A test device and test method for conditions of seepage damage of clay dam slope with variable water level

Abstract

The invention discloses a variable water level clay dam slope seepage damage occurrence condition test device and test method. The device comprises a water storage tank, a water pump, a pressure regulating water tank and a test box. The test box is divided into a closed water storage chamber and an observation chamber at the tail by a partition. The top of the observation chamber is flush with the top of the water storage chamber, and the bottom of the observation chamber is higher than the bottom of the water storage chamber. The water inlet of the water storage chamber is connected with the water outlet of the pressure regulating water tank through a pipeline, and water is supplied and the water pressure is adjusted by the pressure regulating water tank, and the height of the pressure regulating water tank is adjustable. The bottom of the water storage chamber is filled with a sand layer according to a set slope and thickness, a clay covering layer is laid on the top of the sand layer, and osmometer sensors are buried at different positions of the sand layer and the clay covering layer respectively. A sand gushing outlet and a plurality of drainage holes are arranged at the bottom of the observation chamber for observing and judging the seepage damage occurrence condition. The sand gushing outlet and the drainage holes are connected with the sand layer filled in the water storage chamber.

Description

Technical Field

[0001] The invention belongs to the technical field of water conservancy engineering, and in particular relates to a test device and a test method for conditions of seepage damage of a variable water level clay dam slope. Background Art

[0002] Seepage damage is the main factor of seepage instability in clay impermeable bodies (such as clay blankets and clay inclined walls of earth-rock dams). When the clay impermeable body produces a seepage gradient that exceeds its seepage stability due to a large water head, it often produces seepage damage forms such as piping and contact scouring. Therefore, the allowable seepage gradient of the clay impermeable body is the main control indicator. The seepage gradient of the clay impermeable body under fixed head conditions is easy to obtain, but with global climate change, drought and flood disasters are becoming more and more frequent, and water level changes are becoming more and more complex. For example, under the condition of a sudden change from drought to flood, the water level of the clay impermeable body upstream of the earth-rock dam is in a rapid change, and the clay impermeable body is in an unstable seepage state, which will produce a large seepage gradient at the inclined wall or blanket. At the same time, the shrinkage cracks caused by the previous drought on the clay body may also deteriorate the clay impermeability performance. The cracks may produce hydraulic fracturing under the action of high water levels, further increasing the seepage gradient value and the possibility of seepage damage. The defects such as changing water levels and previous cracks have an adverse effect on the seepage damage of the clay impermeable body, bringing greater challenges to the safe operation of the project.

[0003] Conventional test equipment is limited by test conditions and cannot simulate influencing conditions such as changing water head and previous cracks, and cannot observe and measure the seepage gradient of clay impermeable bodies under changing environments. Summary of the invention

[0004] Objective: To overcome the deficiencies in the prior art, the present invention provides a variable water level clay dam slope seepage damage condition test device and test method.

[0005] Technical solution: To solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A variable water level clay dam slope seepage damage occurrence condition test device comprises a water storage tank, a water pump, a pressure regulating water tank and a test box, wherein the test box is divided into a closed water storage chamber and an observation chamber at the tail by a partition; the top of the observation chamber is flush with the top of the water storage chamber, and the bottom of the observation chamber is higher than the bottom of the water storage chamber;

[0007] One end of the water pump is connected to the water tank through a pipeline, and the other end is connected to the pressure regulating water tank. A valve ball is provided inside the pressure regulating water tank, and the height of the valve ball is adjustable; the water inlet of the water storage chamber is connected to the water outlet of the pressure regulating water tank through a pipeline, and water is supplied and the water pressure is adjusted by the pressure regulating water tank, and the height of the pressure regulating water tank is adjustable; the opening and closing of the water pump is controlled by the valve ball in the pressure regulating water tank, and the pressure regulating water tank and the valve ball cooperate to accurately control the water head height in the water storage chamber over a large range;

[0008] The bottom of the water storage chamber is filled with a sand layer; the sand layer at the front of the test box is laid horizontally, and then laid upward at a certain slope toward the tail until it reaches the top of the water storage chamber, a clay covering layer is laid on the top of the sand layer, and osmometer sensors are buried at different positions of the sand layer and the clay covering layer;

[0009] The bottom of the observation chamber is provided with a sand gushing outlet and a plurality of drainage holes for observing and judging the conditions under which seepage damage occurs; the sand gushing outlet and the drainage holes are connected to the sand layer filled in the water storage chamber.

[0010] In some embodiments, the observation chamber is provided with a water-sand discharge pipe; after the gushing sand and water coming out of the sand gushing outlet and the drainage hole enter the observation chamber, they are led out through the water-sand discharge pipe.

[0011] Furthermore, a funnel for collecting gushing sand and water is provided below the outlet of the water-sand discharge pipe; a filtering device is provided in the funnel, and the water filtered out of the funnel is weighed by a balance to record the gushing water volume.

[0012] In some embodiments, the water storage chamber is sealed and has an exhaust hole at the top;

[0013] In some embodiments, the upper end of the observation chamber is open. Furthermore, a cover plate is provided.

[0014] The variable water level clay dam slope seepage damage occurrence condition test device, the pressure regulating water tank is installed on the telescopic frame, can adjust the water head size, and simulate the seepage damage occurrence condition under the action of variable water head.

[0015] In some embodiments, during the variable water level clay impermeable body seepage damage occurrence condition test, the location and process of the clay impermeable body seepage damage occurrence can be analyzed by taking photos and performing digital image processing calculations.

[0016] In some embodiments, the particle gradation and initial moisture content of the sand in the sand layer are the same as the particle gradation and initial moisture content of the original sand;

[0017] In some embodiments, the test box is made of a transparent material, and further, is made of transparent organic glass.

[0018] In a second aspect, a test method for conditions for occurrence of seepage damage of a variable water level clay impermeable body is also provided, comprising:

[0019] 1) A sand layer is laid on the bottom layer of the water storage chamber, and a piezometer sensor is buried in the sand layer. After the sand layer is compacted, the piezometer sensors are arranged at intervals on the surface along the axial direction, and then a clay covering layer is laid on the surface;

[0020] 2) Set the height of the pressure regulating water tank and the valve ball, turn on the water pump to pump water from the water tank into the pressure regulating water tank, and the water flows into the water storage chamber through the pipe;

[0021] 3) Select a smaller water head at the initial height. After the test water is passed, observe the seepage water volume and sand flow at the sand gushing outlet and drainage hole. If the water level is kept constant for a period of time without obvious changes, increase the water level by 10 cm and continue to observe. If sand gushing or the seepage water volume increases significantly at a certain constant water level, it is judged that the seepage damage has occurred. Keep the water level constant and record the water head data. The sand and water enter the observation room through the sand gushing outlet and drainage hole and then settle. The water in the sand is filtered out and discharged from the water and sand discharge pipe. The gushing water is collected by filtering through a funnel, and the gushing water volume in each time period is recorded by a measuring cup or a balance at the same time.

[0022] 4) The above is a conventional seepage damage verification test. This device can also simulate the changing water head. For example, under the condition of stable seepage, the water head is quickly increased by the telescopic frame under the pressure regulating water tank to simulate the conditions of seepage damage of the clay cover layer under the condition of unstable seepage under the condition of sudden water level rise; the speed of water level change can be achieved by adjusting the telescopic frame, such as setting different water level rise speeds such as 10cm / min and 20cm / min, to observe the influence of water level rise speed on the seepage damage of the clay layer, and compare and analyze it with the stable water head condition.

[0023] 5) By presetting crack defects on the clay cover layer, the conditions for hydraulic fracturing seepage damage caused by the coupling of cracks and seepage can be simulated at the same time. Cracks of different shapes can be set on the dam slope and blanket in different parts of the clay layer to observe the impact of cracks on the occurrence of seepage damage; tests can also be conducted with a combination of cracks and variable head factors to better simulate the actual complex operating environment of the project.

[0024] Beneficial effects: The variable water level clay dam slope seepage damage occurrence condition test device and test method provided by the present invention simulate the influence conditions such as changing water head and previous cracks, and observe and measure the seepage slope drop of the clay anti-seepage body under the changing environment. The present invention creatively designs a variable water level clay dam slope seepage damage occurrence condition test device, uses a piezometer sensor to observe the temporal and spatial distribution of the seepage field in the soil body, and can intuitively observe and analyze the changes in the external image of the soil body, simulate the entire process of dam pipe burst damage, and judge the conditions for seepage damage, so as to provide technical support for the safe operation, emergency prevention and decision-making of dams under high water levels.

[0025] The present invention can be used for indoor model tests on dam piping failure. By simulating dam piping failure under different water levels, the temporal and spatial evolution of pore water pressure and the dam deformation and failure process can be analyzed, providing convenient conditions for accurately analyzing dam piping deformation and failure. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a structural schematic diagram of a test device for conditions of seepage damage of clay dam slope with variable water level in an embodiment;

[0027] In the figure: water storage tank 1, water pump 2, valve ball 3, pressure regulating water tank 4, exhaust hole 5, water storage chamber 6, sand layer 7, clay cover layer 8, sand outlet 9, water and sand discharge pipe 10, drainage hole 11, piezometer sensor 12, funnel 13, balance 14. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps set forth in these embodiments do not limit the scope of the present invention. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, methods and equipment known to those of ordinary skill in the relevant field may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be regarded as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may also include different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so that once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0030] Embodiment 1

[0031] A variable water level clay dam slope seepage damage occurrence condition test device, the device comprises a test box, the tail of the test box is divided into a closed water storage chamber 6 and a pipe surge observation chamber at the tail by a partition, the top of the observation chamber is flush with the top of the water storage chamber 6, and the bottom of the observation chamber is higher than the bottom of the water storage chamber 6; the partition is an L-shaped plate;

[0032] One end of the water pump 2 is connected to the water tank 1 through a pipeline, and the other end is connected to the pressure regulating water tank 4. A valve ball 3 is provided inside the pressure regulating water tank 4, and the height of the valve ball 3 is adjustable; the water inlet of the water storage chamber 6 is connected to the water outlet of the pressure regulating water tank 4 through a pipeline, and water is supplied and the water pressure is adjusted by the pressure regulating water tank 4, and the height of the pressure regulating water tank 4 is adjustable; the opening and closing of the water pump 2 is controlled by the valve ball 3 in the pressure regulating water tank 4, and the pressure regulating water tank 4 and the valve ball 3 cooperate to accurately control the water head height in the water storage chamber 6 over a large range;

[0033] The water storage chamber 6 is filled with a sand layer 7 with a certain slope and thickness as required. In some embodiments, Figure 1 As shown, the sand layer 7 at the front of the test box is laid horizontally, and then laid upward at a certain slope toward the rear until it is filled to the top of the water storage chamber 6, and then a clay cover layer 8 is laid on the top of the sand layer 7. Several rows of piezometer sensors 12 are arranged at different positions along the length direction of the test box inside the sand layer 7 and the clay cover layer 8;

[0034] The bottom of the observation chamber is provided with a sand gushing outlet 9 and a plurality of drainage holes 11 for observing and judging the conditions under which seepage damage occurs; the sand gushing outlet 9 and the drainage holes 11 are connected to the sand layer 7 filled in the water storage chamber 6 .

[0035] The observation room is provided with a water-sand discharge pipe 10; after the gushing sand and water coming out of the gushing sand outlet 9 and the drainage hole 11 enter the observation room, they are led out through the water-sand discharge pipe 10. Furthermore, a funnel 13 for collecting the gushing sand and water is provided below the outlet of the water-sand discharge pipe 10; a filtering device is provided in the funnel 13, and the water filtered out of the funnel 13 is weighed by a balance 14 to record the gushing water volume.

[0036] Furthermore, in some embodiments, the water storage chamber 6 is sealed, and a vent hole 5 is provided at the top; the top of the observation chamber is open.

[0037] The opening and closing of the water pump 2 is controlled by the valve ball 3 in the pressure regulating water tank 4. The pressure regulating water tank 4 is placed on a telescopic frame, and can adjust the water head size in a wide range to simulate the conditions for the occurrence of penetration damage under the action of the changing water head.

[0038] The water storage chamber 6 is filled with water and is supplied with water and the water pressure is adjusted through the pressure regulating water tank 4, and the height of the pressure regulating water tank 4 is adjustable; a valve ball 3 is arranged inside the pressure regulating water tank 4, and the height of the valve ball 3 is adjustable. The pressure regulating water tank 4 cooperates with the valve ball 3 to accurately control the water level height.

[0039] The present invention determines the conditions for the occurrence of seepage damage by the change of seepage pressure and the amount of water gushing from the sand gushing outlet 9 and the drainage hole 11; in addition to being able to adjust the water head and simulate the conditions for the occurrence of seepage damage under the condition of changing water head, it is also possible to preset defects such as cracks on the clay impermeable body and simulate the hydraulic splitting conditions of the coupling of cracks and seepage.

[0040] More preferably, the test box is made of transparent material; the water storage chamber 6 is a closed structure, and an exhaust hole 5 is opened at the top of the water storage chamber 6. The water storage chamber 6 is closed and connected to the pressure regulating water tank 4 through a water pipe, and the simulated water head is based on the water head of the pressure regulating water tank 4. The pressure regulating water tank 4 can adjust the height to simulate the required water level, and the internal ball valve controls the water level in the pressure regulating water tank 4 to be constant.

[0041] The particle size distribution and initial moisture content of the sand in the sand layer 7 are the same as those of the original sand;

[0042] The sand layer 7 at the tail is connected to the sand gushing outlet 9, and a piezometer sensor 12 is buried along the pipe gushing development channel to automatically measure the seepage pressure changes at different positions of the sand layer and the clay cover layer 8 in real time.

[0043] In some embodiments, colored glass beads may be buried in the sand layer 7 and the clay cover layer 8 .

[0044] During the test of the conditions for the occurrence of seepage damage of the variable water level clay impermeable body, the location and process of the seepage damage of the clay impermeable body can be analyzed by digital image processing and calculation by taking pictures.

[0045] Embodiment 2

[0046] This embodiment is a test method for the variable water level clay dam slope seepage failure occurrence condition test device in embodiment 1, comprising the following steps:

[0047] 1) A sand layer 7 is laid on the bottom layer of the water storage chamber 6, and a piezometer sensor 12 is buried in the sand layer 7. After the sand layer 7 is compacted, the piezometer sensors 12 are arranged at intervals on the surface along the axial direction, and then a clay covering layer 8 is laid on the surface. At the same time, colored glass beads can also be buried in the sand layer 7.

[0048] 2) Set the height of the pressure regulating water tank 4 and the valve ball 3, turn on the water pump 2 to pump water from the water tank 1 into the pressure regulating water tank 4, and the water flows through the pipe into the water storage chamber 6 for testing.

[0049] 3) Select a smaller water head at the initial height. After the test water is passed, observe the seepage water volume and sand flow at the sand gushing outlet 9 and the drainage hole 11. If the water level is kept constant for a period of time without obvious changes, increase the water level by 10 cm and continue to observe. If sand gushing or the seepage water volume increases significantly at a certain constant water level, it is judged that the seepage damage has occurred. Keep the water level constant and record the water head data. The sand and water enter the observation room through the sand gushing outlet 9 and the drainage hole 11 and then settle. The water in the sand is filtered out and discharged from the water and sand discharge pipe 10. The gushing water is filtered and collected through the funnel 13, and at the same time, the amount of water is collected through the volume The above is a conventional seepage damage verification test. The device can also simulate the change of water head. For example, under the condition of stable seepage, the water head is quickly increased by the telescopic frame under the pressure regulating water tank 4 to simulate the conditions of seepage damage caused by the clay cover layer 8 under the condition of unstable seepage under the condition of sudden water level rise; the speed of water level change can be achieved by adjusting the telescopic frame, such as setting different water level rise speeds such as 10cm / min and 20cm / min, observing the influence of water level rise speed on the seepage damage of the clay layer, and comparing and analyzing it with the stable water head condition.

[0050] 5) By presetting crack defects on the clay cover layer 8, the conditions for hydraulic fracturing seepage damage caused by the coupling of cracks and seepage can be simulated at the same time. Cracks of different shapes can be set on the dam slope and blanket at different parts of the clay layer to observe the impact of cracks on the occurrence of seepage damage; in addition, the device can also conduct tests on multiple factors such as cracks and variable water heads to better simulate the actual complex operating environment of the project.

[0051] The present invention provides a variable water level clay dam slope seepage damage condition test device and test method. When piping occurs, sand particles in the original stable sand layer are displaced. Traditional piping test research mainly focuses on the observation of the critical water head of piping and the overall deformation during piping, but rarely involves quantitative observation of the degree of deformation at the piping location and measurement of the amount of sand inrush combined with the deformation. The present invention creatively designs a variable water level clay dam slope seepage damage condition test device, uses a piezometer sensor to observe the spatiotemporal distribution of the seepage field in the soil, and can intuitively observe and analyze the changes in the external appearance of the soil, simulating the entire process of dam piping damage, and providing technical support for the safe operation, emergency prevention and decision-making of dams under high water levels.

[0052] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the protection content of the present invention.

[0053] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A variable water level clay dam slope seepage damage occurrence condition test device, characterized in that: It comprises a water storage tank (1), a water pump (2), a pressure regulating water tank (4) and a test box, wherein the test box is divided into a sealed water storage chamber (6) and an observation chamber at the rear by a partition; the top of the observation chamber is flush with the top of the water storage chamber (6), and the bottom of the observation chamber is higher than the bottom of the water storage chamber (6); One end of the water pump (2) is connected to the water storage tank (1) through a pipeline, and the other end is connected to the pressure regulating water tank (4). A valve ball (3) is provided inside the pressure regulating water tank (4), and the height of the valve ball (3) is adjustable; the water inlet of the water storage chamber (6) is connected to the water outlet of the pressure regulating water tank (4) through a pipeline, and water is supplied and the water pressure is adjusted through the pressure regulating water tank (4), and the height of the pressure regulating water tank (4) is adjustable; the opening and closing of the water pump (2) is controlled by the valve ball (3) in the pressure regulating water tank (4), and the pressure regulating water tank (4) cooperates with the valve ball (3) to control the water head height in the water storage chamber (6); the pressure regulating water tank (4) is installed on a telescopic frame, and can adjust the water head size to simulate the conditions for the occurrence of penetration damage under the action of a changing water head; The bottom of the water storage chamber (6) is filled with a sand layer (7); the sand layer (7) at the front of the test box is laid horizontally, and then laid upward at a certain slope towards the rear until it reaches the top of the water storage chamber (6); a clay cover layer (8) is laid on the top of the sand layer (7), and osmometer sensors (12) are buried at different positions of the sand layer (7) and the clay cover layer (8); the osmometer sensors (12) are buried in the sand layer (7), and after the sand layer (7) is compacted, the osmometer sensors (12) are arranged at intervals on the surface along the axial direction, and then the clay cover layer (8) is laid on the surface; The bottom of the observation chamber is provided with a sand gushing outlet (9) and a plurality of drainage holes (11) for observing and judging the conditions under which seepage damage occurs; the sand gushing outlet (9) and the drainage holes (11) are connected to the sand layer (7) filled in the water storage chamber (6); the observation chamber is provided with a water-sand discharge pipe (10); the sand and water gushing out through the sand gushing outlet (9) and the drainage holes (11) enter the observation chamber and are then led out through the water-sand discharge pipe (10); a funnel (13) for collecting the gushing sand and water is provided below the outlet of the water-sand discharge pipe (10); a filtering device is provided in the funnel (13), and the water filtered out by the funnel (13) is weighed by a balance (14) to record the amount of water gushing; During the test of the conditions for the occurrence of seepage damage of variable water level clay impermeable body, the location and process of the seepage damage of clay impermeable body were analyzed by taking photos and performing digital image processing calculations.

2. The variable water level clay dam slope seepage damage occurrence condition test device according to claim 1, characterized in that: The water storage chamber (6) is airtight and has an exhaust hole (5) at the top.

3. The variable water level clay dam slope seepage damage occurrence condition test device according to claim 1, characterized in that: The upper end of the observation chamber is open.

4. The variable water level clay dam slope seepage damage occurrence condition test device according to claim 1, characterized in that: The particle size distribution and initial moisture content of the sand in the sand layer (7) are the same as those of the original sand.

5. The variable water level clay dam slope seepage damage occurrence condition test device according to claim 1, characterized in that: The test box is made of transparent material.

6. A test method for the occurrence conditions of seepage damage of variable water level clay impermeable body, characterized in that: Based on the variable water level clay dam slope seepage failure occurrence condition test device according to any one of claims 1 to 5, the method comprises: 1) laying a sand layer (7) on the bottom layer of the water storage chamber (6), burying a piezometer sensor (12) in the sand layer (7), arranging the piezometer sensors (12) at intervals on the surface along the axial direction after compacting the sand layer (7), and then laying a clay cover layer (8) on the surface; 2) Setting the height of the pressure regulating water tank (4) and the valve ball (3), turning on the water pump (2) to pump water from the water storage tank (1) into the pressure regulating water tank (4), and the water flows into the water storage chamber (6) through the pipe; 3) A relatively small water head is selected at the initial height. After the test water is passed, the seepage water volume and sand flow at the sand gushing outlet (9) and the drainage hole (11) are observed. If the water level is kept constant for a period of time without significant changes, the water level is increased by 10 cm and the observation is continued. If sand gushing or the seepage water volume increases significantly at a certain constant water level, it is determined that infiltration damage has occurred. The water level is kept constant and the water head data is recorded. The sand and water enter the observation room through the sand gushing outlet (9) and the drainage hole (11) and then settle. The water in the sand is filtered out and discharged from the water and sand discharge pipe (10). The gushing water is filtered and collected through the funnel (13), and the gushing water volume in each time period is recorded using a measuring cup or a balance. 4) Rapidly increase the water head by using the telescopic frame under the pressure regulating water tank (4) to simulate the conditions under which the clay cover layer (8) is subjected to unstable seepage under the condition of sudden water level rise; adjust the telescopic frame to achieve the speed of water level change, set different water level rise speeds, observe the effect of the water level rise speed on the seepage damage of the clay cover layer (8), and compare and analyze it with the stable water head condition; 5) By presetting crack defects on the clay cover layer (8), the conditions for hydraulic fracturing and seepage damage caused by the coupling of cracks and seepage are simulated; cracks of different shapes are set at different parts of the clay layer to observe the effect of cracks on the occurrence of seepage damage; and tests are conducted by combining multiple factors such as cracks and variable water head to better simulate the actual complex operating environment of the project.

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