Hydrogeological test method for determining the distribution range of "water-conducting skylights" in aquitards

Abstract

The present invention provides a hydrogeological test method for determining the distribution range of the water-conducting "skylight" in the aquitard. This method screens out the boreholes in the actual "skylight" area according to the drawdown coefficient values of the observation boreholes in the upper aquifer, and then delineates the final range of the "skylight" area based on the boreholes in the actual "skylight" area. The present invention first proposes to use the drawdown coefficient values of the observation boreholes in the upper aquifer as an index to determine the actual range of the "skylight" area. This method takes the water level change response as the main index and can more truly reflect the lack of water conductivity of the aquitard.

Description

Technical Field

[0001] The invention belongs to the technical field of mine hydrogeology, relates to the identification of the position of a "skylight" in an impermeable stratum, and specifically relates to a hydrogeological test method for determining the distribution range of a water-conducting "skylight" in an impermeable stratum. Background Art

[0002] Due to the influence of stratum sedimentation, tectonic movement, etc., there is often a "skylight" phenomenon due to the partial loss of strata. When there is a water-conducting "skylight" in the impermeable layer, the hydraulic connection between the upper and lower aquifers will be closer, increasing the amount of water inflow in the mine and even causing water inrush in the mine. Therefore, it is extremely important to find out the location of the "skylight" in the impermeable stratum before mining, which is of great significance for the reasonable evaluation of the hydrogeological conditions and water hazard threats of the mine.

[0003] Generally speaking, the distance between drilling holes for mining geological exploration is more than 500m. Using geological exploration data, we can only preliminarily define the approximate range of the "skylight", but it is difficult to accurately define the actual location. At present, the main methods for identifying the location of the water-conducting "skylight" in the impermeable stratum are geophysical exploration and drilling exploration.

[0004] The geophysical prospecting method is to use electromagnetic exploration, seismic exploration and other means on the ground to indirectly determine the location of the "skylight" through the differences in electrical properties in the strata and the differences in reflected waves. This method has poor applicability under conditions such as complex terrain structure, thick loose layers, and strong water-rich upper aquifers, and the identification accuracy is relatively limited.

[0005] The drilling exploration method is to construct a large number of geological exploration boreholes in the exploration area, identify the strata through coring, logging and other means, and circle the location of the water-conducting "skylight"; although this method can accurately identify the missing range of the impermeable strata (i.e., the "skylight"), it is difficult to determine the area where the impermeable layer is thinner at the edge of the "skylight". In actual situations, the impermeable performance of the thinner impermeable layer is not reliable, which will affect the construction; at the same time, the exploration boreholes used in the drilling exploration method have large apertures, high costs, and are restricted by the terrain during construction, making it difficult to carry out large-scale development. Summary of the invention

[0006] In view of the defects and shortcomings of the prior art, the purpose of the present invention is to provide a hydrogeological test method for determining the distribution range of water-conducting "skylights" in aquicludes, so as to solve the technical problems that the existing methods for identifying the positions of water-conducting "skylights" in aquicludes need to be improved in applicability and identification accuracy under complex environments, and that it is difficult to characterize the thinner aquiclude area at the edge of the "skylight".

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions to achieve the above problems:

[0008] A method for determining the distribution range of water-conducting "skylights" in aquitards. This method adopts hydrogeological test methods to determine the distribution range of water-conducting "skylights" in aquitards; according to the drawdown coefficient values of the observation wells in the upper aquifer, the boreholes in the actual "skylight" area are screened out, and then based on the boreholes in the actual "skylight" area, the final range of the "skylight" area is delineated.

[0009] The present invention further includes the following technical features:

[0010] This method specifically includes the following steps:

[0011] Step 1, delineate the approximate range of the "skylight" area.

[0012] Step 2, determine the groundwater flow direction.

[0013] Step 3, arrange observation wells in the upper aquifer.

[0014] Step 4, arrange pumping wells in the lower aquifer.

[0015] Step 5, pump the pumping wells in the lower aquifer arranged in Step 4, and calculate and obtain the water level drawdown values of all the observation wells in the upper aquifer arranged in Step 3.

[0016] Step 6, obtain the drawdown coefficient values of the observation wells in the upper aquifer:

[0017] Measure the horizontal distance between each observation well in the upper aquifer and each pumping well in the lower aquifer in the plan view. According to the water level drawdown values of the observation wells in the upper aquifer obtained in Step 5, calculate and obtain the drawdown coefficient values of the observation wells in the upper aquifer by using Formula I; the Formula I is as follows:

[0018] B ij =S ij / L ij Formula I;

[0019] In the formula:

[0020] B ij represents the drawdown coefficient value of the i-th observation well in the upper aquifer when the j-th pumping well in the lower aquifer is pumping;

[0021] S ij represents the water level drawdown value of the i-th observation well in the upper aquifer when the j-th pumping well in the lower aquifer is pumping;

[0022] L ij represents the horizontal distance between the i-th observation well in the upper aquifer and the j-th pumping well in the lower aquifer.

[0023] Step 7, based on the drawdown coefficient values of all the observation wells in the upper aquifer obtained in Step 6, screen out the boreholes in the actual "skylight" area.

[0024] Step 8: Drill holes within the actually determined "skylight" area in Step 7 to delimit the final scope of the "skylight" area.

[0025] The present invention also has the following technical features:

[0026] Specifically, Step 1 is as follows: Use the boreholes located at the absence of the aquitard and the boreholes located at the presence of the aquitard to preliminarily delimit the approximate scope of the "skylight" area.

[0027] Specifically, Step 2 is as follows: Collect the existing water level data of the aquifers within the mine field. Through computer interpolation mapping and analysis, draw the equipotential lines of the mine field aquifers by computer interpolation and comprehensive analysis, and draw the flow lines perpendicular to each equipotential line, so as to determine the main flow direction of the groundwater.

[0028] Specifically, Step 3 is as follows: Taking the missing borehole in Step 1 as the center, arrange a row of upper aquifer observation boreholes along the main flow direction of the groundwater determined in Step 1 and the direction perpendicular to the main flow direction of the groundwater in the upper aquifer. The two rows of upper aquifer observation boreholes are arranged in a cross shape, and the approximate scope of the "skylight" area is divided into four quadrants. Preferably, the spacing between adjacent upper aquifer observation boreholes is 100 m, the aperture of the upper aquifer observation boreholes is 50 mm, and the depth of the upper aquifer observation boreholes is half of the depth of the upper aquifer.

[0029] Specifically, Step 4 is as follows: Arrange a lower aquifer pumping borehole in each of the four quadrants of the lower aquifer. The four lower aquifer pumping boreholes are respectively located at the midpoints of the intersection lines of the boundaries of the approximate scope of the "skylight" area and the 45° lines of this quadrant, and isolate the upper aquifer through a water-stop casing.

[0030] Specifically, Step 5 is as follows:

[0031] Record the static water level depth values of all upper aquifer observation boreholes before pumping, and then pump one of the lower aquifer pumping boreholes. Monitor and record the water level changes in all upper aquifer observation boreholes during pumping until the water level in the upper aquifer basically reaches stability, then stop pumping the lower aquifer pumping borehole, and record the water level depth values of all upper aquifer observation boreholes at this time.

[0032] After the water levels of all upper aquifer observation boreholes basically return to the original water level state, repeat the above process and pump the remaining three lower aquifer pumping boreholes in turn; after pumping all the lower aquifer pumping boreholes, subtract the static water level depth value before pumping from the water level depth value at the time of pumping stability, and the water level drawdown value S of all upper aquifer observation boreholes can be obtained. ij 。

[0033] Step 7 is specifically as follows: Compare the drawdown coefficient values of all the observation wells in the upper aquifer obtained in Step 6 with the drawdown coefficient value of the observation well in the upper aquifer at the center of the approximate range of the "skylight" area. If the drawdown coefficient value of a certain observation well in the upper aquifer is greater than the drawdown coefficient value of the observation well in the upper aquifer at the center of the approximate range of the "skylight" area, then mark this observation well in the upper aquifer. If the number of marked times is greater than two, then determine this observation well in the upper aquifer as a borehole within the actual "skylight" area.

[0034] Step 8 is specifically as follows: Select boreholes within the actual "skylight" area at the edge, and then mark the center points of the boreholes within the actual "skylight" area at the edge and the adjacent observation wells in the upper aquifer outside them. Connect the center points with a smooth curve. The range enclosed by this smooth curve is the final range of the "skylight" area.

[0035] Compared with the prior art, the present invention has the following beneficial technical effects:

[0036] (Ⅰ) The present invention first proposes to use the drawdown coefficient value of the observation wells in the upper aquifer as an index to determine the actual range of the "skylight" area. This method takes the water level change response as the main index and can more truly reflect the lack of water conductivity of the aquitard.

[0037] Compared with the traditional geophysical exploration methods, the method of the present invention has better applicability and relatively higher discrimination accuracy under conditions such as complex terrain structure, large thickness of loose layers, and strong water richness in the upper aquifer. Compared with the traditional drilling exploration method, the method of the present invention can also better depict the area where the aquitard at the edge of the "skylight" is relatively thin and has lost its water blocking ability.

[0038] (Ⅱ) The method of the present invention can delineate the actual range of the "skylight" area through the principle of the groundwater flow field. Compared with the traditional drilling exploration method, this method is simple and easy to operate, the construction area occupied by a single observation well in the upper aquifer is small, and the observation well in the upper aquifer is a small-diameter borehole, using coreless drilling construction, less affected by the terrain, with lower costs, and can also avoid the restriction of physical property anomalies caused by geological condition differences. Description of the Drawings

[0039] Figure 1 It is a schematic diagram of the approximate range of the "skylight" area delineated by using geological exploration boreholes.

[0040] Figure 2 It is a schematic cross-sectional view of the approximate range of the "skylight" area.

[0041] Figure 3 It is a schematic layout diagram of the observation wells in the upper aquifer.

[0042] Figure 4 It is a schematic layout diagram of the pumping wells in the lower aquifer.

[0043] Figure 5 Schematic diagram for comparing the final scope defined for the "skylight" area of the present invention with the actual distribution scope of the "skylight" area.

[0044] The meanings of the reference numerals in the figure are as follows: 1 - water - resistant layer, 2 - borehole at the location where the water - resistant layer is missing, 3 - borehole at the location where the water - resistant layer is not missing, 4 - approximate scope of the "skylight" area, 5 - pre - arranged working face, 6 - upper aquifer, 7 - observation well of the upper aquifer, 8 - lower aquifer, 9 - pumping well of the lower aquifer, 10 - borehole within the actual "skylight" area, 11 - final scope of the "skylight" area, 12 - actual distribution scope of the "skylight" area;

[0045] G1, G1 - 2, G1 - 3, G1 - 4, G1 - 5, G2 - 2, G2 - 3, G2 - 4, G2 - 5, G3 - 2, G3 - 3, G3 - 4, G3 - 5, G3 - 6, G4 - 2, G4 - 3, G4 - 4, G4 - 5, and G4 - 6 represent the numbers of the observation wells of the upper aquifer in the embodiments;

[0046] L1, L2, L3, and L4 respectively represent the 45° line intersection lines of the four quadrants in the embodiments.

[0047] The technical solution of the present invention will be further described below in conjunction with embodiments. Specific embodiments

[0048] It should be noted that all the equipment used in the present invention, without special instructions, adopts the equipment known in the art. For example: the water - level automatic monitoring equipment adopts the conventional water - level automatic monitoring equipment known in the prior art.

[0049] In the present invention:

[0050] The borehole 2 at the location where the water - resistant layer is missing and the borehole 3 where the water - resistant layer is not missing are both conventional exploration boreholes known in the prior art.

[0051] Complying with the above - mentioned technical solution, the following specific embodiments of the present invention are given. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent transformations made on the basis of the technical solution of this application fall within the protection scope of the present invention.

[0052] Embodiment:

[0053] This embodiment provides a hydro - geological test method for determining the distribution scope of the water - conducting "skylight" of the water - resistant layer. The method specifically includes the following steps:

[0054] Step 1, delineate the approximate scope of the "skylight" area:

[0055] As Figure 1 and Figure 2As shown in the figure, by using borehole 2 located at the missing area of the aquifuge and borehole 3 located at the area where the aquifuge 1 is not missing, the general range 4 of the "skylight" area is preliminarily delineated.

[0056] In this embodiment, the area of the general range 4 of the "skylight" area is about 0.43 km 2 ; Since the pre-laid working face 5 is located within the general range 4 of the "skylight" area, it may be severely affected by water hazards during the mining process. If the actual distribution range of the "skylight" area can be accurately and precisely judged, it can guide whether it is necessary to adjust the position of the pre-laid working face 5.

[0057] Step two, determine the groundwater flow direction:

[0058] Collect the existing water level data of the aquifers within the mine field. Through computer interpolation mapping and analysis, by computer interpolation and comprehensive analysis, draw the equipotential lines of the mine field aquifers, and draw the flow lines perpendicular to each equipotential line, then the main flow direction of the groundwater can be determined. In this embodiment, the overall groundwater flow direction within the mine field is from west to east.

[0059] Step three, arrange observation holes in the upper aquifer:

[0060] As shown in Figure 2 and Figure 3 , taking the missing borehole 2 in step one as the center, arrange a row of observation holes 7 in the upper aquifer 6 along the east-west direction and the north-south direction respectively. The spacing between adjacent observation holes 7 in the upper aquifer is 100 m, the hole diameter is 50 mm, and the hole depth only needs to enter half of the depth of the upper aquifer 6. The two rows of observation holes 7 in the upper aquifer are arranged in a cross shape, dividing the general range 4 of the "skylight" area into four quadrants.

[0061] As an optional scheme of this embodiment, after arranging the observation holes in the upper aquifer, a water level automatic monitoring device can be installed to facilitate subsequent water level measurement.

[0062] Step four, arrange pumping holes in the lower aquifer:

[0063] As shown in Figure 2 and Figure 4 , arrange a pumping hole 9 in each of the four quadrants of the lower aquifer 8. The four pumping holes 9 in the lower aquifer are respectively located at the midpoints of the intersection lines L1, L2, L3 or L4 of the boundary of the general range 4 of the "skylight" area and the 45° line of this quadrant. Number the four pumping holes 9 in the lower aquifer as 1#, 2#, 3# and 4#, and isolate the upper aquifer 6 through a water-stop casing.

[0064] Step five, pump water from the pumping holes in the lower aquifer arranged in step four, and calculate and obtain the water level drawdown values of all the observation holes in the upper aquifer arranged in step three:

[0065] Using a hydrological automatic monitor or manual measurement method, record the static water level depth values of all the observation holes 7 in the upper aquifer before pumping. Then, pump water from the pumping hole 9 in the lower aquifer of No. 1. During the pumping process, monitor and record the water level changes in all the observation holes 7 in the upper aquifer until the water level in the upper aquifer 6 basically reaches stability. Then, stop pumping water from the pumping hole 9 in the lower aquifer of No. 1 and record the water level depth values of all the observation holes 7 in the upper aquifer at this time.

[0066] After the water levels in all the observation holes 7 in the upper aquifer basically return to the original water level state, repeat the above process and pump water from the pumping hole 9 in the lower aquifer of No. 2, the pumping hole 9 in the lower aquifer of No. 3, and the pumping hole 9 in the lower aquifer of No. 4 in sequence. After pumping water from all the pumping holes 9 in the lower aquifer, subtract the static water level depth value before pumping from the water level depth value at the time of pumping stability, and the water level drawdown value S of all the observation holes 7 in the upper aquifer can be obtained. ij . The results are shown in Table 1:

[0067] Table 1. Water level drawdown values of all the observation holes 7 in the upper aquifer when pumping water from each pumping hole in the lower aquifer

[0068]

[0069]

[0070] Step 6: Obtain the drawdown coefficient values of the observation holes in the upper aquifer:

[0071] Measure the horizontal distance between each observation hole in the upper aquifer and each pumping hole in the lower aquifer in the plan view. According to the water level drawdown values of the observation holes in the upper aquifer obtained in Step 5, calculate and obtain the drawdown coefficient values of the observation holes in the upper aquifer using Formula Ⅰ; Formula Ⅰ is as follows:

[0072] B ij = S ij / L ij Formula Ⅰ;

[0073] In the formula:

[0074] B ij represents the drawdown coefficient value of the i-th observation hole in the upper aquifer when pumping water from the j-th pumping hole in the lower aquifer;

[0075] S ij represents the water level drawdown value of the i-th observation hole in the upper aquifer when pumping water from the j-th pumping hole in the lower aquifer;

[0076] L ij represents the horizontal distance between the i-th observation hole in the upper aquifer and the j-th pumping hole in the lower aquifer.

[0077] Step 7: Based on the drawdown coefficient values of all the observation wells in the upper aquifer obtained in Step 6, screen out the boreholes within the actual "skylight" area:

[0078] Compare the drawdown coefficient values of all the observation wells in the upper aquifer obtained in Step 6 with the drawdown coefficient value of the observation well G1 in the upper aquifer at the center of the approximate range 4 of the "skylight" area. If the drawdown coefficient value of a certain observation well in the upper aquifer is greater than the drawdown coefficient value of the observation well G1 in the upper aquifer at the center of the approximate range 4 of the "skylight" area, then mark this observation well in the upper aquifer. If the number of marked times is greater than two, then determine this observation well in the upper aquifer as a borehole 10 within the actual "skylight" area.

[0079] In this embodiment, the drawdown coefficient values of the observation wells in the upper aquifer are shown in Table 2. After comparison, it is finally determined that a total of four boreholes, namely G1, G3-2, G4-2, and G4-3, belong to the boreholes 10 within the actual "skylight" area, and the results are shown in Table 2.

[0080] Table 2: Drawdown coefficient values of all the observation wells in the upper aquifer when pumping water from each pumping well in the lower aquifer

[0081]

[0082] Step 8: Based on the boreholes within the actual "skylight" area screened out in Step 7, delineate the final range of the "skylight" area:

[0083] As Figure 5 shown, in this embodiment, the boreholes 10 within the actual "skylight" area at the edge are G1, G3-2, and G4-3. Mark the center points of G1 and G1-2, the center points of G1 and G2-2, the center points of G3-2 and G3-3, and the center points of G4-3 and G4-4 respectively, and connect the four center points with a smooth curve. The range delineated by this smooth curve is the final range 11 of the "skylight" area.

[0084] As Figure 5 shown, the actual distribution range 12 of the "skylight" area set in the model is basically consistent with the final range 11 of the "skylight" area delineated in this embodiment, and the error can be controlled within 10%, which can fully guide the on-site engineering implementation. In this embodiment, the minimum distance between the final range 11 of the "skylight" area delineated and the pre-laid working face 5 is 121m. On the premise of doing other water control work well, there is no need to specially adjust the layout of the working face, saving a large amount of design change costs for the mine.

Claims

1. A method for determining the distribution range of water-conducting "skylights" in an aquifuge, characterized in that, This method adopts hydrogeological test methods to determine the distribution range of the water-conducting "skylight" in the aquitard; Based on the drawdown coefficient values of the observation wells in the upper aquifer, boreholes (10) within the actual "skylight" area are selected, and then, based on the boreholes (10) within the actual "skylight" area, the final range (11) of the "skylight" area is delineated; This method specifically includes the following steps: Step 1, delineate the approximate range (4) of the "skylight" area; Step 2, determine the groundwater flow direction; Step 3, arrange observation wells (7) in the upper aquifer; specifically: Taking the missing borehole (2) in Step 1 as the center, in the upper aquifer (6), along the main flow direction of the groundwater determined in Step 1 and the direction perpendicular to the main flow direction of the groundwater, arrange a row of observation wells (7) in the upper aquifer respectively. The two rows of observation wells (7) in the upper aquifer are arranged in a cross shape, dividing the approximate range (4) of the "skylight" area into four quadrants; Step 4, arrange pumping wells (9) in the lower aquifer; specifically: Arrange a pumping well (9) in each of the four quadrants of the lower aquifer (8). The four pumping wells (9) in the lower aquifer are respectively located at the midpoints of the intersection lines of the boundaries of the approximate range (4) of the "skylight" area and the 45° lines of this quadrant, and isolate the upper aquifer (6) through a water-stop casing; Step 5, pump water from the pumping wells (9) in the lower aquifer arranged in Step 4, and calculate and obtain the water level drawdown values of all the observation wells (7) in the upper aquifer arranged in Step 3; specifically: Record the static water level buried depth values of all the observation wells (7) in the upper aquifer before pumping, and then pump water from one pumping well (9) in the lower aquifer. During the pumping process, monitor and record the water level changes in all the observation wells (7) in the upper aquifer until the water level in the upper aquifer (6) is basically stable, then stop pumping water from this pumping well (9) in the lower aquifer, and record the water level buried depth values of all the observation wells (7) at this time; After the water levels of all the observation wells (7) in the upper aquifer have basically returned to the original water level state, repeat the above process and pump water from the remaining three pumping wells (9) in the lower aquifer in sequence; after pumping water from all the pumping wells (9) in the lower aquifer, subtract the buried depth value of the static water level before pumping from the buried depth value of the water level at the time of pumping stability to obtain the drawdown value S of all the observation wells in the upper aquifer ij ; Step 6, obtain the drawdown coefficient values of the observation wells in the upper aquifer: Measure the plane distances between each observation well (7) in the upper aquifer and each pumping well (9) in the lower aquifer in the plan view, and based on the water level drawdown values of the observation wells in the upper aquifer obtained in Step 5, calculate and obtain the drawdown coefficient values of the observation wells in the upper aquifer by using Formula Ⅰ; the said Formula Ⅰ is as follows: B ij =S ij / L ij Formula Ⅰ; In the formula: B ij It represents the drawdown coefficient value of the observation well in the i-th upper aquifer during the pumping of the pumping well in the j-th lower aquifer. S ij Denotes the drawdown value of the observation well in the i-th upper aquifer during pumping of the pumping well in the j-th lower aquifer; L ij represents the horizontal distance between the observation well in the upper aquifer of the i-th number and the pumping well in the lower aquifer of the j-th number; Step 7, based on the drawdown coefficient values of all the observation wells in the upper aquifer obtained in Step 6, select the boreholes (10) within the actual "skylight" area; specifically: Compare the drawdown coefficient values of all the observation wells in the upper aquifer obtained in Step 6 with the drawdown coefficient value of the observation well in the upper aquifer at the center of the approximate range (4) of the "skylight" area. If the drawdown coefficient value of a certain observation well in the upper aquifer is greater than the drawdown coefficient value of the observation well in the upper aquifer at the center of the approximate range (4) of the "skylight" area, then mark this observation well (7). If the number of marked times is greater than two, then determine this observation well (7) as a borehole (10) within the actual "skylight" area; Step 8, based on the boreholes (10) within the actual "skylight" area selected in Step 7, delineate the final range (11) of the "skylight" area; specifically: Drill holes (10) within the actual "skylight" area at the edge, and then mark the center points of the drill holes (10) within the actual "skylight" area at the edge and the adjacent upper aquifer observation holes (7) outside it. Connect the center points with a smooth curve, and the area enclosed by this smooth curve is the final range (11) of the "skylight" area.

2. The method for determining the distribution range of water-conducting "skylights" in an aquifuge according to claim 1, characterized in that, Specifically, step one is as follows: Use the drill holes (2) located at the missing part of the aquitard and the drill holes (3) located at the non-missing part of the aquitard (1) to preliminarily delineate the approximate range (4) of the "skylight" area.

3. The method for determining the distribution range of water-conducting "skylights" in an aquifuge according to claim 2, characterized in that, Specifically, step two is as follows: Collect the existing water level data of the aquifers within the mine field. Through computer interpolation mapping and analysis, by computer interpolation and comprehensive analysis, draw the isopotential lines of the mine area aquifers, and draw the flow lines perpendicular to each isopotential line, and then the main flow direction of the groundwater can be determined.

4. The method for determining the distribution range of water-conducting "skylights" in an aquifuge according to claim 1, characterized in that, The spacing between adjacent upper aquifer observation holes (7) is 100 m, the aperture of the upper aquifer observation holes (7) is 50 mm, and the depth of the upper aquifer observation holes (7) is half of the depth of the upper aquifer (6).

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