CN110132650A - A method for sampling groundwater wells in polluted sites - Google Patents

Abstract

According to a method for sampling groundwater wells in a polluted site of the present invention, sampling the groundwater of each target stratum of N different depths in the area where the groundwater environment is investigated comprises the following steps: the first step, within the scope of the investigation point Set the monitoring center point; the second step, corresponding to N target formations with different depths, set the number N of monitoring wells to be set and the depth of the monitoring wells; the third step is to set the radius according to the number N of monitoring wells R, get the circle centered on the monitoring center point and the radius is R; the fourth step is to set a monitoring well on the monitoring center point, and evenly set N-1 monitoring wells on the circumference; the fifth step corresponds to N For monitoring wells of different depths, N corresponding groundwater monitoring well devices are respectively configured; the sixth step is to install N groundwater monitoring well devices. The groundwater sampling method of the present invention has the advantages of high well construction efficiency and accurate sampling of polluted groundwater in the target layer.

Description

A method for sampling groundwater wells in polluted sites

technical field

The invention belongs to the field of environmental protection, and in particular relates to a method for sampling groundwater well groups in polluted sites.

Background technique

As my country attaches great importance to the environmental risks of polluted soil and groundwater, the number of contaminated site remediation projects is increasing. Before remediation of contaminated sites, environmental investigation and assessment are required, and spot sampling and monitoring of site soil and groundwater are required. Compared with soil sampling, groundwater spot sampling has more problems. The main reason is that it is difficult to accurately know the pollution status of groundwater at different depths of the site, which makes it difficult to accurately determine the volume of groundwater restoration, resulting in unreasonable formulation of restoration technical plans, which further leads to a series of problems in subsequent projects. Secondly, the groundwater sampling method does not fully consider the characteristics of the polluted site, resulting in inaccurate sampling, mainly because most of the existing site groundwater sampling methods for construction of wells refer to the practice of hydrogeological investigation of water resources, and do not fully consider the microcosm of the site Sexuality, pollution, uneven water quality and environmental process characteristics of pollutants; specifically, it is reflected in three aspects, one is the inaccurate position of the water filter pipe, the other is inappropriate water collection methods, and the third is the requirements for well cleaning unreasonable. Again, the existing groundwater well construction method is generally to drill into a hole to place the well pipe and the water filter pipe, then fill the filter material between the water screen pipe and the well wall, fill the sealing layer between the well pipe and the well wall, and finally install the wellhead Protective cover to complete the built well. The efficiency of this method is relatively slow, and the filter material needs to be consumed. After the completion of the groundwater well, it is difficult to remove it. If it remains in place for a long time, it will have a certain impact on the subsequent reuse of the site. At present, there is still a lack of relatively rapid well construction methods.

Patent CN 105954464 A discloses a method for building a soil gas and groundwater monitoring well, in which the soil gas monitoring well and the groundwater monitoring well are constructed synchronously. By designing and drilling a large-diameter well in which soil gas monitoring wells and groundwater monitoring wells coexist in casings, and installing groundwater monitoring well pipes, soil gas probes and air ducts, the construction of soil gas monitoring wells matching groundwater monitoring wells is completed. The groundwater monitoring well built by this patent needs to fill the filter material between the water filter pipe and the well wall, and fill the sealing layer between the well pipe and the well wall, so the well construction efficiency is relatively slow.

Contents of the invention

In view of the problems existing in the sampling of groundwater wells in the above-mentioned polluted sites, the present invention proposes a method for accurately monitoring groundwater sampling at different depths in polluted sites and arranging methods for monitoring well groups. The groundwater pollution status at different depths of groundwater can provide support for the accurate quantification of groundwater restoration volume in contaminated sites.

The invention provides a groundwater well group sampling method in a polluted site, which is used for sampling the groundwater of each target formation of N different depths in the area where the groundwater environment needs to be investigated, and is characterized in that it includes the following steps:

The first step is to set the monitoring center point within the scope of the survey point;

In the second step, corresponding to N target formations with different depths, the number N of monitoring wells to be set and the depth of the monitoring wells are set;

The third step is to set the radius R according to the number N of monitoring wells, and obtain a circle whose center is the monitoring center point and whose radius is R;

The fourth step is to set a monitoring well on the monitoring center point, and set N-1 monitoring wells evenly on the circumference;

The fifth step is to configure N corresponding groundwater monitoring well devices corresponding to N monitoring wells of different depths;

The sixth step is to install N groundwater monitoring well devices.

In the groundwater well group sampling method in a polluted site provided by the present invention, it may also have such a feature: wherein, the number of monitoring wells is 2-10, and the corresponding radius R is 1-4 meters.

In addition, in the groundwater well group sampling method in the polluted site provided by the present invention, it can also have such a feature: wherein, the groundwater monitoring well device includes a plurality of well pipes, a water filter pipe and a water stop ring arranged at the bottom of the well, and the monitoring well The aperture is greater than the sum of the outer diameter of the well pipe and the thickness of the two water stop rings.

In addition, in the groundwater well group sampling method of the polluted site provided by the present invention, it may also have such a feature: wherein, when the soil layer thickness of the target stratum is less than 5 meters, the length of the water filter pipe is less than the thickness of the target stratum.

In addition, in the polluted groundwater well group sampling method provided by the present invention, it may also have such a feature: wherein, in the fourth step, the depth of the monitoring well located on the monitoring center point is set to the deepest or the shallowest, at Among the N-1 monitoring wells evenly arranged on the circumference, the deep monitoring wells and the shallow monitoring wells are arranged alternately.

In addition, in the groundwater well group sampling method in the polluted site provided by the present invention, it may also have such a feature: wherein, the bottom of the water filter pipe in one monitoring well is higher than the top of the water filter pipe in another adjacent monitoring well.

In addition, in the groundwater well group sampling method in the polluted site provided by the present invention, it is characterized in that it also includes the eighth step, the well washing operation, according to the well depth of the monitoring well, in order from shallow to deep. After the monitoring well, the monitoring well at the opposite end of the symmetry is washed.

In addition, in the groundwater well group sampling method in the polluted site provided by the present invention, it may also have such a feature: wherein, the amount of water for washing the wells is 3-5 times the volume from the groundwater surface to the bottom of the well in the groundwater monitoring well device.

In addition, in the polluted site groundwater well group sampling method provided by the present invention, it is characterized in that it also includes a ninth step of sampling groundwater in a plurality of groundwater monitoring well devices, wherein, when measuring dissolved pollutants, The water intake position is located in the middle of the water surface and the bottom in the groundwater monitoring well device. When the water contains light non-aqueous phase liquids, the water intake position is located at the water surface position in the groundwater monitoring well device. When the water contains heavy non-aqueous phase liquids, The water intake position is located at the bottom of the water in the groundwater monitoring well device.

Function and Effect of Invention

According to the groundwater well group sampling method of the polluted site involved in the present invention, the arrangement of the groundwater monitoring well group of the present invention has the advantages of high well construction efficiency and accurate determination of groundwater pollution conditions at different depths in the site.

The well-flushing method of the present invention creatively proposes to use the amount of well-flushing water as the basis, and overcomes the shortcomings of traditionally using stable parameters such as pH value, temperature, electrical conductivity, dissolved oxygen, and redox potential as the basis.

The sampling method aimed at different pollutant characteristics of the present invention has the advantage of accurately sampling the groundwater with the characteristics of the target pollutant in the target layer.

The well pipe of the present invention can be recycled and used, so it has the outstanding advantages of cost economy, environmental friendliness and the like.

Description of drawings

Fig. 1 is a schematic sectional view of formation and groundwater monitoring well device in an embodiment of the present invention;

Fig. 2 is a schematic top view of monitoring well arrangement in an embodiment of the present invention; and

Fig. 3 is the schematic diagram of groundwater monitoring well device in the embodiment of the present invention;

Fig. 4 is a schematic diagram of a water filter pipe body in an embodiment of the present invention;

5 is a schematic cross-sectional view of a through hole in an embodiment of the present invention;

6 is a schematic cross-sectional view of a through hole in an embodiment of the present invention;

Fig. 7 is a schematic view of the filter layer in an embodiment of the present invention; and

Fig. 8 is a schematic diagram of the anti-blocking layer in the embodiment of the present invention.

Detailed ways

In order to make the technical means, creative features, goals and effects of the present invention easy to understand, the following embodiments will specifically describe the sampling system for sampling groundwater in polluted sites of the present invention in conjunction with the accompanying drawings.

Carry out groundwater environmental investigations for possible groundwater environmental impacts at a polluted site. According to the characteristics of the polluted site, it is inferred that the possible main pollutants of groundwater include light non-aqueous phase liquid and heavy non-aqueous phase liquid. According to the geological exploration results of the site, as shown in Figure 1, the strata of the polluted site from top to bottom are miscellaneous fill (monitoring layer 1), silty clay (monitoring layer 2), cohesive soil, and silt (monitoring layer 3).

The sampling system used for environmental investigation of groundwater in polluted sites in this embodiment corresponds to N monitoring wells with different depths set in each target stratum with different depths; corresponding to the configuration of N monitoring wells with different depths N groundwater monitoring well devices,

One monitoring well is set on the predetermined monitoring center point in the survey area, and N-1 monitoring wells are evenly set on the circle with the monitoring center point as the center and the predetermined radius as R.

Alternatively, no monitoring well is provided on the monitoring center point, and N monitoring wells are evenly arranged on a circle with the monitoring center point as the center and a predetermined radius R.

The predetermined radius R is set according to the number N of monitoring wells.

The N groundwater monitoring well devices are correspondingly arranged in the N monitoring wells.

The arrangement of monitoring wells at the same location refers to the same location within a circle with the monitoring center point as the center and a radius R of 1-4 meters. The groundwater quality within this range can be regarded as the same location in the site survey. water quality. 2-10 monitoring wells are arranged within this range, and the monitoring wells are distributed on the center and the circumference of the circle, wherein multiple monitoring wells on the circumference are equally spaced along the circumference.

The radius is small when the number of monitoring wells is small, and the radius is large when the number of monitoring wells is large.

When the number of monitoring wells is large, the location of the monitoring wells can also be in the middle of different radii.

In order to accurately monitor groundwater in polluted sites, when the number of monitoring wells is 2-7, the radius of the circle should not be less than 1.5m. Monitoring wells 18 and monitoring wells 19 can be arranged on a circle with the monitoring center point 16 as the center and a radius of 1.5 m.

With a certain monitoring point 17 in the polluted site as the center of the circle, monitor wells 20, 21, 22, and 23 are arranged on the monitoring center point 17 and on a circle with the monitoring center point 17 as the center and a radius of 2 m.

When the number of monitoring wells is 8, the radius of the circle should not be less than 2m, and when the number of monitoring wells is 9-10, the radius of the circle should not be less than 3m.

When the radius of the circle is r, there is a monitoring well at the center of the circle, and the number of monitoring wells arranged on the circumference is x, considering that the distance between the monitoring wells remains the same, the expression is:

2πr/x=r, if the distances between the monitoring wells are kept as equal as possible, that is, f(r)=2πr/x-r is the smallest, that is, the derivative on both sides is zero, and x=6, that is, 6 monitoring wells are arranged on the circumference, showing a positive When hexagonal, the distance between each monitoring well remains the same.

The depth of the monitoring well located on the monitoring center point is set to the deepest or the shallowest.

For the remaining monitoring wells, deep monitoring wells and shallow monitoring wells are arranged alternately on the circumference.

The groundwater monitoring well device has a water filter pipe, and the water filter pipe is arranged at the bottom of the monitoring well, and the bottom of the well is located in the corresponding target formation.

The water filter pipe at the bottom of each monitoring well corresponds to different soil layers or different depths in the same soil layer. When the thickness of the target layer soil layer is not greater than 5 meters, the length of the water filter pipe should not exceed the total thickness of the target stratum, as shown in Figure 1. Monitoring well installations 12,13.

When the thickness of the target layer is greater than 5 meters, a plurality of monitoring wells of different depths can be excavated in the layer, and corresponding groundwater monitoring well devices are installed in the monitoring wells. The length of the filter pipe in the groundwater monitoring well device should not exceed 3 meters. The groundwater monitoring well device 14,15 in Fig. 1.

When light non-aqueous phase liquid was contained in the site, the upper end of the filter pipe should be higher than the water level of the groundwater, as in the groundwater monitoring well device 13 among Figure 1, the upper end of the filter pipe was higher than the water level of the groundwater, so that the light non-aqueous liquid in the groundwater The phase liquid (LNAPL) will float on the surface of the groundwater in the screen pipe and be collected easily.

When the site contains heavy non-aqueous phase liquid (DNAPL), the bottom of the filter pipe should be positioned on the top of the impermeable layer, as in the groundwater monitoring well device 12 in Figure 1. The bottom of the filter pipe is positioned on the top of the impermeable layer, so that the groundwater The heavy non-aqueous phase liquid in the filter will sink to the bottom of the groundwater in the filter pipe and be collected easily.

The length of the filter pipe can be between 0.5m and 5m according to the accuracy of the site survey. Screen pipes generally do not cross two or several different target aquifers, especially in detailed surveys, and screen pipes do not cross layers.

In order to avoid the cross influence between the monitoring wells during well construction and well cleaning, the depths of the two adjacent monitoring wells on the circumference are different, and the vertical heights corresponding to the lengths of the water filter pipes in the two monitoring wells The lines are non-overlapping, ie the bottom of the screen in one monitoring well is higher than the top of the screen in another adjacently located monitoring well.

When setting the well depth, when the number of monitoring wells on the circumference is an even number, one end of the diameter is a shallow well or a deep well, and the other end of the symmetry is set as a sub-shallow well or a sub-deep well, that is, the two monitoring wells set symmetrically to the monitoring center point Well depths are similar.

If the well depth of a monitoring well is the deepest, the well depth of another monitoring well set symmetrically to the monitoring center point is the second deepest, the adjacent monitoring well is the shallowest, and the other end of its diameter is the second shallowest, so analogy.

As shown in Figure 2, the monitoring wells 18 and 19 are shallow wells. The monitoring well 20 and the monitoring well 22 are shallow wells, the monitoring well 21 and the monitoring well 23 are deep wells, the well depth of the monitoring well 17 is deeper than the monitoring well 23, and the diameter of the monitoring well is 40-160mm.

When the number of monitoring wells on the circumference is odd, the monitoring wells are evenly distributed on the circumference. When one of the wells is selected as the deepest or shallowest, the well farthest from this well is the second deepest or second shallowest, and so on.

The groundwater monitoring well device is used to be installed in the groundwater sampling well, and after filtering the groundwater in a specific formation, the groundwater in a specific formation that needs to be monitored is obtained.

As shown in FIG. 3 , the groundwater monitoring well device includes a plurality of cylindrical well pipes 7 , water filter pipes 11 , water stop rings 10 , wellhead protection covers 6 , and sampling well covers 8 connected sequentially from top to bottom.

The well pipe 7 is cylindrical, and its outer diameter is smaller than the inner diameter of the groundwater sampling well. Two adjacent well pipes 7 are connected by thread connection or buckle connection. The well pipe 7 is made of any material among PPR, PVC and stainless steel. The inner diameter of the well pipe is 40mm-160mm, the length of a single section of the well pipe is 1000mm-3000mm, and the well pipe is threaded. In the embodiment, the well pipe 7 is made of PVC material, the length of a single section of the well pipe is 3 meters, and the outer diameter of the well pipe is 60 mm.

When threaded connection is adopted, the upper end of the well pipe 7 is provided with an internal thread, and the outer diameter of the connection at the lower end is reduced and an external thread matching the internal thread is provided.

In addition, a connecting piece can also be used to connect two adjacent well pipes 7, and the two ends of the well pipe 7 are respectively provided with external threads, the connecting piece is in the shape of a ring, and an internal thread matching the external thread is provided inside the ring.

In the embodiment, the well pipe 7 and the filter pipe 11 are also assembled by threaded connection, and put together into the sampling well, thereby improving the well construction efficiency. The wellhead protection cover 6 is arranged on the uppermost well pipe 7, and the sampling well cover 8 is arranged in a ring shape. On the ground, the well pipe 7 passes through the sampling well cover 8, and the sampling well cover 8 is used to block the gap between the well pipe 7 and the well wall of the sampling well.

The water filter pipe 11 is arranged at the bottom of a groundwater sampling well at a predetermined depth, and includes a cylindrical pipe body 3 , at least one filter layer and an anti-blocking layer 5 .

The tube body 3 is a cylindrical tube body with a tube wall on which a plurality of through holes 2 are arranged. The bottom of the tube body 3 may or may not be closed. In the embodiment, the bottom of the tube body 3 is closed.

As shown in Figure 4, the upper end of the pipe body 3 is provided with an internal thread 1, and the pipe wall of the pipe body 3 is provided with a plurality of through holes 2, and the cross section of the through holes 2 can be round, oval or elongated. any kind.

The direction of the through hole 2 is designed according to different pollutants in the groundwater. In one case, the centerline of the through hole 2 is perpendicular to the centerline of the pipe body 3, so that the direction of water flow through the through hole 2 is perpendicular to the centerline of the pipe body 3. .

Alternatively, the downward angle between the centerline of the through hole 2 and the centerline of the pipe body 3 is an acute angle.

When the water flow direction A passes through the through hole 2 as shown in Figure 5, it is suitable for oily groundwater, because oily substances are easy to float and pass through this kind of hole.

Alternatively, the upward angle between the centerline of the through hole 2 and the centerline of the pipe body 3 is an acute angle.

When the water flow direction B passes through the through hole 2 as shown in FIG. 6 , it is suitable for heavy non-aqueous phase liquid pollutants to pass through this kind of through hole.

When the acute angle is 45 degrees, the flow of water has a better effect.

Further, the through hole 2 is in the shape of a circular arc at the edge of the pipe wall, that is, the connection between the through hole 2 and the pipe wall is in a circular arc shape, so that it is not easy for the suspended matter in the groundwater to deposit at the connection.

The material of the pipe body 3 is any one of PPR, PVC, stainless steel and steel, the inner diameter is 40mm-160mm, the length of a single section of the pipe body 3 is 100mm-4000mm, and the pipe body 3 and the well pipe 7 are connected by threads.

In this embodiment, the pipe body 3 is cylindrical and made of PVC material. The cross-sectional size of the pipe body 3 is the same as that of the well pipe 7. The centerline of the through hole 2 is perpendicular to the centerline of the pipe body 3. The cross section of the hole 2 is elongated. In the embodiment, it is set along the horizontal direction according to the pipe diameter and the hydrogeological conditions of the water intake layer. The long slit can be cut horizontally on the pipe body 3 with an electric saw. The intervals are parallel and staggered. The length of the long slit is 30mm-120mm, the width is 0.15mm-3mm, and the spacing is 3mm-12mm.

At least one filter layer 4 as shown in FIG. 7 is wrapped on the pipe wall of the pipe body 3, and the size of the filter holes in the filter layer 4 is smaller than the size of the through holes.

Among them, the filter layer 4 has multiple layers.

The multi-layer filter layers 4 have the same shape of filter holes, and the positions of the filter holes in two adjacent filter layers 4 are staggered;

Alternatively, the multi-layer filter layer 4 is composed of a plurality of filter layers 4 with different filter hole shapes, and the plurality of filter layers 4 with different filter hole shapes are arranged crosswise.

According to the hydrogeology and water intake requirements of the water intake layer, the filter layer 4 can have 5-20 layers. The filter layer 4 is made of low adsorption stainless steel or organic polymer material.

In the embodiment, the filter layer 4 is wrapped by filter cloths with the same shape of multi-layer filter holes, or wrapped by filter cloths with different shapes of multi-layer filter holes. Organic polymer materials, such as any one of polyester, polypropylene, nylon (nylon), vinylon, polyethylene, mixed fibers, and resins.

The shape of the filter holes in the filter cloth can be rectangular, rhombus, etc. The shapes of the filter holes of each layer of filter cloth can be the same, and the positions of the filter holes in two adjacent filter layers 4 are alternately arranged.

Alternatively, the shapes of the filter holes of each layer of filter cloth may also be different, and a plurality of filter layers 4 with different filter hole shapes are intersected.

The filter layer 4 after multi-layer stacking can obtain smaller filter holes, and can perform the filtering function more effectively.

In the embodiment, the filter holes of the filter cloth are divided into three specifications: coarse, medium and fine, and their mass per unit area are 100g/m ² , 450g/m ² , 800g/m ² respectively, and their equivalent pore diameters are 0.2mm, 0.14mm, 0.07mm, under the normal temperature of groundwater (15-17 degrees Celsius), the filter cloth material is insoluble and organic pollutants, and acid and alkali resistant.

Therefore, the size of the filter holes in the filter layer 4 is smaller than the size of the through holes 2, that is, the largest size of the equivalent pore diameters of the filter layer 4 is smaller than the smallest size of the through holes 2.

In order to avoid fouling of the through hole 2 , an anti-blocking layer 5 is arranged between the pipe body 3 and the filter layer 4 .

The anti-blocking layer 5 with a mesh structure is arranged around the pipe wall and is located between the pipe wall and the filter layer 4, for supporting the filter layer 4 and preventing the through holes from being blocked.

The anti-blocking layer 5 has the function of supporting and isolating anti-blocking. As shown in FIG. 8 , the anti-blocking layer 5 is provided with a plurality of through holes. In the embodiment, an anti-blocking layer 5 made of a plastic mesh is used to separate the filter layer 4 from the outer wall of the pipe body 3 . The length of the plastic mesh is 100mm-4000mm, the thickness is 2mm-5mm, and the mesh of the plastic mesh is diamond-shaped.

At least one water stop ring 10 is arranged around the lower end of the outer surface of the well pipe 7 on the upper part of the water filter pipe 11, between the well pipe 7 and the well wall of the sampling well.

As shown in Figure 3, the water stop ring 10 is arranged on the well pipe 7, and the water stop ring 10 is made of a rubber material that expands when encountering water. The expansion coefficient of the rubber material is 1.5-3, and there is no secondary pollution; or use a water permeable material It is made and wrapped with bentonite after physical and chemical modification in the water-permeable material. The bentonite has good water-swellability at a pH of 2-13, and the expansion coefficient is 0.5-1.5. It is light in weight and has good plasticity. No secondary pollution. The water stop ring 10 is fixed on the outer wall of the well pipe 7 before the well pipe is placed in the monitoring well. The water-swellable water-stop ring of rubber material can be tightened with a tight hoop on the outside, and the water-swellable water-stop ring of expansive soil material needs to be packed into an elastic water-permeable net bag, which is tightened with a tight hoop outside the net bag. The water-swellable water-stop ring has a circumferential length of 5mm-500mm and a thickness of 10mm-30mm.

In the embodiment, the water stop ring 10 is made of a rubber material that expands with water, wherein the expansion coefficient of the rubber material is 2.

The water-swelling water-stop ring 10 is similar to the sealing layer in the traditional well construction method, and expands after encountering water to play the effect of water-stopping. The gap between the well pipe 7 and the well wall of the sampling well is blocked after the water-stopping member 10 expands when meeting water, and the groundwater below the water-stopping member 10 flows into the pipe body 3 from the outside of the pipe body 3 through the filter layer 4 .

The installation method of the water stop ring 10 is simple and convenient, which can effectively improve the well construction efficiency. In addition, the water-swellable water-stop ring 10 will shrink slowly after being dehydrated, which is convenient for taking it back after the monitoring well is used up, and can be recycled after treatment, saving cost.

A groundwater well group sampling method in a polluted site is used for sampling the groundwater of each target formation of N different depths in the area where the groundwater environment needs to be investigated, comprising the following steps:

According to the pollution identification results of groundwater sampling sites, the possible main pollutants in groundwater and the distribution of groundwater structures are inferred.

According to the geological exploration results of the groundwater sampling site, the distribution of the site stratum is obtained.

Set the monitoring center point within the scope of the survey point.

Corresponding to N target formations with different depths, the number N of monitoring wells to be set and the depth of the monitoring wells are set.

The radius R is set according to the number N of monitoring wells, and a circle with the monitoring center point as the center and radius R is obtained.

One monitoring well is set at the monitoring center point, and N-1 monitoring wells are evenly set on the circumference.

The location of the monitoring well is selected, and the well construction operation is carried out.

Select the location of the groundwater monitoring well, select the appropriate drilling method according to the geological structure of the soil layer, and start the drilling operation. The aperture of the well is greater than the sum of the outer diameter of the well pipe and the thickness of the two water stop rings; At -3m, the drilling operation of the monitoring wellbore is completed.

Corresponding to N monitoring wells of different depths, N corresponding groundwater monitoring well devices are respectively configured.

Place the groundwater monitoring well device in the drilled well.

The wellhead protection cover is installed to complete the rapid construction of the groundwater monitoring well device.

According to the well depth of the monitoring wells, several monitoring wells are washed in order from shallow to deep.

Well flushing shall be done in the order of the depth of the groundwater monitoring wells from shallow to deep, and at the same time follow the sequence of washing the monitoring well at one end first and then washing the monitoring well at the other symmetrical end.

As shown in FIG. 2 , the cleaning sequence of monitoring wells at monitoring point 17 is monitoring well 20 , monitoring well 22 , monitoring well 21 , monitoring well 23 and monitoring well 17 .

Considering the heterogeneity of pollution in the polluted site, the groundwater quality of the site varies greatly. Therefore, the volume of well washing water should not be too large to avoid affecting the distribution of surrounding groundwater. Generally, the volume of well washing water is 3% of the volume from the groundwater surface in the well pipe to the bottom of the well. -5 times is enough, and it is not recommended to use the parameters such as pH value, temperature, conductivity, dissolved oxygen, and redox potential as the end point of well flushing when they are stable.

Groundwater sampling in groundwater monitoring well installations.

Different sampling methods are used for different pollutants. When measuring dissolved pollutants, the water intake position is generally in the middle of the water surface and the bottom of the well.

When the water contains light non-aqueous phase liquids, the water intake location should be at the water surface in the well.

When the water contains heavy non-aqueous phase liquid, the water intake location should be at the bottom of the well.

Embodiment two

The other structures of this embodiment are the same as those of the first embodiment, except that the body structure of the filter pipe is different from that of the first embodiment.

In this embodiment, the tube body is a cylindrical tube body with a tube wall, and a plurality of through holes are arranged on the tube wall, and the bottom of the tube body may or may not be closed. In an embodiment, the bottom of the tube is closed.

Wherein, the pipe wall includes an upper wall part, a middle wall part and a lower wall part from top to bottom,

The plurality of through holes include an upper through hole disposed on the upper wall portion, a middle through hole disposed on the middle wall portion, and a lower through hole disposed on the lower wall portion.

The angle between the centerline of the upper through hole and the downward direction of the centerline of the pipe body is an acute angle.

The centerline of the through hole is perpendicular to the centerline of the pipe body.

The angle between the centerline of the lower through hole and the upward direction of the centerline of the pipe body is an acute angle.

Embodiment three

The other structures of this embodiment are the same as those of the first embodiment, except that the structure of the filter pipe and the installation position of the water stop ring are different from those of the first embodiment.

The water filter pipe includes a pipe body, at least one filter layer and a water stop ring.

The cylindrical pipe body has a pipe wall, including an upper part of the pipe wall and a lower part of the pipe wall, and the lower part of the pipe wall is provided with a plurality of through holes;

At least one filter layer is wrapped around the lower part of the pipe wall;

The water stop ring is arranged around the upper part of the pipe wall and is located between the well pipe 7 and the well wall of the sampling well.

Wherein, the center line of the through hole is perpendicular to the center line of the pipe body,

Alternatively, the downward angle between the centerline of the through hole and the centerline of the pipe body is an acute angle,

Or, the angle between the centerline of the through hole and the upward direction of the centerline of the pipe body is an acute angle.

Embodiment four

The other structures of this embodiment are the same as those of the third embodiment, except that the structure of the pipe body is different from that of the third embodiment.

In this embodiment, the lower part of the tube wall includes an upper wall part, a middle wall part and a lower wall part from top to bottom.

The plurality of through holes include an upper through hole disposed on the upper wall portion, a middle through hole disposed on the middle wall portion, and a lower through hole disposed on the lower wall portion.

The angle between the centerline of the upper through hole and the downward direction of the centerline of the pipe body is an acute angle.

The centerline of the through hole is perpendicular to the centerline of the pipe body.

The angle between the centerline of the lower through hole and the upward direction of the centerline of the pipe body is an acute angle.

Example 1

In view of the possible impact of a tailings pond on the groundwater environment in the surrounding area, it is necessary to conduct a groundwater environment investigation. According to the characteristics of the tailings, it is inferred that the possible main pollutants of groundwater are chloride ions, heavy metal ions, cyanide and so on. According to the geological exploration results of the site, the strata of the site from top to bottom are miscellaneous fill, gravel sand, strongly differentiated granite, and moderately weathered granite. The groundwater of the site mainly exists in the gravel sand layer, the thickness of the gravel sand layer is about 8m, and the grain size of the gravel sand is 2mm~5mm. Groundwater environmental investigation needs to establish a groundwater well sampling system in the polluted site. After confirming that there are no underground facilities at the drilling point, take a certain monitoring point in the polluted site as an example. Since the thickness of the target aquifer is greater than 5m, two different depths can be set at this point. monitoring well. Assemble the new PVC water filter pipe 5m and the new PVC well pipe 20m as the monitoring well 1 and the new water filter pipe 3m and the new well pipe 22m as the monitoring well 2, and put them into the well, the pipe diameter is 50mm. According to the pollutants that may exist in the groundwater and the particle size of the gravel, the filter cloth is selected with a specification of 100g/m ² and wrapped in 5 layers. The length of the water filter seam is 30mm, the width is 1mm, and the spacing is 5mm. The amount of water for washing the well should be 3-5 times the inner volume of the well pipe below the groundwater level of the well. Install the wellhead protection cover and the wellhead sealing ring to complete the construction of the monitoring point.

Function and effect of embodiment

According to the groundwater well group sampling method of the polluted site involved in this embodiment, the arrangement of the groundwater monitoring well group of the present invention has the advantages of high well construction efficiency and accurate sampling of the polluted groundwater of the target layer.

Furthermore, the well flushing method in this embodiment creatively proposes to use the volume of well flushing water as the basis, which overcomes the shortcomings of traditionally using stable parameters such as pH value, temperature, electrical conductivity, dissolved oxygen, and redox potential as the basis.

Further, the sampling method for different pollutant characteristics in this embodiment has the advantage of accurately sampling the groundwater with the characteristics of the target pollutant in the target layer.

Further, the water filter pipe of this embodiment is arranged at the bottom of the groundwater sampling well for water quality detection of groundwater in a specific formation, and the water filter pipe has at least one filter layer wrapped on the pipe body for filtering soil particles and Suspended matter does not need to be filled with a filter layer between the filter pipe and the well wall, which not only saves material and transportation labor costs, but also facilitates the removal of the groundwater well after use, without affecting the subsequent development of the site.

Furthermore, the groundwater monitoring well device is connected with multiple well pipes and filter pipes made of modularization, which is not only convenient for assembly and installation, but also the well pipes and water filter pipes can be retrieved after the monitoring well is used up, and can be recycled after treatment. It has outstanding advantages such as cost economy and environmental friendliness.

Furthermore, the water-stop ring arranged between the well pipe and the drilling well wall expands when it encounters water, and then seals the gap between the well pipe and the drilling well wall, preventing the exchange of groundwater between different target layers. This method is simple and easy Compared with the traditional method of filling the filter layer of quartz sand between the well pipe and the well wall, it greatly simplifies the well construction procedure and significantly improves the work efficiency.

Therefore, the groundwater well group sampling method in the polluted site of the present invention can not only effectively simplify the well construction process, improve the well construction efficiency, shorten the well construction time, but also the well pipe and the water filter pipe can be removed conveniently, which is beneficial to the subsequent development and utilization of the site, and Well pipes and filter pipes can be recycled after simple treatment, saving costs.

The above embodiments are preferred examples of the present invention, and are not intended to limit the protection scope of the present invention.

Claims (9)

1. a kind of contaminated site underground water gang of wells method of sampling, the N in region for needing to investigate groundwater environment The underground water of each formation at target locations of a different depth is sampled, which comprises the following steps:

First step sets monitoring center's point in the range of the investigation point；

Second step, corresponding to the formation at target locations of N number of different depth, the quantity N for the monitoring well that setting needs to be arranged and described The depth of monitoring well；

Third step sets radius R according to the quantity N of the monitoring well, obtains using monitoring center's point as the center of circle and radius For the circumference of the R；

A monitoring well is arranged on monitoring center's point, N-1 institute is uniformly arranged on the circumference for four steps State monitoring well；

N number of corresponding groundwater monitoring well device is respectively configured corresponding to the monitoring well of N number of different depth in 5th step；

6th step installs N number of groundwater monitoring well device.

2. the contaminated site underground water gang of wells method of sampling according to claim 1, it is characterised in that:

Wherein, the quantity of the monitoring well is 2-10 mouthfuls, and the corresponding radius R is 1-4 meters.

3. the contaminated site underground water gang of wells method of sampling according to claim 1, it is characterised in that:

Wherein, the groundwater monitoring well device includes multiple well casings, the filter pipe and seal ring that shaft bottom is arranged in,

The aperture of the monitoring well is greater than the sum of the thickness of the well casing outer diameter and 2 seal rings.

4. the contaminated site underground water gang of wells method of sampling according to claim 3, it is characterised in that:

Wherein, when the soil thickness of the formation at target locations is less than 5 meters, the drainage length of tube is less than the thickness of the formation at target locations Degree.

5. the contaminated site underground water gang of wells method of sampling according to claim 1, it is characterised in that:

Wherein, in four steps, the depth of the monitoring well on monitoring center's point is set as most deep or most shallow ,

It is uniformly arranged on the circumference in the N-1 monitoring wells, the deep monitoring well and the shallow monitoring well are to hand over Mistake setting.

6. the contaminated site underground water gang of wells method of sampling according to claim 3, it is characterised in that:

Wherein, the bottom of the filter pipe in a monitoring well is higher than in another the described monitoring well being disposed adjacent The top of the filter pipe.

7. the contaminated site underground water gang of wells method of sampling according to claim 1, which is characterized in that further include:

8th step, well-flushing operation are carried out according to the well depth of the monitoring well according to order from shallow to deep,

Wherein, first wash the monitoring well of one end, after wash the monitoring well of the symmetrical other end.

8. the contaminated site underground water gang of wells method of sampling according to claim 7, it is characterised in that:

Wherein, the water of well-flushing is the groundwater level in the groundwater monitoring well device to 3-5 times of volume of shaft bottom.

9. the contaminated site underground water gang of wells method of sampling according to claim 1, which is characterized in that further include:

9th step carries out the sampling of underground water in multiple groundwater monitoring well devices respectively,

Wherein, when measuring dissolubility pollutant, water intaking position is located at the water surface and bottom in the groundwater monitoring well device Middle position,

When containing lightweight nonaqueous phase liquid in water, water intaking position is located at the water surface site in the groundwater monitoring well device,

When containing heavy nonaqueous phase liquid in water, water intaking position is located at the water bottom location in the groundwater monitoring well device.