A device and method for testing a reduction coefficient of external water pressure

Abstract

The application discloses a kind of outside water pressure reduction coefficient testing devices, it is related to engineering survey, geotechnical test field.It includes surface and water-bearing zone, and vertical borehole is arranged in the direction of inclination of water-bearing zone, and exploration flat hole is arranged below water-bearing zone;Water level observation tube is installed in vertical borehole, and water level observation tube bottom is inserted into water-bearing zone;Exploration flat hole is inserted into water-bearing zone by horizontal borehole, and one end of hollow steel pipe is located in horizontal borehole, and the other end is located in exploration flat hole, and hollow steel pipe in exploration flat hole is connected with pressure gauge.Combination of the present invention and existing exploration borehole and flat hole, according to water level, water pressure observation data and correlation of water-bearing zone at different depths in wet season and dry season to determine the outside water pressure reduction coefficient, the result obtained by the present application is accurate and reliable, and effectively solves the problem of how to determine the outside water pressure reduction coefficient of underground cavern.The application also relates to the testing method of the outside water pressure reduction coefficient testing device.

Description

Technical Field

[0001] This invention relates to the fields of engineering surveying and geotechnical testing, and more specifically, to a device for testing the external water pressure reduction factor. The invention also relates to a testing method for this water pressure reduction factor testing device. Background Technology

[0002] In the construction of tunnels and other underground engineering projects, groundwater is a major unavoidable adverse factor. The external water pressure caused by groundwater, especially the greater the burial depth of the tunnel, has a significant impact on the design of the underground tunnel support lining, construction, and operational safety. External water pressure is the product of the water column pressure in the underground tunnel and the external water pressure reduction factor. Therefore, determining the external water pressure reduction factor is the basic data for calculating external water pressure and is also a major task of engineering investigation.

[0003] Current technical standards do not specify a method for testing the external water pressure reduction factor. Currently, the engineering community considers two factors—the state of groundwater activity and the permeability of the aquifer—and sets the external water pressure reduction factor between 0 and 1. This method is essentially based on experience, and different engineers propose different external water pressure reduction factors based on their own understanding of geological conditions. This makes it impossible to accurately obtain the external water pressure, especially since the difference in external water pressure in deeply buried underground caverns is even greater, sometimes by orders of magnitude.

[0004] Therefore, it is essential to develop a device and method for testing the external water pressure reduction coefficient. Summary of the Invention

[0005] The primary objective of this invention is to overcome the shortcomings of the aforementioned background technology and to provide a device for testing the external water pressure reduction factor.

[0006] A second objective of this invention is to provide a testing method for this water pressure reduction factor testing device.

[0007] To achieve the aforementioned first objective, the technical solution of the present invention is as follows: an external water pressure reduction coefficient testing device, comprising a surface and an aquifer, characterized in that: a vertical borehole is provided in the inclined direction of the aquifer, and an exploration tunnel is provided below the aquifer; a water level observation pipe is installed in the vertical borehole, and the bottom of the water level observation pipe is inserted into the aquifer; the exploration tunnel is inserted into the aquifer through a horizontal borehole, with one end of a hollow steel pipe located in the horizontal borehole and the other end located in the exploration tunnel, and the hollow steel pipe located in the exploration tunnel is connected to a pressure gauge.

[0008] In the above technical solution, a vertical rubber plug is provided between the water level observation pipe and the vertical borehole. The vertical rubber plug is located above the water level observation pipe inserted into the water-bearing zone, and cement slurry is filled between the water level observation pipe above the vertical rubber plug and the vertical borehole.

[0009] In the above technical solution, there is a horizontal rubber plug between the horizontal drill hole and the hollow steel pipe.

[0010] In the above technical solution, the diameter of the vertical borehole is 75-150mm, the diameter of the exploration tunnel is 2-3m, and the diameter of the horizontal borehole is 40-60mm.

[0011] In the above technical solution, the diameter of the water level observation tube is 50mm, and the bottom of the water level observation tube is inserted into the water-bearing zone for 5m;

[0012] In the above technical solution, the diameter of the hollow steel pipe is 30mm.

[0013] To achieve the second objective mentioned above, the technical solution of the present invention is: a testing method for an external water pressure reduction coefficient testing device, characterized by comprising the following steps:

[0014] Step 1: Observe the spatial distribution of the aquifer on the surface, and arrange vertical boreholes in the vicinity of the aquifer's dip direction; install water level observation pipes in the vertical boreholes, with the bottom of the water level observation pipes inserted into the aquifer; use vertical rubber plugs and cement grout to seal the water level observation pipes and the vertical boreholes.

[0015] Step 2: Drill a horizontal borehole in the exploration tunnel below the aquifer. The horizontal borehole is drilled from the bottom of the exploration tunnel into the aquifer and inserted into the aquifer. One end of the hollow steel pipe is located in the horizontal borehole and the other end is located in the exploration tunnel. The hollow steel pipe located in the exploration tunnel is connected to a pressure gauge. There is a horizontal rubber plug between the horizontal borehole and the hollow steel pipe.

[0016] Step 3: Simultaneously observe the water level in the vertical borehole and the water pressure in the horizontal borehole inside the exploration tunnel to obtain the water column height H in the vertical borehole and the water head h in the horizontal borehole. The observation period shall be no less than one hydrological year.

[0017] The water column height H in the vertical borehole is the distance from the water level in the vertical borehole to the hollow steel pipe, in meters; the water head h in the horizontal borehole is converted from the pressure gauge reading P, i.e., h = P × 100, where h is in meters and P is in megapascals.

[0018] Step 4: Compile the data on the water column height H of the vertical borehole and the water head h of the horizontal borehole during the observation period, and plot the relationship between the water column height H of the vertical borehole and the water head h of the horizontal borehole and time t, namely the Ht curve and the ht curve, with the unit of time t being months;

[0019] Step 5: On the graph showing the relationship between the water column height H of the vertical borehole and the water head h of the horizontal borehole and time t, determine the water column height H1 of the vertical borehole during the wet season, the water column height H2 of the vertical borehole during the dry season, the water head h1 of the horizontal borehole during the wet season, and the water head h2 of the horizontal borehole during the dry season.

[0020] Step 6: Calculate the external water pressure reduction coefficient K1 during the wet season and K2 during the dry season. The maximum value of K1 and K2 is the external water pressure reduction coefficient K of the aquifer. The external water pressure reduction coefficient K1 during the wet season is equal to h1 / H1, and the external water pressure reduction coefficient K2 during the dry season is equal to h2 / H2. K = max(K1, K2).

[0021] In the above technical solution, in step 4, the horizontal axis of the graph showing the relationship between the water column height H of the vertical borehole and the water head h of the horizontal borehole and time t is time t, with the rightward direction being positive; the left vertical axis is the water column height H of the vertical borehole, with the upward direction being positive; and the right vertical axis is the water head h of the horizontal borehole, with the upward direction being positive.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] Compared with the prior art, the advantages of the present invention are as follows:

[0024] This invention combines existing exploratory boreholes and adits, and determines the external water pressure reduction coefficient based on water level and water pressure observation data and correlations at different depths of the aquifer during the wet and dry seasons. The results obtained by this invention are accurate and reliable, and effectively solve the problem of how to determine the external water pressure reduction coefficient of underground caverns, as verified by the monitoring results of external seepage pressure of underground cavern lining during the construction period. Attached Figure Description

[0025] Figure 1 This is a flowchart of the present invention.

[0026] Figure 2 This is a schematic diagram of the structure of the present invention.

[0027] Figure 3 This is a graph showing the relationship between the water column height in vertical boreholes and the water head in horizontal boreholes and time.

[0028] Among them, 1-surface, 2-aquifer, 3-vertical borehole, 31-water level observation pipe, 32-vertical rubber plug, 33-cement grout, 4-exploration tunnel, 5-horizontal borehole, 51-hollow steel pipe, 52-pressure gauge, 53-horizontal rubber plug. Detailed Implementation

[0029] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings, but these descriptions are not intended to limit the invention and are merely illustrative. The advantages of the present invention will become clearer and easier to understand through this description.

[0030] Referring to the attached drawings, an external water pressure reduction coefficient testing device includes a surface 1 and an aquifer 2. A vertical borehole 3 is provided in the inclined direction of the aquifer 2, and an exploration tunnel 4 is provided below the aquifer 2. A water level observation pipe 31 is installed in the vertical borehole 3, and the bottom of the water level observation pipe 31 is inserted into the aquifer 2. The exploration tunnel 4 is inserted into the aquifer 2 through a horizontal borehole 5. One end of a hollow steel pipe 51 is located in the horizontal borehole 5, and the other end is located in the exploration tunnel 4. The hollow steel pipe 51 located in the exploration tunnel 4 is connected to a pressure gauge 52.

[0031] A vertical rubber plug 32 is provided between the water level observation pipe 31 and the vertical borehole 3. The vertical rubber plug 32 is located above the part of the water level observation pipe 31 that is inserted into the water-bearing zone 2. Cement grout 33 is filled between the water level observation pipe 31 and the vertical borehole 3 located above the vertical rubber plug 32.

[0032] A horizontal rubber plug 53 is provided between the horizontal borehole 5 and the hollow steel pipe 51.

[0033] The vertical borehole 3 has a diameter of 75-150mm, the exploration tunnel 4 has a diameter of 2-3m, and the horizontal borehole 5 has a diameter of 40-60mm.

[0034] The water level observation tube 31 has a diameter of 50 mm, and the bottom of the water level observation tube 31 is inserted 5 m into the water-bearing zone 2.

[0035] The hollow steel pipe 51 has a diameter of 30mm.

[0036] A testing method for an external water pressure reduction factor testing device, characterized by comprising the following steps:

[0037] Step 1: Observe the spatial distribution of the aquifer 2 on the surface 1, and arrange the vertical borehole 3 in the vicinity of the dip direction of the aquifer 2; install the water level observation pipe 31 in the vertical borehole 3, with the bottom of the water level observation pipe 31 inserted into the aquifer 2; use a vertical rubber plug 32 and cement grout 33 to seal the water level observation pipe 31 and the vertical borehole 3.

[0038] Step 2: Drill a horizontal borehole 5 in the exploration tunnel 4 below the aquifer 2. The horizontal borehole 5 is drilled from the bottom of the exploration tunnel 4 into the aquifer 2 and inserted into the aquifer 2. One end of the hollow steel pipe 51 is located in the horizontal borehole 5 and the other end is located in the exploration tunnel 4. The hollow steel pipe 51 located in the exploration tunnel 4 is connected to the pressure gauge 52. There is a horizontal rubber plug 53 between the horizontal borehole 5 and the hollow steel pipe 51.

[0039] Step 3: Simultaneously observe the water level in the vertical borehole 3 and the water pressure in the horizontal borehole 5 inside the exploration tunnel 4 to obtain the water column height H in the vertical borehole 3 and the water head h in the horizontal borehole 5. The observation period shall be no less than one hydrological year.

[0040] The water column height H of the vertical borehole 3 is the distance from the water level 34 of the vertical borehole to the hollow steel pipe 51, in meters; the water head h of the horizontal borehole 5 is converted from the reading P of the pressure gauge 52, that is, h = P × 100, where h is in meters and P is in megapascals.

[0041] Step 4: Compile the data on the water column height H of vertical borehole 3 and the water head h of horizontal borehole 5 during the observation period, and plot the relationship between the water column height H of vertical borehole 3 and the water head h of horizontal borehole 5 and time t, namely the Ht curve and the ht curve, with the unit of time t being months;

[0042] Step 5: On the graph showing the relationship between the water column height H of the vertical borehole 3 and the water head h of the horizontal borehole 5 and time t, determine the water column height H1 of the vertical borehole 3 during the wet season, the water column height H2 of the vertical borehole 3 during the dry season, the water head h1 of the horizontal borehole 5 during the wet season, and the water head h2 of the horizontal borehole 5 during the dry season.

[0043] Step 6: Calculate the external water pressure reduction coefficient K1 during the wet season and K2 during the dry season. The maximum value of K1 and K2 is the external water pressure reduction coefficient K of the aquifer. The external water pressure reduction coefficient K1 during the wet season is equal to h1 / H1, and the external water pressure reduction coefficient K2 during the dry season is equal to h2 / H2. K = max(K1, K2).

[0044] In step 4, the graph showing the relationship between the water column height H of the vertical borehole 3 and the water head h of the horizontal borehole 5 and time t is as follows: the horizontal axis represents time t, with the positive direction to the right; the left vertical axis represents the water column height H of the vertical borehole 3, with the positive direction upward; and the right vertical axis represents the water head h of the horizontal borehole 5, with the positive direction upward.

[0045] Example

[0046] A test method for an external water pressure reduction factor testing device, as follows: Figure 1 As shown, where:

[0047] like Figure 2As shown, in step 1, the aquifer 2 is observed at the surface 1. The aquifer 2 is a fault with a thickness of about 10m, extending along the slope direction. The fault plane of the aquifer 2 dips inward. Vertical borehole 3 is arranged in the dip direction of the fault of the aquifer 2 (i.e., inward). The closest distance of vertical borehole 3 to the fault is about 200m. Vertical borehole 3 is an exploratory borehole carried out during the geological exploration of the underground cavern, with a borehole diameter of 91-150mm. After the completion of this exploratory borehole... Using it as a water level observation hole, a water level observation pipe 31 is installed in the vertical borehole 3. The water level observation pipe 31 has a diameter of 50 mm and its bottom is located 5 m inside the fault aquifer. To prevent surface water or groundwater from other aquifers from mixing into this aquifer, the water level observation pipe 31 and the vertical borehole 3 should be sealed with a vertical rubber plug 32 and cement grout 33. To prevent blockage inside the water level observation pipe 31, protective measures should be taken at the pipe opening of the water level observation pipe 31.

[0048] like Figure 2 As shown, in step 2, the exploration tunnel 4 is located about 380m below the aquifer 2. The exploration tunnel 4 is an exploration tunnel implemented during the geological exploration of the underground cavern, and is also used for water pressure observation of the aquifer. To facilitate mechanical slag removal and construction, the diameter of the exploration tunnel 4 is 3m. The horizontal borehole 5 is drilled from the bottom of the exploration tunnel 4 into the aquifer and should enter the aquifer 2 to a certain depth. The diameter of the horizontal borehole 5 is 60mm. In the horizontal borehole 5, a hollow steel pipe 51 with a horizontal rubber plug 53 at one end for water stop and a pressure gauge 52 at the other end is installed. The diameter of the hollow steel pipe 51 is 30mm.

[0049] like Figure 2 As shown, in step 3, the water level 34 in the vertical borehole and the water pressure in the horizontal borehole in the exploration tunnel 4 are observed simultaneously, with an observation period of one hydrological year, for example, from May 2021 to April 2022; the water column height H in the vertical borehole 3 is the distance from the water level 34 in the vertical borehole to the hollow steel pipe 51, in meters; the water head h in the horizontal borehole 5 is converted from the reading P of the pressure gauge 52, i.e., h = P × 100;

[0050] like Figure 3 As shown, in step 4, the data such as H and h for one hydrological year of observation are sorted out and the relationship between H and ht is plotted, that is, two curves, Ht and ht; the horizontal axis is time, the unit is month, and the rightward direction is positive; the vertical axis H is the height of the borehole water column, and the vertical axis h is the horizontal borehole water head, both in meters, and the upward direction is positive.

[0051] like Figure 3As shown in step 5, in the H-ht relationship diagram, the water column height of vertical borehole 3 is H1=336.7 meters during the wet season and H2=298.2 meters during the dry season. The water head of horizontal borehole 5 is h1=121 meters during the wet season and h2=95 meters during the dry season. The ht curve lags behind the Ht curve by 15 days, but the overall variation patterns of the two are basically the same.

[0052] In step 6, the external water pressure reduction coefficient during the wet season is K1 = h1 / H1 = 121 / 336.7 = 0.36, and the external water pressure reduction coefficient during the dry season is K2 = h2 / H2 = 95 / 298.2 = 0.32. The maximum value of K1 and K2 is taken as the external water pressure reduction coefficient K of the aquifer, that is, K = max(0.36, 0.32) = 0.36.

[0053] This invention relates to a device and method for testing the external water pressure reduction coefficient. It has been successfully applied in the geological survey of the Zhala Hydropower Station on the Yuqu River in Tibet Autonomous Region and the Fangxian Pumped Storage Hydropower Station in Hubei Province. The results of the external seepage pressure monitoring of the underground cavern lining during the construction period have verified that the results obtained by this invention are accurate and reliable, and effectively solve the problem of how to determine the external water pressure reduction coefficient of underground caverns.

[0054] All other unspecified parts belong to the prior art.

Claims

1. A testing method for an external water pressure reduction coefficient testing device, characterized in that: The external water pressure reduction coefficient testing device includes a surface (1) and an aquifer (2). A vertical borehole (3) is provided in the dip direction of the aquifer (2), and an exploration tunnel (4) is provided below the aquifer (2). A water level observation pipe (31) is installed in the vertical borehole (3), and the bottom of the water level observation pipe (31) is inserted into the aquifer (2). The exploration tunnel (4) is inserted into the aquifer (2) through a horizontal borehole (5). One end of a hollow steel pipe (51) is located in the horizontal borehole (5), and the other end is located in the exploration tunnel (4). The hollow steel pipe (51) located in the exploration tunnel (4) is connected to a pressure gauge (52). A vertical rubber plug (32) is provided between the water level observation pipe (31) and the vertical borehole (3). The vertical rubber plug (32) is located above the part of the water level observation pipe (31) inserted into the water-bearing zone (2). Cement grout (33) is filled between the water level observation pipe (31) above the vertical rubber plug (32) and the vertical borehole (3). The method includes the following steps: Step 1: Observe the spatial distribution of the aquifer (2) on the surface (1), and arrange the vertical borehole (3) in the vicinity of the dip direction of the aquifer (2); install the water level observation pipe (31) in the vertical borehole (3), and insert the bottom of the water level observation pipe (31) into the aquifer (2); use a vertical rubber plug (32) to stop water and cement grout (33) to seal the water level observation pipe (31) and the vertical borehole (3); Step 2: Drill a horizontal borehole (5) in the exploration tunnel (4) below the aquifer (2). The horizontal borehole (5) is drilled from the bottom of the exploration tunnel (4) into the aquifer (2) and inserted into the aquifer (2). One end of the hollow steel pipe (51) is located in the horizontal borehole (5) and the other end is located in the exploration tunnel (4). The hollow steel pipe (51) located in the exploration tunnel (4) is connected to the pressure gauge (52). There is a horizontal rubber plug (53) between the horizontal borehole (5) and the hollow steel pipe (51). Step 3: Simultaneously observe the water level of the vertical borehole (3) and the water pressure of the horizontal borehole (5) in the exploration tunnel (4) to obtain the water column height H of the vertical borehole (3) and the water head h of the horizontal borehole (5). The observation period shall be no less than one hydrological year. The water column height H of the vertical borehole (3) is the distance from the water level (34) of the vertical borehole to the hollow steel pipe (51), in meters; the water head h of the horizontal borehole (5) is converted from the pressure gauge (52) reading P, that is, h=P×100, h is in meters, and P is in megapascals. Step 4: Compile the data of water column height H of vertical borehole (3) and water head h of horizontal borehole (5) during the observation period, and draw the relationship between water column height H of vertical borehole (3) and water head h of horizontal borehole (5) and time t, namely the Ht curve and the ht curve, where the unit of time t is months; Step 5: On the graph showing the relationship between the water column height H of the vertical borehole (3) and the water head h of the horizontal borehole (5) and time t, determine the water column height H1 of the vertical borehole (3) during the wet season, the water column height H2 of the vertical borehole (3) during the dry season, the water head h1 of the horizontal borehole (5) during the wet season, and the water head h2 of the horizontal borehole (5) during the dry season. Step 6: Calculate the external water pressure reduction coefficient K1 during the wet season and K2 during the dry season. The maximum value of K1 and K2 is the external water pressure reduction coefficient K of the aquifer. The external water pressure reduction coefficient K1 during the wet season is equal to h1 / H1, and the external water pressure reduction coefficient K2 during the dry season is equal to h2 / H2. K = max(K1, K2).

2. The testing method of the external water pressure reduction coefficient testing device according to claim 1, characterized in that: A horizontal rubber plug (53) is provided between the horizontal borehole (5) and the hollow steel pipe (51).

3. The testing method of the external water pressure reduction coefficient testing device according to claim 2, characterized in that: The diameter of the vertical borehole (3) is 75-150mm, the diameter of the exploration tunnel (4) is 2-3m, and the diameter of the horizontal borehole (5) is 40-60mm.

4. The testing method of the external water pressure reduction coefficient testing device according to claim 3, characterized in that: The water level observation tube (31) has a diameter of 50 mm, and the bottom of the water level observation tube (31) is inserted 5 m into the water-bearing zone (2).

5. The testing method of the external water pressure reduction coefficient testing device according to claim 4, characterized in that: The hollow steel pipe (51) has a diameter of 30 mm.

6. The testing method of the external water pressure reduction coefficient testing device according to claim 5, characterized in that, In step 4, the horizontal axis of the graph showing the relationship between the water column height H of the vertical borehole (3) and the water head h of the horizontal borehole (5) and time t is time t, with the rightward direction being positive; the left vertical axis is the water column height H of the vertical borehole (3), with the upward direction being positive. The right vertical axis h represents the water head h of the horizontal borehole (5), with upward being the positive direction.

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