Method for selecting length of arbitrary section in water pressure test

Abstract

The application discloses a selection method for water pressure test of any section length, and belongs to the technical field of water conservancy and hydropower engineering geological exploration, and comprises the following steps: arranging and completing a drilling hole; carrying out high-definition three-dimensional laser scanning in the hole to obtain point cloud data and construct a three-dimensional geological model; interpreting a structural surface of the three-dimensional geological model; dividing and segmenting rock mass according to completeness; preliminarily segmenting rock mass with different water permeability; and selecting a section length and a position for water pressure test according to the preliminary segmentation result. The application can select a section length and a position for water pressure test, realize selection of water pressure test of any section length, eliminate the disadvantages of blindness, inefficiency, inaccuracy, lack of pertinence and uneconomicalness of traditional water pressure test, and achieve the purpose of improving quality and increasing efficiency.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of water conservancy and hydropower engineering geological exploration, and particularly relates to a method for selecting an arbitrary length of a water pressure test. BACKGROUND

[0002] The main task of the borehole water pressure test is to measure the water permeability of the rock mass, to provide basic data for dam foundation permeation stability evaluation and anti-seepage scheme design, and to lay a foundation for ensuring the normal play of the benefits of water conservancy and hydropower projects. Therefore, the borehole water pressure test is one of the main work contents in the water conservancy and hydropower engineering geological exploration.

[0003] The traditional water pressure test needs to be carried out every 5m in the drilling process of the borehole according to the regulations, and the water pressure test is carried out on the whole hole section from top to bottom or from bottom to top, the test process is carried out section by section, and each two sections need to overlap a certain length to ensure continuity. After the test is completed, the water permeability of the whole hole rock mass is analyzed according to the test results such as the water pressure test section length, the water pressure test section length, and the test section length, and then the water permeability of the hole rock mass is segmented.

[0004] The traditional test method has a wide coverage, but also has certain defects. On the one hand, it is difficult to ensure that the plug position can avoid the structure surface dense area or the broken rock mass section, which leads to inaccurate water pressure test flow, and the water pressure test result does not match the actual situation. On the other hand, for deep holes in water conservancy and hydropower engineering and tunnel engineering, the number of water pressure test sections often reaches dozens or more, the water pressure test workload is large, and there are many invalid section lengths (structure surface section) in the statistical process. For the micro new rock mass with large burial depth, the water permeability has stability, and the water pressure test result changes little, but according to the specification, the whole hole section water pressure test must be carried out, which leads to blindness and inefficiency of the water pressure test. The direct impact of repeated tripping and tripping of the plug on the construction efficiency of the borehole is not economical. Most importantly, the specification requires a water pressure test every 5m, which averages the water permeability of the "good" and "bad" rock mass, cannot objectively grasp the water permeability of the dam foundation rock mass, often leads to the determination of the relative water-resisting layer being too deep, and thus the design depth of the anti-seepage curtain is too large, which is not economical and increases the construction difficulty and construction period. SUMMARY

[0005] The purpose of the present application is to provide a method for selecting an arbitrary length of a water pressure test, to grasp the reliable water permeability of the dam foundation rock mass, to provide a technical basis for the engineering rock and soil permeability classification and the anti-seepage scheme design, and to achieve the purposes of rapid, accurate, efficient, and high-precision test and rock mass permeability analysis.

[0006] The technical scheme adopted by the present application is a method for selecting an arbitrary length of a water pressure test, comprising the following steps:

[0007] Step 1, arranging and completing a borehole;

[0008] Step 2, carry out full-section high-definition three-dimensional laser scanning in the hole, acquire point cloud data, and construct a three-dimensional geological model;

[0009] Step 3, interpret the structural plane of the three-dimensional geological model;

[0010] Step 4, divide and segment the rock mass according to the completeness;

[0011] Step 5, preliminarily segment the rock mass with different water permeability;

[0012] Step 6, according to the preliminary segmentation result, select the segment length and position that need to be subjected to the water pressure test.

[0013] Preferably, after the step 1 is completed, the alum should be precipitated for more than 24 hours to ensure that the hole wall is clear and visible.

[0014] Preferably, the structural plane interpretation in the step 3 includes the occurrence, development number, development interval, opening degree, extension length and filling of the structural plane in the whole hole, and the calculation of the structural plane line crack rate, line density and line RQD value of the rock mass.

[0015] Preferably, the line density is the number of structural plane development groups per unit footage, and the structural plane statistics removes the structural plane with siliceous, ferruginous and calcareous cementation.

[0016] Preferably, the rock mass completeness division in the step 4 is qualitative classification, which is divided into five categories of complete, relatively complete, relatively broken, broken and extremely broken according to the development of the structural plane.

[0017] Preferably, the step 5 preliminarily segments the rock mass with different water permeability according to the correlation between the rock mass completeness and the rock mass water permeability.

[0018] Preferably, the rock mass completeness and the rock mass water permeability are in a negative correlation.

[0019] Preferably, the preliminary segmentation in the step 5 includes five categories of relatively impermeable, slightly permeable, weakly permeable, moderately permeable and strongly permeable.

[0020] Preferably, the step 6 specifically includes selecting the start and end positions of the rock mass with different completeness in the hole according to the preliminary segmentation result, placing a plug at the start and end positions, performing a water pressure test, and realizing the selection of the water pressure test segment length.

[0021] The beneficial effects of the present application are:

[0022] Before the water pressure test, according to the three-dimensional laser scanning results of the borehole, the occurrence of the structural plane in the hole is directly measured, the development number, development interval, opening degree, extension length and filling of the structural plane in the whole hole are obtained, the line fracture rate, line density and line RQD value of the rock mass structural plane are calculated, then the completeness of the rock mass in the hole is segmented, the water permeability of the rock mass is preliminarily segmented according to the correlation between the completeness of the rock mass and the water permeability, the length and position of the segment needing to be subjected to the water pressure test are selected according to the preliminary segmentation results, the selection of the length of the segment subjected to the water pressure test is realized, the blindness, inefficiency, inaccuracy, non-targetedness and uneconomicalness of the traditional water pressure test are eliminated, the purpose of improving quality and efficiency is achieved, the operation amount of the test personnel is greatly reduced, and the method is advanced. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is the work flow chart of the embodiment of the present application;

[0024] Figure 2 is the schematic diagram of the working principle of the three-dimensional laser scanner of the borehole;

[0025] Figure 3 is the segmentation result of the completeness of the rock mass and the selected result of the length of the segment subjected to the water pressure test, wherein (a) is the segmentation result of the completeness of the rock mass, and (b) is the selected length of the segment subjected to the water pressure test;

[0026] Figure 4 is the example diagram of the three-dimensional laser scanning result, wherein (a) is the diagram of the borehole depth of 14.7-16.7m, (b) is the diagram of the borehole depth of 22.7-24.7m, and (c) is the diagram of the borehole depth of 38.7-40.7m.

[0027] In the figure: 1, digital display instrument; 2, electric pulley; 3, underground water level line; 4, three-dimensional laser scanner probe. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical scheme and advantages of the present application more clear and explicit, the technical scheme of the present application will be clearly and completely described below in combination with the drawings.

[0029] The three-dimensional laser scanning technology in the hole is a non-contact active measurement technology, can collect three-dimensional data of spatial borehole wall geological information with large depth and high density, has the characteristics of high point measurement precision, large density of collected spatial points and fast speed, and the data contains various information such as target body reflection intensity and color, the obtained three-dimensional geological model is clear, the rock mass structure and structural plane are easy to identify, and there is great advantage for the technical personnel to directly judge the borehole geological information, and the application technology of the three-dimensional laser scanning technology in the borehole has become mature at present.

[0030] As Figure 2As shown, when the three-dimensional laser scanner works, the electric pulley 2 drives the three-dimensional laser scanner probe 4 to descend, performs scanning work, and data is transmitted to the digital display instrument 1, which is used for displaying real-time data and recording historical data.

[0031] The method for selecting the length of the pressure water test section of the application comprises the following steps, as shown in the following: Figure 1

[0032] Step 1: A borehole is arranged in the test area, drilling and hole cleaning are completed, and the process should be completed according to the relevant requirements of NB / T 35115-2018 “Water and Hydropower Engineering Drilling Regulations”; after completion, alum is precipitated in the hole for more than 24 hours to ensure that the hole wall is clear and visible.

[0033] Step 2: High-definition three-dimensional laser scanning is carried out in the hole to obtain point cloud data and build a three-dimensional geological model; the scanning probe 4 should be uniformly lowered by the electric pulley 2 and ensure that it does not rotate, and the digital display instrument 1 is used to observe whether there are any abnormal conditions during the scanning process;

[0034] Step 3: Based on the developed three-dimensional laser scanning image, structural plane interpretation is carried out to obtain the occurrence, development number, development spacing, opening degree, extension length and filling of the structural plane in the whole hole, and the structural plane cemented by siliceous, ferruginous and calcareous should be removed during statistics; and the rock mass structural plane linear fissure rate, linear density and linear RQD value (rock quality designation) are calculated;

[0035] Step 4: According to the structural plane interpretation results, the rock mass is divided and segmented according to the provisions of Table 3.2.3 in GB / T 50218-2014 “Engineering Rock Mass Classification Standard”, as shown in the following: Figure 3 (a) figure, the process is qualitative division; generally, it is divided into five categories of complete, relatively complete, relatively broken, broken and extremely broken according to the development of the structural plane;

[0036] Step 5: According to the negative correlation between the rock mass integrity and the rock mass permeability, the rock mass with different permeability is preliminarily segmented, generally including five categories of relatively impermeable, slightly permeable, weakly permeable, moderately permeable and strongly permeable, and the rock mass integrity and the rock mass permeability are negatively correlated;

[0037] Step 6: According to the preliminary segmentation results, the start and end positions of the rock mass with different integrity in the borehole are selected, the upper plug and the lower plug are placed at the selected start and end positions, and the pressure water test is carried out to realize the selection of the length of the pressure water test section, as shown in the following: Figure 3 (b) is the selection result of the length of the pressure water test section.

[0038] ​In step 1, drilling and hole cleaning should be completed according to NB / T 35115-2018 "Water and Hydropower Engineering Drilling Regulations", and after completion, alum should be added and precipitated for more than 24 hours to ensure that the hole wall is clear and visible.

[0039] In step 3, the specific method for interpreting the structure surface is as follows:

[0040] In the three-dimensional laser point cloud data of the borehole, the occurrence of the structure surface is solved by applying geometric and mathematical knowledge. For the structure surface, a plane is used for fitting to obtain the general equation of the fitting plane:

[0041] Ax+By+Cz+D=0 (1)

[0042] Where A, B, C, and D are equation parameters (A, B, and C are not zero, and are the normal vector coordinates of the plane n={A, B, C}).

[0043] According to the general equation of the plane, the following calculation formulas for the occurrence parameters of the structure surface are derived:

[0044] When the above three parameters (A, B, and C) are not "0":

[0045]

[0046]

[0047]

[0048]

[0049] Where E, S, W, and N represent the directions of east, south, west, and north, respectively.

[0050] The above discussion is for the structure surface in the general case, i.e., when A, B, and C are not "0". When A, B, and C are "0" or "1", the calculation of the occurrence parameters of the structure surface is shown in Table 1.

[0051]

[0052] Table 1 Calculation of structure surface parameters in special cases

[0053] In step 3, the line density should be the number of structure surface development groups per unit footage; and when counting the structure surface, the structure surface with siliceous, ferruginous, and calcareous cementation should be removed.

[0054] In step 3, the calculation of the line fracture rate, line density, and line RQD value of the rock mass structure surface is a known technology for those skilled in the art, and will not be repeated here.

[0055] In step 4, the rock mass integrity degree is divided into qualitative classification, which should meet the provisions of table 3.2.3 in GB / T 50218-2014 "Engineering rock mass classification standard".

[0056] In step 5, the rock mass integrity degree is negatively correlated with the rock mass permeability.

[0057] In step 6, the water pressure test method should meet the relevant provisions of NB / T 35113-2018 "Water and electricity engineering drilling water pressure test regulations".

[0058] Embodiment 1:

[0059] This embodiment is a partial three-dimensional laser scanning result of a drilling depth of 14.7-40.7m, as shown in FIG. 1, and the partial scanning results are shown in Table 2. Figure 4

[0060]

[0061] Table 2: Three-dimensional laser scanning results and analysis

[0062] From the above embodiment, it can be seen that the traditional water pressure test specification requires one section every 5m, so the drilling needs to be done for 5 sections of water pressure, and due to the different structures of the rock mass in the hole, the different densities of the fissure development, and the different opening degrees of the fissures, the water pressure test results obviously produce unreasonable phenomena, and the depth of the anti-seepage curtain should be selected at the position of 25m. Although the embodiment of the present application also selects 5 sections of water pressure test according to the rock mass structure and the fissure development degree, according to the water pressure test results, the depth of the anti-seepage curtain should be selected at the position of 23m, which reduces the curtain depth, saves the engineering investment, and reduces the construction period.​

Claims

1. A method for selecting a length of a pressurized water test section, characterized by, It comprises the following steps: Step 1, arranging and completing a borehole; Step 2, carrying out full-section high-definition three-dimensional laser scanning in the borehole, acquiring point cloud data, and constructing a three-dimensional geological model; Step 3, interpreting structural planes of the three-dimensional geological model; Step 4, dividing and segmenting rock masses according to completeness, which is divided into five categories, i.e., complete, relatively complete, relatively broken, broken and extremely broken, according to the development of structural planes; Step 5, preliminarily segmenting rock masses with different water permeability according to the correlation between rock mass completeness and water permeability, including five categories, i.e., relatively impermeable, slightly permeable, weakly permeable, moderately permeable and strongly permeable, and the rock mass completeness and water permeability are negatively correlated; Step 6, according to the preliminary segmentation result, selecting the start and end positions of rock masses with different completeness in the borehole, placing a plug at the start and end positions, and carrying out a water pressure test to realize the selection of the length of the water pressure test section.

2. The method of claim 1, wherein the method further comprises: After the completion of the step 1, alum should be precipitated for more than 24 hours to ensure that the hole wall is clear and visible.

3. The method of claim 1, wherein the method further comprises: The structural plane interpretation in the step 3 includes the occurrence, development number, development spacing, opening degree, extension length and filling of the structural plane in the whole hole, and the calculation of the linear fracture rate, linear density and linear RQD value of the rock mass structural plane.

4. The method for selecting a length of a pressure test section according to claim 3, wherein The linear density is the number of structural plane development per unit footage, and the structural plane statistics removes the structural plane with siliceous, ferruginous and calcareous cementation.

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