CN110763400A - Method and system for detecting defects of vertical impervious curtain - Google Patents
Method and system for detecting defects of vertical impervious curtain Download PDFInfo
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- CN110763400A CN110763400A CN201910870139.4A CN201910870139A CN110763400A CN 110763400 A CN110763400 A CN 110763400A CN 201910870139 A CN201910870139 A CN 201910870139A CN 110763400 A CN110763400 A CN 110763400A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M3/00—Investigating fluid-tightness of structures
- G01M3/02—Investigating fluid-tightness of structures by using fluid or vacuum
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- 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
- E02D19/18—Restraining of underground water by damming or interrupting the passage of underground water by making use of sealing aprons, e.g. diaphragms made from bituminous or clay material
Abstract
The invention provides a method and a system for detecting defects of a vertical impervious curtain, wherein the method comprises the following steps: step S1: arranging a plurality of groups of test wells around the vertical impervious curtain, wherein each group of test wells comprises a pumping well positioned on one side of the vertical impervious curtain and an observation well positioned on the other side of the vertical impervious curtain; step S2: performing a background water level determination test on the observation wells of each group of the test wells to obtain data of the change of the background water level of the observation wells along with time; step S3: carrying out pumping tests on the pumping wells of each group of test wells to obtain data of the dynamic water level of the observation well changing along with time; step S4: and comparing the data of the background water level changing along with the time of each group of test wells with the data of the dynamic water level changing along with the time to judge the defect condition of the vertical impervious curtain. According to the invention, the defect condition of the vertical impervious wall can be accurately judged.
Description
Technical Field
The invention relates to the field of garbage disposal, in particular to a method and a system for detecting defects of a vertical impervious curtain.
Background
Along with the development of national economy, the living standard of people is increasingly improved, the population of cities is continuously increased, the number of municipal solid wastes is increased, and the wastes must be treated in order to prevent the wastes from polluting the environment.
A safety landfill is a disposal facility for disposing or storing hazardous waste garbage in soil, the purpose of which is to bury or change the characteristics of hazardous waste, and is suitable for landfill disposal of hazardous waste which cannot recycle its useful components and cannot recycle its energy. The general aim of a safety landfill is to isolate the hazardous waste from the environment as much as possible, so that a containment curtain must be placed around the safety landfill. The anti-seepage performance of the anti-seepage curtain influences the safety of the surrounding environment. In the prior art, a geophysical prospecting method is often used to detect the structural integrity of the vertical impervious curtains.
Due to the poor adaptability of the geophysical prospecting technology to complex engineering conditions and detection environments and the limited detection precision of the equipment, the defect condition in the vertical impervious curtain cannot be accurately judged.
Therefore, there is a need for a system and method for detecting defects in a vertical impervious curtain, which solves the problems of the prior art.
Disclosure of Invention
In this summary, concepts in a simplified form are introduced that are further described in the detailed description. This summary of the invention is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
The invention provides a method for detecting defects of a vertical impervious curtain, which comprises the following steps:
step S1: arranging a plurality of groups of test wells around the vertical impervious curtain, wherein each group of test wells comprises a pumping well positioned on one side of the vertical impervious curtain and an observation well positioned on the other side of the vertical impervious curtain;
step S2: performing a background water level determination test on the observation wells of each group of the test wells to obtain data of the change of the background water level of the observation wells along with time;
step S3: carrying out pumping tests on the pumping wells of each group of test wells to obtain data of the dynamic water level of the observation well changing along with time;
step S4: comparing the data of the background water level changing with time and the data of the dynamic water level changing with time of each group of the test wells to judge the defect condition of the vertical impervious curtain, wherein,
when the dynamic water level of the observation well in the test well is unchanged or the change of the dynamic water level of the observation well is smaller than the change of the background water level of the observation well, the dynamic water level of the observation well is judged to be normal, and the integrity of the vertical impervious curtain is good; otherwise, judging that the dynamic water level of the observation well is abnormal, and the vertical impervious curtain has defects.
Exemplarily, the step S1 includes:
step S11: determining the distance between the well position of the test well and the impervious curtain;
step S12: determining the distance between the well positions of two adjacent groups of test wells and the detection range of each group of test wells;
step S13: constructing to dig a well according to the distance between the test well positions and the impervious curtains determined in the step S11, the distance between two adjacent groups of the test well positions determined in the step S12 and the detection range of each group of the test wells.
Illustratively, the test well is pumped and washed during the step S1 of arranging the test well so that the water pumped from the test well is free of silt.
Illustratively, the distance between the well testing position and the impervious curtain in the step S11 is 1.5-2.5 times of the aperture of the well testing.
Illustratively, in the step S12, the distance d between adjacent test wells satisfies R ≦ d ≦ 2R, where R is based on an empirical formula
And determining that S is water level depth reduction and K is a permeability coefficient, setting the intersection point of the connecting line of the pumping well and the observation well and the vertical impervious curtain as a central point, and setting the detection range of each group of the test well as the range of the distance central point in the vertical impervious curtain to be less than or equal to R.
Exemplarily, in the step S2, the method further includes plotting a time-varying curve of the background water level of the observation well according to the time-varying data of the background water level of the observation well; and
in step S3, the method further includes drawing a time-varying curve of the dynamic water level of the observation well according to the time-varying data of the dynamic water level of the observation well.
Illustratively, the step of comparing the time-dependent background water level data and the time-dependent dynamic water level data for each set of the test wells comprises comparing a time-dependent background water level profile of the observation wells with a time-dependent dynamic water level profile of the observation wells.
Illustratively, when the vertical impervious curtain is judged to have defects, the range of the positions of the defects is further judged.
Illustratively, the step of further judging the range in which the defect position exists includes:
and when the distance d between two adjacent groups of test well positions is equal to 2R, the integrity of the vertical impervious wall in the detection range of each group of test wells is directly judged according to a relation curve of the dynamic water level changing along with time, which is measured by a pumping test of the vertical impervious wall.
Illustratively, the step of further judging the range in which the defect position exists includes:
when the distance d between two adjacent groups of the test well positions satisfies that R is more than or equal to d and less than 2R,
if the dynamic water level of the observation well of one group of the test wells is abnormal, and the dynamic water level of the observation well of the other group of the test wells is normal, determining that the defect is located in the range that the center point of the test well with the abnormal dynamic water level of the observation well is close to one side of the test well with the abnormal dynamic water level of the observation well and the radius of one side of the test well is R;
and if the dynamic water levels of the observation wells of each group of the test wells are abnormal, judging that:
1) 1 defect exists between the central points of the two adjacent groups of test wells, and the defect is located in a range with the center point between the central points of the two groups of test wells as the circle center and the radius of d/2; or
2) There are more than 2 defects, and 2 defects belong to any one of the following three cases:
the two adjacent groups of the test wells comprise a first group of the test wells and a second group of the test wells which are adjacent,
a: the radius of the center point of the first group of test wells close to one side of the second group of test wells is within a range d;
b: the second group of the test well center points are close to the area within the range of the radius d of one side of the first group of the test wells;
c: and taking the midpoint between the central points of the two groups of test wells as the circle center and the radius of the midpoint as the range of d/2.
The present invention also provides a system for detecting defects of a vertical impervious curtain, comprising:
a plurality of groups of test wells arranged around the vertical impervious curtain, wherein each group of test wells comprises a pumping well positioned in the inner area of the vertical impervious curtain and an observation well positioned in the outer area of the vertical impervious curtain;
the water pumping measuring device is used for performing a water pumping test on the water pumping well;
the water level detection device is used for detecting the water level of the observation well before the water pumping test is carried out on the water pumping well by the water pumping measuring device or during the water pumping test so as to respectively obtain data of the change of the background water level of the observation well with time and data of the change of the dynamic water level of the observation well with time.
Illustratively, the test well comprises an underground pipe and a subterranean pipe, wherein the subterranean pipe comprises a sedimentation pipe, a water filter pipe and a well wall pipe which are arranged in sequence from bottom to top;
the above-ground tubular comprises a wellhead casing comprising a protective casing, a plastic cover plate and a protective cover plate.
According to the method and the system for detecting the defects of the vertical impervious curtain, disclosed by the invention, the periodic change rule of underground water and the dynamic change characteristics of the underground water level are obtained by observing the background water level and the dynamic water level of the test well, the hydraulic connection strength of the underground water on two sides of the vertical impervious curtain is determined, and therefore whether the vertical impervious wall really has structural defects can be effectively detected and judged.
Drawings
The following drawings of the invention are included to provide a further understanding of the invention. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
In the drawings:
FIG. 1 is a flowchart of a method for detecting defects in a vertical impervious curtain according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a test well in a method for detecting defects in a vertical impervious curtain according to an embodiment of the present invention;
FIG. 3 is a schematic view of a test well arranged in a detection area of a vertical impervious curtain in a method for detecting defects of the vertical impervious curtain according to an embodiment of the present invention;
4A-4E are graphs of pumping well water level depression versus time for a pumping test on a pumping well having 5 sets of test wells according to one example of the present invention; and
figures 5A-5E are graphs of water level drop in observation wells as a function of time for a pumping trial of a pumping well having 5 test wells according to one example of the invention.
Detailed Description
In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without one or more of these specific details. In other instances, well-known features have not been described in order to avoid obscuring the invention.
In order to provide a thorough understanding of the present invention, a detailed description will be provided in the following description to illustrate a method and system for detecting defects of a vertical impervious curtain of the present invention. It will be apparent that the practice of the invention is not limited to the specific details known to those skilled in the art of waste treatment. The following detailed description of the preferred embodiments of the invention, however, the invention is capable of other embodiments in addition to those detailed.
It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular is intended to include the plural unless the context clearly dictates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
Exemplary embodiments according to the present invention will now be described in more detail with reference to the accompanying drawings. These exemplary embodiments may, however, be embodied in many different forms and should not be construed as limited to only the embodiments set forth herein. It is to be understood that these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of these exemplary embodiments to those skilled in the art. In the drawings, the thicknesses of layers and regions are exaggerated for clarity, and the same elements are denoted by the same reference numerals, and thus the description thereof will be omitted.
A safety landfill is a disposal facility for disposing or storing hazardous waste garbage in soil, the purpose of which is to bury or change the characteristics of hazardous waste, and is suitable for landfill disposal of hazardous waste which cannot recycle its useful components and cannot recycle its energy. The general aim of a safety landfill is to isolate the hazardous waste from the environment as much as possible, so that a containment curtain must be placed around the safety landfill. The anti-seepage performance of the anti-seepage curtain influences the safety of the surrounding environment. In the prior art, a geophysical prospecting method is often used to detect the structural integrity of the vertical impervious curtains.
Due to the poor adaptability of the geophysical prospecting technology to complex engineering conditions and detection environments and the limited detection precision of the equipment, the defect condition in the vertical impervious curtain cannot be accurately judged.
Example one
In order to solve the problems in the prior art, the present invention provides a method for detecting defects of a vertical impervious curtain, comprising:
arranging a test well and an observation well, wherein the test well is positioned in the inner area of the vertical impervious curtain, and the observation well is positioned in the outer area of the vertical impervious curtain;
step S1: arranging a plurality of groups of test wells around the vertical impervious curtain, wherein each group of test wells comprises a pumping well positioned on one side of the vertical impervious curtain and an observation well positioned on the other side of the vertical impervious curtain;
step S2: performing a background water level determination test on the observation wells of each group of the test wells to obtain data of the change of the background water level of the observation wells along with time;
step S3: carrying out pumping tests on the pumping wells of each group of test wells to obtain data of the dynamic water level of the observation well changing along with time;
step S4: comparing the data of the background water level changing with time and the data of the dynamic water level changing with time of each group of the test wells to judge the defect condition of the vertical impervious curtain, wherein
When the dynamic water level of the observation well in the test well is unchanged or the change of the dynamic water level of the observation well is smaller than the change of the background water level of the observation well, the dynamic water level of the observation well is judged to be normal, and the integrity of the vertical impervious curtain is good; otherwise, judging that the dynamic water level of the observation well is abnormal, and the vertical impervious curtain has defects.
Referring to FIGS. 1-3, 4A-4E, and 5A-5E, a method for detecting a defect in a vertical impervious curtain of the present invention is schematically described, wherein FIG. 1 is a flowchart of a method for detecting a defect in a vertical impervious curtain according to an embodiment of the present invention; FIG. 2 is a schematic diagram of a test well in a method for detecting defects in a vertical impervious curtain according to an embodiment of the present invention; FIG. 3 is a schematic view of a test well arranged in a detection area of a vertical impervious curtain in a method for detecting defects of the vertical impervious curtain according to an embodiment of the present invention; 4A-4E are graphs of pumping well water level depression versus time for a pumping test on a pumping well having 5 sets of test wells according to one example of the present invention; and figures 5A-5E are graphs of water level drop in observation wells as a function of time for a pumping trial of a pumping well having 5 test wells according to one example of the invention.
Referring first to fig. 1, step S1 is performed: and arranging a plurality of groups of test wells around the vertical impervious curtain, wherein each group of test wells comprises a pumping well positioned on one side of the vertical impervious curtain and an observation well positioned on the other side of the vertical impervious curtain.
As shown in fig. 2, a schematic of a test well according to the present invention is shown. According to the invention, the extraction well and the observation well of the test well have the same structure, which is only described as an example. Illustratively, the pumping well comprises an underground pipe below the earth surface A and an underground pipe above the earth surface A, wherein the underground pipe comprises a sedimentation pipe 1, a water filter pipe 2 and a well wall pipe 5 which are arranged from bottom to top along the ground, a filling layer is arranged outside the underground pipe, and the filling layer sequentially comprises quartz sand 3, a clay layer 4 and a concrete layer 6 along the direction from the ground to the earth surface. The above ground pipe comprises a wellhead casing comprising a protective casing 7, a plastic cover plate 8 and a protective cover plate 9.
Illustratively, the extraction well and the observation well have different apertures, wherein the aperture of the extraction well is large. In one example according to the invention, the extraction well aperture is 600mm and the observation well aperture is 300 mm.
Illustratively, the pumping well and the observation well are of different materials.
With continued reference to fig. 2, clay layer 4 comprises clay ball layer and clay layer, according to an example of the present invention, the settling tube 1, the strainer 2 and the casing tube 5 in the observation well are all HDPE tubes with a diameter of 110 mm; in the pumping well, the settling tube 1, the strainer 2 and the casing tube 5 are all steel tubes, and the tube diameters are 273 mm.
It should be understood that the structure, aperture, material of the pipe and arrangement of the pipe diameter of the pumping well and the observation well are only exemplary, and those skilled in the art can arrange other forms according to the needs. In accordance with one example of the present invention, 5 sets of test wells are arranged, it being understood that the number of test wells set to 5 is exemplary only, and one skilled in the art will appreciate that any number of sets of test wells are suitable for use in the present invention.
According to one example of the invention, the suction well is located in an area inside the vertical impervious curtain and the observation well is located in an area outside the vertical impervious curtain. The water pumping well is arranged to be located in the inner area of the vertical impervious curtain, and the observation well is arranged to be located in the outer area of the vertical impervious curtain, so that the significance of water level change in the observation well in a subsequent water pumping test can be improved, and the obtained result is more convenient to analyze.
Illustratively, the step of arranging the test wells in the step S1 includes:
step S11: and determining the distance between the well position of the test well and the impervious curtain. Illustratively, the distance between the well position of the test well and the impervious curtain is 1.5-2.5 times of the aperture of the pumping well. The phenomenon that the distance between the well position of the test well and the impervious curtain is too small to damage the impervious wall in the experimental process, and the water level change responsiveness in the observation well in the subsequent dynamic water level determination test step is small to influence the observation result due to the fact that the distance between the well position of the test well and the impervious curtain is too large is avoided; according to one example of the invention, the distance between the test well site and the impervious curtain is twice the bore diameter of the test well.
Step S12: and determining the distance between two adjacent groups of test wells and the detection range of each group of test wells. The distance d between adjacent test wells satisfies that R is more than or equal to d and less than or equal to 2R, wherein R is according to an empirical formula
Determining that S is water level lowering and K is a permeability coefficient, setting the intersection point of a connecting line of the pumping well and the observation well and the vertical impervious curtain as a central point, and setting the detection range of each group of test wells as a range within the vertical impervious curtain, wherein the distance from the central point is less than or equal to R;
in one example according to the invention, the bore diameter of the pumping well is 600mm, and the distance between the test well site and the impervious curtain should be 1200mm, wherein the pumping well is arranged 1200mm inside the vertical impervious wall and the observation well is arranged 1200mm outside the vertical impervious wall. The bottom of the observation well is about 2m away from the bottom of the impervious wall, the aperture of the observation well is 300mm, the diameter of the underground pipe is 110mm, the sedimentation pipe 1 is positioned from 12m underground to 11.5m underground, the water filter pipe 2 is positioned from 11.5m underground to 2.5m underground, the well wall pipe 5 is positioned from 2.5m underground to the surface, the quartz sand layer 3 is positioned from 12m underground to 2.0m underground, the clay layer 4 is positioned from 2.0m underground to 0.5m underground, and the concrete layer 6 is positioned from 0.5m underground to the surface. In the process of arranging the test well, the water level depression S is estimated according to experience before shaft sinking, and the permeability coefficient K is an empirical value determined according to the stratum. Illustratively, the water level drop S is estimated to be 13m, the permeability coefficient K is determined to be 0.0518m/d, R is about 29.6m, and the distance between adjacent test wells is about 29.6m, so that the blank detection section of the impervious curtain in the water pumping test is prevented.
Step S13: constructing to dig a well according to the distance between the test well positions and the impervious curtains determined in the step S11, the distance between two adjacent groups of the test well positions determined in the step S12 and the detection range of each group of the test wells.
As shown in fig. 3, a schematic of a test well deployed around a landfill in accordance with one example of the invention. Vertical impervious curtains 302 are arranged on the periphery of the refuse landfill 301, a plurality of groups of test wells are arranged around the refuse landfill for detecting whether the vertical impervious curtains 302 have defects, each test well comprises a pumping well 303P arranged on the inner side of the vertical impervious curtain 302 and an observation well 303M arranged on the outer side of the vertical impervious curtain.
Illustratively, the test well is pumped and flushed in step S13 so that the water pumped from the test well does not contain silt.
Exemplarily, the step S13 includes the steps of:
step S131: construction preparation: and (5) setting test well points according to the layout of the test wells in the step S1, measuring well placement positions, and excavating a mud pit which is communicated with the well mouths of the test wells.
Step S132: and (3) well head pipe descending: and (8) carrying out manual excavation on the well position measured and released in the step S21, and lowering the wellhead pipe.
Step S133: drilling to form a hole: naturally making slurry in the wellhead pipe in the step S22 by adopting a drilling tool, drilling a well to form a hole, and controlling the density of the slurry to be 1.1-1.2 g/cm3After drilling to the designed depth, lifting the drilling tool to a position 20-30 cm away from the bottom of the hole, and removing sediments in the hole, wherein the sediments in the hole are smaller than 20 cm;
step S134: a well pipe is lowered: arranging the sedimentation pipe 1, the strainer 2 and the casing pipe 5 in advance, and putting the sedimentation pipe 1, the strainer 2 and the casing pipe 5 into the hole drilled in the step S23;
step S135: gravel throwing: uniformly putting the quartz sand layer 3 around the sedimentation pipe 1 and the water filter pipe 2 in the step 14 until the height of the quartz sand layer 3 reaches the designated height;
step S136: water stopping: putting clay balls above the quartz sand layer 3 in the step 25, checking the water stopping effect, if the water stopping effect is poor, continuing to put the clay balls, otherwise, if the water stopping effect is good, turning to the step 27;
step S137: hole sealing: putting clay blocks above the clay balls in the step 26, and after the clay blocks are put to a certain height, sealing and filling concrete to finish the test well preliminarily;
step S138: well flushing: and (5) continuously pumping water from the test well obtained in the step S27 by using a water pump until the test well does not contain sediment.
Referring next to fig. 1, step S2 is performed: and carrying out a background water level determination test on the observation wells of each group of the test wells to obtain data of the change of the background water level of the observation wells along with time.
Illustratively, background water level data is collected using a wireless water level monitor.
Exemplarily, in the step S2, the pumping well and the observation well are not processed, the water level data in the observation well is collected only at intervals of a predetermined time, and recorded, until the water level data in the observation well measured for a predetermined number of consecutive times are the same or the difference does not exceed a certain value, it is determined that the background water level of the observation well is stable, the collection operation is ended, the obtained data is used as the background water level data to be compared with the dynamic water level data in the observation well when the pumping well pumps water, if the dynamic water level data is not much different from the background water level data, it is indicated that no water permeates through the vertical impervious curtain during the pumping well, and further, it is indicated that the vertical impervious curtain is not damaged, otherwise, the two data are greatly different, it is indicated that water permeates through the vertical impervious curtain, and further, the vertical impervious curtain is damaged. According to the method, the hydraulic connection strength of the underground water on the two sides of the vertical impervious curtain is determined, whether the vertical impervious wall has the structural defect or not is effectively detected and judged, and therefore the defect condition of the vertical impervious wall can be accurately judged.
In one example according to the present application, the acquisition frequency is to record water level data three times every 30 minutes, and the acquisition time is 24 hours; and mastering the static change rule of the underground water according to the acquired water level data, and judging that the hydrostatic level of the test well is stable if the water level values of the test well measured for 4 hours are the same or the water level difference does not exceed 2 cm.
Specifically, in the actual monitoring process, after background water level data are collected by the wireless water level monitor, a graph is drawn through Excel.
In one example according to the present invention, a background water level was observed for an observation well having 5 sets of test wells. The result shows that the observation wells in each group of test wells have relatively consistent underground water level changes and have fluctuation with a certain amplitude, but the fluctuation range is relatively small and is not more than 0.056m at most. Since the project site is only about 2.8km close to the yellow sea, the fluctuation of the hydrostatic level may be affected by the peripheral yellow sea tides.
Referring next to fig. 1, step S3 is performed: and carrying out pumping test on the pumping wells of each group of test wells to obtain data of the dynamic water level of the observation well changing along with time.
Illustratively, the pumping test includes a pumping water level observation and a pumping water amount observation.
Illustratively, a wireless water level monitor is adopted to collect dynamic water level data during water pumping.
Illustratively, the water pumping quantity observation adopts a water meter to measure the water output of a pumping well in the water pumping process.
Specifically, in the actual detection process, after background water level data are collected by the wireless water level monitor, a graph is drawn through Excel.
In one example according to the invention, pumping tests were performed on pumping wells with 5 groups of test wells, observing an average water inflow of 2.04m for pumping well number 13D, the stable dynamic water level of the No. 1 pumping well is about-8.25 m; average water inflow of No. 2 pumping well is 1.97m3The stable dynamic water level of the No. 2 pumping well is about-12.71 m; the average water inflow of No. 3 pumping well is 2.03m3The stable dynamic water level of the No. 3 pumping well is about-12.54 m; the average water inflow of No. 4 pumping well is 3.07m3The stable dynamic water level of the No. 4 pumping well is about-11.16 m; the average water inflow of No. 5 pumping well is 2.51m3And d, the stable dynamic water level of the No. 5 pumping well is about-10.21 m.
Next, with continued reference to fig. 1, step S4 is performed: comparing the data of the background water level changing with time of each group of test wells with the data of the dynamic water level changing with time to judge the defect condition of the vertical impervious curtain, wherein when the dynamic water level of the observation well in the test wells is unchanged or is changed less than the background water level of the observation well, the dynamic water level of the observation well is judged to be normal, and the integrity of the vertical impervious curtain is good; otherwise, judging that the dynamic water level of the observation well is abnormal, and the vertical impervious curtain has defects.
Referring to fig. 4A-4E and 5A-5E, graphs of water level drop in a suction well and an observation well over time for a suction well having 5 sets of trial wells in a suction trial according to one example of the invention are shown. Wherein, fig. 4A is a graph showing the relation between the water level lowering of the pumping well No. 1 and the time variation; FIG. 4B is a graph of water level drop versus time for pumping well No. 2; FIG. 4C is a graph of water level drop versus time for pumping well # 3; FIG. 4D is a graph of water level drop versus time for pumping well # 4; FIG. 4E is a graph of water level drop versus time for pumpout No. 5; FIG. 5A is a graph of water level lowering versus time for observation well # 1; FIG. 5B is a graph of water level lowering versus time for observation well # 2; FIG. 5C is a graph of water level lowering versus time for observation well # 3; FIG. 5D is a graph of water level lowering versus time for observation well # 4; FIG. 5E is a graph of water level lowering versus time for observation well # 5.
It can be seen from the figure that the water level in the pumping well fluctuates in a large range because the groundwater contains a certain amount of silt particles, the water inflow is small in the pumping process, and the silt particles are gradually deposited in the drainage pipe along with the time, so that the water inflow is reduced, and the water level is slowly increased; after the large flow is adjusted again, the water level is reduced and gradually increased; the water level in the observation well shows corresponding water level change, the water level falling depths of the No. 3 observation well and the No. 4 observation well are relatively large, the falling amplitudes respectively reach 1.12m and 1.5m, and the water level falling amplitudes of other observation wells are 0.33-0.50 m. Compared with the result of observing the background water level of the observation well with 5 groups of test wells (the water level change is not more than 0.056m at most), the vertical impervious wall has structural defects, wherein the defects at the positions of the vertical impervious walls corresponding to the No. 3 observation well and the No. 4 observation well are larger than the defects at the positions of the vertical impervious walls corresponding to other observation wells.
Illustratively, the method for detecting the defect of the vertical impervious curtain further comprises the step of further judging the range of the defect position when the defect of the vertical impervious curtain is judged.
Illustratively, when the distance d between two adjacent groups of test wells is equal to 2R, the integrity of the vertical impervious wall in the detection range of each group of test wells is directly judged according to the relation curve of the dynamic water level changing along with the time measured by the pumping test of the vertical impervious wall.
Illustratively, when the distance d between two adjacent groups of the test wells satisfies R ≦ d < 2R, the following two cases are discussed:
if the dynamic water level of the observation well of one group of the test wells is abnormal, and the dynamic water level of the observation well of the other group of the test wells is normal, the defect is determined to be located in the range that the radius of the center point of the test well with the abnormal dynamic water level of the observation well, which is close to the test well with the abnormal dynamic water level of the observation well, is R.
And if the dynamic water levels of the observation wells of each group of the test wells are abnormal, judging that:
1) 1 defect exists between the central points of the two adjacent groups of test wells, and the defect is located in a range with the center point between the central points of the two groups of test wells as the circle center and the radius of d/2; or
2) There are more than 2 defects, and 2 defects belong to any one of the following three cases:
the two adjacent groups of the test wells comprise a first group of the test wells and a second group of the test wells which are adjacent,
a: the radius of the center point of the first group of test wells close to one side of the second group of test wells is within a range d;
b: the second group of the test well center points are close to the area within the range of the radius d of one side of the first group of the test wells;
c: and taking the midpoint between the central points of the two groups of test wells as the circle center and the radius of the midpoint as the range of d/2.
Referring to fig. 3, a result determination of a vertical impervious curtain according to a water level change in a test well and an observation well according to an example of the present invention will be exemplarily described.
As shown in fig. 3, a schematic of a test well deployed around a landfill in accordance with one example of the invention. Vertical impervious curtains 302 are arranged on the periphery of the refuse landfill 301, a plurality of groups of test wells are arranged around the refuse landfill for detecting whether the vertical impervious curtains 302 have defects, each test well comprises a pumping well 303P arranged on the inner side of the vertical impervious curtain 302 and an observation well 303M arranged on the outer side of the vertical impervious curtain. Three groups of test wells in the figure: test wells P1-M1, P2-M2, and P3-M3 are illustrated as examples:
when the distance d between two adjacent groups of test wells is equal to 2R, the integrity of the vertical impervious wall in the detection range of each group of test wells can be directly judged according to the pumping test result;
when the distance d between two adjacent groups of test wells meets the following relation that R is not less than d and less than 2R, if the water pumping result of the test wells P2-M2 is abnormal, but the water pumping result of the test wells P1-M1 is not abnormal, the defect is positioned in the range of d-R on the left side of the central point O2; if the water pumping result of the test well P2-M2 is abnormal and the test well P1-M1 is also abnormal, 2 possibilities are shown:
1) 1 defect exists between the observation well with the center point O1 and the observation well with the center point O2, and the distance between the two sides of the midpoint between the center point O1 and the center point O2 is a range with the radius of d/2;
2) there are more than 2 defects, and 2 defects belong to:
a: the right side of the center point O1 is in a range with the radius d;
b: a region within a radius d on the left side of the center point O2;
c: the distance between the center point O1 and the midpoint of the center point O2 is d/2.
According to the judging method, the integrity of the vertical impervious curtain in the detection range of each group of test wells and the water pumping condition of the adjacent test wells is detected in sequence, and all defects and positions of the defects on the whole vertical impervious curtain can be identified.
Example two
In order to solve the problems of the prior art, the present invention also provides a system for detecting defects of a vertical impervious curtain, comprising:
a plurality of groups of test wells arranged in the detection area of the vertical impervious curtain, wherein each group of test wells comprises a pumping well positioned in the inner area of the vertical impervious curtain and an observation well positioned in the outer area of the vertical impervious curtain;
the water pumping measuring device is used for performing a water pumping test on the water pumping well;
the water level detection device is used for detecting the water level of the observation well before the water pumping test is carried out on the water pumping well by the water pumping determination device or during the water pumping test, so as to respectively obtain data of the change of the background water level of the observation well with time and data of the change of the dynamic water level of the observation well with time.
Illustratively, the test well comprises an underground pipe and a subterranean pipe, wherein the subterranean pipe comprises a sedimentation pipe, a water filter pipe and a well wall pipe which are arranged in sequence from bottom to top;
the above-ground tubular comprises a wellhead casing comprising a protective casing, a plastic cover plate and a protective cover plate.
As shown in fig. 2, a schematic of a test well according to the present invention is shown. The underground pipe comprises an underground pipe below the earth surface A and an underground pipe above the earth surface A, wherein the underground pipe comprises a sedimentation pipe 1, a water filter pipe 2 and a well wall pipe 5 which are arranged along the underground from the bottom up, a filling layer is arranged outside the underground pipe, and the filling layer sequentially comprises quartz sand 3, a clay layer 4 and a concrete layer 6 along the underground direction to the earth surface. The clay layer 4 includes clay ball layer and clay layer, and according to an example of the present invention, the settling tube 1, the strainer 2 and the casing tube 5 are all HDPE tubes. The above ground pipe comprises a wellhead casing comprising a protective casing 7, a plastic cover plate 8 and a protective cover plate 9.
Illustratively, the distance between the well position of the test well and the impervious curtain is 1.5-2.5 times of the aperture of the pumping well.
The distance d between adjacent test wells satisfies that R is more than or equal to d and less than or equal to 2R, wherein R is according to an empirical formulaDetermining that S is water level lowering and K is a permeability coefficient, setting the intersection point of a connecting line of the pumping well and the observation well and the vertical impervious curtain as a central point, and setting the detection range of each group of test wells as a range within the vertical impervious curtain, wherein the distance from the central point is less than or equal to R;
in one example according to the invention, the bore diameter of the pumping well is 600mm, and the distance between the test well site and the impervious curtain should be 1200mm, wherein the pumping well is arranged 1200mm inside the vertical impervious wall and the observation well is arranged 1200mm outside the vertical impervious wall. The bottom of the observation well is about 2m away from the bottom of the impervious wall, the aperture of the observation well is 300mm, the diameter of the underground pipe is 110mm, the sedimentation pipe 1 is positioned from 12m underground to 11.5m underground, the water filter pipe 2 is positioned from 11.5m underground to 2.5m underground, the well wall pipe 5 is positioned from 2.5m underground to the surface, the quartz sand layer 3 is positioned from 12m underground to 2.0m underground, the clay layer 4 is positioned from 2.0m underground to 0.5m underground, and the concrete layer 6 is positioned from 0.5m underground to the surface. In the process of arranging the test well, the water level depression S is estimated according to experience before shaft sinking, and the permeability coefficient K is an empirical value determined according to the stratum. Illustratively, the water level drop S is estimated to be 13m, the permeability coefficient K is determined to be 0.0518m/d, R is about 29.6m, and the distance between adjacent test wells is about 29.6m, so that the blank detection section of the impervious curtain in the water pumping test is prevented.
As shown in fig. 3, a schematic of a test well deployed around a landfill in accordance with one example of the invention. Vertical impervious curtains 302 are arranged on the periphery of the refuse landfill 301, a plurality of groups of test wells are arranged around the refuse landfill for detecting whether the vertical impervious curtains 302 have defects, each test well comprises a pumping well 303P arranged on the inner side of the vertical impervious curtain 302 and an observation well 303M arranged on the outer side of the vertical impervious curtain.
Illustratively, the suction determination device includes a suction pump.
Illustratively, the water level detection device comprises a wireless water level detector.
The method for detecting the defects of the vertical impervious curtain by adopting the system for detecting the defects of the vertical impervious curtain can refer to the method steps described in the first embodiment, and the detailed description is omitted.
According to the method and the system for detecting the defects of the vertical impervious curtain, disclosed by the invention, the periodic change rule of underground water and the dynamic change characteristics of the underground water level are obtained by observing the background water level and the dynamic water level of the test well, the strength of underground water on two sides of the vertical impervious curtain under the hydraulic connection is determined, and therefore whether the structural defects exist in the vertical impervious wall or not can be effectively detected and judged.
The present invention has been illustrated by the above embodiments, but it should be understood that the above embodiments are for illustrative and descriptive purposes only and are not intended to limit the invention to the scope of the described embodiments. Furthermore, it will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and that many variations and modifications may be made in accordance with the teachings of the present invention, which variations and modifications are within the scope of the present invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (12)
1. A method for detecting defects in a vertical impervious curtain, comprising:
step S1: arranging a plurality of groups of test wells around the vertical impervious curtain, wherein each group of test wells comprises a pumping well positioned on one side of the vertical impervious curtain and an observation well positioned on the other side of the vertical impervious curtain;
step S2: performing a background water level determination test on the observation wells of each group of the test wells to obtain data of the change of the background water level of the observation wells along with time;
step S3: carrying out pumping tests on the pumping wells of each group of test wells to obtain data of the dynamic water level of the observation well changing along with time;
step S4: comparing the data of the background water level changing with time and the data of the dynamic water level changing with time of each group of the test wells to judge the defect condition of the vertical impervious curtain, wherein,
when the dynamic water level of the observation well in the test well is unchanged or the change of the dynamic water level of the observation well is smaller than the change of the background water level of the observation well, the dynamic water level of the observation well is judged to be normal, and the integrity of the vertical impervious curtain is good; otherwise, judging that the dynamic water level of the observation well is abnormal, and the vertical impervious curtain has defects.
2. The method of claim 1, wherein the step S1 includes:
step S11: determining the distance between the well position of the test well and the impervious curtain;
step S12: determining the distance between the well positions of two adjacent groups of test wells and the detection range of each group of test wells;
step S13: constructing to dig a well according to the distance between the test well positions and the impervious curtains determined in the step S11, the distance between two adjacent groups of the test well positions determined in the step S12 and the detection range of each group of the test wells.
3. The method of claim 1, wherein the test well is pumped and flushed during the step S1 of deploying the test well so that the water pumped from the test well is free of silt.
4. The method as claimed in claim 2, wherein the distance between the test well position and the impervious curtain is 1.5 times to 2.5 times the diameter of the pumping well hole in the step S11.
5. The method of claim 2, wherein in step S12, the spacing d between adjacent test wells satisfies R ≦ d ≦ 2R, wherein R is based on empirical formula
And determining that S is water level depth reduction and K is a permeability coefficient, setting the intersection point of the connecting line of the pumping well and the observation well and the vertical impervious curtain as a central point, and setting the detection range of each group of the test well as the range of the distance central point in the vertical impervious curtain to be less than or equal to R.
6. The method as recited in claim 1, in said step S2, further comprising plotting the background water level of said observation well over time based on the data of the background water level of said observation well over time; and
in step S3, the method further includes drawing a time-varying curve of the dynamic water level of the observation well according to the time-varying data of the dynamic water level of the observation well.
7. The method of claim 4, wherein the step of comparing the time-dependent background water level data and the time-dependent dynamic water level data for each set of the test wells comprises comparing a time-dependent background water level profile of the observation wells to a time-dependent dynamic water level profile of the observation wells.
8. The method of claim 5, further comprising, when it is determined that the vertical impervious curtain has a defect, further determining a range where the defect exists.
9. The method of claim 8, wherein the step of further determining the range in which the defect location exists comprises:
and when the distance d between two adjacent groups of test well positions is equal to 2R, the integrity of the vertical impervious wall in the detection range of each group of test wells is directly judged according to a relation curve of the dynamic water level changing along with time, which is measured by a pumping test of the vertical impervious wall.
10. The method of claim 8, wherein the step of further determining the range in which the defect location exists comprises:
when the distance d between two adjacent groups of the test well positions satisfies that R is more than or equal to d and less than 2R,
if the dynamic water level of the observation well of one group of the test wells is abnormal, and the dynamic water level of the observation well of the other group of the test wells is normal, determining that the defect is located in the range that the center point of the test well with the abnormal dynamic water level of the observation well is close to one side of the test well with the abnormal dynamic water level of the observation well and the radius of one side of the test well is R;
and if the dynamic water levels of the observation wells of each group of the test wells are abnormal, judging that:
1) 1 defect exists between the central points of the two adjacent groups of test wells, and the defect is located in a range with the center point between the central points of the two groups of test wells as the circle center and the radius of d/2; or
2) There are more than 2 defects, and 2 defects belong to any one of the following three cases:
the two adjacent groups of the test wells comprise a first group of the test wells and a second group of the test wells which are adjacent,
a: the radius of the center point of the first group of test wells close to one side of the second group of test wells is within a range d;
b: the second group of the test well center points are close to the area within the range of the radius d of one side of the first group of the test wells;
c: and taking the midpoint between the central points of the two groups of test wells as the circle center and the radius of the midpoint as the range of d/2.
11. A system for detecting defects in a vertical impervious curtain, comprising:
a plurality of groups of test wells arranged around the vertical impervious curtain, wherein each group of test wells comprises a pumping well positioned in the inner area of the vertical impervious curtain and an observation well positioned in the outer area of the vertical impervious curtain;
the water pumping measuring device is used for performing a water pumping test on the water pumping well;
the water level detection device is used for detecting the water level of the observation well before the water pumping test is carried out on the water pumping well by the water pumping measuring device or during the water pumping test so as to respectively obtain data of the change of the background water level of the observation well with time and data of the change of the dynamic water level of the observation well with time.
12. The system of claim 9, wherein the test well comprises an underground tubular and a subterranean tubular, the subterranean tubular comprising a settling tube, a strainer, and a casing tube arranged in that order from bottom to top;
the above-ground tubular comprises a wellhead casing comprising a protective casing, a plastic cover plate and a protective cover plate.
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