CN112900504B  Method and system for identifying water leakage of waterproof curtain of foundation pit  Google Patents
Method and system for identifying water leakage of waterproof curtain of foundation pit Download PDFInfo
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 CN112900504B CN112900504B CN202110040301.7A CN202110040301A CN112900504B CN 112900504 B CN112900504 B CN 112900504B CN 202110040301 A CN202110040301 A CN 202110040301A CN 112900504 B CN112900504 B CN 112900504B
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 E—FIXED CONSTRUCTIONS
 E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
 E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
 E02D33/00—Testing foundations or foundation structures

 E—FIXED CONSTRUCTIONS
 E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
 E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
 E02D19/00—Keeping dry foundation sites or other areas in the ground
 E02D19/06—Restraining of underground water
 E02D19/10—Restraining of underground water by lowering level of ground water

 E—FIXED CONSTRUCTIONS
 E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
 E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
 E02D19/00—Keeping dry foundation sites or other areas in the ground
 E02D19/06—Restraining of underground water
 E02D19/12—Restraining of underground water by damming or interrupting the passage of underground water

 G—PHYSICS
 G06—COMPUTING; CALCULATING OR COUNTING
 G06F—ELECTRIC DIGITAL DATA PROCESSING
 G06F30/00—Computeraided design [CAD]
 G06F30/10—Geometric CAD
 G06F30/13—Architectural design, e.g. computeraided architectural design [CAAD] related to design of buildings, bridges, landscapes, production plants or roads

 G—PHYSICS
 G06—COMPUTING; CALCULATING OR COUNTING
 G06F—ELECTRIC DIGITAL DATA PROCESSING
 G06F30/00—Computeraided design [CAD]
 G06F30/20—Design optimisation, verification or simulation
 G06F30/23—Design optimisation, verification or simulation using finite element methods [FEM] or finite difference methods [FDM]
Abstract
The invention provides a method and a system for identifying foundation pit waterproof curtain leakage water, wherein the method is used for dynamic monitoring, analysis and early warning of waterproof curtain leakage in the foundation pit construction precipitation process and comprises the steps of system building, numerical analysis model building, field construction, sequential inversion of multiple rounds of soil layer permeability coefficients and waterproof curtain permeability coefficients in a circulating mode and identification of potential leakage areas of the waterproof curtain; the system can measure the water level and the water pumping speed of a dewatering well according to a certain frequency and transmit the water level and the water pumping speed to a computer system of the central processing module to make analysis and judgment. The method combines automatic remote monitoring, numerical simulation and intelligent analysis, has high scientificity and accuracy, and is beneficial to improving the safety of foundation pit construction.
Description
Technical Field
The invention relates to the technical field of foundation pit engineering, in particular to a method and a system for identifying water leakage of a foundation pit waterproof curtain.
Background
The water leakage of the waterproof curtain of the foundation pit is one of important risk sources in the foundation pit engineering. The existing foundation pit waterproof curtain leakage detection methods generally have two types: the first type is a method for indirectly reflecting the construction quality of the curtain, such as uniaxial compressive strength detection, light dynamic sounding and the like of a curtain consolidation body, but the whole waterproof effect of the waterproof curtain cannot be accurately evaluated. And the second method is to detect the whole waterproof effect of the curtain by carrying out a water pumping test on the stratum within the enclosure range, wherein a water level observation hole is required to be arranged outside the waterproof curtain, and the waterproof effect of the waterproof curtain and the general position of the hidden leakage point are judged by observing the condition of water level change in the water pumping process. However, the method needs to specially arrange a large number of water level observation holes, so that the construction period is long, the cost is high, in addition, the water level holes outside the pit have large intervals, the continuous arrangement cannot be realized, some hidden leakage points are easy to leak, and the effects of time and labor waste are poor.
Prior to this patent, there have been many proposed methods for detecting leakage from a waterproof curtain. Chinese patent 'a foundation pit permeability coefficient calculation method and an automatic monitoring device thereof' (patent number 201711262007.0) uses a least square method to fit the relation of water pumping quantity, permeability coefficient and water pressure, and obtains the actual permeability coefficient of the foundation pit according to the actually measured water pumping quantity and water pressure, and the method is suitable for the situation that the value range of the permeability coefficient is small and is not easy to popularize; the Chinese patent 'a plane leakage detection method for an ultradeep foundation pit enclosure structure' (patent number 201910213805.7) utilizes the electroosmosis principle to measure the leakage condition of a complex underground structure with high sensitivity by weak ion movement at the leakage position, the method lacks the integral control on the underground flow field information, and the possible leakage area is difficult to predict based on the primary flow field fluctuation; chinese patent ' a foundation pit enclosure system groundwater seepage detection system ' (patent number 201721450591.8) ' the detection system realizes the monitoring of groundwater flow direction, realizes the monitoring of groundwater level through the design of scale on the waterproof pipe, but this method is more based on the observation of groundwater seepage phenomenon, there are some difficulties in directly pushing out the seepage condition of the waterproof curtain by the phenomenon; the Chinese patent 'a soft soil area underground diaphragm wall leakage detection system' (patent number 201610701537.X) observes the migration process of underground ions and the gathering process of the underground ions in real time, so that the specific position of a leakage point can be obtained quickly and accurately, but the electroosmosis method is suitable for a soft soil layer, and the waterstop curtain leakage detection effect on a nonsoft soil area is possibly poor.
Aiming at the situation, the foundation pit waterproof curtain water leakage identification method and system are provided, and the defects of the previous methods in the field are overcome.
Disclosure of Invention
The invention aims to provide a method and a system for identifying leakage water of a waterproof curtain of a foundation pit, so as to solve the technical problem of leakage detection in the engineering practice.
In order to solve the technical problems, the invention adopts the technical scheme that:
on one hand, the embodiment of the invention provides a method for identifying water leakage of a waterproof curtain of a foundation pit, which comprises the following steps:
1) system construction: a precipitation module, an information acquisition module and a central processing module are set up, and the precipitation module and the information acquisition module are connected with the central processing module;
2) constructing a numerical analysis model: introducing a stratum model, constructing a threedimensional seepage finite element model for foundation pit excavation, wherein the threedimensional seepage finite element model comprises a soil layer unit, a dewatering well unit and a waterproof curtain unit, and assigning an initial horizontal permeability coefficient and a vertical permeability coefficient to the soil layer unit according to the permeability coefficient given by a geotechnical engineering investigation report;
3) and (3) field construction: pumping water into the precipitation well according to the precipitation scheme at the current stage until the water pumping process is stable, measuring the water level and the flow rate according to certain data acquisition frequency by using the information acquisition module in the water pumping process, and transmitting the measured water level and flow rate data to the central processing module;
4) soil layer permeability coefficient inversion;
5) inverting the permeability coefficient of the waterproof curtain;
6) the steps 4) and 5) are circulated, successive inversion of the soil layer permeability coefficients and the waterproof curtain permeability coefficients of multiple rounds is carried out until the change rate of the error D after the inversion of the two rounds is smaller than the change rate threshold eta;
7) identification of potential leakage areas of the waterproof curtain: setting the permeability coefficient above a permeability coefficient threshold k_{a}The waterproof curtain unit is marked as a high leakage risk area, and once the high leakage risk area appears, the central processing module automatically alarms;
8) and (5) repeating the steps 3) to 7), and automatically identifying the leakage risk of the waterproof curtain in each precipitation stage until the project is finished.
Preferably, the soil layer permeability coefficient inversion in the step 4) includes:
a. the horizontal permeability coefficient and the vertical permeability coefficient of each soil layer of the soil layer unit are adjusted one by one and are respectively 0.90k_{s}、0.95k_{s}、1.00k_{s}、1.05k_{s}And 1.10k_{s}Form a set of examples, k_{s}Adjusting the horizontal permeability coefficient or the vertical permeability coefficient of one soil layer at each time for adjusting the horizontal permeability coefficient or the vertical permeability coefficient of the current soil layer; the central system processing module simulates threedimensional seepage of foundation pit groundwater according to a current stage rainfall design scheme, wherein the boundary condition of the water level in the model precipitation well unit is assigned according to actually monitored water level data, numerical simulation is operated until a seepage stable state is reached, and the sum of the mean square deviation of actual measurement and simulated flow velocity of each precipitation well unit, namely an error D, is calculated for each calculation example simulation result;
b. for each set of calculation examples in the previous step, fitting error D and permeability coefficient k by using a linear function_{s}The slope of the fit is the rate of change of error with permeability coefficient, expressed asWherein i is 12 n, n is the number of soil layers,k_{s,1}—k_{s,n}denotes the horizontal permeability coefficient, k, of the soil of the 1 st to n th layers_{s,1+n}—k_{s,2n}The vertical permeability coefficient of the soil of the 1 st to the n th layers is shown;
c. updating the permeability coefficient by gradient descent, i.e. according to the formulaAdjusting the horizontal permeability coefficient and the vertical permeability coefficient of each soil layer;
d. and (c) circularly performing multiple rounds of soil layer permeability coefficient inversion in the steps ac until the change rate of the error D after the inversion of the front and the back rounds is smaller than the change rate threshold eta.
Preferably, the step 5) of stopping the inversion of the water curtain permeability coefficient comprises the following steps:
a. setting the permeability coefficient of the waterstopping curtain unit in the row closest to each dewatering well unit as 0.6k for each dewatering well of one pair of dewatering well units_{w}、0.8k_{w}、1.0k_{w}、1.2k_{w}And 1.4k_{w}Form a set of examples, k_{w}Adjusting the permeability coefficient of the waterstopping curtain unit related to one precipitation well for the current permeability coefficient of the waterstopping curtain unit; the central processing module simulates threedimensional seepage of foundation pit groundwater according to a precipitation design scheme at the current stage, wherein the boundary condition of the water level in the precipitation well is assigned according to actually monitored water level data, numerical simulation is carried out until a seepage stable state is achieved, and for each example simulation result, the sum of the mean square deviation of actual measurement and simulated flow rate of each precipitation well, namely an error D, is calculated;
b. for each set of calculation examples in the previous step, fitting error D and permeability coefficient k by using a linear function_{w}The slope of the fit is the rate of change of error with permeability coefficient, expressed asWherein i is 1m, m is the number of dewatering wells, k_{w,i}Representing the permeability coefficient of a row of waterproof curtain units closest to the ith precipitation well;
c. updating the permeability coefficient of the waterstopping curtain by gradient descent, i.e. according toAccording to the formulaAdjusting the permeability coefficient of a row of waterproof curtain units closest to each dewatering well;
d. and (4) circularly performing multiple rounds of waterproof curtain permeability coefficient inversion in the steps ac until the change rate of D after the inversion of the front and the back rounds is smaller than a change rate threshold eta.
Preferably, the gradient descent method is a Momentum method or an adagard method.
As a preferred scheme, the stratum model is determined according to a soil layer structure around a foundation pit disclosed by a geotechnical engineering investigation report, and the periphery and the bottom of the threedimensional seepage finite element model are fixed pore pressure boundaries.
On the other hand, the invention provides a foundation pit waterproof curtain water leakage recognition system, wherein a plurality of dewatering wells are arranged in the foundation pit, and waterproof curtains are arranged around the foundation pit, and the system comprises: the precipitation module is arranged on the foundation pit and used for extracting seepage water in the precipitation well; the information acquisition module is arranged in the precipitation well, and is used for measuring water level and flow rate data in the precipitation well and transmitting the data to the central processing module; the central processing module is used for receiving the water level and flow rate data, calculating a highrisk leakage area of the waterproof curtain according to the foundation pit waterproof curtain water leakage identification method in any one of claims 1 to 5, and alarming according to setting; and the power supply module is connected with the precipitation module, the information acquisition module and the central processing module and is used for providing electric energy.
Preferably, the precipitation module comprises a plurality of water pumps, a water pumping hose and a water collecting pipe, one end of each water pump is connected with the water collecting pipe, the other end of each water pump is connected with the water pumping hose, and the other end of each water pumping hose extends into the precipitation well.
As a preferred scheme, the information acquisition module comprises a water level pipe, a water level meter, a flow velocity meter, a data acquisition and local wireless transmission instrument and a 4G wireless transmission instrument, the water level pipe is arranged inside the dewatering well, the water level meter is positioned above the flow velocity meter, the water level meter and the flow velocity meter are respectively arranged inside the water level pipe and the pumping hose, the water level meter and the flow velocity meter are connected with the data acquisition and local wireless transmission instrument through data transmission lines, and the data acquisition and local wireless transmission instrument is wirelessly connected with the central processing module through the 4G wireless transmission instrument.
Preferably, the central processing module comprises a 4G signal receiver and a computer system, and the 4G signal receiver is used for receiving water level and flow rate data of all dewatering wells and inputting the data into the computer system for processing.
As a preferred scheme, the top of the dewatering well is provided with a bracket platform, the side length of the short edge of the bracket platform is larger than the diameter of the dewatering well, the bracket platform is provided with a data acquisition and local wireless transmission instrument and a waterproof battery, and the waterproof battery is connected with the data acquisition and local wireless transmission instrument through a waterproof wire and used for providing electric energy.
Compared with the prior art, the invention has the beneficial effects that:
(1) combining the actually measured water level and flow velocity information in the precipitation well with threedimensional finite element seepage simulation, obtaining the horizontal permeability coefficient, the vertical permeability coefficient and the waterstopping curtain permeability coefficient of a soil layer by adopting a gradient descent method and sequentially inverting the soil layer permeability coefficient and the waterstopping curtain permeability coefficient through multiple rounds, and identifying the potential permeability area of the waterstopping curtain based on the waterstopping curtain permeability coefficient, wherein the method is high in scientificity and accuracy;
(2) the leakage condition of the foundation pit waterproof curtain can be remotely and automatically monitored, analyzed and automatically alarmed, the automation and the intellectualization of foundation pit engineering monitoring can be improved, and the foundation pit construction safety can be improved.
Drawings
The disclosure of the present invention is illustrated with reference to the accompanying drawings. It is to be understood that the drawings are designed solely for the purposes of illustration and not as a definition of the limits of the invention. In the drawings, like reference numerals are used to refer to like parts. Wherein:
FIG. 1 is a schematic flow chart of a method for identifying water leakage of a waterproof curtain of a foundation pit according to an embodiment of the invention;
FIG. 2 is a schematic structural diagram of a system for identifying water leakage of a waterproof curtain of a foundation pit according to an embodiment of the invention;
FIG. 3 is a schematic structural diagram of a threedimensional percolation finite element model according to an embodiment of the present invention;
FIG. 4 is a schematic diagram showing the variation of error D with permeability coefficient according to the embodiment of the present invention;
FIG. 5 is a schematic diagram of a change relation between an error D and a soil permeability coefficient inversion turn according to an embodiment of the invention;
FIG. 6 is a schematic diagram showing a relationship between errors D and inversion turns of soil permeability coefficients and waterstop curtain permeability coefficients according to an embodiment of the present invention;
FIG. 7 is a schematic view of the arrangement of the internal equipment of the dewatering well according to the embodiment of the invention;
fig. 8 is a schematic layout view of equipment at the top of a dewatering well according to an embodiment of the invention.
Reference numbers in the figures: 1a water pump, 2a water pumping hose, 3a water collecting pipe, 4a waterstop curtain, 5a dewatering well, 64G signal receiving instruments, 7a computer system, 8a water level pipe, 9a water level meter, 10a flow rate meter, 11a water inlet, 12a data transmission line, 13a bracket platform, 14a waterproof battery, 15a waterproof wire, 16a data acquisition and local wireless transmission instrument, 174G wireless transmission instrument and 18an uninterruptible power supply.
Detailed Description
It is easily understood that according to the technical solution of the present invention, a person skilled in the art can propose various alternative structures and implementation ways without changing the spirit of the present invention. Therefore, the following detailed description and the accompanying drawings are merely illustrative of the technical aspects of the present invention, and should not be construed as all of the present invention or as limitations or limitations on the technical aspects of the present invention.
An embodiment according to the present invention is shown in connection with fig. 1. A method for identifying water leakage of a foundation pit waterproof curtain comprises the steps of S1S8.
Step S1, the system builds: and constructing a precipitation module, an information acquisition module and a central processing module, wherein the precipitation module and the information acquisition module are connected with the central processing module.
Referring to fig. 2, a schematic structural diagram of a foundation pit waterproof curtain water leakage identification system is shown. In the embodiment of the invention, the plane width of a rectangular foundation pit is 70m, the plane length is 100m, the excavation depth is 15m, the depth of a waterproof curtain is 45m, 23 dewatering wells are arranged in the foundation pit, and the depth of the dewatering wells inserted below the pit bottom is 27 m. A water pump, a water pumping hose and a water collecting pipe are sequentially connected to form a precipitation module on a construction site; a bracket platform is arranged at the top of each precipitation well in a construction site, a water pump, a water level gauge, a flow velocity meter and a water level pipe are arranged in the precipitation well, a data acquisition and local wireless transmission instrument and a waterproof battery are arranged on the bracket platform and are connected through a data transmission line, so that an information acquisition module is built, and a central processing module is built in a background office.
Step S2, constructing a numerical analysis model: and (3) introducing a stratum model, determining the stratum model according to the soil layer structure around the foundation pit disclosed by the geotechnical engineering investigation report, and constructing a threedimensional seepage finite element model for foundation pit excavation, wherein the threedimensional seepage finite element model comprises a soil layer unit, a dewatering well unit and a waterproof curtain unit, and the periphery and the bottom of the threedimensional seepage finite element model are fixed pore pressure boundaries. And assigning initial horizontal permeability coefficients and vertical permeability coefficients to the soil layer units according to the permeability coefficients given by the geotechnical engineering investigation report.
Specifically, as shown in fig. 3, according to the geotechnical engineering investigation report, the ground groundwater level is 2m below the ground surface, the ground pit precipitation influence range of the ground is divided into 3 layers, namely, the 1 st clay layer (the horizontal permeability coefficient is 8 × 10)^{5}cm/s, vertical permeability coefficient 6X 10^{5}cm/s), layer 2 silt layer (horizontal permeability coefficient 7X 10)^{4}cm/s, vertical permeability coefficient 7X 10^{4}cm/s), layer 3 of fine sand (horizontal permeability coefficient 1X 10)^{3}cm/s, vertical permeability coefficient 1X 10^{3}cm/s). The permeability coefficient of the waterproof curtain unit is far smaller than that of the dewatering well, such as: the permeability coefficient of the waterproof curtain unit is 1 multiplied by 10^{6}And cm/s, and taking the permeability coefficient of the dewatering well as 1 cm/s.
Step S3, site construction: and pumping water to the precipitation well unit according to the precipitation scheme at the current stage until the water pumping process is stable, measuring the water level and the flow rate according to certain data acquisition frequency by using the information acquisition module in the water pumping process, and transmitting the measured water level and flow rate data to the central processing module.
Starting a water pump according to the current stage precipitation scheme until the water pumping process is stable and the water level is reduced to 6m below the ground surface; and measuring the water level and the flow rate every 20min in the water pumping process, and transmitting the measured water level and flow rate data to the central processing module.
And step S4, soil layer permeability coefficient inversion. The method specifically comprises the following steps:
a. the horizontal permeability coefficient and the vertical permeability coefficient of each soil layer of the soil layer unit are adjusted one by one and are respectively 0.90k_{s}、0.95k_{s}、1.00k_{s}、1.05k_{s}And 1.10k_{s}Form a set of examples, k_{s}And adjusting the horizontal permeability coefficient or the vertical permeability coefficient of one soil layer at each time for the current adjustment of the horizontal permeability coefficient or the vertical permeability coefficient of the soil layer.
In a specific embodiment, the soil layer units are 3 layers, 6 groups of calculation examples are formed, the horizontal permeability coefficient of the 1 st soil layer is adjusted, the vertical permeability coefficient of the 1 st soil layer is adjusted, the horizontal permeability coefficient of the 2 nd soil layer is adjusted, the vertical permeability coefficient of the 2 nd soil layer is adjusted, the horizontal permeability coefficient of the 3 rd soil layer is adjusted, and the vertical permeability coefficient of the 3 rd soil layer is adjusted, wherein 30 calculation examples are calculated in each group of 5 calculation examples.
And the central system processing module simulates the threedimensional seepage of the underground water of the foundation pit according to the precipitation design scheme at the current stage, wherein the boundary condition of the water level in the model precipitation well unit is assigned according to the actually monitored water level data, the numerical simulation is operated until the seepage stable state is reached, and the sum of the mean square deviations of the actually measured flow speed and the simulated flow speed of each precipitation well unit, namely the error D, is calculated for each calculation example simulation result.
In a specific embodiment, the boundary conditions of the water levels in the 23 precipitation wells in the model are assigned according to the actually monitored water level data received by the central processing module, and the numerical simulation is operated until the seepage stable state is reached; and calculating the sum of the mean square deviations of the measured flow rate and the simulated flow rate of each dewatering well according to the simulation result of each calculation example: namely the error D, is obtained by subtracting the error D,
wherein j represents the number of the precipitation well, q_{c,j}For measured flow rate, q_{s,j}To simulate the flow rate.
b. For each set of examples in the previous step, a linear function is used to fit the error D (dependent variable) and permeability coefficient k_{s}(independent variable) relationship, the slope of the fit is the rate of change of the error with the permeability coefficient, expressed asWhere i is 12 n, n is the number of soil layers, k_{s,1}—k_{s,n}Denotes the horizontal permeability coefficient, k, of the soil of the 1 st to n th layers_{s,1+n}—k_{s,2n}The vertical permeability coefficient of the soil of the 1 st to the n th layers is shown.
In one embodiment, i is 16, k_{s,1}、k_{s,2}、k_{s,3}Represents the horizontal permeability coefficient, k, of the soil of the 1 st, 2 nd and 3 rd layers_{s,4}、k_{s,5}、k_{s,6}The vertical permeability coefficients of the 4 th, 5 th and 6 th layers of soil are expressed; in the first round of inversion, the fitting of a linear function of the horizontal permeability coefficient of the 2 nd layer soil is shown in FIG. 4, and the fitting slope is1.679 × 10^{5}I.e. byThe data of the other groups of the calculation examples are processed by the same method.
c. Updating the permeability coefficient by gradient descent, i.e. according to the formulaAnd adjusting the horizontal permeability coefficient and the vertical permeability coefficient of each soil layer. The parameter alpha needs to be determined according to trial calculation, the value of the parameter alpha can ensure the stability and convergence of the gradient descent method, and the parameter alpha is 10 after trial^{10}. Alternatively, the gradient descent method may be replaced by other more optimized gradient descent methods, such as Momentum method or adagradad method.
d. And (c) circularly performing multiple rounds of soil layer permeability coefficient inversion in the steps ac until the change rate of the error D after the inversion of the front and the back rounds is smaller than the change rate threshold eta. In this example, η is 0.05. In this example, 47 rounds of calculation are generally performed to reach the end condition, and a typical variation process of D is shown in FIG. 5.
And step S5, inverting the waterstop curtain permeability coefficient. The method specifically comprises the following steps:
a. setting the permeability coefficient of the waterstopping curtain unit in the row closest to each dewatering well unit as 0.6k for each dewatering well of one pair of dewatering well units_{w}、0.8k_{w}、1.0k_{w}、1.2k_{w}And 1.4k_{w}Form a set of examples, k_{w}And adjusting the permeability coefficient of only the waterstopping curtain unit related to one dewatering well at a time for the current permeability coefficient of the row of waterstopping curtain units. In one embodiment, 23 dewatering wells are arranged, so that 23 groups of calculation examples are provided, each group comprises 5 calculation examples, and the total number is 115 calculation examples;
the central processing module simulates threedimensional seepage of foundation pit underground water according to a precipitation design scheme at the current stage, wherein water level boundary conditions in 23 precipitation wells are assigned according to actually monitored water level data, numerical simulation is carried out until a seepage stable state is achieved, and for each example simulation result, the sum of the mean square difference of actual measurement and simulated flow velocity of each precipitation well, namely an error D, is calculated. The algorithm of the error D is the same as the substep a in the step S4, and is not described herein.
b. For each set of examples in the previous step, a linear function is used to fit the error D (dependent variable) and permeability coefficient k_{w}(independent variable) relationship, the slope of the fit is the rate of change of the error with the permeability coefficient, expressed asWherein i is 1m, m is the number of dewatering wells, m is 23, k in the embodiment of the invention_{w,i}And (c) representing the permeability coefficient of a row of waterproof curtain units closest to the ith precipitation well, wherein the specific method is the same as the substep b in the step S4, and details are not repeated here.
c. Updating the permeability coefficient of the waterproof curtain by gradient descent method, i.e. according to formulaAdjusting the permeability coefficient of a row of waterproof curtain units closest to each dewatering well, wherein the parameter beta needs to be determined according to trial calculation, the value of the parameter beta can ensure the stability and convergence of the gradient descent method, and the parameter beta is 10 after trial^{12}. The gradient descent method may also be replaced by other more optimized gradient descent methods, such as Momentum method or adagradad method.
d. And (4) circularly performing multiple rounds of waterproof curtain permeability coefficient inversion in the steps ac until the change rate of D after the inversion of the front and the back rounds is smaller than a change rate threshold eta. In this example, the end condition is reached by taking the value of η to 0.05 and performing generally 9 to 12 rounds of calculations, and the typical variation of D is similar to that of fig. 5 and is not specifically shown here.
And step S6, repeating the steps 4) and 5) to perform successive inversion of the soil layer permeability coefficients and the waterproof curtain permeability coefficients of multiple rounds until the change rate of the error D after the inversion of the front round and the rear round is smaller than the change rate threshold eta. In this example, the eta value is 0.05, and the final condition can be reached by performing 34 rounds of calculation, and the typical variation process of D is shown in FIG. 6.
Step S7, identifying potential leakage areas of the waterproof curtain: setting the permeability coefficient above a permeability coefficient threshold k_{a}The waterproof curtain unit is marked as a high leakage risk area, and once the high leakage risk area appears, the central processing module automatically alarms. In this example, k is taken_{a}Is 2 x 10^{5}cm/s, the inversion permeability coefficient of a column of waterstopping curtain units near a certain dewatering well in figure 3 reaches 4 multiplied by 10^{5}And cm/s, marking the area as a high leakage risk area, and automatically sending alarm information by the central processing module.
And S8, repeating the steps S1 to S7, and automatically identifying the leakage risk of the waterproof curtain in each precipitation stage until the project is finished.
It should be understood that excavation of the foundation pit may be divided into a plurality of stages according to the construction plan, each stage excavating a soil layer of a certain thickness, such as: in the embodiment of the invention, the depth of the foundation pit is 15 meters, the excavation can be divided into 4 times, namely 4 stages, wherein 4 meters, 3 meters and 5 meters are excavated in each time, and the foundation pit waterproof curtain water leakage identification method is used for onetime detection in each stage.
Referring to fig. 2, 7 and 8, the invention provides a foundation pit waterproof curtain water leakage recognition system, a plurality of dewatering wells 5 are arranged in the foundation pit, and waterproof curtains 4 are arranged around the foundation pit, the system comprises: the system comprises a precipitation module, an information acquisition module, a central processing module and a power supply module, wherein the precipitation module is arranged on the foundation pit and used for extracting seepage water in a precipitation well 5; the information acquisition module is arranged in the precipitation well 5 and used for measuring water level and flow rate data in the precipitation well 5 and transmitting the data to the central processing module; the central processing module is used for receiving water level and flow rate data, calculating a highrisk leakage area of the waterproof curtain 4 according to the foundation pit waterproof curtain water leakage identification method, and giving an alarm according to setting; the power supply module is connected with the precipitation module, the information acquisition module and the central processing module and used for providing electric energy.
Specifically, abovementioned precipitation module includes water pump 1, water hose 2 and collector pipe 3, and the quantity of water pump 1 is a plurality of, and 1 one end of water pump links to each other with collector pipe 3, and the other end links to each other with water hose 2, and the water hose 2 other end stretches into inside precipitation well 5.
The information acquisition module includes water level pipe 8, water level gauge 9, velocity of flow meter 10, data acquisition and local wireless transmission appearance 16 and 4G wireless transmission appearance 17, water level pipe 9 is located precipitation well 5 insidely, and water level pipe 8 bottom has the opening, 2 tip inserts in water level pipe 8 of water pumping hose, water level gauge 9 is located velocity of flow meter 10 top, and water level gauge 9 and velocity of flow meter 10 locate water level pipe 8 and water pumping hose 2 respectively inside, 8 upper portions of water level pipe expose the surface of water intercommunication atmospheric pressure, the inside infiltration of water pumping hose 2 extraction water level pipe 8 of water pump 1 connection, water level gauge 9 is apart from 1m to 2m with water pumping hose 2's water inlet 11.
The water level meter 9 and the flow meter 10 are connected with a data acquisition and local wireless transmission instrument 16 through a data transmission line 12, and the data acquisition and local wireless transmission instrument 16 is wirelessly connected with the central processing module through a 4G wireless transmission instrument 17. In the embodiment of the invention, the 4G wireless transmission instrument 17 and the central processing module adopt an uninterrupted power supply 18 which can provide stable power guarantee.
Further, a bracket platform 13 is arranged at the top of the dewatering well 5, a data acquisition and local wireless transmission instrument 16 and a waterproof battery 14 are arranged on the bracket platform 13, the bracket platform 13 is a rectangular metal bearing platform arranged above the water level pipe 8, the side length of the short side of the bracket platform is larger than the diameter of the dewatering well 5, and the functions of fixing the water level pipe 8 and placing the waterproof battery 14 and the data acquisition and local wireless transmission instrument 16 are achieved. The waterproof battery 14 is connected with the data acquisition and local wireless transmission instrument 16 through a waterproof wire 15 and is used for providing electric energy.
The central processing module comprises a 4G signal receiver 6 and a computer system 7, wherein the 4G signal receiver 6 is used for receiving water level and flow rate data of all dewatering wells 5 and inputting the data into the computer system 7 for processing. The computer system 7 is a parallel computing server with ABAQUS finite element analysis software installed, which can run up to 150 threedimensional leakage examples simultaneously.
In summary, the invention discloses a method and a system for identifying water leakage of a waterproof curtain of a foundation pit, which have the beneficial effects that: combining the actually measured water level and flow velocity information in the precipitation well with threedimensional finite element seepage simulation, obtaining the horizontal permeability coefficient, the vertical permeability coefficient and the waterstopping curtain permeability coefficient of a soil layer by adopting a gradient descent method and sequentially inverting the soil layer permeability coefficient and the waterstopping curtain permeability coefficient through multiple rounds, and identifying the potential permeability area of the waterstopping curtain based on the waterstopping curtain permeability coefficient, wherein the method is high in scientificity and accuracy; the leakage condition of the foundation pit waterproof curtain can be remotely and automatically monitored, analyzed and automatically alarmed, the automation and the intellectualization of foundation pit engineering monitoring can be improved, and the foundation pit construction safety can be improved.
The technical scope of the present invention is not limited to the above description, and those skilled in the art can make various changes and modifications to the abovedescribed embodiments without departing from the technical spirit of the present invention, and such changes and modifications should fall within the protective scope of the present invention.
Claims (10)
1. A method for identifying water leakage of a waterproof curtain of a foundation pit is characterized by comprising the following steps:
1) system construction: a precipitation module, an information acquisition module and a central processing module are set up, and the precipitation module and the information acquisition module are connected with the central processing module;
2) constructing a numerical analysis model: introducing a stratum model, constructing a threedimensional seepage finite element model for foundation pit excavation, wherein the threedimensional seepage finite element model comprises a soil layer unit, a dewatering well unit and a waterproof curtain unit, and assigning an initial horizontal permeability coefficient and a vertical permeability coefficient to the soil layer unit according to the permeability coefficient given by a geotechnical engineering investigation report;
3) and (3) field construction: pumping water into the precipitation well according to the precipitation scheme at the current stage until the water pumping process is stable, measuring the water level and the flow rate according to certain data acquisition frequency by using the information acquisition module in the water pumping process, and transmitting the measured water level and flow rate data to the central processing module;
4) soil layer permeability coefficient inversion;
5) inverting the permeability coefficient of the waterproof curtain;
6) circulating the steps 4) and 5) to successively invert the soil layer permeability coefficients and the waterproof curtain permeability coefficients of multiple rounds until the change rate of an error D obtained after the inversion of the two rounds is smaller than a change rate threshold eta, wherein the error D is the sum of the mean square deviations of the actual measurement and the simulated flow rate of each dewatering well unit;
7) identification of potential leakage areas of the waterproof curtain: setting the permeability coefficient above a permeability coefficient threshold k_{a}The waterproof curtain unit is marked as a high leakage risk area, and once the high leakage risk area appears, the central processing module automatically alarms;
8) and (5) repeating the steps 3) to 7), and automatically identifying the leakage risk of the waterproof curtain in each precipitation stage until the project is finished.
2. The foundation pit waterproof curtain water leakage identification method according to claim 1, wherein the soil layer permeability coefficient inversion in the step 4) comprises the following steps:
a. the horizontal permeability coefficient and the vertical permeability coefficient of each soil layer of the soil layer unit are adjusted one by one and are respectively 0.90k_{s}、0.95k_{s}、1.00k_{s}、1.05k_{s}And 1.10k_{s}Form a set of examples, k_{s}Adjusting the horizontal permeability coefficient or the vertical permeability coefficient of the current soil layer only by one soil layer each timePermeability coefficient or vertical permeability coefficient; the central system processing module simulates threedimensional seepage of foundation pit groundwater according to a current stage rainfall design scheme, wherein the boundary condition of the water level in the model precipitation well unit is assigned according to actually monitored water level data, numerical simulation is operated until a seepage stable state is reached, and the sum of the mean square deviation of actual measurement and simulated flow velocity of each precipitation well unit, namely an error D, is calculated for each calculation example simulation result;
b. for each set of calculation examples in the previous step, fitting error D and permeability coefficient k by using a linear function_{s}The slope of the fit is the rate of change of error with permeability coefficient, expressed asWhere i is 12 n, n is the number of soil layers, k_{s,1}—k_{s,n}Denotes the horizontal permeability coefficient, k, of the soil of the 1 st to n th layers_{s,1+n}—k_{s,2n}The vertical permeability coefficient of the soil of the 1 st to the n th layers is shown;
c. updating the permeability coefficient by gradient descent, i.e. according to the formulaAdjusting the horizontal permeability coefficient and the vertical permeability coefficient of each soil layer;
d. and (c) circularly performing multiple rounds of soil layer permeability coefficient inversion in the steps ac until the change rate of the error D after the inversion of the front and the back rounds is smaller than the change rate threshold eta.
3. The method for identifying the water leakage of the waterproof curtain of the foundation pit according to claim 1, wherein the step 5) of stopping inversion of the permeability coefficient of the waterproof curtain comprises the following steps:
a. setting the permeability coefficient of the waterstopping curtain unit in the row closest to each dewatering well unit as 0.6k for each dewatering well of one pair of dewatering well units_{w}、0.8k_{w}、1.0k_{w}、1.2k_{w}And 1.4k_{w}Form a set of examples, k_{w}Adjusting the permeability coefficient of the waterstopping curtain unit related to one precipitation well for the current permeability coefficient of the waterstopping curtain unit;the central processing module simulates threedimensional seepage of foundation pit groundwater according to a precipitation design scheme at the current stage, wherein the boundary condition of the water level in the precipitation well is assigned according to actually monitored water level data, numerical simulation is carried out until a seepage stable state is achieved, and for each example simulation result, the sum of the mean square deviation of actual measurement and simulated flow rate of each precipitation well, namely an error D, is calculated;
b. for each set of calculation examples in the previous step, fitting error D and permeability coefficient k by using a linear function_{w}The slope of the fit is the rate of change of error with permeability coefficient, expressed asWherein i is 1m, m is the number of dewatering wells, k_{w,i}Representing the permeability coefficient of a row of waterproof curtain units closest to the ith precipitation well;
c. updating the permeability coefficient of the waterproof curtain by gradient descent method, i.e. according to formulaAdjusting the permeability coefficient of a row of waterproof curtain units closest to each dewatering well;
d. and (4) circularly performing multiple rounds of waterproof curtain permeability coefficient inversion in the steps ac until the change rate of D after the inversion of the front and the back rounds is smaller than a change rate threshold eta.
4. The method for identifying water leakage of the foundation pit waterproof curtain according to claim 3, wherein the gradient descent method is a Momentum method or an adarad method.
5. The method for identifying water leakage of the foundation pit waterproof curtain according to claim 1, wherein the stratum model is determined according to a foundation pit peripheral soil structure disclosed by a geotechnical engineering investigation report, and the periphery and the bottom of the threedimensional seepage finite element model are fixed pore pressure boundaries.
6. The utility model provides a foundation ditch stagnant water curtain percolating water identification system, be equipped with many mouthfuls of precipitation wells in the foundation ditch, and be located the foundation ditch is equipped with stagnant water curtain all around, its characterized in that, the system includes:
the precipitation module is arranged on the foundation pit and used for extracting seepage water in the precipitation well;
the information acquisition module is arranged in the precipitation well, and is used for measuring water level and flow rate data in the precipitation well and transmitting the data to the central processing module;
the central processing module is used for receiving the water level and flow rate data, calculating a highrisk leakage area of the waterproof curtain according to the foundation pit waterproof curtain water leakage identification method in any one of claims 1 to 5, and alarming according to setting;
and the power supply module is connected with the precipitation module, the information acquisition module and the central processing module and is used for providing electric energy.
7. The foundation pit waterproof curtain water leakage identification system according to claim 6, wherein the dewatering module comprises a plurality of water pumps, a water pumping hose and a water collecting pipe, one end of each water pump is connected with the water collecting pipe, the other end of each water pump is connected with the water pumping hose, and the other end of each water pumping hose extends into the dewatering well.
8. The foundation pit waterproof curtain water leakage recognition system according to claim 7, wherein the information acquisition module comprises a water level pipe, a water level gauge, a flow meter, a data acquisition and local wireless transmission instrument and a 4G wireless transmission instrument, the water level pipe is arranged inside the dewatering well, the water level gauge is positioned above the flow meter, the water level gauge and the flow meter are respectively arranged inside the water level pipe and the pumping hose, the water level gauge and the flow meter are connected with the data acquisition and local wireless transmission instrument through data transmission lines, and the data acquisition and local wireless transmission instrument is wirelessly connected with the central processing module through the 4G wireless transmission instrument.
9. The foundation pit waterproof curtain water leakage identification system according to claim 6, wherein the central processing module comprises a 4G signal receiver and a computer system, and the 4G signal receiver is used for receiving water level and flow rate data of all dewatering wells and inputting the data into the computer system for processing.
10. The foundation pit waterproof curtain water leakage recognition system according to claim 6, wherein a bracket platform is arranged at the top of the dewatering well, the length of the short side of the bracket platform is larger than the diameter of the dewatering well, a data acquisition and local wireless transmission instrument and a waterproof battery are arranged on the bracket platform, and the waterproof battery is connected with the data acquisition and local wireless transmission instrument through a waterproof wire and used for providing electric energy.
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