CN101718800A - Haplopore dilution method for determining seepage direction by electrical conductivity - Google Patents

Abstract

The invention discloses a conductivity single hole dilution method for measuring the seepage direction, belonging to the field of seepage and groundwater movement observation. The method includes selecting a measuring hole location and drilling a hole, selecting a tracer according to the difference in electrical conductivity of the drilled water body on site, and measuring the seepage direction by using an analytical technique on a sand body adsorbed with the tracer. The method of the invention is easy and reliable to operate, the tracer is selected as non-toxic strong electrolyte solution or deionized aqueous solution, the principle is clear, the measurement process is simple, convenient and safe, the result is accurate and reliable, environmental protection and safety, and can completely replace the existing radioactive single-hole flow direction measurement method.

Description

Conductivity Single Pore Dilution Method for Determination of Percolation Direction

technical field

The invention discloses a conductivity single-hole dilution method for measuring the seepage direction, which relates to the measurement of groundwater movement by a tracer dilution method, in particular a method for calculating the seepage direction by measuring changes in conductivity, which belongs to the field of seepage and groundwater movement observation.

Background technique

The principle of the tracer dilution method to measure flow rate was first proposed by Kocherin. The basic principle is that in a vertically exposed aquifer, the aquifer is isolated with a plug, and then a certain tracer is used to mark the groundwater, and the water body Mix evenly, the concentration of the tracer will decrease continuously with the water flow, and the tracer concentration before and after the section of the water column is measured twice with the probe, and the infiltration flow rate of the aquifer can be calculated. Later, the method was gradually perfected by researchers such as Moser and Drost.

Under the assumption that the groundwater flow is stable, the tracer concentration in the test hole section is always mixed uniformly, and there is no vertical water flow interference, in 1957, Moser proposed the radioactive single-hole dilution method for measuring the seepage velocity of groundwater. The isotopes act as tracers to label groundwater.

In the 1980s, Chinese scientific and technological personnel successively introduced radioisotope velocity measurement methods from abroad, and made new developments and breakthroughs in isotope tracer equipment and methods, and successfully applied this technology to water conservancy projects, metallurgy, Coal field logging, water resources, environmental protection and other fields have achieved gratifying results. In 1988, this method was included in the national standard "Code for Hydrogeological Survey of Water Supply (GBJ27-88)".

The principle of the radioactive single-hole dilution method: under a certain hydraulic gradient, the stronger the permeability of the medium, the greater the flow through the drilled section, and the faster the dilution rate of the radioactive indicator concentration. The detected seepage flow is marked with a small amount of radioactive indicator, and its movement law is determined according to the rate at which the radioactive indicator is diluted by the groundwater flow in the borehole and the direction it is brought out.

At present, the isotope single hole dilution method is the most commonly used method for determining the direction of seepage, but its disadvantages are:

The isotope single-well dilution test is a radioactive operation during the tracer injection process, and radioactive accidents are prone to occur in the storage, on-site injection, protection, testing, and cooperation of auxiliary personnel.

Contents of the invention

The purpose of the present invention is to provide a non-toxic, non-radioactive, simple and accurate method for determining the seepage direction by using the change of the conductivity of the tracer sand in the measuring hole.

The single-hole dilution method for measuring the conductivity of the seepage direction includes: selecting the location of the hole and drilling a hole; selecting a tracer according to the conductivity of the drilled water on site;

The above-mentioned selection of the measuring hole position and drilling is to select a geologically stable location in the area to be measured, drilling at a location without a fracture zone, the hole depth is below the estimated seepage layer, and the measuring hole has a built-in filter tube;

There is a gravel layer or no gravel layer outside the above-mentioned filter pipe. When the size of the filter tube and the measuring hole is suitable, the gravel filling layer may not be set. When the filter tube is too small, the gravel filling layer can be used to help the filter tube stabilize in the measuring hole.

The above-mentioned selection of tracer according to the conductivity of the borehole water means that when the conductivity of the borehole water is low, a strong electrolyte solution is selected as the tracer; when the conductivity of the borehole water is high, deionized water is selected as the tracer .

When the conductivity of the above-mentioned water body is low, the conductivity of the measured hole water body is 0-15ms/cm;

When the above-mentioned conductivity of the water body is relatively high, it means that the conductivity of the measured hole water body is >15ms/cm.

The above method of measuring the seepage direction by using the analysis technique adsorbed on the tracer sand body is: when using a strong electrolyte tracer solution, first use a 2mol/l strong electrolyte solution, and fill the sand soaked in the solution to saturation and drained. In the filter screen, put the filter screen into the drill hole to be tested, take out the filter screen after placing it for 8 to 15 minutes, divide the tracer sand into 8 pieces with the center of the screen cylinder as the center of the circle, and use 4 diameters as the dividing line. Take out the same amount of tracer sand from the outside of each piece, put it into the same amount of deionized water, and measure the conductivity of the 8 soaking solutions after fully stirring.

The strong electrolyte used as a tracer in the present invention mainly utilizes the property that its conductivity after being dissolved in water is directly proportional to the concentration, so there is no regulation on which strong electrolyte to use specifically, such as NaCl, KCl, NaNO _etc. Most salts of strong acids and strong bases can be used as strong electrolyte tracers in the present invention.

The time for the filter screen filled with tracer sand body to be placed in the borehole is related to the actual seepage velocity of the borehole. The inventor has found through many tests that in most cases, the flow direction can be accurately obtained after being placed for 8 to 15 minutes. . The purpose of dividing into 8 equal parts is to give the position of the flow direction in these 8 equal parts.

When the above 8 conductivity values are symmetrical along a certain dividing line, the flow direction of the groundwater is along the dividing line, from the minimum value to the maximum value. The conductivity value is symmetrical along a certain dividing line, which means that the conductivity value is relatively close on both sides of the dividing line, and the difference does not exceed 0.5ms/cm. The inventor has found through many tests that when the conductivity value is generally symmetrical along a certain dividing line, the conductivity values at the same position on both sides of the dividing line will generally not be exactly the same, but the difference will not be large. The side difference will not exceed 0.5ms/cm. If it exceeds this value, the following asymmetric method can be used to calculate the flow direction. This symmetric method is a special case of the asymmetric method. Using this method can reduce analysis time when symmetric methods are met.

When the above-mentioned 8 conductivity values are asymmetrical along any dividing line, the method of barycentric coordinates is used for flow direction analysis, and the direction from the corresponding origin to the barycentric coordinates is the flow direction.

The above-mentioned method of measuring the seepage direction by using the analytical technique of adsorbed tracer sand body is as follows: when deionized water is used as the tracer, fill the filter screen with the sand soaked in deionized water until saturated and drained, and put the filter screen into the filter screen. Put it into the borehole to be tested, take out the filter screen after placing it for 8-15 minutes, divide the tracer sand into 8 pieces with the center of the screen cylinder as the center of the circle, and use 4 diameters as the dividing line, and take out the same amount of tracer sand from the outside of each piece. Put the sand into the same amount of deionized water respectively, and measure the conductivity values of 8 soaking solutions after fully stirring.

When the above 8 conductivity values are symmetrical along a certain dividing line, the flow direction of groundwater is along the dividing line, from the maximum value to the minimum value direction. The conductivity value is symmetrical along a certain dividing line, which means that the conductivity value is relatively close on both sides of the dividing line, and the difference does not exceed 0.5ms/cm.

When the above 8 conductivity values are asymmetric along any dividing line, the method of barycentric coordinates is used to analyze the flow direction, and the opposite direction from the corresponding origin to the barycentric coordinate direction is the flow direction.

Specifically, the present invention has the following advantages:

The operation is simple and reliable, the tracer is selected as non-toxic strong electrolyte solution or deionized water, the principle is clear, the measurement process is simple, convenient and safe, the result is accurate and reliable, environmental protection and safety, and can completely replace the existing radioactive single-hole flow direction determination method.

Description of drawings

Fig. 1 measures the conductivity single-hole dilution method drilled cross-sectional schematic view of the seepage direction;

Fig. 2 measures the electric conductivity single-hole dilution method screen cylinder schematic diagram of seepage direction;

Fig. 3 is a schematic diagram of the tracer sand equalization of the conductivity single-hole dilution method for the determination of the seepage direction;

Fig. 4 measures the flow direction schematic diagram of the conductivity single hole dilution method center of gravity coordinate method analysis seepage direction;

Fig. 5 measures the coordinate system used by the conductivity single hole dilution method center of gravity coordinate method in the seepage direction;

Fig. 6 measures the conductivity single hole dilution method embodiment three flow direction schematic diagrams of seepage direction;

Fig. 7 is a schematic diagram of the flow direction of Example 4 of the conductivity single-hole dilution method for determining the seepage direction.

Detailed ways

The following examples are only used to illustrate the characteristics of the invention, and are not intended to limit the protection scope of the present invention.

Embodiment one

The single-hole dilution method for measuring the conductivity of the seepage direction includes: selecting the location of the hole and drilling a hole; selecting a tracer according to the conductivity of the drilled water on site;

The above-mentioned selection of the measuring hole position and drilling is to select geological stability in the area to be measured, and drill hole 2 at a position without a broken zone.

The outside of the above-mentioned filter pipe is a gravel layer 4 .

The conductivity value of the above-mentioned on-site borehole water body measurement is 0.53ms/cm, which belongs to low conductivity water body, and the strong electrolyte KCl solution is selected as the tracer.

The above-mentioned analytical technique using the tracer sand body to measure the seepage direction is to use 2mol/l KCl solution, filter the soaked and saturated tracer sand and fill it into the filter cylinder 5, as shown in Figure 2, put the filter cylinder 5 Put it into the filter tube 3, take out the filter cylinder 5 and the tracer sand in it after 10 minutes, divide the filter cylinder 5 into 8 pieces with the center of the cylinder as the center, see Figure 4, take out 10g tracer sand from the outside of each piece , put into 50ml of deionized water respectively, and measure the conductivity of the water after fully analyzing. The measured conductivity of each block of water is shown in Table 1.

Table 1 The measured data of Example 1 Unit: ms/cm

Block S1 S2 S3 S4 S5 S6 S7 S8 Conductivity 5.23 5.13 4.61 3.65 3.59 4.67 5.12 5.28

It can be seen that the symmetry of blocks S1 and S8, S2 and S7, S3 and S6, S4 and S5 is better, the maximum conductivity is block S1 and S8, and the minimum conductivity is block S4 and S5. Between blocks S4 and S5, the water outlet direction is between blocks S1 and S8, that is, the groundwater seepage direction is AA' in Fig. 4 .

Embodiment two

The single-hole dilution method for measuring the conductivity of the seepage direction includes: selecting the location of the hole and drilling a hole; selecting a tracer according to the conductivity of the drilled water on site;

The above-mentioned selection of the measuring hole position and drilling is to select geological stability in the area to be measured, and drill hole 2 at a position without a broken zone.

The outside of the above-mentioned filter pipe is a gravel layer 4 .

The conductivity value of the above-mentioned on-site borehole water measurement is 0.5ms/cm, which belongs to low conductivity water, and the strong electrolyte KCl solution is selected as the tracer.

The above-mentioned analytical technique using the tracer sand body to measure the seepage direction is to use 2mol/l KCl solution, filter the soaked and saturated tracer sand and fill it into the filter cylinder 5, as shown in Figure 2, put the filter cylinder 5 Put it into the filter tube 3, take out the filter cylinder 5 and the tracer sand in it after 10 minutes, divide the filter cylinder 5 into 8 pieces with the center of the cylinder as the center, see Figure 3, take out 10g tracer sand from the outside of each piece , put into 50ml of deionized water respectively, and measure the conductivity of the water after fully analyzing. The measured conductivity of each block of water is shown in Table 2.

Table 2 The measured data of Example 2 Unit: ms/cm

Block S1 S2 S3 S4 S5 S6 S7 S8 Conductivity 5.32 5.13 4.70 3.44 3.68 4.90 4.98 5.19

The method of center of gravity coordinates is used to analyze the flow direction, and the conductivity of multiple blocks is drawn on the plan according to the size. The corresponding coordinate system is shown in Figure 4. The data points intersect with the coordinate axis and the straight line y=x and y=-x respectively at points E, F, G, H, I, J, K, and L, and the conductance readings of each block are e, f, g, h, i, j, k, l, the coordinates of each point are as shown in Figure 5, the coordinates of the center of gravity of the points on the plane are X=-0.38, Y=-0.17, and the north direction and the x-axis are 162 °, calculate The direction of flow is 42° west by north.

Embodiment three

The single-hole dilution method for measuring the conductivity of the seepage direction includes: selecting the location of the hole and drilling a hole; selecting a tracer according to the conductivity of the drilled water on site;

The above-mentioned selection of the measuring hole position and drilling is to select geological stability in the area to be measured, and drill hole 2 at a position without a broken zone.

The outside of the above-mentioned filter pipe is a gravel layer 4 .

The conductivity value of the above-mentioned on-site borehole water body measurement is 16.4ms/cm, which belongs to high conductivity water body, and deionized water is selected as the tracer.

The above method of measuring the seepage direction by using the analytical technique of adsorbed tracer sand body is to drain the tracer sand soaked in deionized water and fill it into the filter cylinder 5, as shown in Figure 2, and put the filter cylinder 5 into the filter tube 3, take out the filter cylinder 5 and the tracer sand in it after 8 minutes, and divide the filter cylinder 5 into 8 pieces with the center of the cylinder as the center, as shown in Figure 4, take out 10g of tracer sand from the outside of each piece, and put 50ml of In the deionized water, the conductivity of the water was measured after fully analyzing, and the measured conductivity of each block of water is shown in Table 3.

Table 3 Measured data of Example 3 Unit: ms/cm

Block S1 S2 S3 S4 S5 S6 S7 S8 Conductivity 2.66 1.98 2.01 2.65 3.59 4.47 4.45 3.62

It can be seen from Table 3 that the blocks S1 and S4, S2 and S3, S5 and S8, S6 and S7 have better symmetry, the maximum conductivity is the blocks S6 and S7, and the minimum conductivity is the blocks S2 and S3. The water inlet direction is between blocks S2 and S3, and the water outlet direction is between blocks S6 and S7, that is, the groundwater seepage direction is BB' in Fig. 6 .

Embodiment four

The single-hole dilution method for measuring the conductivity of the seepage direction includes: selecting the location of the hole and drilling a hole; selecting a tracer according to the conductivity of the drilled water on site;

The above-mentioned selection of the measuring hole position and drilling is to select geological stability in the area to be measured, and drill hole 2 at a position without a broken zone.

The outside of the above-mentioned filter pipe is a gravel layer 4 .

The conductivity value of the above-mentioned on-site borehole water body measurement is 16.4ms/cm, which belongs to high conductivity water body, and deionized water is selected as the tracer.

The above method of measuring the seepage direction by using the analytical technique of adsorbed tracer sand body is to drain the tracer sand soaked in deionized water and fill it into the filter cylinder 5, as shown in Figure 2, and put the filter cylinder 5 into the filter tube 3, after 12 minutes, take out the filter cylinder 5 and the tracer sand in it, and divide the filter cylinder 5 into 8 pieces with the center of the cylinder as the center, as shown in Figure 4, take out 10g of tracer sand from the outside of each piece, and put in 50ml of In deionized water, the conductance of the water was measured after full analysis, and the measured conductivities of each block of water are shown in Table 4.

Table 4 Measured data of Example 4 Unit: ms/cm

Block S1 S2 S3 S4 S5 S6 S7 S8 Conductivity 2.17 2.73 3.57 4.44 4.75 3.90 2.98 2.29

The method of center of gravity coordinates is used to analyze the flow direction, and the conductivity of multiple blocks is drawn on the plan according to the size. The corresponding coordinate system is shown in Figure 4. The data points intersect with the coordinate axis and the straight line y=x and y=-x respectively at points E, F, G, H, I, J, K, and L, and the conductance readings of each block are e, f, g, h, i, j, k, l, the coordinates of each point are as shown in Figure 7, the coordinates of the center of gravity of the points on the plane are X=0.62, Y=0.16, the center of gravity and the positive angle of the X axis are 14 °, The opposite direction is an angle of 194° with the positive direction of the X-axis, and the angle between the north direction and the positive direction of the X-axis is 162°, and the flow direction is 32° from north to west.

Claims (10)

1. measure the conductivity single hole dilution method of seepage direction, it is characterized in that: described method comprises: select the gaging hole position and the hole of drilling;

Difference according to scene boring water body conductivity is chosen tracer agent;

Utilization is adsorbed with the analytic technique of tracer agent sand body and measures seepage direction.

2. the conductivity single hole dilution method of mensuration seepage direction according to claim 1, it is characterized in that: described selection gaging hole position and punching are for selecting geology stable in zone to be measured, the punching of no shatter belt position, hole depth is to estimating below the seepage flow layer the built-in chimney filter of gaging hole;

Gravel bed is filled out in the outer existence of described chimney filter;

Described chimney filter does not exist outward fills out gravel bed.

3. the conductivity single hole dilution method of mensuration seepage direction according to claim 1 is characterized in that: described difference according to scene boring water body conductivity is chosen tracer agent and is referred to hole the water body conductivity when low, and choosing strong electrolyte solution is tracer agent; When boring water body conductivity was higher, choosing deionized water was tracer agent.

4. the conductivity single hole dilution method of mensuration seepage direction according to claim 3 is characterized in that: when described water body conductivity is low, refer to that on-the-spot boring water body conductivity is 0～15ms/cm; When described water body conductivity is higher, refer to that on-the-spot boring water body conductivity is greater than 15ms/cm.

5. the conductivity single hole dilution method of mensuration seepage direction according to claim 1, it is characterized in that: the analytic technique measurement seepage direction that described utilization is adsorbed with the tracer agent sand body is: when adopting strong electrolyte tracer agent solution, use the strong electrolyte solution of 2mol/l earlier, insert in the filter screen soaking this solution to sand saturated and that drain, filter screen is put into tested boring, place and take out filter screen after 8～15 minutes, to net tube is that the center of circle is that cut-off rule is divided into 8 with tagged sand with 4 diameters with the tube heart, equivalent tagged sand is taken out in the every outside, drop into respectively in the deionized water of equivalent and soak, measure above-mentioned 8 soaking solution conductivity respectively after fully stirring.

6. the conductivity single hole dilution method of mensuration seepage direction according to claim 5, it is characterized in that: described 8 soaking solution conductivity values are during along certain bar cut-off rule symmetry, the phreatic flow direction is along this cut-off rule, flows to the maximal value direction from minimum value.

7. the conductivity single hole dilution method of mensuration seepage direction according to claim 5, it is characterized in that: described 8 conductivity values are along any cut-off rule when asymmetric, adopt the method for barycentric coordinates to flow to analysis, corresponding initial point to the direction of barycentric coordinates promptly is to flow to.

8. the conductivity single hole dilution method of mensuration seepage direction according to claim 1, it is characterized in that: the analytic technique measurement seepage direction that described utilization is adsorbed with the tracer agent sand body is: when adopting deionized water to be tracer agent, insert in the filter screen soaking deionized water to sand saturated and that drain, filter screen is put into tested boring, place and take out filter screen after 8～15 minutes, to net tube is that the center of circle is that cut-off rule is divided into 8 with tagged sand with 4 diameters with the tube heart, equivalent tagged sand is taken out in the every outside, drop into respectively in the deionized water of equivalent and soak, measure the conductivity value of above-mentioned 8 soaking solutions after fully stirring.

9. the conductivity single hole dilution method of mensuration seepage direction according to claim 8 is characterized in that: described 8 conductivity values are during along certain bar cut-off rule symmetry, and the phreatic flow direction is along this cut-off rule, flows to the minimum value direction from maximal value.

10. the conductivity single hole dilution method of mensuration seepage direction according to claim 8, it is characterized in that: described 8 conductivity values are along any cut-off rule when asymmetric, adopt the method for barycentric coordinates to flow to analysis, corresponding initial point oppositely promptly is to flow to the barycentric coordinates direction.

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