CN105369812A - Pressure bearing water level determining method for constant-flow water pumping of lower foundation pit of suspension type waterproof curtain - Google Patents

Abstract

The invention provides a pressure bearing water level determining method for constant-flow water pump of a lower foundation pit of a suspension type waterproof curtain. According to the method, the ground water level when the waterproof curtain doesn't enter an aquifer and the ground water level change caused by the waterproof curtain are determined in a constant-flow water pumping process based on obtained soil layer information and water pumping information of the pressure bearing aquifer and according to the Darcy law and the water volume conservation principle. Thus, pressure bearing water levels in and out the lower foundation pit of the suspension type waterproof curtain in constant-flow water pump can be determined. By means of combination of the Darcy law, the water volume conservation principle and the ground water percolation theory, the distribution of pressure bearing water levels in and out the foundation pit can be visually reflected in foundation pit dewatering. Therefore, basis for analyzing effects of foundation pit dewatering on the surroundings is provided. The method is simple, practical, convenient to popularize and large in application value.

Description

The pressure water head defining method of foundation ditch pumping with constant rate under suspension type water-stop curtain

Technical field

The present invention relates to the construction technology in the underground engineering field such as a kind of building, water conservancy, traffic, environment, particularly, relate to the pressure water head defining method of foundation ditch pumping with constant rate under a kind of suspension type water-stop curtain.

Background technology

Base pit engineering is the important component part of high-rise building construction and underground space engineering, and foundation pit dewatering is then the committed step of excavation, and the sedimentation of effect to the safety of excavation of foundation pit and foundation ditch surrounding ground of foundation pit dewatering has significant impact.Along with the progress of the expansion of city size, the rise of cost of land and construction technology, China's base pit engineering presents dark, large trend gradually, and part foundation depth reaches 40m.The excavation of deep big foundation pit, needs to reduce artesian water water level usually.For reducing precipitation to the impact of surrounding enviroment, often utilize water-stop curtain to completely cut off the hydraulic connection in the outer aquifer with foundation ditch in foundation ditch around foundation ditch, the seepage flow weakening underground water is movable.But because artesian aquifer thickness is large, artesian aquifer can not cut off by most of foundation pit waterproof curtain completely, thus presents a kind of underslung curtain.When drawing water in foundation ditch, the existence of water-stop curtain makes the reduction of seepage action of ground water area, seepage direction changes, percolation path extends, and makes underground water inside and outside foundation ditch occur head difference, thus reaches the object of protection of the environment.Be subject to the impact of the factor such as site condition and construction; observation well limited amount in base pit engineering; foundation ditch outward appearance well logging quantity does not seldom even have; be difficult to the excursion judging underground water inside and outside foundation ditch; therefore the change of pressure water head inside and outside foundation ditch during precipitation is determined under water-stop curtain effect in foundation ditch, significant to instructing base pit engineering construction, protection foundation ditch external environment condition and reducing surface settlement.

Through finding prior art literature search, current engineering circles commonly uses the WATER LEVEL CHANGES that foundation pit dewatering under the effect of numerical method analog computation water-stop curtain causes.Liu Guofeng equals the distribution being analyzed under the different diaphragm wall degree of depth in hole Analysis of Ground-water Seepage Field inside and outside foundation ditch during precipitation in " diaphragm wall buried depth is to the influence research of the ultra-deep foundation pit dewatering effect " literary composition delivered on " engineering investigation " for 2014 by Three-dimension Numerical Model detailed comparisons.But it is comparatively complicated to set up numerical model, site engineer is difficult to direct application.Wang Junhui equals the defining method proposing seepage field SEA LEVEL VARIATION when the impact of strip structure is issued to stable state in " underground structure intercepts the parsing-semi analytical method of problem on the seepage field " literary composition delivered in " hydrogeological engineering geology " for 2009.The method of Wang Junhui etc. is only confined to without source sink term in research range, and the situation that aquifer cuts off in horizontal or vertical direction by structure completely.In addition, the method only can determine underground water by during structure bottom and seepage area reduce the SEA LEVEL VARIATION produced, can not determine that seepage direction changes impact on water level, also do not consider the anisotropy in aquifer, result is less than normal.For pumping with constant rate problem in foundation ditch under water-stop curtain effect, still directly do not determine the method for pressure water head inside and outside foundation ditch at present, be therefore necessary to make further research on the one hand at this.

Summary of the invention

For defect of the prior art, the object of this invention is to provide the pressure water head defining method of foundation ditch pumping with constant rate under a kind of suspension type water-stop curtain, obtaining artesian aquifer soil layer information and drawing water on the basis of information, according to Darcy's law and mass conservation principle, for constant flow pump process in foundation ditch, determine the changing value of the groundwater table that groundwater level when water-stop curtain does not enter aquifer and water-stop curtain cause, thus artesian water water level inside and outside foundation ditch during pumping with constant rate in foundation ditch under determining suspension type water-stop curtain.

For realizing above object, the invention provides the pressure water head defining method of foundation ditch pumping with constant rate under a kind of suspension type water-stop curtain, described method realizes through the following steps:

The first step, the compartmentalize soil obtaining foundation ditch place and artesian aquifer transmission coefficient and thickness, that is:

Obtained the compartmentalize soil in foundation ditch place by boring extracting soil method, utilize the soil sample gathered to carry out results of permeability tests to determine the transmission coefficient of artesian aquifer, according to the thickness b of compartmentalize soil information determination artesian aquifer;

Second step, in conjunction with design of foundation pit and precipitation scheme, determine foundation pit waterproof curtain information and dewatering well information;

3rd step, the radius of influence R determining when many mouthfuls of dewatering wells draw water;

4th step, determine when water-stop curtain does not enter artesian aquifer, the pressure water head h of any point in aquifer under each water withdrawal effect when many mouthfuls of dewatering wells draw water _ni(r _i);

5th step, water-stop curtain reduces the SEA LEVEL VARIATION Δ h of the artesian aquifer that the artesian aquifer cross-section of river causes when determining water withdrawal _1i(r _i);

6th step, determine that water-stop curtain in water withdrawal process changes the SEA LEVEL VARIATION Δ h of any point in the artesian aquifer that percolation path causes _2i(r _i);

7th step, in conjunction with the 4th step, the 5th step and the 6th step, to determine under suspension type water-stop curtain in foundation ditch the pressure water head h of any point in artesian aquifer during water withdrawal _i(r _i);

8th step, in conjunction with the 7th step, the pressure water head h of artesian aquifer any point when determining that in foundation ditch, many mouthfuls of dewatering wells draw water.

Preferably, in the first step:

Described boring extracting soil method refers to: within the scope of 2.5 times of the design of foundation pit degree of depth, utilizes heavy wall soil sampler to choose 3 soil samples at each soil layer;

Described results of permeability tests refers to: utilize the cutting ring of Φ 200 respectively to cut 3 oblate cylinder soil samples along each solum horizontal to vertical, soil sample is put into permeameter, according to the change determining water level and the water yield in the time, determine the horizontal-hole blasting k of artesian aquifer _xwith vertical osmotic coefficient k _ztest method.

Preferably, in second step, described foundation pit waterproof curtain information refers to: foundation pit waterproof curtain enters the degree of depth b of artesian aquifer _band water-stop curtain intercepts Thickness Ratio ε, wherein:

Described b _bcompartmentalize soil according to design of foundation pit scheme and foundation ditch place is determined;

Described ε refers to: the thickness of water-stop curtain and the ratio of artesian aquifer thickness in artesian aquifer, and ε meets formula: $\mathrm{\ϵ}=\frac{b_b}{b}.$

Preferably, in second step, described dewatering well information refers to: the position of dewatering well and quantity, the length of strainer, the initial water level h of artesian aquifer ₀and the stable pump-out Q of dewatering well _w, wherein:

The initial water level h of described artesian aquifer ₀refer to: dewatering well Cheng Jinghou, lining rope put in well, measure water level above for three days on end, measure 3 every day, obtain water level average be the initial water level of artesian aquifer;

Described filter length refers to: the length of dewatering well cross-section of river in artesian aquifer;

The stable pump-out Q of described dewatering well _wrefer to: the water yield of extracting out in the dewatering well unit interval, Q _wremain unchanged in pump process, it is recorded by water meter measurement.

More preferably, described water meter measurement refers to: accessed by water meter in the gutter near pumped well well head, starts suction pump, treats that gutter starts the initial reading of water meter under water outlet postscript, read the real time readouts of water meter after 24 hours, the difference of two numbers is the pump-out of this pumped well every day.

Preferably, in the 3rd step, determine that radius of influence R when many mouthfuls of described dewatering wells draw water comprises the steps:

(1) the drawdown S of single port dewatering well when determining that many mouthfuls of dewatering wells draw water _wi, S _wimeet following formula:

S _wi＝h ₀-h _wi，

Wherein: h _wifor the fixed level of i-th mouthful of dewatering well when many mouthfuls of dewatering wells draw water; h ₀for the initial water level of artesian aquifer;

(2) determine radius of influence R when many mouthfuls of dewatering wells draw water, R meets following formula:

$R=10S_{max}\sqrt{k_x},$

Wherein: S _maxfor each dewatering well drawdown S _wimaximum value; k _xfor the horizontal-hole blasting of artesian aquifer.

More preferably, in step (1), the fixed level h of i-th mouthful of described dewatering well _wirefer to: after many mouthfuls of dewatering wells draw water and stablize, lining rope is put in i-th mouthful of dewatering well, read this dewatering well water level every 2 ~ 3 hours, when the dewatering well water level error of continuous 3 readings is within 1%, the average getting this water level of three times is the final fixed level of this dewatering well.

Preferably, in the 4th step, described h _ni(r _i) meet following formula:

$h_{ni}\left(r_i\right)=\frac{Q_{wi}ln(r_i/R)}{2{\mathrm{\πk}}_{x}b}+h_0,$

Wherein: Q _wiit is the stable pump-out of i-th mouthful of dewatering well; r _ifor water level point to be asked in stratum is to the horizontal range of i-th mouthful of dewatering well, it is recorded by steel ruler; R is the radiuses of influence of many mouthfuls of dewatering wells when drawing water; k _xfor the horizontal-hole blasting of artesian aquifer; B is the thickness of artesian aquifer; h ₀for the initial water level of artesian aquifer.

Preferably, in the 5th step, determine described Δ h _1i(r _i) comprise the steps:

(1) when determining water withdrawal, seepage area reduces the pressure water head h of any point in the artesian aquifer caused _1i(r _i), h _1i(r _i) meet following formula:

Wherein: Q _wiit is the stable pump-out of i-th mouthful of dewatering well; h ₀for the initial water level of artesian aquifer; ε is the obstruct Thickness Ratio of water-stop curtain; θ _ifor on the sectional elevation that water level point to be asked and i-th mouthful of dewatering well central axis are determined, i-th mouthful of dewatering well central axis is to this side foundation pit waterproof curtain inward flange distance r _1iwith outward flange distance r _2iratio, θ _imeet formula r _1iwith r _2idrawn along ground measurement by steel ruler; R is the radiuses of influence of many mouthfuls of dewatering wells when drawing water; k _xfor the horizontal-hole blasting of artesian aquifer; B is the thickness of artesian aquifer;

(2) when determining water withdrawal, water-stop curtain reduces the SEA LEVEL VARIATION Δ h of the artesian aquifer that the artesian aquifer cross-section of river causes _1i(r _i), Δ h _1i(r _i) meet following formula:

Δh _1i(r _i)＝h _ni(r _i)-h _1i(r _i)。

Preferably, in the 6th step, described Δ h _2i(r _i) meet following formula:

Δh _2i(r _i)＝mΔh _1i(r _i)，

In formula, m meets following formula:

$m=\left\{\begin{array}{cc}1.32b(1-\mathrm{\&epsiv;}){\left(\frac{k_x}{k_z}\right)}^{\frac{5}{8}}{\left(\frac{10}{b}\right)}^{0.3668\ln b-0.852}& \mathrm{\&epsiv;}<0.25\\ \sqrt{\frac{1}{8}}ln\left(\frac{6{\mathrm{\&epsiv;}}^{1.1}}{{(1-\mathrm{\&epsiv;})}^{2.23}}\right)\frac{(1-\mathrm{\&epsiv;})b}{\mathrm{\&epsiv;}}{\left(\frac{k_x}{k_z}\right)}^{\frac{5}{8}}{\left(\frac{10}{b}\right)}^{0.3668\ln b-0.852}& \mathrm{\&epsiv;}\&GreaterEqual;0.25\end{array}\right.$

Wherein: b is the thickness of artesian aquifer; ε is the obstruct Thickness Ratio of water-stop curtain; k _xfor the horizontal-hole blasting of artesian aquifer; k _zfor the vertical transmission coefficient of artesian aquifer.

Preferably, in the 7th step, described h _i(r _i) meet following formula:

Wherein: Q _wiit is the stable pump-out of i-th mouthful of dewatering well; h ₀for the initial water level of artesian aquifer; ε is the obstruct Thickness Ratio of water-stop curtain; θ _ifor on the sectional elevation that water level point to be asked and i-th mouthful of dewatering well central axis are determined, i-th mouthful of dewatering well central axis is to this side foundation pit waterproof curtain inward flange distance r _1iwith outward flange distance r _2iratio, θ _imeet formula r _1iwith r _2idrawn along ground measurement by steel ruler; R is the radiuses of influence of many mouthfuls of dewatering wells when drawing water; k _xfor the horizontal-hole blasting of artesian aquifer; B is the thickness of artesian aquifer.

Preferably, in the 8th step, described h meets following formula:

$h=\underset{i=1}{\overset{n}{\&Sigma;}}{h}_i\left(r_i\right)-(n-1)h_0,$

Wherein: n is dewatering well quantity.

Compared with prior art, the present invention has following beneficial effect:

The present invention is theoretical in conjunction with Darcy's law, mass conservation principle and seepage action of ground water, provide and directly to calculate under water-stop curtain effect in foundation ditch during pumping with constant rate, the formula of pressure water head inside and outside foundation ditch, the distribution of pressure water head inside and outside foundation ditch when can reflect foundation pit dewatering intuitively, thus provide foundation for analyzing the impact of foundation pit dewatering on surrounding enviroment.This method is simple, practical, is convenient to promote, and has very large using value.

Accompanying drawing explanation

By reading the description with reference to the following drawings, other features of the present invention, object and advantage will become more apparent.

Fig. 1 is that many wells of one embodiment of the invention draw water schematic diagram;

Fig. 2 is the foundation ditch of one embodiment of the invention and the position relationship plan view of dewatering well;

Pressure water head distribution map inside and outside foundation ditch while that Fig. 3 being two mouthfuls of dewatering wells of one embodiment of the invention during precipitation.

Detailed description of the invention

Below in conjunction with specific embodiment, the present invention will be described in detail.Following examples will contribute to those skilled in the art and understand the present invention further, but not limit the present invention in any form.It should be pointed out that to those skilled in the art, without departing from the inventive concept of the premise, still can make some distortion and improvement.These all belong to protection scope of the present invention.

Below provide specific embodiment, do not have the part described in detail to record with reference to summary of the invention in embodiment and carry out.

Embodiment

Certain Circular Pit is positioned at the top of artesian aquifer, carries out twin-well and draws water, and the position relationship plane of foundation ditch and dewatering well as shown in Figure 2.

As shown in Figure 1-Figure 3, the present embodiment provides the pressure water head defining method of foundation ditch pumping with constant rate under a kind of suspension type water-stop curtain, and described method realizes through the following steps:

Step one, the compartmentalize soil obtaining foundation ditch place and artesian aquifer transmission coefficient and thickness

Compartmentalize soil information is obtained as follows by boring extracting soil:

Buried depth 0.00-1.82m scope is miscellaneous fill, buried depth 1.82-14.12m scope is grey sandy silt, buried depth 14.12-20.12m scope is grey Muddy Bottoms clay, buried depth 20.12-24.12m scope is grey clay, buried depth 24.12-28.00m scope is dark green-olive drab(O．D) silty clay, and buried depth 28.00-38.00m scope is straw colour ~ grey flour sand.

The artesian aquifer obtained by boring extracting soil is straw colour ~ grey flour sand, and thickness is 10m; The horizontal-hole blasting k of the artesian aquifer obtained by results of permeability tests _xwith vertical osmotic coefficient k _zbe 4m/d.

Step 2, in conjunction with design of foundation pit and precipitation scheme, determine foundation pit enclosure structure design information, dewatering well information

In the present embodiment, foundation ditch adopts diaphragm wall as space enclosing structure, and foundation ditch radius is 18m; Diaphragm wall is as water-stop curtain, and width is 1m, and water-stop curtain enters the degree of depth b of artesian aquifer _bfor 9m, it is 0.9 that water-stop curtain intercepts Thickness Ratio ε, and foundation ditch adopts two mouthfuls of dewatering wells to draw water, and as shown in Figure 2, No. 1 dewatering well central axis and foundation ditch central axes, two mouthfuls of dewatering well filter length are 10m to particular location, artesian aquifer initial water level h ₀for-1m, two mouthfuls of dewatering wells stablize pump-out Q _wbe 100m ³/ d.

Step 3, the radius of influence R determining when many mouthfuls of dewatering wells draw water

Specifically comprise:

(1) drawdown S when two mouthfuls of dewatering wells draw water is determined _w1and S _w2lining rope is put in well, read dewatering well water level every 2 ~ 3 hours, when No. 1 continuous dewatering well water level read for 3 times of dewatering well is respectively-5.9m ,-5.86m and-5.82m, water level error is within 1%, and the average getting this water level of three times is the final fixed level h of this well _w1, i.e. h _w1for-5.86m, No. 1 dewatering well drawdown S _w1=h ₀-h _w1, obtain S _w1=4.86m; Same method records the water level h of No. 2 dewatering wells _w2for-6.80, No. 2 dewatering well drawdown S _w2=h ₀-h _w2=5.80m.

(2) radius of influence R when two mouthfuls of dewatering wells draw water is determined:

(S _maxfor each dewatering well drawdown S _wimaximum value, namely get 5.80m).

Step 4, determine when water-stop curtain does not enter artesian aquifer, the pressure water head h of any point in aquifer under each water withdrawal effect when many mouthfuls of dewatering wells draw water _ni(r _i)

Described h _ni(r _i) meet following formula:

$h_{ni}\left(r_i\right)=\frac{Q_{wi}ln(r_i/R)}{2{\mathrm{\&pi;k}}_{x}b}+h_0,$

Thus determine No. 1 dewatering well and No. 2 pressure water head hs of dewatering well at any point place _n1(r ₁) and h _n2(r ₂), design formulas is respectively:

$h_{n1}\left(r_1\right)=\frac{500ln(r_1/117)}{80\mathrm{\&pi;}}-1=1.99\ln r_1-9.47;$

$h_{n2}\left(r_2\right)=\frac{500ln(r_2/117)}{80\mathrm{\&pi;}}-1=1.99\ln r_2-\mathrm{9.47.}$

Step 5, water-stop curtain reduces the SEA LEVEL VARIATION Δ h of the artesian aquifer that the artesian aquifer cross-section of river causes when determining water withdrawal _1i(r _i)

Comprise the steps:

(1) the pressure water head h of any point in artesian aquifer when No. 1 dewatering well and No. 2 dewatering wells draw water is calculated ₁₁(r ₁) and h ₁₂(r ₂), by formula:

Obtain the Δ h of the present embodiment No. 1 well and No. 2 wells ₁₁(r ₁) and Δ h ₁₂(r ₂):

(2) when determining that No. 1 dewatering well and No. 2 dewatering wells draw water, water-stop curtain reduces the SEA LEVEL VARIATION Δ h that the artesian aquifer cross-section of river causes ₁₁(r ₁) and Δ h ₁₂(r ₂), by formula:

Δh _1i(r _i)＝h _ni(r _i)-h _1i(r _i)

Obtain the Δ h of the present embodiment No. 1 dewatering well and No. 2 dewatering wells ₁₁(r ₁) and Δ h ₁₂(r ₂):

Step 6, determine that water-stop curtain in water withdrawal process changes the SEA LEVEL VARIATION Δ h of any point in the artesian aquifer that percolation path causes _2i(r _i)

Described Δ h _2i(r _i) meet following formula: Δ h _2i(r _i)=m Δ h _1i(r _i),

M meets following formula:

$m=\left\{\begin{array}{cc}1.32b(1-\mathrm{\&epsiv;}){\left(\frac{k_x}{k_z}\right)}^{\frac{5}{8}}{\left(\frac{10}{b}\right)}^{0.3668\ln b-0.852}& \mathrm{\&epsiv;}<0.25\\ \sqrt{\frac{1}{8}}ln\left(\frac{6{\mathrm{\&epsiv;}}^{1.1}}{{(1-\mathrm{\&epsiv;})}^{2.23}}\right)\frac{(1-\mathrm{\&epsiv;})b}{\mathrm{\&epsiv;}}{\left(\frac{k_x}{k_z}\right)}^{\frac{5}{8}}{\left(\frac{10}{b}\right)}^{0.3668\ln b-0.852}& \mathrm{\&epsiv;}\&GreaterEqual;0.25\end{array}\right.;$

In the present embodiment, because intercepting than ε=0.9>0.25,

$m=\sqrt{\frac{1}{8}}ln\left(\frac{6\&times;{0.9}^{1.1}}{{(1-0.9)}^{2.23}}\right)\frac{(1-0.9)\&times;10}{0.9}{\left(\frac{4}{4}\right)}^{\frac{5}{8}}{\left(\frac{10}{10}\right)}^{0.3668\ln 10-0.852}=2.68$

In No. 1 dewatering well and No. 2 dewatering well pump process, water-stop curtain changes the SEA LEVEL VARIATION Δ h of any point in the artesian aquifer that percolation path causes ₂₁(r ₁) and Δ h ₂₂(r ₂) be respectively:

Δh ₂₁(r ₁)＝2.68Δh ₁₁(r ₁)；

Δh ₂₂(r ₂)＝2.68Δh ₁₂(r ₂)。

Step 7, to determine under suspension type water-stop curtain in foundation ditch the pressure water head h of any point in artesian aquifer during water withdrawal _i(r _i)

Described h _i(r _i) meet following formula:

The pressure water head h of any point in artesian aquifer when No. 1 dewatering well and No. 2 dewatering wells draw water in foundation ditch under the present embodiment suspension type water-stop curtain ₁(r ₁) and h ₂(r ₂) be respectively:

Step 8, the pressure water head h of artesian aquifer any point when determining that in foundation ditch, many mouthfuls of dewatering wells draw water

Described h meets following formula:

$h=\underset{i=1}{\overset{n}{\&Sigma;}}{h}_i\left(r_i\right)-(n-1)h_0$

Obtain the pressure water head h of artesian aquifer any point when No. 1 dewatering well and No. 2 dewatering wells draw water in foundation ditch:

Each point pressure water head in calculating chart 2 on I-I section also makes water level distribution map, and as shown in Figure 3, in Fig. 3, abscissa is the horizontal range of each point to 1 well central axis to result.

Pressure water head when the pressure water head defining method of foundation ditch pumping with constant rate can calculate that in foundation ditch, multiple dewatering well draws water rapidly and accurately under suspension type water-stop curtain in the present invention in stratum, significant to instructing Practical Project.This method is simple, practical, is convenient to promote, and has very large using value.

Above specific embodiments of the invention are described.It is to be appreciated that the present invention is not limited to above-mentioned particular implementation, those skilled in the art can make various distortion or amendment within the scope of the claims, and this does not affect flesh and blood of the present invention.

Claims (10)

1. the pressure water head defining method of foundation ditch pumping with constant rate under suspension type water-stop curtain, it is characterized in that, described method realizes through the following steps:

The first step, the compartmentalize soil obtaining foundation ditch place and artesian aquifer transmission coefficient and thickness, that is:

Obtained the compartmentalize soil in foundation ditch place by boring extracting soil method, utilize the soil sample gathered to carry out results of permeability tests to determine the transmission coefficient of artesian aquifer, according to the thickness b of compartmentalize soil information determination artesian aquifer;

Second step, in conjunction with design of foundation pit and precipitation scheme, determine foundation pit waterproof curtain information and dewatering well information;

3rd step, the radius of influence R determining when many mouthfuls of dewatering wells draw water;

4th step, determine when water-stop curtain does not enter artesian aquifer, the pressure water head h of any point in aquifer under each water withdrawal effect when many mouthfuls of dewatering wells draw water _ni(r _i);

5th step, water-stop curtain reduces the SEA LEVEL VARIATION Δ h of the artesian aquifer that the artesian aquifer cross-section of river causes when determining water withdrawal _1i(r _i);

6th step, determine that water-stop curtain in water withdrawal process changes the SEA LEVEL VARIATION Δ h of any point in the artesian aquifer that percolation path causes _2i(r _i);

7th step, in conjunction with the 4th step, the 5th step and the 6th step, to determine under suspension type water-stop curtain in foundation ditch the pressure water head h of any point in artesian aquifer during water withdrawal _i(r _i);

8th step, in conjunction with the 7th step, the pressure water head h of artesian aquifer any point when determining that in foundation ditch, many mouthfuls of dewatering wells draw water.

2. the pressure water head defining method of foundation ditch pumping with constant rate under a kind of suspension type water-stop curtain according to claim 1, is characterized in that, in the first step:

Described boring extracting soil method refers to: within the scope of 2.5 times of the design of foundation pit degree of depth, utilizes heavy wall soil sampler to choose 3 soil samples at each soil layer;

Described results of permeability tests refers to: utilize the cutting ring of Φ 200 respectively to cut 3 oblate cylinder soil samples along each solum horizontal to vertical, soil sample is put into permeameter, according to the change determining water level and the water yield in the time, determine the horizontal-hole blasting k of artesian aquifer _xwith vertical osmotic coefficient k _ztest method.

3. the pressure water head defining method of foundation ditch pumping with constant rate under a kind of suspension type water-stop curtain according to claim 1, it is characterized in that, in second step, described foundation pit waterproof curtain information refers to: foundation pit waterproof curtain enters the degree of depth b of artesian aquifer _band water-stop curtain intercepts Thickness Ratio ε, wherein:

Described b _bcompartmentalize soil according to design of foundation pit scheme and foundation ditch place is determined;

Described ε refers to: the thickness of water-stop curtain and the ratio of artesian aquifer thickness in artesian aquifer, and ε meets formula:

$\mathrm{\&epsiv;}=\frac{b_b}{b}.$

4. the pressure water head defining method of foundation ditch pumping with constant rate under a kind of suspension type water-stop curtain according to claim 1, it is characterized in that, in second step, described dewatering well information refers to: the position of dewatering well and quantity, the length of strainer, the initial water level h of artesian aquifer ₀and the stable pump-out Q of dewatering well _w, wherein:

The initial water level h of described artesian aquifer ₀refer to: dewatering well Cheng Jinghou, lining rope put in well, measure water level above for three days on end, measure 3 every day, obtain water level average be the initial water level of artesian aquifer;

Described filter length refers to: the length of dewatering well cross-section of river in artesian aquifer;

The stable pump-out Q of described dewatering well _wrefer to: the water yield of extracting out in the dewatering well unit interval, Q _wremain unchanged in pump process, it is recorded by water meter measurement; Described water meter measurement refers to: accessed by water meter in the gutter near pumped well well head, start suction pump, treat that gutter starts the initial reading of water meter under water outlet postscript, read the real time readouts of water meter after 24 hours, the difference of two numbers is the pump-out of this pumped well every day.

5. the pressure water head defining method of foundation ditch pumping with constant rate under a kind of suspension type water-stop curtain according to claim 1, is characterized in that, in the 3rd step, determine radius of influence R when many mouthfuls of described dewatering wells draw water, comprise the steps:

(1) the drawdown S of single port dewatering well when determining that many mouthfuls of dewatering wells draw water _wi, S _wimeet following formula:

S _wi＝h ₀-h _wi，

Wherein: h ₀for the initial water level of artesian aquifer; h _wifor the fixed level of i-th mouthful of dewatering well when many mouthfuls of dewatering wells draw water, h _wirefer to: after many mouthfuls of dewatering wells draw water and stablize, lining rope is put in i-th mouthful of dewatering well, read this dewatering well water level every 2 ~ 3 hours, when the dewatering well water level error of continuous 3 readings is within 1%, the average getting this water level of three times is the final fixed level of this dewatering well;

(2) determine radius of influence R when many mouthfuls of dewatering wells draw water, R meets following formula:

$R=10S_{max}\sqrt{k_x},$

Wherein: S _maxfor each dewatering well drawdown S _wimaximum value; k _xfor the horizontal-hole blasting of artesian aquifer.

6. in the 4th step, described h _ni(r _i) meet following formula:

$h_{ni}\left(r_i\right)=\frac{Q_{wi}ln(r_i/R)}{2{\mathrm{\&pi;k}}_{x}b}+h_0,$

Wherein: Q _wiit is the stable pump-out of i-th mouthful of dewatering well; r _ifor water level point to be asked in stratum is to the horizontal range of i-th mouthful of dewatering well, it is recorded by steel ruler; R is the radiuses of influence of many mouthfuls of dewatering wells when drawing water; k _xfor the horizontal-hole blasting of artesian aquifer; B is the thickness of artesian aquifer; h ₀for the initial water level of artesian aquifer.

7. the pressure water head defining method of foundation ditch pumping with constant rate under a kind of suspension type water-stop curtain according to claim 1, is characterized in that, in the 5th step, determine described Δ h _1i(r _i) comprise the steps:

(1) when determining water withdrawal, seepage area reduces the pressure water head h of any point in the artesian aquifer caused _1i(r _i), h _1i(r _i) meet following formula:

Wherein: h ₀for the initial water level of artesian aquifer; ε is the obstruct Thickness Ratio of water-stop curtain; θ _ifor on the sectional elevation that water level point to be asked and i-th mouthful of dewatering well central axis are determined, i-th mouthful of dewatering well central axis is to this side foundation pit waterproof curtain inward flange distance r _1iwith outward flange distance r _2iratio, θ _imeet formula r _1iwith r _2idrawn along ground measurement by steel ruler; r _ifor water level point to be asked in stratum is to the horizontal range of i-th mouthful of dewatering well;

(2) when determining water withdrawal, water-stop curtain reduces the SEA LEVEL VARIATION Δ h of the artesian aquifer that the artesian aquifer cross-section of river causes _1i(r _i), Δ h _1i(r _i) meet following formula:

Δh _1i(r _i)＝h _ni(r _i)-h _1i(r _i)。

8. the pressure water head defining method of foundation ditch pumping with constant rate under a kind of suspension type water-stop curtain according to claim 1, is characterized in that, in the 6th step, and described Δ h _2i(r _i) meet following formula:

Δh _2i(r _i)＝mΔh _1i(r _i)，

In formula, m meets following formula:

$m=\left\{\begin{array}{cc}1.32b(1-\mathrm{\&epsiv;}){\left(\frac{k_x}{k_z}\right)}^{\frac{5}{8}}{\left(\frac{10}{b}\right)}^{0.3668\ln b-0.852}& \mathrm{\&epsiv;}<0.25\\ \sqrt{\frac{1}{8}}\ln \left(\frac{6{\mathrm{\&epsiv;}}^{1.1}}{{(1-\mathrm{\&epsiv;})}^{2.23}}\right)\frac{(1-\mathrm{\&epsiv;})b}{\mathrm{\&epsiv;}}{\left(\frac{k_x}{k_z}\right)}^{\frac{5}{8}}{\left(\frac{10}{b}\right)}^{0.3668\ln b-0.852}& \mathrm{\&epsiv;}\&GreaterEqual;0.25\end{array}\right.$

Wherein: b is the thickness of artesian aquifer; ε is the obstruct Thickness Ratio of water-stop curtain; k _xfor the horizontal-hole blasting of artesian aquifer; k _zfor the vertical transmission coefficient of artesian aquifer.

9. the pressure water head defining method of foundation ditch pumping with constant rate under a kind of suspension type water-stop curtain according to claim 1, is characterized in that, in the 7th step, and described h _i(r _i) meet following formula:

10. the pressure water head defining method of foundation ditch pumping with constant rate under a kind of suspension type water-stop curtain according to claim 1, it is characterized in that, in the 8th step, described h meets following formula:

$h=\underset{i=1}{\overset{n}{\&Sigma;}}{h}_i\left(r_i\right)-(n-1)h_0,$

Wherein: n is dewatering well quantity, h ₀for the initial water level of artesian aquifer.