A groundwater flowability surveying method based on borehole in-hole dispersion test

Abstract

A groundwater flowability survey method based on borehole in-hole dispersion test, main steps including: carrying out borehole one-dimensional dispersion test, obtaining measured value; carrying out data interpolation on borehole one-dimensional test data; processing data of single hole to obtain ion migration characteristic value and leakage characteristic value; judging groundwater activity in borehole according to obtained ion migration characteristic value and leakage characteristic value. The method can obtain borehole leakage point in single borehole by using ion marking measurement method based on seepage field characteristics of the borehole, and objectively quantitatively evaluate with high accuracy and simple organization and implementation.

Description

Technical Field

[0001] This invention relates to the fields of geology and geotechnical engineering, and in particular to a method for investigating groundwater flowability based on borehole in-hole dispersion tests. Background Technology

[0002] Groundwater leakage (surges) is a major problem faced by water conservancy and hydropower, transportation engineering, underground construction, and mineral development projects, and is a key factor restricting the safety of project construction and stable operation. Accurate identification and location of underwater leakage channels are of great significance for preventing water resource loss, ensuring the safety of engineering structures, and protecting the ecological environment. In engineering projects, after initially determining the location of leakage channels, methods such as borehole pressure tests, borehole flow meters, and borehole pumping tests are often used for verification.

[0003] The current testing method obtains representative indicators such as permeability, flow velocity, and permeability, and then plots the corresponding indicator-pore depth distribution curve. Based on the curve and the core data, the abnormal range is delineated, and it is determined whether there are leakage channels and the possible locations of leakage channels.

[0004] Currently, the data collection and processing of exploration methods are quite complex. Water pressure tests require the drilling rig to be raised and lowered in coordination with the supporting water pressure equipment. Due to the inherent problems of the instrument itself, flow meters can only determine whether there is leakage. Pumping tests have certain requirements for the borehole diameter and require a lot of supporting pumping equipment, making the operation complicated and only providing a framework judgment. Summary of the Invention

[0005] This disclosure provides a groundwater flowability investigation method based on borehole in-hole dispersion test. It utilizes the characteristics of the seepage field inside the borehole, uses ions to identify the entire borehole, obtains abnormal characteristic values ​​based on the ion dispersion law and measured ion migration, and processes and analyzes the raw data based on the correlation between the characteristic values ​​and leakage to achieve quantitative judgment.

[0006] The groundwater flowability exploration method based on borehole in-hole dispersion test disclosed herein mainly includes the following steps:

[0007] S1, Conduct a one-dimensional dispersion test in the borehole and obtain the measured value;

[0008] S2, for one-dimensional borehole data, monitor the continuous process of natural ion migration in the vertical direction, and perform data interpolation based on the measured values;

[0009] S3. For data from a single pore, dimensionless processing is performed according to its own spatiotemporal variation law to obtain ion transport characteristic values ​​and leakage characteristic values.

[0010] S4. Based on the obtained ion transport characteristic values ​​and leakage characteristic values, determine the groundwater activity in the borehole.

[0011] Furthermore, the specific method of step S1 includes:

[0012] Ion labeling was performed on the entire borehole using a water-permeable carrier containing labeling reagents, and the changes in conductivity within the borehole were measured multiple times based on set time and distance intervals.

[0013] Furthermore, in step S1, based on a set time interval and distance interval, the change in conductivity within the hole is measured multiple times, specifically including:

[0014] Before and within 12-24 hours after power-on, the changes in conductivity inside the hole were measured multiple times at vertical intervals of 2-5 meters, based on the basic time points of before power-on, 0 hours after power-on, 1 hour after power-on, 2 hours after power-on, 4 hours after power-on, 8 hours after power-on, 16 hours after power-on, and 24 hours after power-on.

[0015] Furthermore, in step S3, the specific calculation methods for the ion transport characteristic value and the leakage characteristic value include:

[0016] Let the data series obtained in step S2 be (Z, T, Wzt).

[0017] The characteristic values ​​of ion transport are:

[0018]

[0019] In the formula:

[0020] Qzi is the ion transport characteristic value of the Z elevation at time i in the borehole, and the calculated result is dimensionless;

[0021] Δt is the time since the last observation;

[0022] Wzi is the measured conductivity value at elevation z and time i, and Wz(i-Δt) represents the measured conductivity value at elevation z and time i-Δt.

[0023] The leakage characteristic value is:

[0024]

[0025] In the formula:

[0026] Sz is the characteristic value of ion leakage at elevation Z in the borehole, and the calculated result is dimensionless.

[0027] Furthermore, in step S4, the principles for determining the groundwater activity within the borehole include:

[0028] The closer Qz is to 0, the weaker the groundwater activity at that elevation in the test borehole; positive values ​​represent ion migration, negative values ​​represent ion migration, and the larger the absolute value, the stronger the groundwater activity at that elevation;

[0029] The presence of a maximum value on the Sz value curve indicates the existence of a leakage channel in the borehole; the larger the extreme value, the higher the probability that the location is a leakage channel.

[0030] Furthermore, the method also includes the following steps:

[0031] For a single borehole, plot the ion migration characteristic value Qzi and the leakage characteristic value Sz curves at different times. Based on the migration rate (referring to the speed of change of ion concentration at a certain elevation) and the permeability characteristic curve, classify the connectivity level of the leakage channel.

[0032] Furthermore, after initially assessing the intensity of groundwater activity within the borehole, the following steps are also included:

[0033] The borehole one-dimensional dispersion test was repeated in the zone of intense groundwater activity. The vertical interval of the conductivity monitoring points was reduced to 0.5m. Steps S1-S4 were repeated to accurately delineate the zone of intense groundwater activity in the borehole.

[0034] This disclosure performs interpolation and normalization processing on measured borehole data to obtain ion transport characteristics. Based on the leakage characteristic value curve, the location of leakage channels is determined, and the connectivity of the leakage channels is determined based on the magnitude of the leakage characteristic value. Compared with the prior art, the beneficial effects of this disclosure are: ① It can obtain the borehole leakage point by using the seepage field characteristics within a single borehole and measuring it with ion labeling; ② It provides objective quantitative assessment with high accuracy; ③ It can accurately delineate areas of intense groundwater activity within the borehole; ④ It is easy to organize and implement and highly feasible. Attached Figure Description

[0035] The above and other objects, features and advantages of this disclosure will become more apparent from the more detailed description of exemplary embodiments of this disclosure taken in conjunction with the accompanying drawings, in which the same reference numerals generally represent the same components.

[0036] Figure 1 Here is a flowchart of the groundwater flowability investigation method based on borehole in-hole dispersion test according to this disclosure;

[0037] Figure 2 These are exemplary ion transport characteristics in boreholes;

[0038] Figure 3 The following is a curve of leakage characteristic values ​​obtained from borehole calculation as an example. Detailed Implementation

[0039] Preferred embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While preferred embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the present disclosure will be thorough and complete, and will fully convey the scope of the present disclosure to those skilled in the art.

[0040] This disclosure provides a method for groundwater flowability investigation based on borehole in-hole dispersion tests. An exemplary embodiment flowchart is attached. Figure 1 As shown, the main steps include:

[0041] 1. Conduct a one-dimensional dispersion test in the borehole to obtain measured data.

[0042] First, the original temperature and electrical conductivity data W inside the borehole were measured and studied.

[0043] Then, a water-permeable carrier containing labeling reagents (such as salt, iron powder, and other reagents that affect the conductivity of water) is used for full-hole ion labeling in the borehole;

[0044] Within 12-24 hours after power-on, the changes in conductivity inside the hole were measured multiple times at vertical intervals of 2-5 meters, based on the basic time points of before power-on, 0 hours after power-on, 1 hour after power-on, 2 hours after power-on, 4 hours after power-on, 8 hours after power-on, 16 hours after power-on, and 24 hours after power-on.

[0045] Based on the variation law of conductivity, the measurement time interval and the spacing between measurement points can be shortened.

[0046] The borehole dispersion test is a one-dimensional line (single hole).

[0047] II. Data Interpolation

[0048] For the one-dimensional borehole data, necessary data interpolation is performed based on the measured values. The measured data are represented in the data series (Z, T, Wzt).

[0049] III. Single-hole data processing

[0050] For data from a single pore, dimensionless processing is performed according to its spatiotemporal variation patterns to obtain ion transport characteristic values.

[0051] Dedimensionalization of single borehole data

[0052] A single borehole is a typical example of one-dimensional data, reflecting the characteristics of the vertical seepage field along the borehole. Dimensionless processing of single borehole data involves processing the data series (Z, T, Wzt).

[0053] Ion transport characteristic values

[0054]

[0055] In the formula:

[0056] Qzi is the characteristic value of ion transport at elevation Z at time i in the borehole, and the calculated result is dimensionless;

[0057] Δt is the time since the last observation;

[0058] Wzi represents the measured conductivity value at elevation z and time i, and Wz(i+Δt) represents the measured conductivity value at elevation z and time i-Δt.

[0059] The closer Qz is to 0, the weaker the groundwater activity at that elevation in the test borehole; positive values ​​represent ion migration, negative values ​​represent ion migration, and the larger the absolute value, the stronger the groundwater activity at that elevation.

[0060] Leakage characteristic values:

[0061]

[0062] Sz is the characteristic value of ion leakage at elevation Z in the borehole, and the calculated result is dimensionless.

[0063] The presence of a maximum value on the Sz value curve indicates the existence of a leakage channel in the borehole. The larger the extreme value, the higher the probability that the location is a leakage channel.

[0064] IV. Analysis of Indicator Values

[0065] For a single borehole, plot the ion migration characteristic value Qzi and the leakage characteristic value Sz curves at different times, and classify the connectivity of leakage channels as good, average, and poor according to the migration rate and the permeability characteristic curve.

[0066] In this embodiment, the box plot of ion transport characteristic values ​​in the in-hole dispersion test of borehole ZZK3 (numbered) is attached. Figure 2 As shown in the figure, the time range, median, mean, and outliers of ion transport characteristic values ​​at a certain elevation are marked. A positive ion transport characteristic value represents ion inflow, and a negative ion transport characteristic value represents ion outflow. In this experiment, the entire well was marked with artificial source input markers; therefore, when the ion transport characteristic value is positive, it is necessary to manually remove positive outliers introduced by the source input. The smaller the box-shaped range, the smaller the range of variation of the ion transport characteristic value, indicating that the groundwater at this elevation is less affected by seepage channels.

[0067] The characteristic value curve of leakage in borehole dispersion test of ZZK3 is attached. Figure 3 As shown in the figure, the horizontal axis represents the elevation of an observation point within the borehole, and the vertical axis represents the leakage characteristic value. A maximum value on the curve indicates the potential existence of a leakage channel at that location; the larger the extreme value, the greater the likelihood that a leakage channel exists at the elevation corresponding to that extreme value.

[0068] It can be seen that when there is no leakage channel in the borehole:

[0069] Due to the vertical movement of ions caused by gravity, the characteristic values ​​of ion transport will exhibit the following features: the mean is close to zero, there are no outliers, and the box shape is almost symmetrical along y=0.

[0070] The leakage characteristic value is a stepped curve. The initial elevation of the observation is a positive value, which gradually decreases as the elevation decreases. After the inflection point, the leakage characteristic value drops sharply to 0. The position of the inflection point in the curve decreases as the final observation time is delayed.

[0071] In addition, as a preferred embodiment, after initially determining the intensity of groundwater activity within the borehole, the following steps are also included:

[0072] The borehole one-dimensional dispersion test was repeated in the zone of intense groundwater activity. The vertical interval of the conductivity monitoring points was reduced to 0.5m. The aforementioned steps were repeated to accurately delineate the zone of intense groundwater activity in the borehole.

[0073] The above technical solutions are merely exemplary embodiments of the present invention. For those skilled in the art, based on the application methods and principles disclosed in the present invention, it is easy to make various types of improvements or modifications, and not limited to the methods described in the specific embodiments of the present invention. Therefore, the methods described above are merely preferred and not restrictive.

Claims

1. A method for investigating groundwater flowability based on borehole in-hole dispersion tests, characterized in that, Includes the following steps: S1, Conduct a one-dimensional dispersion test in the borehole and obtain the measured value; S2, for one-dimensional borehole data, monitor the continuous process of natural ion migration in the vertical direction, and perform data interpolation based on the measured values; S3. For data from a single pore, dimensionless processing is performed according to its own spatiotemporal variation law to obtain ion transport characteristic values ​​and leakage characteristic values. S4. Based on the obtained ion transport characteristic values ​​and leakage characteristic values, determine the groundwater activity in the borehole; In step S3, the specific calculation methods for the ion transport characteristic value and the leakage characteristic value include: Let the data series obtained in step S2 be (Z, t, Wzt). The characteristic values ​​of ion transport are: In the formula: Qzi is the ion transport characteristic value of the Z elevation at time i in the borehole, and the calculated result is dimensionless; This is the time since the last observation; Wzi is the measured conductivity value at elevation Z and time i, where Wz(i- () represents the elevation at Z, i- The measured conductivity value at that time; The leakage characteristic value is: In the formula: Sz is the characteristic value of ion leakage at elevation Z in the borehole, and the calculated result is dimensionless.

2. The method according to claim 1, characterized in that, The specific method of step S1 includes: Ion labeling was performed on the entire borehole using a water-permeable carrier containing labeling reagents, and the changes in conductivity within the borehole were measured multiple times based on set time and distance intervals.

3. The method according to claim 2, characterized in that, In step S1, based on a set time interval and distance interval, the change in conductivity inside the hole is measured multiple times, specifically including: Before and within 12-24 hours after power-on, the changes in conductivity inside the hole were measured multiple times at vertical intervals of 2-5 meters, based on the basic time points of before power-on, 0 hours after power-on, 1 hour after power-on, 2 hours after power-on, 4 hours after power-on, 8 hours after power-on, 16 hours after power-on, and 24 hours after power-on.

4. The method according to claim 1, characterized in that, In step S4, the method for determining the groundwater activity within the borehole includes: The closer Qz is to 0, the weaker the groundwater activity at that elevation in the test borehole; positive values ​​represent ion migration, negative values ​​represent ion migration, and the larger the absolute value, the stronger the groundwater activity at that elevation; The presence of a maximum value on the Sz value curve indicates the existence of a leakage channel in the borehole; the larger the extreme value, the higher the probability that the location is a leakage channel.

5. The method according to claim 1, characterized in that, It also includes the following steps: For a single borehole, ion migration characteristic value Qzi and leakage characteristic value Sz curves were plotted at different times. Based on the migration rate and the permeability characteristic curves, the connectivity level of the leakage channels was classified.

6. The method according to any one of claims 1-5, characterized in that, After initially determining the groundwater activity within the borehole in step S4, the following steps are also included: In areas where groundwater activity exceeds the threshold, the borehole one-dimensional dispersion test is repeated, with the vertical interval of conductivity monitoring points reduced to 0.5m. Steps S1-S4 are repeated to accurately delineate the zone of intense groundwater activity within the borehole.

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