Method for calculating pressure and parameters of high pressure water test

Abstract

The invention discloses a method for calculating pressure and parameters of a high-pressure water pressure test, which specifically comprises the following steps: drilling a hole at a position to be tested and measuring a stable water level in the hole; measuring the length and depth of the water pressure test section and the height from the center of the surface pressure gauge to the ground; carrying out a high-pressure water pressure test on the hole, recording different surface test pressures and their corresponding flow values; using the collected data, calculating the water permeability of the rock mass where the water pressure test section is located according to the method in the "Regulations for Water Pressure Test of Drilling Holes for Hydropower Engineering" NB / T 35113-2018. q According to the external water pressure reduction coefficient table in Appendix W of the "Regulations on Geological Investigation for Water Conservancy and Hydropower Engineering" GB50487-2022, the water permeability q As the basis for calculating the reduction coefficient; select different calculation formulas to calculate the additional water pressure and test pressure, and calculate the true permeability of the rock mass according to the test pressure. This paper introduces the external water pressure reduction coefficient to make the calculation result more accurate.

Description

Technical Field

[0001] The invention belongs to the field of engineering geological survey, and specifically relates to a method for calculating the pressure of a high-pressure water pressure test. The invention also relates to a method for calculating high-pressure water pressure parameters. Background Art

[0002] As an important component of clean energy, pumped storage power stations play an important role in power grid peak regulation, frequency regulation, emergency standby and other aspects. At present, the working head of pumped storage power stations is generally 400m~600m, and the maximum can reach thousands of meters. Due to the large water level difference between the upper and lower reservoirs and the high working head, extremely high requirements are placed on the surrounding rocks of key parts such as diversion tunnels and high-pressure bifurcations during project operation. These parts must withstand high water pressure and face the test of high osmotic pressure difference and high hydraulic gradient. The anti-seepage performance of rock mass mainly depends on its own characteristics and integrity, and various joints, cracks and other structural surfaces are inevitably present in the rock mass. When the water pressure reaches or exceeds the bearing limit of the structural surface, the permeability characteristics of the rock mass will change. Often, the permeability of micro-permeable or weakly permeable rock layers under low pressure will become significantly stronger under high water pressure, and even hydraulic splitting damage will occur, thereby affecting the normal operation of the project. Therefore, when conducting water pressure tests on rock mass in high head parts, water pressure tests should be carried out according to the actual head pressure borne by the rock mass to truly reflect the permeability characteristics of the rock mass. At present, the maximum test pressure of conventional borehole water pressure test is only 1.0MPa, which obviously cannot truly reflect the permeability characteristics of rock mass under high head pressure. Therefore, high pressure water pressure test is usually used to study the permeability characteristics of rock mass under high head pressure. Obtaining rock mass permeability parameters through high pressure water pressure test and using it as a design basis has become an indispensable workflow in the investigation and design of pumped storage power stations. How to accurately measure and calculate rock mass permeability parameters through high pressure water pressure test, so as to more accurately guide engineering design, is particularly important.

[0003] At present, the test pressures for conventional water pressure tests and high-pressure water pressure tests are specified in the "Regulations for Water Pressure Tests for Hydropower Engineering Boreholes" (NB / T 35113-2018) and "Engineering Geology Manual". P The following formula is used for calculation:

[0004]

[0005] Where: ——Pressure displayed on the ground pressure gauge (MPa); ——Additional water pressure, equal to the water column pressure from the center of the ground pressure gauge to the zero line of pressure calculation (MPa); ——Pipeline pressure loss (MPa).

[0006] Additional water pressure in existing specifications It is equal to the water column pressure from the center of the surface pressure gauge to the pressure calculation zero line, and the determination of the pressure calculation zero line is as follows: (1) When the groundwater level is above the test section, the pressure calculation zero line is the groundwater level line; (2) When the groundwater level is within the test section, the pressure calculation zero line is the horizontal line passing through the midpoint of the test section above the groundwater level; (3) When the groundwater level is below the test section, the pressure calculation zero line is the horizontal line passing through the midpoint of the test section. This provision is based on the assumption that the external water pressure reduction coefficient is not considered, that is, it is assumed that the external water pressure of the borehole water level on the test section is completely equal to its water column pressure. This assumption is not obvious in shallow holes due to the small water level difference, but in deep holes, especially when the difference between the groundwater level and the depth of the test section is large, if the external water pressure reduction coefficient is still not considered, the error between the calculated test pressure and the actual pressure acting on the test section cannot be ignored, and may even cause the test parameters to deviate seriously from the actual values, thereby misleading the design plan. Summary of the invention

[0007] The purpose of the present invention is to provide a method for measuring the high-pressure water pressure test pressure, which method can more accurately measure the high-pressure water pressure test pressure.

[0008] Another object of the present invention is to provide a method for calculating high-pressure water pressure test parameters.

[0009] The technical solution adopted by the present invention is a method for measuring the pressure of a high-pressure water pressure test, comprising the following steps:

[0010] Step 1: Drill a hole at the location to be tested and measure the stable water level in the hole, recorded as h w ;

[0011] Step 2: Lower the packer and the upper packer in the borehole in sequence. The section between the lower packer and the upper packer is the water pressure test section, and its length is recorded as L. The height from the upper packer to the surface is the test section depth, recorded as H. Install a surface pressure tester on the high-pressure water inlet pipe on the ground, and measure the height from the center of the surface pressure gauge to the ground, recorded as Δh ;

[0012] Step 3: Conduct a high pressure water test on the borehole and record the time t Surface test pressure P P and its corresponding flow Q value, plot P P -Qt Relationship curve, according to which the surface test pressure corresponding to the splitting point of the rock mass where the water pressure test section is located is determined P P And its corresponding flow Q;

[0013] Step 4: Calculate the surface test pressure corresponding to the splitting point in step 3P and flow Q , calculate the permeability of the rock mass where the water pressure test section is located according to the method in the "Hydropower Engineering Borehole Water Pressure Test Code" (NB / T 35113-2018) q According to the external water pressure reduction coefficient table in Appendix W of the "Regulations on Geological Investigation for Water Conservancy and Hydropower Engineering" (GB50487-2022), the water permeability q The reduction factor is calculated based on β e ;

[0014] Step 5: Determine H and h w Calculate the additional water pressure P z ,

[0015] like h w <H, P z The calculation formula is formula (1):

[0016] (1)

[0017] If H< h w <H+L, P z The calculation formula is formula (2):

[0018] (2)

[0019] like h w >H+L, P z The calculation formula is formula (3):

[0020] (3);

[0021] Step 6, according to P z , use formula (4) to calculate the test pressure P ,

[0022] (4).

[0023] The present invention is also characterized in that:

[0024] Step 1: After the drilling is completed, flush the borehole and continue to observe the changes in the borehole water level until the borehole water level stabilizes, and measure the stable borehole water level.

[0025] The surface pressure tester includes a surface pressure sensor or a surface pressure gauge.

[0026] The test pressure difference of the high-pressure water pressure test in step 3 is 1.0Mpa.

[0027] Step 3: Use an automatic data acquisition instrument to record different surface test pressures P P And its corresponding flow Q value.

[0028] The split point in step 3 is the point on the curve corresponding to when the flow rate suddenly increases or the pressure suddenly decreases at a certain pressure level during the pressure increase process.

[0029] Reduction factor for step 4 β e Water permeability q Based on the interpolation calculation method.

[0030] Another technical solution adopted by the present invention is a method for calculating the parameters of a high-pressure water pressure test, and calculating the true permeability of the rock mass according to the test pressure calculated by the above-mentioned method for calculating the pressure of the high-pressure water pressure test. q ’ , the calculation formula is formula (5),

[0031] (5)

[0032] in P is the test pressure, i.e. the rock splitting pressure, is the flow rate corresponding to the splitting point.

[0033] The beneficial effects of the present invention are:

[0034] 1. The present invention introduces the external water pressure reduction coefficient into the calculation formula for calculating the additional water pressure, thereby determining a new, more reasonable and more accurate method for calculating the additional water pressure, the test pressure and related parameters. This new method can more accurately calculate the water pressure test parameters, and further accurately guide the engineering design and construction, thus avoiding the waste of engineering investment and engineering construction period caused by conservative design.

[0035] 2. The water permeability calculated by the method of the present invention is closer to the real water permeability of the rock mass, and the value is also smaller. In addition, the present invention calculates the high-pressure water pressure test pressure, i.e., the splitting pressure, which can more accurately reflect the splitting pressure of the real state of the rock mass and better exert the anti-splitting potential of the rock mass. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of measuring the stable water level of the borehole when it is above the water pressure test section of the present invention;

[0037] Figure 2 It is a schematic diagram of measuring the stable water level of the borehole of the present invention when it is within the range of the water pressure test section;

[0038] Figure 3 It is a schematic diagram of measuring the stable water level of the borehole of the present invention when it is below the water pressure test section;

[0039] Figure 4 It is drawn by Example 1 of the present invention P P -Qt Relationship graph;

[0040] Figure 5 It is drawn by Example 2 of the present invention P P -Qt Relationship graph;

[0041] Figure 6 It is drawn by Example 3 of the present invention P P -Qt Relationship graph;

[0042] Figure 7 It is drawn by Example 4 of the present invention P P -Qt Relationship graph;

[0043] Figure 8 It is drawn by Example 5 of the present invention P P -Qt Relationship graph;

[0044] Fig. 9 It is drawn by Example 6 of the present invention P P -Qt Relationship graph;

[0045] Fig.10 It is drawn by Example 7 of the present invention P P -Qt Relationship graph;

[0046] Fig.11 It is drawn by Example 8 of the present invention P P -Qt Relationship graph.

[0047] In the figure: Δh -The distance from the center of the pressure gauge to the ground; H-The distance from the ground to the upper part of the test section; L-The length of the water pressure test section; h w - Drill holes to stabilize water levels. DETAILED DESCRIPTION

[0048] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0049] The present invention discloses a method for measuring the pressure of a high-pressure water pressure test, which specifically comprises the following steps:

[0050] Step 1: Drill a hole on the ground at the location to be tested. The drilling location should be on the surface of the building to be built, and the drilling depth should be greater than the depth of the underground building floor. After the hole is drilled to the designed depth, flush the hole. After flushing, continue to observe the changes in the water level of the hole until it stabilizes, and measure the final stable water level of the hole. h w ;

[0051] Step 2: Select a representative test depth according to the location of the underground building and the conditions of the drill core, and lower the packer and the upper packer in sequence. The section between the lower packer and the upper packer is a water pressure test section, the length of which is recorded as L. Measure the height from the upper packer to the surface, recorded as H, where H represents the depth of the test section; install a surface pressure tester on the high-pressure water inlet pipe on the ground, and measure the height from the center of the surface pressure gauge to the ground, recorded as Δh ;

[0052] Step 3: Conduct a high-pressure water pressure test on the borehole and use an automatic data acquisition instrument to record the t Surface test pressure P P and its corresponding flow Q value, plot P P -Qt Relationship curve, according to which the surface test pressure corresponding to the splitting point of the rock mass where the water pressure test section is located is determined P P And its corresponding flow Q;

[0053] Step 4: Use the pressure and flow data collected in step 3 to calculate the permeability of the rock mass in the test section according to the method in the "Hydropower Engineering Borehole Water Pressure Test Code" (NB / T35113-2018) q According to the external water pressure reduction coefficient table in Appendix W of the Geological Survey Code for Water Conservancy and Hydropower Engineering (GB50487-2022), the water permeability q To calculate the reduction factor based on interpolation β e ;

[0054] Step 5: Determine H and h w Calculate the additional water pressure P z :

[0055] ① If the stable water level of the borehole is above the water pressure test section, that is h w <H, if Figure 1As shown, additional water pressure P z The calculation formula is formula (1):

[0056] (1),

[0057] In the formula, γ w is the weight of water, the value is 9.8 KN / m 3 ;

[0058] ② If the borehole stable water level is within the water pressure test section, that is, H < h w <H+L, such as Figure 2 As shown, additional water pressure P z The calculation formula is formula (2):

[0059] (2);

[0060] ③ If the borehole stable water level is in the water pressure test section, that is h w >H+L, such as Figure 3 As shown, additional water pressure P z The calculation formula is formula (3):

[0061] (3);

[0062] Step 6: Additional water pressure calculated according to step 5 The test pressure is calculated using formula (4): P , and based on the measured flow value Q and test section length L , use formula (5) to calculate the true permeability of the rock mass q ’ ;

[0063] (4),

[0064] (5),

[0065] in, P s The value is small and has little effect on the calculation results, so it is ignored in the present invention.

[0066] The underground powerhouse of a certain project is located in the deep rock mass below the ridge between the upper and lower reservoirs. The ridge ground elevation is about 1230m, the powerhouse top arch is buried at a depth of 570m, and the powerhouse floor is buried at a depth of about 630m. In order to study and evaluate the permeability characteristics and critical pressure of the underground powerhouse area and surrounding rock mass under high-pressure water conditions, a ZK202 test borehole with a depth of 650m was arranged on the surface of the underground powerhouse. The bottom of the hole was 20m below the powerhouse floor. According to the core conditions and the location of the powerhouse building, a total of 6 test sections were selected to carry out high-pressure water pressure tests: Section 1 575.5m~580.5m; Section 2 585.9m~590.9m; Section 3 601.2m~606.2m; Section 4 615.8m~620.8m; Section 5 622.1m~627.1m; Section 6 628.1m~633.1m. The length of the test section is 5.0m, the upper and lower ends are blocked by double plug method, the plug length is 1.0m, the test level difference is 1.0MPa, the rapid method is used to increase the pressure step by step, and the pressure stabilization time is 5min. The rated pressure of the high-pressure water pump is 12MPa, and the maximum flow rate is 100L / min.

[0067] Example 1

[0068] The present invention provides a method for calculating pressure and parameters of a high-pressure water pressure test, which specifically comprises the following steps:

[0069] Step 1: Arrange the borehole according to the engineering design plan, design the borehole depth to 650m, and carry out the drilling work. After the borehole is drilled to the designed depth, flush the borehole and continuously observe the changes in the borehole water level until it stabilizes, and measure the stable water level of the borehole. h w =86.0m;

[0070] Step 2: Select the first section to carry out the high-pressure water pressure test, and measure the test depth H = 575.5m, the test section length L = 5m, and the height from the center of the surface pressure gauge to the ground Δh =0;

[0071] Step 3: Conduct a high-pressure water pressure test. During the process of increasing the test pressure (measured pressure of the surface pressure gauge) from 1.0MPa to 6.0MPa, the flow rate increases from 6.28L / min to 7.46L / min. Use an automatic data acquisition instrument to record different surface test pressures. P P And the corresponding flow Q value, plot P P -Qt Relationship curve, such as Figure 4As shown in the figure, during the pressure increase process, the flow rate suddenly increases or the pressure suddenly decreases at a certain level of pressure. At this time, hydraulic fracturing occurs on the hole wall rock mass, the hole wall cracks change from a closed state to an open state, and the water flow state changes from laminar flow to turbulent flow. The corresponding pressure at this time is called the critical pressure of the rock mass, also known as the hydraulic fracturing pressure, which directly reflects the ability of the test section rock mass to bear the pressure head. It can be seen from the curve that when the pressure increases to 6.96MPa, the flow rate suddenly increases to 98.6L / min, and the rock mass undergoes splitting and destruction. Therefore, the surface test pressure corresponding to the splitting point is P P =6.96MPa, corresponding flow rate Q=7.46L / min;

[0072] Step 4: According to the "Regulations for Water Pressure Test of Hydropower Engineering Boreholes" (NB / T 35113-2018), P = P P + P z =6.96+0.86=7.82MPa, L=5.0m, Q=7.46L / min, substitute it into formula (5) to calculate the permeability q =0.191Lu; According to the external water pressure reduction coefficient table in Appendix W of the Geological Investigation Code for Water Conservancy and Hydropower Engineering (GB50487-2022), the water permeability q= 0.191Lu is the reduction factor obtained by interpolation. β e =0.110;

[0073] Step 5: Determine the test section depth H and stable water level h w relationship, choose P z Calculation formula: According to formula (1), we can get P z =5.24MPa, and the test pressure is calculated according to formula (4), that is, the splitting pressure P =6.96+5.24=12.20MPa;

[0074] Step 6: Set Q=7.46L / min, L=5.0m, P =12.20MPa Substitute into formula (5) to calculate the true permeability of the rock mass q ’ =0.122Lu.

[0075] Comparative Example 1

[0076] A method for measuring the pressure of a high-pressure water pressure test specifically comprises the following steps:

[0077] Step 1-3: Same as step 1-3 of Example 1;

[0078] Step 4: Calculate the additional water pressure according to the provisions of the "Regulations for Water Pressure Test of Hydropower Engineering Boreholes" (NB / T 35113-2018) P z =0.86MPa, according to formula (4), the test pressure P=6.96+0.86=7.82MPa, that is, the splitting pressure is 7.82MPa;

[0079] Step 5: Set Q=7.46L / min, L=5.0m, P =7.82MPa Substitute into formula (5) to calculate the true permeability of the rock mass q =0.191Lu.

[0080] Example 2

[0081] The present invention provides a method for calculating pressure and parameters of a high-pressure water pressure test, which specifically comprises the following steps:

[0082] Step 1: Same as step 1 in Example 1;

[0083] Step 2: Select the second section to carry out the high-pressure water pressure test, and measure the test depth H = 585.9m, the test section length L = 5m, and the height from the center of the surface pressure gauge to the ground Δh =0;

[0084] Step 3: Conduct a high-pressure water pressure test. During the test, the test pressure (measured pressure of the surface pressure sensor) is gradually increased from 1.0MPa to 5.0MPa, and the flow rate is increased from 6.49L / min to 7.53L / min. The different surface test pressures are recorded using an automatic data acquisition instrument. P P The corresponding flow Q value is plotted PP-Qt Relationship curve, such as Figure 5 As shown in the curve, when the pressure increases to 5.65MPa, the flow rate suddenly increases to 97.0L / min, and the rock mass undergoes splitting failure. Therefore, the surface test pressure corresponding to the splitting point is P P =5.65MPa, corresponding flow rate Q=7.53L / min;

[0085] Step 4: According to the "Regulations for Water Pressure Test of Hydropower Engineering Boreholes" (NB / T 35113-2018), P = P P + P z=5.65+0.86=6.51MPa, L=5.0m, Q=7.53L / min, substitute it into formula (5) to calculate the permeability q =0.231Lu; According to the external water pressure reduction coefficient table in Appendix W of the Geological Survey Code for Water Conservancy and Hydropower Engineering (GB50487-2022), the water permeability q= 0.231Lu is the reduction factor obtained by interpolation. β e =0.115;

[0086] Step 5: Determine the test section depth H and stable water level h w relationship, choose P z Calculation formula: According to formula (1), we can get P z =5.33MPa, and the splitting pressure is calculated according to formula (4) P =5.65+5.33=10.98MPa;

[0087] Step 6: Substitute P in step 5 into formula (5) to calculate the true permeability of the rock mass: q ’ =0.122Lu.

[0088] Comparative Example 2

[0089] A method for measuring the pressure of a high-pressure water pressure test specifically comprises the following steps:

[0090] Step 1-3: Same as step 1-3 of Example 2;

[0091] Step 4: Calculate the additional water pressure according to the provisions of the "Regulations for Water Pressure Test of Hydropower Engineering Boreholes" (NB / T 35113-2018) P z =0.86MPa, according to formula (4) the test pressure P =5.65+0.86=6.51MPa, that is, the splitting pressure is 6.51MPa;

[0092] Step 5: Replace the P Substitute into formula (5) to calculate the true permeability of the rock mass q =0.232Lu.

[0093] Example 3

[0094] The present invention provides a method for calculating pressure and parameters of a high-pressure water pressure test, which specifically comprises the following steps:

[0095] Step 1: Same as step 1 in Example 1;

[0096] Step 2: Select the third section to carry out the high-pressure water pressure test, and measure the test depth H = 601.2m, the test section length L = 5m, and the height from the center of the surface pressure sensor to the ground Δh =0;

[0097] Step 3: Carry out high-pressure water pressure test. During the process of increasing the test pressure (measured pressure of the surface pressure sensor) from 1.0MPa to 4.0MPa, the flow rate increases from 6.49L / min to 7.08L / min. Use the automatic data acquisition instrument to record different surface test pressures. P P The corresponding flow Q value is plotted PP-Qt Relationship curve, such as Figure 6 As shown in the curve, when the pressure increases to 4.67MPa, the flow rate suddenly increases to 96.7L / min, and the rock mass undergoes splitting failure. Therefore, the surface test pressure corresponding to the splitting point is P P =4.67MPa, corresponding flow rate Q=7.08L / min;

[0098] Step 4: According to the "Regulations for Water Pressure Test of Hydropower Engineering Boreholes" (NB / T 35113-2018), P = P P + P z =4.67+0.86=5.53MPa, L=5.0m, Q=7.08L / min, substitute it into formula (5) to calculate the permeability q =0.256Lu; According to the external water pressure reduction coefficient table in Appendix W of the Geological Investigation Code for Water Conservancy and Hydropower Engineering (GB50487-2022), the water permeability q =0.2561Lu is the reduction factor obtained by interpolation. β e =0.117;

[0099] Step 5: Determine the test section depth H and stable water level h w relationship, choose P z Calculation formula: According to formula (1), we can get P z =5.47MPa, and the splitting pressure is calculated according to formula (4) P =4.67+5.47=10.14MPa;

[0100] Step 6: Replace the P Substitute into formula (5) to calculate the true permeability of the rock mass q ’ =0.140Lu.

[0101] Comparative Example 3

[0102] A method for measuring the pressure of a high-pressure water pressure test specifically comprises the following steps:

[0103] Step 1-3: Same as step 1-3 of Example 3;

[0104] Step 4: Calculate the additional water pressure according to the provisions of the "Regulations for Water Pressure Test of Hydropower Engineering Boreholes" (NB / T 35113-2018) P z =0.86MPa, according to formula (4) the test pressure P =4.67+0.86=5.53MPa, that is, the splitting pressure is 5.53MPa;

[0105] Step 5: Replace the P Substitute into formula (5) to calculate the true permeability of the rock mass q =0.257Lu.

[0106] Example 4

[0107] The present invention provides a method for calculating pressure and parameters of a high-pressure water pressure test, which specifically comprises the following steps:

[0108] Step 1: Same as step 1 in Example 1;

[0109] Step 2: Select the 4th section to carry out the high-pressure water pressure test, and measure the test depth H = 615.8m, the test section length L = 5m, and the height from the center of the surface pressure gauge to the ground Δh =0;

[0110] Step 3: Carry out high-pressure water pressure test. During the process of increasing the test pressure (measured pressure of the surface pressure sensor) from 1.0MPa to 5.0MPa, the flow rate increases from 6.58L / min to 7.76L / min. Use the automatic data acquisition instrument to record different surface test pressures. P P The corresponding flow Q value is plotted PP-Qt Relationship curve, such as Figure 7 As shown in the curve, when the pressure increases to 5.56MPa, the flow rate suddenly increases to 96.7L / min, and the rock mass undergoes splitting failure. Therefore, the surface test pressure corresponding to the splitting point is P P =5.56MPa, corresponding flow rate Q=7.76L / min;

[0111] Step 4: According to the "Regulations for Water Pressure Test of Hydropower Engineering Boreholes" (NB / T 35113-2018), P = PP + P z =5.56+0.86=6.42MPa, L=5.0m, Q=7.76L / min, substitute it into formula (5) to calculate the permeability q =0.242Lu; According to the external water pressure reduction coefficient table in Appendix W of the Geological Survey Code for Water Conservancy and Hydropower Engineering (GB50487-2022), the water permeability q =0.242Lu is the reduction factor obtained by interpolation. β e =0.116;

[0112] Step 5: Determine the test section depth H and stable water level h w relationship, choose P z Calculation formula: According to formula (1), we can get P z =5.60MPa, and the splitting pressure is calculated according to formula (4) P =5.56+5.60=11.16MPa;

[0113] Step 6: Replace the P Substitute into formula (5) to calculate the true permeability of the rock mass q ’ =0.139Lu.

[0114] Comparative Example 4

[0115] A method for measuring the pressure of a high-pressure water pressure test specifically comprises the following steps:

[0116] Step 1-3: Same as step 1-3 of Example 4;

[0117] Step 4: Calculate the additional water pressure according to the provisions of the "Regulations for Water Pressure Test of Hydropower Engineering Boreholes" (NB / T 35113-2018) P z =0.86MPa, according to formula (4), the test pressure P=5.56+0.86=6.42MPa, that is, the splitting pressure is 6.42MPa;

[0118] Step 5: Replace the P Substitute into formula (5) to calculate the true permeability of the rock mass q =0.242Lu.

[0119] Example 5

[0120] The present invention provides a method for calculating pressure and parameters of a high-pressure water pressure test, which specifically comprises the following steps:

[0121] Step 1: Same as step 1 in Example 1;

[0122] Step 2: Select the 5th section to carry out the high-pressure water pressure test, and measure the test depth H = 622.1m, the test section length L = 5m, and the height from the center of the surface pressure gauge to the ground Δh =0;

[0123] Step 3: Carry out high-pressure water pressure test. During the process of increasing the test pressure (measured pressure of the surface pressure sensor) from 1.0MPa to 5.0MPa step by step, the flow rate increases from 6.47L / min to 7.85L / min. Use the automatic data acquisition instrument to record different surface test pressures. P P The corresponding flow Q value is plotted PP-Qt Relationship curve, such as Figure 8 As shown in the curve, when the pressure increases to 6.04MPa, the flow rate suddenly increases to 95.0L / min, and the rock mass undergoes splitting failure. Therefore, the surface test pressure corresponding to the splitting point is P P =6.04MPa, corresponding flow rate Q=7.85L / min;

[0124] Step 4: According to the "Regulations for Water Pressure Test of Hydropower Engineering Boreholes" (NB / T 35113-2018), P = P P + P z =6.04+0.86=6.90MPa, L=5.0m, Q=7.85L / min, substitute it into formula (5) to calculate the permeability q =0.228Lu; According to the external water pressure reduction coefficient table in Appendix W of the Geological Investigation Code for Water Conservancy and Hydropower Engineering (GB50487-2022), the water permeability q =0.228Lu is the reduction factor obtained by interpolation. β e =0.114;

[0125] Step 5: Determine the test section depth H and stable water level h w relationship, choose Pz Calculation formula: According to formula (1), we can get P z =5.65MPa, and the splitting pressure is calculated according to formula (4) P =6.04+5.65=11.69MPa;

[0126] Step 6: Replace the P Substitute into formula (5) to calculate the true permeability of the rock mass q’ =0.134Lu.

[0127] Comparative Example 5

[0128] A method for measuring the pressure of a high-pressure water pressure test specifically comprises the following steps:

[0129] Step 1-3: Same as step 1-3 of Example 5;

[0130] Step 4: Calculate the additional water pressure according to the provisions of the "Regulations for Water Pressure Test of Hydropower Engineering Boreholes" (NB / T 35113-2018) P z =0.86MPa, according to formula (4) the test pressure P =6.04+0.86=6.90MPa, that is, the splitting pressure is 6.90MPa;

[0131] Step 5: Replace the P Substitute into formula (5) to calculate the true permeability of the rock mass q =0.228Lu.

[0132] Example 6

[0133] The present invention provides a method for calculating pressure and parameters of a high-pressure water pressure test, which specifically comprises the following steps:

[0134] Step 1: Same as step 1 in Example 1;

[0135] Step 2: Select the 6th section to carry out the high-pressure water pressure test, and measure the test depth H = 628.1m, the test section length L = 5m, and the height from the center of the surface pressure gauge to the ground Δh =0;

[0136] Step 3: Carry out high-pressure water pressure test. During the process of increasing the test pressure (measured pressure of the surface pressure sensor) from 1.0MPa to 5.0MPa step by step, the flow rate increases from 6.24L / min to 6.93L / min. Use the automatic data acquisition instrument to record different surface test pressures. P P The corresponding flow Q value is plotted PP-Qt Relationship curve, such as Figure 7 As shown in the curve, when the pressure increases to 5.91MPa, the flow rate suddenly increases to 95.6L / min, and the rock mass undergoes splitting failure. Therefore, the surface test pressure corresponding to the splitting point is P P =5.91MPa, corresponding flow rate Q=6.93L / min;

[0137] Step 4: According to the "Regulations for Water Pressure Test of Hydropower Engineering Boreholes" (NB / T 35113-2018),P = P P +P z =5.91+0.86=6.77MPa, L=5.0m, Q=6.93L / min, substitute it into formula (5) to calculate the permeability q =0.205Lu; According to the external water pressure reduction coefficient table in Appendix W of the Geological Survey Code for Water Conservancy and Hydropower Engineering (GB50487-2022), the water permeability q =0.205Lu is the basis for interpolation to obtain the reduction factor β e =0.112;

[0138] Step 5: Determine the test section depth H and stable water level h w relationship, choose P z Calculation formula: According to formula (1), we can get P z =5.71MPa, and the splitting pressure is calculated according to formula (4) P =5.91+5.71=11.62MPa;

[0139] Step 6: Replace the P Substitute into formula (5) to calculate the true permeability of the rock mass q ’ =0.119Lu.

[0140] Comparative Example 6

[0141] The existing method for calculating the pressure and parameters of the high-pressure water pressure test specifically includes the following steps:

[0142] Step 1-3: Same as step 1-3 of Example 6;

[0143] Step 4: Calculate the additional water pressure according to the provisions of the "Regulations for Water Pressure Test of Hydropower Engineering Boreholes" (NB / T 35113-2018) P z =0.86MPa, according to formula (4) the test pressure P =5.91+0.86=6.77MPa, that is, the splitting pressure is 6.77MPa;

[0144] Step 5: Replace the P Substitute into formula (5) to calculate the true permeability of the rock mass q =0.205Lu.

[0145] The above comparative examples 1-6 are method 1, and the parameters of the 650m borehole high pressure water pressure test are calculated according to the additional water pressure provisions of the specification. Examples 1-6 are method 2, and the external water pressure reduction coefficient is considered for calculation according to the method of the present invention. The calculation results are shown in the following Tables 1 and 2:

[0146] Table 1 Calculation table of rock mass permeability using two methods

[0147]

[0148] As shown in Table 1, the water permeability calculated by method 1 is 0.19Lu~0.26Lu, and the water permeability calculated by method 2 is 0.12Lu~0.14Lu. Method 2 is 36.0%~41.8% lower than the former.

[0149] Table 2 Calculation table of rock splitting pressure using two methods

[0150]

[0151] As shown in Table 2, the splitting pressure calculated by method 1 is 5.52MPa~7.81MPa, with an average value of 6.65MPa; the splitting pressure calculated by method 2 is 10.14MPa~12.20MPa, with an average value of 11.30MPa. The latter can be increased by 56.2%~83.7% compared with method 1, and the average value is increased by 70%.

[0152] Example 7

[0153] The present invention provides a method for calculating pressure and parameters of a high-pressure water pressure test, which specifically comprises the following steps:

[0154] Step 1: Same as step 1 in Example 1;

[0155] Step 2: Select the test depth H=60.0m to carry out the high pressure water test. The test section length L is set to 5m. Measure the height from the center of the surface pressure gauge to the ground. Δh =0;

[0156] Step 3: Conduct high-pressure water pressure test and use automatic data acquisition instrument to record different surface test pressures and its corresponding flow Q value, plot P P -Qt Relationship curve, such as Fig.10 As shown, the surface test pressure corresponding to the splitting point is determined on the curve. P P =3.86MPa, corresponding to flow rate Q =5.38L / min;

[0157] Step 4: According to the "Regulations for Water Pressure Test of Hydropower Engineering Boreholes" (NB / T 35113-2018), P = P P +P z =3.86+0.625=4.485MPa, L=5.0m, Q=5.38L / min, substitute it into formula (5) to calculate the permeability q= 0.240Lu; According to the external water pressure reduction coefficient table in Appendix W of the Geological Survey Code for Water Conservancy and Hydropower Engineering (GB50487-2022), the water permeability q= 0.240Lu is the reduction factor obtained by interpolation. β e =0.116;

[0158] Step 5: Determine the test section depth H and stable water level h w relationship, choose P z Calculation formula: According to formula (3), we can get P z =0.625MPa, splitting pressure P =3.86+0.625=4.485MPa;

[0159] Step 6: Substitute Q = 5.38 L / min, L = 5.0 m, P = 4.485 MPa into formula (5) to calculate the true permeability of the rock mass. q ’ =0.240Lu.

[0160] Comparative Example 7

[0161] The existing method for calculating the pressure and parameters of the high-pressure water pressure test specifically includes the following steps:

[0162] Step 1: Same as step 1 in Example 7;

[0163] Step 2: Same as step 2 in Example 7;

[0164] Step 3: Calculate the additional water pressure according to the provisions of the "Hydropower Engineering Borehole Water Pressure Test Code" (NB / T 35113-2018) =0.625MPa, test pressure P=3.86+0.625=4.485MPa, that is, the splitting pressure is 4.485MPa;

[0165] Step 4: Based on the flow recorded by the data acquisition instrument, Q = 5.38 L / min, L = 5.0 m, P = 4.485 MPa, calculate the true permeability of the rock mass according to formula (5): q =0.240Lu.

[0166] Example 8

[0167] The present invention provides a method for calculating pressure and parameters of a high-pressure water pressure test, which specifically comprises the following steps:

[0168] Step 1: Same as step 1 in Example 1;

[0169] Step 2: Select the test depth H=82.0m to carry out the high-pressure water pressure test. The test section length L is set to 5m. Measure the height from the center of the surface pressure gauge to the ground. Δh =0;

[0170] Step 3: Conduct high-pressure water pressure test and use automatic data acquisition instrument to record different surface test pressures And the corresponding flow Q value, plot P P -Qt Relationship curve, such as Fig.11 As shown in the curve, it can be seen that the surface test pressure corresponding to the splitting point P P =3.97MPa, corresponding to flow rate Q =5.94L / min;

[0171] Step 4: According to the "Hydropower Engineering Borehole Water Pressure Test Code" (NB / T 35113-2018), P = P P +P =3.97+0.84=4.81MPa, L=5.0m, Q=5.94L / min, substitute it into formula (5) to calculate the permeability q= 0.247Lu; According to the external water pressure reduction coefficient table in Appendix W of the Geological Investigation Code for Water Conservancy and Hydropower Engineering (GB50487-2022), the water permeability q= 0.247Lu is the reduction factor obtained by interpolation. β e =0.116;

[0172] Step 5: Determine the test section depth H and stable water level h w relationship, choose Pz Calculation formula: According to formula (2), we can get P z =0.844MPa, and the splitting pressure is calculated according to formula (4) P =3.97+0.844=4.814MPa;

[0173] Step 6: Substitute Q = 5.94 L / min, L = 5.0 m, and P = 4.814 MPa into formula (5) to calculate the true permeability of the rock mass. q ’ =0.2468Lu.

[0174] Comparative Example 8

[0175] The existing method for calculating the pressure and parameters of the high-pressure water pressure test specifically includes the following steps:

[0176] Step 1-3: Same as step 1-3 of Example 8;

[0177] Step 4: Calculate the additional water pressure according to the provisions of the "Regulations for Water Pressure Test of Hydropower Engineering Boreholes" (NB / T 35113-2018) P z =0.84MPa, according to formula (4) the test pressure P =3.97+0.84=4.81MPa, that is, the splitting pressure is 4.81MPa;

[0178] Step 5: Set Q=5.94L / min, L=5.0m, P =4.81MPa Substitute into formula (5) to calculate the true permeability of rock mass q =0.2470Lu.

[0179] The splitting pressure value obtained by the reduction coefficient method of the present invention is much greater than that of the standard method, especially at the depth of the groundwater level. h w When the distance difference from the test section depth H is large, compared with the standard method, the reduction coefficient method can reflect the permeability and splitting pressure of the real state of the rock mass, and can better exert the potential of the rock mass to resist penetration damage, which is important for optimizing the design scheme and saving engineering costs.

Claims

1. A method for calculating the pressure of a high-pressure water pressure test, characterized in that: The following steps are involved: Step 1: Drill a hole at the location to be tested and measure the stable water level in the hole, recorded as h w ; Step 2: Lower the packer and the upper packer in the borehole in sequence. The section between the lower packer and the upper packer is the water pressure test section, and its length is recorded as L. The height from the upper packer to the surface is the test section depth, recorded as H. Install a surface pressure tester on the high-pressure water inlet pipe on the ground, and measure the height from the center of the surface pressure gauge to the ground, recorded as Δh ; Step 3: Conduct a high pressure water test on the borehole and record the time t Surface test pressure P P and its corresponding flow Q value, plot P P -Qt Relationship curve, according to which the surface test pressure corresponding to the splitting point of the rock mass where the water pressure test section is located is determined P P And its corresponding flow Q; Step 4: Calculate the surface test pressure corresponding to the splitting point in step 3 P and flow Q Calculate the permeability of the rock mass where the water pressure test section is located according to the method in the "Hydropower Engineering Borehole Water Pressure Test Code" NB / T 35113-2018 q According to the external water pressure reduction coefficient table in Appendix W of the "Regulations on Geological Survey for Water Conservancy and Hydropower Engineering" GB50487-2022, the water permeability q The reduction factor is calculated based on ; Step 5: Determine H and h w Calculate the additional water pressure , like h w <H, The calculation formula is formula (1): （1） If H< h w <H+L, The calculation formula is formula (2): （2） like h w >H+L, The calculation formula is formula (3): （3）； Step 6, according to , use formula (4) to calculate the test pressure P , （4）， in P s is the pipeline pressure loss.

2. The method for calculating the high pressure water pressure test pressure according to claim 1, characterized in that: The step 1 is to flush the borehole after the drilling is completed, and continuously observe the change of the borehole water level until the borehole water level is stable, and measure the stable borehole water level.

3. The method for calculating the high pressure water pressure test pressure according to claim 1, characterized in that: The surface pressure tester includes a surface pressure sensor or a surface pressure gauge.

4. The method for calculating the high pressure water test pressure according to claim 1, characterized in that: The test pressure difference of the high-pressure water pressure test in step 3 is 1.0 MPa.

5. The method for calculating the high pressure water test pressure according to claim 1, characterized in that: In step 3, an automatic data acquisition instrument is used to record different surface test pressures. P P And its corresponding flow Q value.

6. The method for calculating the high pressure water test pressure according to claim 1, characterized in that: The split point in step 3 is the corresponding point on the curve when the flow rate suddenly increases or the pressure suddenly decreases at a certain pressure level during the pressure increase process.

7. The method for calculating the high pressure water test pressure according to claim 1, characterized in that: The reduction factor of step 4 Water permeability q Based on the interpolation calculation method.

8. A method for calculating high pressure water pressure test parameters, characterized in that: Calculate the true water permeability of the rock mass by the test pressure calculated according to the method for calculating the high-pressure water pressure test pressure described in any one of claims 1 to 7 q ’ , the calculation formula is formula (5), （5） in P is the test pressure, i.e. the rock splitting pressure, is the flow rate corresponding to the splitting point.

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