CN105386474B - Method for determining the impact of water-stop curtain leakage on the surrounding environment above the excavation surface of foundation pit - Google Patents

Abstract

The invention provides a method for determining influences of leakage of a waterproof curtain above a foundation pit excavation face on the surrounding environment. According to the method, the leakage situation of the waterproof curtain is observed according to soil layer information and foundation pit materials, and the leakage area and the actual leakage amount of the leakage position are measured on site; a three-dimensional finite element model is established, a user-defined leakage unit is set at the corresponding position of the model according to the leakage area, and the osmotic coefficient of the leakage position is determined according to the relative relational graph of the leakage amount and the osmotic coefficient in the three-dimensional model; and the osmotic coefficient of the leakage position is set for the user-defined leakage unit, foundation pit excavation and seepage solidification are simulated in sequence, and the foundation pit surrounding underground water level and the ground settling volume caused by leakage of the waterproof curtain above the foundation pit excavation face are finally determined. The method is simple and convenient to popularize and has very high application value. The method is suitable for the problem of the leakage of the waterproof curtain above the foundation pit excavation face.

Description

Method for determining the impact of water-stop curtain leakage on the surrounding environment above the excavation surface of foundation pit

technical field

The invention relates to a method in the technical field of construction engineering, in particular to a method for determining the influence of leakage of a water-stop curtain above the excavation surface of a foundation pit on the surrounding environment.

Background technique

Since the 21st century, the development of underground space has been continuously deepened. The large-scale construction of urban subways, the increasing number of underground shopping malls and underground garages have effectively relieved the pressure on the above-ground space. Along with the development of underground space, a large number of foundation pit projects have emerged. At present, there are more and more foundation pit projects with an excavation depth of 20-30m, and some even reach more than 40m, which is a deep foundation pit. For deep and large foundation pits, the method of combining well point dewatering and water-stop curtains is widely used now to reduce the groundwater level in the foundation pit. Among them, in the excavation of deep foundation pits, the water-stop curtain can not only play the role of retaining soil, but also prevent the lateral seepage of groundwater. It is a technical means to avoid excessive deformation around the pit due to groundwater seepage. However, in actual engineering, due to construction technology, construction technology and other reasons, the water-stop curtain often leaks to varying degrees. If the seepage occurs in the saturated sand layer above the excavation surface of the foundation pit, serious seepage may occur. The phenomenon of quicksand occurs, which leads to disasters such as ground subsidence, pipeline damage, and building cracking. For this reason, it is of great significance to determine the influence of the leakage of the water-stop curtain above the excavation surface of the foundation pit on the seepage environment for the safe excavation of the foundation pit.

After searching the existing technical literature, it is found that the research on the leakage of the water-stop curtain mainly focuses on the impact of leakage on the groundwater level, and is aimed at the leakage of the water-stop curtain on the confined aquifer below the excavation surface of the foundation pit , the existing analysis method adopts the two-dimensional finite element method. For example, in "Amethodology for characterizing the hydraulic effectiveness of an annular low-permeability barrier" published by Vilarrasa in "Engineering Geology" in 2011, using the numerical simulation results of the two-dimensional finite element method to draw the Judgment diagram of water level drawdown over time, but it is applicable to the situation where the water-stop curtain completely cuts off the aquifer. In "Hydraulic characterization of diaphragm walls for cut and cover tunneling" published in "Engineering Geology" in 2012, Pujades used the two-dimensional finite element method to draw the relationship between the water level drawdown derivative and time under different seepage conditions, and proposed Some analytical calculation formulas can be used to calculate the permeability coefficient of the water-stop curtain through the combination of the two, but its disadvantage is that it is only applicable to strip foundations under certain conditions.

In fact, the leakage of the water-stop curtain is a space problem, and the two-dimensional finite element method is aimed at the simplified plane problem, which is not as practical as the three-dimensional finite element method for the space problem. Therefore, it is necessary to establish a three-dimensional numerical model to simulate The impact of the leakage of water-stop curtain above the excavation surface of foundation pit on the surrounding environment. However, for the 3D model, if solid elements are used, then in the part with a small leakage area, the meshing needs to be very small, resulting in too many meshes, resulting in cumbersome calculations and even affecting the convergence of calculations. It is impossible to determine the impact of the leakage of the water-stop curtain above the excavation surface of the foundation pit on the surrounding environment.

Contents of the invention

Aiming at the deficiencies of the prior art, the present invention provides a method for determining the impact of the leakage of the water-stop curtain above the excavation surface of the foundation pit on the surrounding environment. On the basis of understanding the soil layer information and foundation pit data, according to the observed Curtain leakage situation, on-site measurement of the leakage area and actual leakage amount; establish a three-dimensional finite element model, set a custom leakage unit in the corresponding position of the three-dimensional finite element model according to the leakage area, and refer to the three-dimensional finite element Determine the seepage coefficient of the seepage position by the correlation diagram of the seepage amount and the seepage coefficient in the model; set the seepage coefficient of the seepage position for the custom seepage unit, simulate the foundation pit excavation and seepage consolidation in sequence, and finally determine the foundation pit opening The groundwater level and ground subsidence around the foundation pit caused by the leakage of the water-stop curtain above the excavation surface.

The present invention is achieved through the following technical solutions:

The invention provides a method for determining the influence of leakage of a water-stop curtain above the excavation surface of a foundation pit on the surrounding environment. The method includes the following steps:

The first step is to carry out on-site investigation of the foundation pit to determine the soil layer division information and groundwater distribution, and conduct indoor geotechnical tests by drilling soil to obtain the physical and mechanical parameters of the soil layer;

The second step is to obtain the plane size of the foundation pit, the excavation depth, and the thickness, embedding depth, elastic modulus, and permeability coefficient of the water-stop curtain, and determine the equivalent elastic modulus E' of the water-stop curtain considering the strength reduction effect;

The third step is to observe the leakage situation of the water-stop curtain above the excavation surface of the foundation pit, record the location and shape of the leakage, and determine the leakage area D and the actual leakage quantity Q _k of the water-stop curtain leakage;

The fourth step is to use the finite element analysis software to establish a three-dimensional fluid-solid coupling model of the leakage of the water-stop curtain above the excavation surface of the foundation pit; according to the field investigation, the corresponding leakage position in the three-dimensional fluid-solid coupling model is set according to the leakage area. Leakage unit, simulating the excavation process of the foundation pit;

The fifth step is to assume different orders of magnitude of permeability coefficient k _j for the self-defined seepage unit, activate the seepage boundary inside the water-stop curtain above the excavation surface of the foundation pit, and determine the seepage of the water-stop curtain for a period of time under each working condition (for example, 1 days) after the leakage Q;

The sixth step is to establish a Cartesian rectangular coordinate system, the horizontal axis is the permeability coefficient k _j of different orders, and the vertical axis is the leakage Q, draw the correlation diagram between the leakage Q and the permeability coefficient k _j , and determine according to the relationship diagram The actual leakage Q _k measured on site corresponds to the permeability coefficient k of the leakage location;

The seventh step is to set the seepage coefficient k of the seepage location for the self-defined seepage unit in the 3D fluid-solid coupling model, and perform seepage consolidation simulation to determine the groundwater around the foundation pit caused by the leakage of the water-stop curtain above the excavation surface of the foundation pit level and ground subsidence.

Preferably, in the first step, the division of the soil layer refers to: divide the soil layer within the range of 2.5 times the depth of the foundation pit below the surface of the foundation pit by the method of drilling and taking soil, and then obtain the soil samples of the construction site for indoor Geotechnical test, obtain the soil layer division information and geological information at the construction site, and determine the soil properties of each soil layer and the thickness of the corresponding soil layer;

Preferably, in the first step, the distribution of groundwater refers to: use a borehole water detector to drill groundwater at the foundation pit site, and judge the type and thickness of the aquifer from the exposed soil type; The stable water level of different aquifers, for the confined aquifer, water-proof measures are taken to isolate the measured aquifer from other aquifers, and then measure the stable water level.

Preferably, in the first step, said drilling for soil refers to: using a thin-walled soil tool to obtain on-site soil samples around the foundation pit, and the number of soil samples should be three test pieces.

Preferably, in the first step, the indoor geotechnical test refers to: density test, specific gravity test, moisture content test, triaxial test, conventional unidirectional compression test, load test and indoor penetration test.

Preferably, in the first step, the physical and mechanical parameters refer to: the weight of the soil, void ratio, effective cohesion, internal friction angle, compression modulus, Poisson's ratio, deformation modulus, horizontal permeability coefficient and Vertical permeability coefficient.

Preferably, in the second step, the equivalent elastic modulus E' of the waterproof curtain satisfies the following formula:

E'=ηE _s ,

Among them: η is the modulus reduction coefficient, take 1/5; E _s is the elastic modulus of reinforced concrete.

Preferably, in the second step, the permeability coefficient of the water-stop curtain is divided into the horizontal direction and the vertical direction, and the permeability coefficients in the horizontal direction and the vertical direction are both taken as the concrete permeability coefficient.

Preferably, in the third step, the leakage position refers to: the position coordinates of the leakage area in the entire foundation pit plane, and the depth in the vertical direction of the foundation pit.

Preferably, in the third step, the leakage shape refers to the leakage shape presented when the groundwater seeps into the foundation pit through the water-stop curtain.

Preferably, in the third step, the leakage area D of the leakage of the water-stop curtain is determined in the following manner:

Visually measure the approximate position of the leakage area on the ground surface, select a reference object on the ground surface near the excavated foundation pit (the reference object has position coordinates on the foundation pit plan), measure the distance between the reference object and the leakage area, and determine The position coordinates of the leakage area in the entire foundation pit plane; put the measuring rope at the plane position coordinates of the leakage area, and measure the topmost depth h ₁ , the bottommost depth h ₂ of the leakage area and the two sides of the leakage area The distance L between the sides gives the leakage area D:

D=L×(h ₂ −h ₁ ).

Preferably, in the third step, the actual leakage _Qk is determined in the following manner:

Place a drum directly below the leakage of the water-stop curtain above the excavation surface of the foundation pit, measure the diameter d of the bottom surface of the drum, the height h ₃ of the drum, and the height h ₄ of the water in the drum; measure 2 leaking locations on site The size of the hourly leakage Q _2k ; the Q _2k satisfies the following formula:

Q _2k =NV+(πd ² /4)×h ₄ ,

In the formula: N is the number of buckets of leaking water connected in 2 hours, V is the volume of the drum; the volume of the drum V satisfies the following formula:

V=(πd ² /4)×h ₃ ;

Based on the 2-hour leakage Q _2k measured on site, the actual leakage Q _k 1 day after the leakage is estimated, that is, Q _k = 12Q _2k .

Preferably, in the fourth step, the self-defined leakage unit refers to a two-node line unit with certain permeability and stiffness, the self-defined leakage unit shares nodes with the solid unit in the three-dimensional model, and has three basic Parameters: leakage area D _z , permeability coefficient k and elastic modulus E. Specifically, the leakage area D _z is determined by the measured leakage area D in the third step, which satisfies the formula: D _z =D/n, where n is the grid node passed by the leakage position of the water stop curtain; the permeability coefficient k is passed through It is determined by setting the permeability coefficient k _j of different orders; the elastic modulus E is taken as 0.01.

Preferably, in the fourth step, the three-dimensional fluid-solid coupling model refers to: the scope of the model is centered on the foundation pit, and the horizontal direction is greater than the influence radius R of the precipitation well; the vertical direction of the model is greater than the depth of the bottom plate of the confined aquifer; The model is meshed, the soil parameters and water level are input, and the initial conditions and boundary conditions of the model are set. Among them: the initial conditions of the model are: the pore pressure of the water level line is zero, and the displacement is zero; the boundary conditions are: around the model It is the constant water head boundary, and the bottom is a fixed boundary condition; both the soil body and the water-stop curtain adopt 8-node pore pressure elements, and a contact surface is set between the water-stop curtain and the soil body, and the friction coefficient of the contact surface is 0.25. More preferably, the influence radius R of the precipitation well adopts the empirical formula of the confined aquifer:

In the formula: S is the water level drawdown (m), and K is the horizontal permeability coefficient of the confined aquifer (m/d).

Preferably, in the fourth step, the simulated foundation pit excavation process refers to: weakening the soil inside the foundation pit, removing the soil unit inside the foundation pit to complete the foundation pit excavation simulation, and the soil loss rate passing through the inside of the foundation pit The degree of weakening of the soil is adjusted and controlled within 1%.

Preferably, in the fifth step, the permeability coefficients kj of different orders of magnitude are 10 ^-6 m/ _s , 10 ^-5 m/s, 10 ^-4 m/s, 10 ^-3 m/s, 10 ^-2 m/s.

Preferably, in the fifth step, activating the seepage boundary condition inside the water-stop curtain above the excavation surface of the foundation pit refers to setting the pore water pressure inside the water-stop curtain above the excavation surface of the foundation pit to zero.

Preferably, in the sixth step, the permeability coefficient k corresponding to the leakage position of the actual leakage amount Q _k is determined in the following manner:

Mark the position of the actual leakage Q _k on the vertical axis of the correlation diagram, draw a horizontal line, intersect with the Q~k _j correlation diagram at a point, and draw a vertical line at this point to obtain the actual leakage Q _k The permeability coefficient k corresponding to the leak location.

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

In the leakage model of the water-stop curtain above the excavation surface of the foundation pit, the present invention sets a self-defined leakage unit for the leakage, which solves the difficulties of grid division and cumbersome calculation in the three-dimensional model, and finally determines the foundation pit opening. The impact of the leakage of the water-stop curtain above the excavation surface on the surrounding environment. The method of the invention is simple, easy to popularize and has great application value. The invention is applicable to the problem of leakage of the water-stop curtain above the excavation surface of the foundation pit.

Description of drawings

Fig. 1 a is a partial enlarged view of the grid of the model under the leakage of the water-stop curtain above the excavation surface of the foundation pit according to an embodiment of the present invention;

Fig. 1b is a three-dimensional grid diagram of the model under the leakage of the water-stop curtain above the excavation surface of the foundation pit according to an embodiment of the present invention;

Fig. 2 is a schematic diagram of a self-defined leakage unit according to an embodiment of the present invention;

Fig. 3 is a correlation diagram between the amount of leakage Q and _kj under the leakage of the water-stop curtain in an embodiment of the present invention (after 1 day of leakage);

Fig. 4 is the first confined aquifer section I-I ' water level drawdown figure (stable) under the seepage of the water-stop curtain of an embodiment of the present invention;

Fig. 5 is a ground subsidence diagram (100 days) of section I-I' under the seepage of the water-stop curtain according to an embodiment of the present invention.

detailed description

Below in conjunction with accompanying drawing, the embodiment of the present invention is described in detail: present embodiment is implemented on the premise of the technical solution of the present invention, has provided detailed embodiment and specific operation process, but protection scope of the present invention is not limited to following implementation example.

A foundation pit project is a circular foundation pit, and high-pressure jet grouting piles are used as a water-stop curtain. The aquifer system at the location of the foundation pit is a multi-layer aquifer-impermeable layer interlayer. During the excavation of the foundation pit, the water-stop curtain above the excavation surface of the foundation pit leaked.

This embodiment provides a method for determining the impact of the leakage of the water-stop curtain above the excavation surface of the foundation pit on the surrounding environment. The method includes the following steps:

The first step is to carry out on-site investigation of the foundation pit to determine the information on the division of soil layers and the distribution of groundwater, and conduct indoor geotechnical tests by drilling soil to obtain the physical and mechanical parameters of the soil layer.

The soil layer where the foundation pit is located is determined from top to bottom by the method of drilling soil:

The first layer is silt and silty clay with a thickness of 14m, which belongs to the diving layer;

The second layer is silty clay with a thickness of 7m, which belongs to the first aquitard;

The third layer is silt with a thickness of 10m, which belongs to the first confined aquifer;

The fourth layer is silty clay with a thickness of 5m, which belongs to the II aquitard;

The fifth layer is silt with a thickness of 18m, the II confined aquifer;

The sixth layer is silty clay with a thickness of 6m, which belongs to the third aquitard.

The physical and mechanical properties of the foundation pit soil layer obtained by taking soil for routine laboratory tests are as follows:

The first layer of silt and silty clay has a weight of 19.6kN/m ³ , a Poisson's ratio of 0.25, a void ratio of 0.80, a compressive modulus of 6530KPa, an internal friction angle of 25°, and a horizontal permeability coefficient of 6.94×10 ^{- 8} m/s, the vertical permeability coefficient is 3.47×10 ^{- 8} m/s;

The second layer of silty clay has a weight of 19.8kN/m ³ , a Poisson's ratio of 0.30, a compressive modulus of 5410KPa, an internal friction angle of 21°, a void ratio of 0.71, and a horizontal permeability coefficient of 2.31×10 ^-8 m/ s, the vertical permeability coefficient is 8.10×10 ^-9 m/s;

The third layer of silt has a gravity of 20.4kN/m ³ , a Poisson’s ratio of 0.25, a void ratio of 0.58, a deformation modulus of 16000KPa, an internal friction angle of 30°, an effective cohesion of 4.0kPa, and a horizontal permeability coefficient of 4.86×10 ^-5 m/s, vertical permeability coefficient is 1.74×10 ^-5 m/s;

The fourth layer of silty clay has a weight of 20.2kN/m ³ , a Poisson’s ratio of 0.30, a void ratio of 0.72, a compressive modulus of 6260KPa, an internal friction angle of 24°, and a horizontal permeability coefficient of 1.16×10 ^-8 m/ s, the vertical permeability coefficient is 4.64×10 ^-9 m/s;

The fifth layer of silt has a weight of 20.3kN/m ³ , a Poisson’s ratio of 0.25, a void ratio of 0.68, a deformation modulus of 12570KPa, an internal friction angle of 30°, an effective cohesion of 4.8kPa, and a horizontal permeability coefficient of 2.31×10 ^-5 m/s, vertical permeability coefficient is 9.26×10 ^-6 m/s;

The sixth layer of silty clay has a weight of 20.0kN/m ³ , a Poisson’s ratio of 0.30, a void ratio of 0.68, a compressive modulus of 5350KPa, an internal friction angle of 22°, and a horizontal permeability coefficient of 9.29×10 ^-9 m/ s, the vertical permeability coefficient is 4.63×10 ^-9 m/s;

The second step is to obtain the plane size of the foundation pit, the excavation depth, the thickness of the water-stop curtain, the embedding depth, the elastic modulus, and the permeability coefficient information, and determine the equivalent elastic modulus of the water-stop curtain considering the strength reduction effect.

The foundation pit in this embodiment is a circular foundation pit with a radius of 18m and an excavation depth of 32m; the thickness of the water-stop curtain is 1.2m, the depth is 48m, the gravity is 25kN/m ³ , and the horizontal permeability coefficient is 1.0×10 ^{- 9} m/s, and the vertical permeability coefficient is 1.0×10 ^{- 9} m/s. The equivalent elastic modulus E' of the waterproof curtain considering the strength reduction effect satisfies the following formula:

E'=ηE _s ,

Wherein: η is modulus reduction factor, gets 1/5; E _s is the modulus of elasticity of reinforced concrete, gets its value as:

The third step is to observe the leakage of the water-stop curtain above the excavation surface of the foundation pit. In the entire foundation pit plane, the leakage position A (as shown in Figure 1a) is located at the water-stop curtain in the direction of 45° east to north of the center of the foundation pit On the inner wall, and the leakage form is a vertical linear leakage; by lowering the measuring rope, the top depth h ₁ =21m, the bottom depth h ₂ =24m of the leakage area are measured, and the distance between the two sides of the leakage area The distance between them is L=5cm, so the leakage area D=0.15m ² ; the actual leakage amount Q _k is determined by the following method:

Place a drum with a bottom diameter d of 1m and a bucket height h3 _of 1.5m directly below the leakage of the water-stop curtain above the excavation surface of the foundation pit, and measure the leakage Q _2k at the leakage location for 2 hours on site , the height h ₄ of the water in the bucket after 2 hours is 1.046m, where Q _2k satisfies the following formula:

In the formula: N is the number of barrels of leaking water connected in 2 hours, which is 1, V is the volume of the drum, and V satisfies the following formula:

V=(πd ² /4)×h ₃ =(π×1 ² /4)×1.5=1.1781m ³ .

Based on the 2-hour leakage Q _2k measured on site, the actual leakage Q _k after 1 day of leakage is estimated, namely:

Q _k =12Q _2k =12×1.9996=23.9952m ³ .

The fourth step is to use the finite element analysis software to establish a three-dimensional fluid-solid coupling model of the leakage of the water-stop curtain above the excavation surface of the foundation pit; according to the field investigation, the corresponding leakage position in the three-dimensional fluid-solid coupling model is set according to the leakage area. The seepage unit simulates the excavation process of the foundation pit.

Determine the influence radius R of the dewatering well. In this example, the permeability coefficient of the first confined aquifer is 4.86×10 ^-5 m/s, that is, 4.2m/d. During the excavation of the foundation pit, the first confined aquifer in the foundation pit The water level is 1m below the excavation surface of the foundation pit, that is, the confined water level is -25m. The initial confined water level of this project is -1m, so the water level drawdown is 24m, and the influence radius R of the dewatering well is:

The analysis model takes the foundation pit as the center, and the horizontal direction is greater than the influence radius of the dewatering well of 492m, and extends outward by 500m to eliminate the influence of boundary conditions on the calculation results; on the plane, the research range is 1000×1000m ² ; on the vertical direction, the calculated depth It is 60m. In the horizontal direction, the finite element grid changes from dense to sparse from the foundation pit outward, and each plane contains 2920 nodes and 2829 units; in the vertical direction, it is divided into 17 layers. The whole model has a total of 54720 nodes and 48093 units.

As shown in Figure 1a and Figure 1b, the local enlarged view and three-dimensional grid map of the model grid under the leakage of the water-stop curtain above the excavation surface of the foundation pit. Input the soil parameters and water level, and set the initial conditions and boundary conditions of the model. in:

The initial conditions of the model are: the initial water level of each aquifer in the analysis model is 1m below the ground, the pore pressure of the water level line is zero, and the displacement is zero;

The boundary conditions are: constant head boundary around the model and fixed boundary condition at the bottom.

Both the soil body and the water-stop curtain adopt 8-node pore pressure units, and a contact surface is set between the water-stop curtain and the soil body, and the friction coefficient of the contact surface is 0.25.

According to the field investigation, a custom leakage unit is set at the corresponding leakage position A of the analysis model (as shown in Figure 1a). _z = D/n = 0.15/3 = 0.05m ² , Figure 2 is a schematic diagram of the self-defined leakage unit.

In this embodiment, the simulated foundation pit excavation process refers to: weakening the soil inside the foundation pit, removing the soil unit inside the foundation pit to complete the foundation pit excavation simulation, and the soil loss rate is determined by the soil mass inside the foundation pit. The degree of weakening is adjusted and controlled within 1%.

The fifth step is to assume different orders of magnitude of permeability coefficient k _j for the self-defined seepage unit, activate the seepage boundary inside the water-stop curtain above the excavation surface of the foundation pit, and determine the seepage of the water-stop curtain above the excavation surface of the foundation pit under each working condition The amount of leakage Q after 1 day of leakage at the leak.

The permeability coefficients k _j of different orders of magnitude described in this example are taken as 10 ^-6 m/s, 10 ^-5 m/s, 10 ^-4 m/s, 10 ^-3 m/s, 10 ^-2 m/s .

The activation of the seepage boundary condition inside the water-stop curtain above the excavation surface of the foundation pit described in this embodiment refers to setting the pore water pressure inside the water-stop curtain above the excavation surface of the foundation pit to zero.

The sixth step is to establish a Cartesian rectangular coordinate system, the horizontal axis is the permeability coefficient k _j of different orders of magnitude, the vertical axis is the leakage Q, and the correlation diagram between the leakage Q and the permeability coefficient k _j is drawn (as shown in Figure 3 ), according to the actual leakage measured on site Q _k =23.9952m ³ , find this point on the vertical axis of the correlation diagram, and draw a horizontal line, the abscissa corresponding to the intersection point of the horizontal line and the correlation diagram is the leakage position Permeability coefficient k:

k=1.0×10 ⁻⁵ m/s.

The seventh step is to set the seepage coefficient k=1.0×10 ^-5 m/s for the self-defined seepage unit in the 3D fluid-solid coupling model, and perform seepage consolidation simulation, and finally obtain the above excavation surface of the foundation pit The water level drawdown diagram (stable) of section II′ of the first confined aquifer under the linear leakage at position A of the water-stop curtain leakage (stable) (as shown in Figure 4), and the land subsidence diagram of section II′ (100 days) (as shown in Fig. 5).

This embodiment can accurately determine the impact of the leakage of the water-stop curtain above the excavation surface of the foundation pit on the surrounding environment, and finally obtain the groundwater level and ground subsidence around the leakage of the water-stop curtain above the excavation surface of the foundation pit. It is more comprehensive, more scientific and more reliable to focus on the research of seepage on groundwater level.

Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims (11)

1. it is a kind of to determine the method that excavation of foundation pit face top water stopping curtain seepage affects on surrounding enviroment, it is characterised in that described Method comprises the steps：

The first step, to foundation ditch site inspection is carried out, and determines soil layer division information and groundwater occurrence situation, and by boring extracting soil Laboratory soil test is carried out, the physical and mechanical parameter of soil layer is obtained；

Second step, obtains foundation ditch planar dimension, cutting depth, and water-stop curtain thickness, buried depth, elastic modelling quantity, infiltration Coefficient, it is determined that considering the water-stop curtain equivalent elastic modulus E ' of strength degradation effect；

3rd step, observes the leakage scenarios of excavation of foundation pit face top water-stop curtain, record leak location, seepage form, it is determined that only Leakage area D, actual seepage quantity Q at water curtain seepage_k；

4th step, using finite element analysis software the solid coupled mode of three-dimensional flow of excavation of foundation pit face top water stopping curtain seepage is set up Type；According to field investigation, self-defined seepage list is set according to leakage area in the corresponding leak location of three-dimensional fluid structure interaction mode Unit, Simulation of Excavation Process；

Described self-defined seepage unit refers to the two nodal line units with certain permeability and rigidity, the self-defined seepage list Solid element conode in unit and threedimensional model, and have three basic parameters：Leakage area D_z, leak location infiltration coefficient K and elastic modulus E；Wherein：Leakage area D_zDetermined by the leakage area D surveyed in the 3rd step, meet formula：D_z=D/n, formula The grid node that middle n is passed through by water stopping curtain seepage position；The osmotic coefficient k of leak location is by setting varying number level Osmotic coefficient k_jTo determine；

5th step, to self-defined seepage unit the osmotic coefficient k of varying number level is assumed_j, activation excavation of foundation pit face top sealing curtain Curtain on the inside of seepage boundary, determine water-stop curtain under each operating mode seepage for a period of time after leakage Q；

6th step, sets up Descartes's rectangular coordinate system, and transverse axis is the osmotic coefficient k of varying number level_j, the longitudinal axis is leakage Q, is made Go out leakage Q and osmotic coefficient k_jDependency relation figure, and actual seepage quantity Q of on-site measurement is determined according to graph of a relation_kCorrespondence is oozed The osmotic coefficient k of leakage position；

7th step, to three-dimensional fluid structure interaction mode in self-defined seepage unit arrange leak location osmotic coefficient k, oozed Stream consolidation simulation, determines level of ground water and ground settlement around the foundation ditch that excavation of foundation pit face top water stopping curtain seepage causes.

2. the side that a kind of determination excavation of foundation pit face top according to claim 1 water stopping curtain seepage affects on surrounding enviroment Method, it is characterised in that in the first step：

Described soil layer is divided and referred to：By the method for boring extracting soil to 2.5 times of foundation depths below earth's surface in foundation ditch in the range of Soil layer divided, subsequently obtaining job site soil sample carries out laboratory soil test, obtains job site soil layer division information And geological information, determine each soil layer soil nature and corresponding the thickness of the layer；

Described groundwater occurrence situation is referred to：Water instrument is visited using drilling underground water drilling is carried out to foundation ditch place and verified, by taking off The soil body type of dew judges the type and thickness in water-bearing layer；The fixed level of different water cut layer is observed in drilling well, aqueous for pressure-bearing Layer takes water proof measure to survey its fixed level behind tested water-bearing layer and other water-bearing layer isolation.

3. the side that a kind of determination excavation of foundation pit face top according to claim 1 water stopping curtain seepage affects on surrounding enviroment Method, it is characterised in that in second step, described water-stop curtain equivalent elastic modulus E ' meets below equation：

E '=η E_s,

Wherein：η is modulus reduction coefficient, takes 1/5；E_sFor the elastic modelling quantity of armored concrete.

4. the side that a kind of determination excavation of foundation pit face top according to claim 1 water stopping curtain seepage affects on surrounding enviroment Method, it is characterised in that in second step, described water-stop curtain infiltration coefficient is divided into horizontal direction and vertical direction, horizontal direction Concrete filtration coefficient is taken with the infiltration coefficient of vertical direction.

5. the side that a kind of determination excavation of foundation pit face top according to claim 1 water stopping curtain seepage affects on surrounding enviroment Method, it is characterised in that in the 3rd step：

Described leak location is referred to：Seepage region whole foundation ditch plane position coordinates, and in foundation ditch vertical direction Depth size；

Described seepage form is referred to：Underground water Jing water-stop curtains penetrate into the seepage shape presented during foundation ditch.

6. the side that a kind of determination excavation of foundation pit face top according to claim 1 water stopping curtain seepage affects on surrounding enviroment Method, it is characterised in that in the 3rd step, leakage area D determines in the following manner at described water stopping curtain seepage：

Range estimation seepage region is located at the Position Approximate of ground surface, and on the ground surface near institute's excavation pit object of reference is chosen, and joins There is position coordinates on foundation ditch plan according to thing, measure the distance in object of reference and seepage region, determine seepage region in whole base The position coordinates of hole plane；Lining rope is transferred at the plan-position coordinate in seepage region, seepage region top depth is measured respectively Degree h₁, lowermost end depth h₂And the distance between seepage region Liang Ge sides L, obtain leakage area D：

D=L × (h₂-h₁)。

7. the side that a kind of determination excavation of foundation pit face top according to claim 1 water stopping curtain seepage affects on surrounding enviroment Method, it is characterised in that in the 3rd step, described actual seepage quantity Q_kDetermine in the following manner：

A drum is laid in underface at water stopping curtain seepage above excavation of foundation pit face, measures basal diameter d, the bucket of drum Height h₃, in bucket water height h₄；Leakage Q of 2 hours of on-site measurement leak location_2kSize；The Q_2kMeet with Lower formula：

Q_2k=NV+ (π d²/4)×h₄,

In formula：N is drum volume by meeting within 2 hours the barrelage of percolating water, V；Drum volume V meets below equation：

V=(π d²/4)×h₃；

By leakage Q of the 2 of on-site measurement hours_2k, estimate actual seepage quantity Q of the seepage after 1 day_k, i.e. Q_k=12Q_2k。

8. the side that a kind of determination excavation of foundation pit face top according to claim 1 water stopping curtain seepage affects on surrounding enviroment Method, it is characterised in that in the 4th step：Elastic modulus E takes 0.01；

Described three-dimensional fluid structure interaction mode is referred to：Centered on foundation ditch, horizontal direction affects half to model scope more than dewatering well Footpath R；Model vertical direction is more than artesian aquifer base plate place depth；Carry out stress and strain model to model, input Soil Parameters and Water level, and the primary condition and boundary condition of setting model, wherein：The primary condition of model is：Waterline pore pressure is zero, Displacement is zero；Boundary condition is：Model surrounding is constant water level boundary, and bottom is fixed boundary condition；The soil body and water-stop curtain are equal Using 8 node pore pressure units, contact surface is set between water-stop curtain and the soil body；

Described Simulation of Excavation Process is referred to：Weaken the foundation ditch inner side soil body, remove foundation ditch inside soil body unit and complete foundation ditch Excavation simulation, ground loss rate is adjusted by the weakening degree of the foundation ditch inner side soil body, is controlled within 1%.

9. the side that a kind of determination excavation of foundation pit face top according to claim 8 water stopping curtain seepage affects on surrounding enviroment Method, it is characterised in that described dewatering well radius of influence R adopts the empirical equation of artesian aquifer：

$R=10S\sqrt{K},$

In formula：S is drawdown (m), and K is the horizontal-hole blasting (m/d) of artesian aquifer；

The contact surface coefficient of friction is 0.25.

10. a kind of determination excavation of foundation pit face top water stopping curtain seepage according to any one of claim 1-9 is to peripheral ring The method that border affects, it is characterised in that in the 5th step：

The osmotic coefficient k of described varying number level_jTake 10^-6m/s、10^-5m/s、10^-4m/s、10^-3m/s、10^-2m/s；

The boundary condition of seepage flow on the inside of described activation excavation of foundation pit face top water-stop curtain is referred to：Excavation of foundation pit face top is stopped Pore water pressure on the inside of water curtain is set to zero.

A kind of 11. determination excavation of foundation pit face top water stopping curtain seepages according to any one of claim 1-9 are to peripheral ring The method that border affects, it is characterised in that in the 6th step, described actual seepage quantity Q_kThe osmotic coefficient k of correspondence leak location leads to Cross in the following manner determination：

Actual seepage quantity Q is marked on the longitudinal axis of dependency relation figure_kPosition, and horizontal line is made, with Q～k_jDependency relation figure Intersect at a point, in the point vertical line is made, that is, obtain actual seepage quantity Q_kThe osmotic coefficient k of correspondence leak location.