value H of sensor for pore water pressure _ij0, obtain the drawdown △ H of t sensor for pore water pressure _ijt, the average getting each sensor for pore water pressure drawdown of t obtains t drawdown H _it, draw and obtain drawdown H _itand the curve relation figure between time t is used for monitoring analysis; Pre-set target depth H, when reaching target depth H, system alarm prompting stops pumping, after water level rezime to certain altitude, re-start and draw water and monitoring analysis, wherein i=1,2 ..., n is well numbering, j=1,2 ..., n is the numbering of sensor for pore water pressure from top to bottom, and t is the time.

T in step (2), the pore water pressure force value P of each sensor for pore water pressure _ijtconvert and obtain the water level depth value H of respective aperture pressure sensor _ijtcomputational methods as follows:

$H_{i1t}=h_{i2t}-h_{i1t}=\frac{P_{i1t}}{{\mathrm{\γ}}_w}$

$H_{i2t}=h_{i3t}+h_{i2t}-h_{i1t}=\frac{P_{i2t}}{{\mathrm{\γ}}_w}$

$H_{i3t}=h_{i4t}+h_{i3t}+h_{i2t}-h_{i1t}=\frac{P_{i3t}}{{\mathrm{\γ}}_w}$

…………

H _int＝h _int+h _i(n-1)t+h _i(n-2)t-h _i1t＝P _int/r _w

Wherein h _i1tbe the elevation of i-th mouthful of well the 1st sensor for pore water pressure in t, h _ijtbe the elevation of i-th mouthful of well jth sensor for pore water pressure in t, i=1,2 ..., n is well numbering, j=1,2 ..., n is the numbering of sensor for pore water pressure from top to bottom, and t is the time, γ _wfor the severe (kN/m of water ³);

As drawdown H _it>h _i2t-h _i1t, namely drawdown has exceeded the degree of depth of first sensor for pore water pressure, then first sensor for pore water pressure hole pressure value P _i1tbe zero, then cancel Δ H _i1tmean value calculation; Work as H _it>h _i3+ h _i2-h _i1, cancel Δ H _i2tmean value calculation, the like.

Described chimney filter comprises reinforcing cage that diameter is 200mm ~ 300mm and is coated on the filter screen of described reinforcing cage periphery, and the aperture of described filter screen is 1 ~ 2mm, and the particle diameter of described gravel filtrate is 3 ~ 15mm.

The aperture of described monitor well is 550 ~ 600mm, and the diameter of described downcast well pipe is 300 ~ 450mm; The mouth of pipe of described downcast well pipe is above the ground level 0.50-1m.

Described sensor for pore water pressure is pore water pressure sensor, and its diameter is 1.5 ~ 12mm, and range is 100kPa ~ 500kPa.

Compared with prior art, the invention has the advantages that: a kind of deep foundation ditch artesian water precipitation dynamic monitoring system of the present invention and monitoring method, during by well casing sinking, in desired depth, pressure sensor is arranged on well casing inwall, and each sensor conductor is connected to data collecting instrument and computer, form a complete artesian water drawdown dynamic monitoring system, the pore water pressure of each degree of depth is measured by a series of sensor for pore water pressure, and then conversion calculates the degree of depth of each measuring point of acquisition below groundwater table, after precipitation starts, each measuring point pore water pressure changes, reduce gradually, data collecting instrument automatic acquisition each sensor pore water pressure reading, obtain the pore water pressure force value of any time, and the dynamic monitoring system sending it to computer carry out conversion obtain each measuring point water level depth change △ H (drawdown), and get the average of all measuring point △ H, thus obtain the drawdown H in this moment, and draw drawdown time-histories H ~ t curve.In monitoring system, can set target drawdown, drawdown arrives target drawdown, and system automatic alarm prompting termination is drawn water.Test result of the present invention is accurately reliable, applied widely, and technique is simple, easy to operate, can reduce workload and the error of artificial reading, can monitor drawdown in real time, dynamically, for deep foundation ditch artesian water precipitation construction control of drawing water provides reliable foundation.

Accompanying drawing explanation

Fig. 1 is the structural representation of deep foundation ditch artesian water precipitation dynamic monitoring system;

Fig. 2 is the H that specific embodiment three is drawn _1tthe drawdown time history of ~ t;

1-precipitation pipe well, 2-sealing of hole clay, 3-sensor for pore water pressure, 4-sealing clay, 5-grit filtrate, 6-chimney filter, 7-sediment tube, 8-data collecting instrument, 9-monitor computer, 10-monitor well, 11-artesian aquifer to be measured, 12-drinking-water pipe.

Detailed description of the invention

Below in conjunction with accompanying drawing embodiment, the present invention is described in further detail.

Embodiment one

A kind of deep foundation ditch artesian water precipitation dynamic monitoring system, as shown in Figure 1, comprise monitor well 10, downcast well pipe 1 is provided with in monitor well 10, the bottom of downcast well pipe 1 is provided with chimney filter 6 in artesian aquifer 11 region to be measured, the bottom of chimney filter 6 is provided with the sediment tube 7 for precipitating sand, the sealed bottom of sediment tube 7 is arranged, sealing of hole clay 2 is filled with between the top of downcast well pipe 1 and the hole wall of monitor well 10, sealing clay 4 is filled with between the bottom of downcast well pipe 1 and the hole wall of monitor well 10, gravel filtrate 5 is filled with between the hole wall of chimney filter 6 and monitor well 10 and between the hole wall of sediment tube 7 and monitor well 10, the inwall of downcast well pipe 1 is longitudinally evenly equipped with several sensor for pore water pressures 3, each sensor for pore water pressure 3 is respectively by wire connection data Acquisition Instrument 8, data collecting instrument 8 connects monitoring computer 9, chimney filter 6 is communicated with outside suction pump by drinking-water pipe 12.

In this particular embodiment, chimney filter 6 comprises reinforcing cage that diameter is 200mm ~ 300mm and is coated on the filter screen (not shown) of reinforcing cage periphery, and the aperture of filter screen is 1 ~ 2mm, and the particle diameter of gravel filtrate 5 is 3 ~ 15mm; The aperture of monitor well 10 is 550 ~ 600mm, and the diameter of downcast well pipe 1 is 300 ~ 450mm; The mouth of pipe of downcast well pipe 1 is above the ground level 0.50-1m.Sensor for pore water pressure 3 is pore water pressure sensor, and its diameter is 1.5 ~ 12mm, and range is 100kPa ~ 500kPa, and the permeability of sealing clay is little, and its transmission coefficient is 1.0 × 10 ^-8cm/s ~ 1.0 × 10 ^-10cm/s.

In this particular embodiment, data collecting instrument 8 has 20 to 120 passages, 4 ~ 6 half-resolution, 0.004% ~ 0.004% basic DC precision, 200 ~ 250 passages/second scan rate, 10000 ~ 50000 readings storages.Outside suction pump can adopt centrifugal water pump, immersion submersible pump or deep well pump etc., and pump amount, lift must meet water yield and the well depth of each well, and each downcast well pipe 1 is separately with a pumping for water pump.Monitoring computer 9 is provided with Water level trend monitoring analysis software, and this Water level trend monitoring analysis software possesses data processing, analysis, drawing and warning function.

Embodiment two

A kind of deep foundation ditch artesian water precipitation dynamic monitoring method, specifically comprises the following steps:

(1) artesian water precipitation dynamic monitoring system is arranged

The inwall of downcast well pipe 1 is longitudinally equidistantly installed several sensor for pore water pressures 3, the bottom of downcast well pipe 1 is connected successively chimney filter 6 and sediment tube 7, and shut bottom sediment tube 7, adopt diving to bore mud off and offer monitor well 10, sediment tube 7 is divided into successively from down to up in monitor well 10, chimney filter 6 and downcast well pipe 1, and sediment tube 7 and chimney filter 6 are arranged in artesian aquifer 11 region to be measured, gravel filtrate 5 is backfilled by between the hole wall of monitor well 10 and sediment tube 7 and between the hole wall of monitor well 10 and chimney filter 6, sealing clay 4 is backfilled by between the hole wall of monitor well 10 and downcast well pipe 1 bottom, sealing of hole clay 2 is backfilled by between the hole wall of monitor well 10 and downcast well pipe 1 top, each sensor for pore water pressure 3 is wired on data collecting instrument 8, data collecting instrument 8 is connected on monitoring computer 9, form a complete artesian water precipitation dynamic monitoring system,

(2) Dynamic Data Acquiring analysis

Extend chimney filter 6 by drinking-water pipe 12, open pumping for water pump, and after stable level, time t is set to initial value 0, gather the initial pore water pressure value P of each sensor for pore water pressure 3 _ij0, convert and obtain the degree of depth of respective aperture pressure sensor 3 below water level, and be set to the ID value H of sensor for pore water pressure 3 with this _ij0; Continue to draw water, water level decreasing, gathers t, the pore water pressure force value P of each sensor for pore water pressure 3 _ijt, convert and obtain the depth value H of t respective aperture pressure sensor 3 _ijt; By the depth value H of t sensor for pore water pressure 3 _ijtdeduct the ID value H of sensor for pore water pressure 3 _ij0, obtain the drawdown △ H of t sensor for pore water pressure 3 _ijt, the average getting each sensor for pore water pressure 3 drawdown of t obtains t drawdown H _it, draw and obtain drawdown H _itand the curve relation figure between time t is used for monitoring analysis; Pre-set target depth H, when reaching target depth H, system alarm prompting stops pumping, after water level rezime to certain altitude, re-start and draw water and monitoring analysis, wherein i=1,2 ..., n is well numbering, j=1,2 ..., n is the numbering of sensor for pore water pressure from top to bottom, and t is the time;

Because each well initial water level may be inconsistent, carry out data analysis explanation, suppose that it has 3 sensor for pore water pressures 3 for i-th mouthful of well, then the initial pore water pressure value of each sensor for pore water pressure 3 is respectively P _i10, P _i20,p _i30, the initial water level degree of depth in dewatering well is h _i1, first following degree of depth of sensor for pore water pressure 3 water level is h _i2-h _i1, second following degree of depth of sensor for pore water pressure 3 water level is h _i3+ h _i2-h _i1, the 3rd the following degree of depth of sensor for pore water pressure 3 water level is h _i4+ h _i3+ h _i2-h _i1, then the initial pore water pressure value of each sensor for pore water pressure 3 and water level depth are closed and are

$H_{i10}=h_{i2}-h_{i1}=\frac{P_{i10}}{{\mathrm{\γ}}_w}$

$H_{i20}=h_{i3}+h_{i2}-h_{i1}=\frac{P_{i20}}{{\mathrm{\γ}}_w}$

$H_{i30}={h_{i4}+h}_{i3}+h_{i2}-h_{i1}=\frac{P_{i30}}{{\mathrm{\γ}}_w}$

After beginning of drawing water, water level decreasing, each sensor for pore water pressure 3 reading also declines thereupon.In any t, the initial pore water pressure value of each sensor for pore water pressure 3 is respectively P _i1t, P _i2t,p _i3t, then the water level depth value of each sensor for pore water pressure 3 of t is:

$H_{i1t}=h_{i2t}-h_{i1t}=\frac{P_{i1t}}{{\mathrm{\γ}}_w}$

$H_{i2t}=h_{i3t}+h_{i2t}-h_{i1t}=\frac{P_{i2t}}{{\mathrm{\γ}}_w}$

$H_{i3t}=h_{i4t}+h_{i3t}+h_{i2t}-h_{i1t}=\frac{P_{i3t}}{{\mathrm{\γ}}_w}$

In any t, the drawdown that each sensor for pore water pressure 3 records is respectively:

$\mathrm{\Δ}{H}_{i1t}=-\frac{P_{i1t}-P_{i10}}{{\mathrm{\γ}}_w}$

$\mathrm{\Δ}{H}_{i2t}=-\frac{P_{i2t}-P_{i20}}{{\mathrm{\γ}}_w}$

$\mathrm{\Δ}{H}_{i3t}=-\frac{P_{i3t}-P_{i30}}{{\mathrm{\γ}}_w}$

Then t, the drawdown H of i-th mouthful of well _itfor,

$H_{\mathrm{it}}=\frac{\mathrm{\Δ}{H}_{i1t}+\mathrm{\Δ}{H}_{i2t}+\mathrm{\Δ}{H}_{i3t}}{3}$

In monitoring system, automatically give H processed by above formula _itthe drawdown time-history curves of ~ t.

Work as H _it>h _i2-h _i1, namely drawdown has exceeded the degree of depth of first sensor for pore water pressure 3, this sensor for pore water pressure 3 hole pressure value P _i1tbe zero, then cancel Δ H _i1tmean value calculation.Work as H _it>h _i3+ h _i2-h _i1, cancel Δ H _i2tmean value calculation, the like.Wherein h _i1tbe the elevation (i.e. sensor for pore water pressure 3 height overhead) of i-th mouthful of well the 1st sensor for pore water pressure 3 in t, h _ijtbe the elevation of i-th mouthful of well jth sensor for pore water pressure 3 in t, i=1,2 ..., n is well numbering, j=1,2 ..., n is the numbering of sensor for pore water pressure 3 from top to bottom, and t is the time, γ _wfor the severe (kN/m of water ³).

In this particular embodiment, chimney filter 6 comprises reinforcing cage that diameter is 200mm ~ 300mm and is coated on the filter screen (not shown) of reinforcing cage periphery, and the aperture of filter screen is 1 ~ 2mm, and the particle diameter of gravel filtrate 5 is 3 ~ 15mm; The aperture of monitor well 10 is 550 ~ 600mm, and the diameter of downcast well pipe 1 is 300 ~ 450mm; The mouth of pipe of downcast well pipe 1 is above the ground level 0.50-1m.Sensor for pore water pressure 3 is pore water pressure sensor, and its diameter is 1.5 ~ 12mm, and range is that the permeability of 100kPa ~ 500kPa sealing clay 4 is little, and its transmission coefficient is 1.0 × 10 ^-8cm/s ~ 1.0 × 10 ^-10cm/s.

In this particular embodiment, data collecting instrument 8 has 20 to 120 passages, 4 ~ 6 half-resolution, 0.004% ~ 0.004% basic DC precision, 200 ~ 250 passages/second scan rate, 10000 ~ 50000 readings storages.Outside suction pump can adopt centrifugal water pump, immersion submersible pump or deep well pump etc., and pump amount, lift must meet water yield and the well depth of each well, and each downcast well pipe 1 is separately with a pumping for water pump.Monitoring computer 9 is provided with Water level trend monitoring analysis software, and this Water level trend monitoring analysis software possesses data processing, analysis, drawing and warning function.

Embodiment three

The northeast side of Ningbo track traffic municipal government erect-position in East Zhongshan Road with liberation intersection, North Road is now municipal administration greenery patches, sunlight square.Wide 20.5 ~ the 24.8m of Line 1 station pit, is about 168.6m.Western end well foundation ditch is 25.3m deeply; The dark about 23.8m of standard paragraphs foundation ditch.Diving static level high (being only 5.0m apart from earth's surface), tier I porous confined groundwater is composed and is stored in 6. ₅8. ₁in layer flour sand, fine sand, coarse sand, gravelly sand and gravel layer, good water permeability, average permeate coefficient is about 30.5m/d, artesian water head 1.8m, and the water yield is enriched.According to engineering geology, hydrogeological conditions that prospecting data provides, carry out the calculating of Foundation Pit Pouring possibility, and according to seepage flow formula, Pit Discharge is calculated.Result shows, in Excavation Process, 8. ₁layer artesian aquifer can have impact to station agent structure excavation, and prominent emerging in large numbers may be caused to resemble.For guaranteeing security of foundation ditch construction, reduced pressure treatment need be carried out to it.Due to this engineering excavation degree of depth and surrounding enviroment complexity (adjoin municipal government, business district, construction of structures is intensive), therefore need at foundation ditch artesian water Precipitation Process keep under strict control precipitation depth and amount of precipitation, effectively control the impact on environment.

1, pipe well quantity n is determined

According to result of calculation, 8. the foundation ditch of this project subject structure need arrange altogether ₁the monitor well six mouthfuls of layer and wellhole for subsequent use (observation well of holding concurrently) two mouthfuls; Well depth 60.0m, manages large (the individual well yield 800 ~ 1500m of dark 52.0 ~ 59.0m water yield of well ³/ d).

2, dewatering well structure design

Open monitor well 10 diameter: (well construction figure refers to accompanying drawing 1);

Well head: 0.3 ~ 0.5m above ground level, well head periphery adopts cohesive soil packing, and its degree of depth is not less than 2.00m;

Downcast well pipe 1: adopt welded steel pipe, wall thickness 4mm, diameter

Chimney filter 6: adopt circular hole bag net filter pipe, wall thickness 4mm, diameter outsourcing 20 order zinc-iron silk screen;

Filtrate: adopt gravelly sand to make filtrate, enclosing raising degree is 1.0 ~ 2.0m on the top board of shaft bottom to aquifer.

Sealing: filtrate section top clay ball sealing, sealing height 5.0 ~ 6.0m;

Enclose and fill out: the above position of sealing section adopts cohesive soil backfill to close;

Sediment tube 7: footpath same with chimney filter 6, length 2.0m, sealing bottom sediment tube 7.

The deep foundation ditch artesian water precipitation dynamic monitoring system adopted is specifically as described in above-mentioned specific embodiment one.

3, construction technology program

Adopt mud circulation to creep into, pipe becomes well construction technique under mechanical hoisting

Well point measurement and positioning → the mouth that digs a well, Hospice Center's cylinder → driller insertion → boring → backfill shaft bottom sand cushion → tie up bamboo chip, nylon wire → hang well casing → sensor install → backfill in gravel filtration beds → well-flushing between well casing and hole wall, well casing divide into water pump, pumping control circuit → connection data Acquisition Instrument is installed and computer → examination draw water → dewatering well normally works → precipitation is complete pulls out well casing → shut-in well.

Consider precipitation well depth 60.0m, installation 5 sensor for pore water pressures 3 be set in every mouthful of well, arrange the degree of depth to be respectively under earth's surface-5 ,-15 ,-25 ,-35 ,-50m place.According to the difference of each sensor for pore water pressure 3 fitting depth, sensor for pore water pressure 3 and wire are sticked be posted on downcast well pipe 1 inwall, with downcast well pipe 1 sinking to the corresponding degree of depth in advance.Before formally drawing water, each sensor for pore water pressure 3 is wired to data collecting instrument 8 and computer 9, form a complete artesian water drawdown dynamic monitoring system, and after stable level, continuous acquisition each sensor for pore water pressure 3 reading, frequency is not less than 3 times/day, converts and obtains the degree of depth of each sensor for pore water pressure 3 below water level, and be set to sensor for pore water pressure 3 degree of depth initial value h with this _ij0, it is i is well numbering, j=1,2 ..., 5 is sensor number from top to bottom.

Because each well initial water level may be inconsistent, carry out data analysis explanation for the 1st mouthful of well, 5 initial pore water pressure values of sensor are respectively P _i10, P _i20, P _i30, P _i40, P _i50.Drawing water any t after starting, the initial pore water pressure value of each sensor is respectively P _i1t, P _i2t, P _i3t, P _i4t, P _i5t, then the initial pore water pressure value of each sensor and water level depth are closed and are

$\mathrm{\Δ}{H}_{i1t}=-\frac{P_{i1t}-P_{i10}}{{\mathrm{\γ}}_w}$

$\mathrm{\Δ}{H}_{i2t}=-\frac{P_{i2t}-P_{i20}}{{\mathrm{\γ}}_w}$

$\mathrm{\Δ}{H}_{i3t}=-\frac{P_{i3t}-P_{i30}}{{\mathrm{\γ}}_w}$

$\mathrm{\Δ}{H}_{i4t}=-\frac{P_{i4t}-P_{i40}}{{\mathrm{\γ}}_w}$

$\mathrm{\Δ}{H}_{i5t}=-\frac{P_{i5t}-P_{i50}}{{\mathrm{\γ}}_w}$

Then t, the drawdown H of the 1st mouthful of well _itfor,

$H_{1t}=\frac{\mathrm{\Δ}{H}_{i1t}+\mathrm{\Δ}{H}_{i2t}+\mathrm{\Δ}{H}_{i3t}+\mathrm{\Δ}{H}_{i4t}+{\mathrm{\ΔH}}_{i5t}}{5}$

In monitoring system, automatically give H processed by above formula _1tthe drawdown time-history curves of ~ t.Be correlated with and draw water data as shown in Figure 2.In Fig. 2, S1 is No. 1 dewatering well, and S2, S3 are observation well.Before precipitation, three mouthfuls of Well Water Levels respectively 5.246,4.905,5.057m, 19:30 divided and started to draw water on August 3rd, 2009, divided end, S1 well drawdown 7.48m to 21:10.Stop pumping, water level recovers rapidly.

Specific embodiment four

A kind of deep foundation ditch artesian water precipitation dynamic monitoring system also as depicted in figs. 1 and 2.Rail Transit Line 3 Yong Da way station of Ningbo City total length is about 166.059m, and be four layers of underground station, standard paragraphs width is 19.7m, intends adopting Open Cut Method construction.Standard paragraphs foundation depth is 27.31m, and end well place foundation depth is 28.91m.Place I _-1layer porous confined groundwater is mainly composed and is stored in 6. _2Tin layer powder soil horizon, transmission coefficient about 10 ^-3cm/s, belongs to aquitard; Local distribution, water yield is little, and watery is poor, and water outflow from single well is 50 ~ 100m ³/ d, artesian water depth to water is at about 1.65m, and water quality is salt water.It is to planning to build foundation pit construction tool adverse effect.I ₂layer porous confined groundwater is composed and is stored in 8. ₁in layer powder fine sand soil, transmission coefficient about 10 ^-2cm/s, water permeability belongs to medium, and the water yield is enriched, water outflow from single well 1500 ~ 1800m ³/ d, depth to water is 2.94m.According to calculating, 6. _2Tlayer and 8. ₁all there is prominent risk of gushing in layer, therefore must shift to an earlier date the prominent foundation ditch gushed of likely generation and process.

1, pipe well quantity n is determined

According to result of calculation, 8. the foundation ditch of this project subject structure need arrange altogether ₁the monitor well 10 8 mouthfuls of layer and reserve well (observation well of holding concurrently) two mouthfuls; Well depth 62.0m, manages large (the individual well yield 800 ~ 1500m of dark 54.0 ~ 60.0m water yield of well ³/ d).

2, dewatering well structure design

Dewatering well structure design is with described in above-mentioned specific embodiment three.

3, construction technology program

Construction technology program is with described in above-mentioned specific embodiment three.Consider precipitation well depth 62.0m, installation 6 pore water pressure sensors be set in every mouthful of well, arrange the degree of depth to be respectively under earth's surface-5 ,-15 ,-25 ,-35 ,-40m ,-55m place.Relevant test data calculates with described in above-mentioned specific embodiment three.Then t, the drawdown H of the 1st mouthful of well _itfor,

$H_{1t}=\frac{\mathrm{\Δ}{H}_{i1t}+\mathrm{\Δ}{H}_{i2t}+\mathrm{\Δ}{H}_{i3t}+\mathrm{\Δ}{H}_{i4t}+{\mathrm{\ΔH}}_{i5t}+\mathrm{\Δ}{H}_{i6t}}{6}$

In monitoring system, automatically give H processed by above formula _1tthe drawdown time-history curves of ~ t.

Certainly, above-mentioned explanation is not limitation of the present invention, and the present invention is also not limited to above-mentioned citing.Those skilled in the art are in essential scope of the present invention, and the change made, remodeling, interpolation or replacement, also should belong to protection scope of the present invention.

Claims (10)

1. a deep foundation ditch artesian water precipitation dynamic monitoring system, comprise monitor well, it is characterized in that: in described monitor well, be provided with downcast well pipe, the bottom of described downcast well pipe is provided with chimney filter in artesian aquifer region to be measured, the bottom of described chimney filter is provided with the sediment tube for precipitating sand, the sealed bottom of described sediment tube is arranged, sealing of hole clay is filled with between the top of described downcast well pipe and the hole wall of described monitor well, sealing clay is filled with between the bottom of described downcast well pipe and the hole wall of described monitor well, gravel filtrate is filled with between the hole wall of described chimney filter and described monitor well and between the hole wall of described sediment tube and described monitor well, the inwall of described downcast well pipe is longitudinally evenly equipped with several sensor for pore water pressures, sensor for pore water pressure described in each is respectively by wire connection data Acquisition Instrument, described data collecting instrument connects monitoring computer, described chimney filter is communicated with outside suction pump by drinking-water pipe.

2. deep foundation ditch artesian water precipitation dynamic monitoring system according to claim 1, it is characterized in that: described chimney filter comprises reinforcing cage that diameter is 200mm ~ 300mm and is coated on the filter screen of described reinforcing cage periphery, the aperture of described filter screen is 1 ~ 2mm, and the particle diameter of described gravel filtrate is 3 ~ 15mm.

3. deep foundation ditch artesian water precipitation dynamic monitoring system according to claim 1, it is characterized in that: the aperture of described monitor well is 550 ~ 600mm, the diameter of described downcast well pipe is 300 ~ 450mm; The mouth of pipe of described downcast well pipe is above the ground level 0.50-1m.

4. deep foundation ditch artesian water precipitation dynamic monitoring system according to claim 1, it is characterized in that: described sensor for pore water pressure is pore water pressure sensor, its diameter is 1.5 ~ 12mm, and range is 100kPa ~ 500kPa.

5. deep foundation ditch artesian water precipitation dynamic monitoring system according to claim 1, is characterized in that: the transmission coefficient of described sealing clay is 1.0 × 10 ^-8cm/s ~ 1.0 × 10 ^-10cm/s.

6. a deep foundation ditch artesian water precipitation dynamic monitoring method, is characterized in that specifically comprising the following steps:

(1) artesian water precipitation dynamic monitoring system is arranged

The inwall of downcast well pipe is longitudinally equidistantly installed several sensor for pore water pressures, the bottom of downcast well pipe is connected chimney filter and sediment tube successively, and shuts bottom sediment tube, adopt diving to bore mud off and offer monitor well, sediment tube is divided into successively from down to up in monitor well, chimney filter and downcast well pipe, and sediment tube and chimney filter are arranged in artesian aquifer region to be measured, gravel filtrate is backfilled by between the hole wall of monitor well and sediment tube and between the hole wall of monitor well and chimney filter, sealing clay is backfilled by between the hole wall of monitor well and downcast well pipe bottom, sealing of hole clay is backfilled by between the hole wall of monitor well and downcast well pipe top, each sensor for pore water pressure is wired on data collecting instrument, data collecting instrument is connected on monitoring computer, form a complete artesian water precipitation dynamic monitoring system,

(2) Dynamic Data Acquiring analysis

Extend chimney filter by drinking-water pipe, open pumping for water pump, and after stable level, time t is set to initial value 0, gather the initial pore water pressure value P of each sensor for pore water pressure _ij0, convert and obtain the degree of depth of respective aperture pressure sensor below water level, and be set to the ID value H of sensor for pore water pressure with this _ij0; Continue to draw water, water level decreasing, gathers t, the pore water pressure force value P of each sensor for pore water pressure _ijt, convert and obtain the depth value H of t respective aperture pressure sensor _ijt; By the depth value H of t sensor for pore water pressure _ijtdeduct the ID value H of sensor for pore water pressure _ij0, obtain the drawdown △ H of t sensor for pore water pressure _ijt, the average getting each sensor for pore water pressure drawdown of t obtains t drawdown H _it, draw and obtain drawdown H _itand the curve relation figure between time t is used for monitoring analysis; Pre-set target depth H, when reaching target depth H, system alarm prompting stops pumping, after water level rezime to certain altitude, re-start and draw water and monitoring analysis, wherein i=1,2 ..., n is well numbering, j=1,2 ..., n is the numbering of sensor for pore water pressure from top to bottom, and t is the time.

7. a kind of deep foundation ditch artesian water precipitation dynamic monitoring method according to claim 6, is characterized in that t in step (2), the pore water pressure force value P of each sensor for pore water pressure _ijtconvert and obtain the water level depth value H of respective aperture pressure sensor _ijtcomputational methods as follows:

$H_{i1t}=h_{i2t}-h_{i1t}=\frac{P_{i1t}}{{\mathrm{\γ}}_w}$

$H_{i2t}=h_{i3t}+h_{i2t}-h_{i1t}=\frac{P_{i2t}}{{\mathrm{\γ}}_w}$

$H_{i3t}=h_{i4t}+h_{i3t}+h_{i2t}-h_{i1t}=\frac{P_{i3t}}{{\mathrm{\γ}}_w}$

…………

H _int＝h _int+h _i(n-1)t+h _i(n-2)t-h _i1t＝P _int/r _w

Wherein h _i1tbe the elevation of i-th mouthful of well the 1st sensor for pore water pressure in t, h _ijtbe the elevation of i-th mouthful of well jth sensor for pore water pressure in t, i=1,2 ..., n is well numbering, j=1,2 ..., n is the numbering of sensor for pore water pressure from top to bottom, and t is the time, γ _wfor the severe (kN/m of water ³);

As drawdown H _it>h _i2t-h _i1t, namely drawdown has exceeded the degree of depth of first sensor for pore water pressure, then first sensor for pore water pressure hole pressure value P _i1tbe zero, then cancel Δ H _i1tmean value calculation; Work as H _it>h _i3+ h _i2-h _i1, cancel Δ H _i2tmean value calculation, the like.

8. deep foundation ditch artesian water precipitation dynamic monitoring method according to claim 6, it is characterized in that: described chimney filter comprises reinforcing cage that diameter is 200mm ~ 300mm and is coated on the filter screen of described reinforcing cage periphery, the aperture of described filter screen is 1 ~ 2mm, and the particle diameter of described gravel filtrate is 3 ~ 15mm.

9. deep foundation ditch artesian water precipitation dynamic monitoring method according to claim 6, it is characterized in that: the aperture of described monitor well is 550 ~ 600mm, the diameter of described downcast well pipe is 300 ~ 450mm; The mouth of pipe of described downcast well pipe is above the ground level 0.50-1m.

10. deep foundation ditch artesian water precipitation dynamic monitoring method according to claim 6, it is characterized in that: described sensor for pore water pressure is pore water pressure sensor, its diameter is 1.5 ~ 12mm, and range is 100kPa ~ 500kPa.