CN114241876B - Experimental method of karst collapse experimental device containing dominant channels based on upper cover layer - Google Patents
Experimental method of karst collapse experimental device containing dominant channels based on upper cover layer Download PDFInfo
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Abstract
The invention relates to the technical field of karst collapse, in particular to an experimental method of a karst collapse experimental device containing a dominant channel based on an upper cover layer. The karst collapse experiment device comprises a model box, a rainfall device positioned above the model box, a water supply box positioned below the model box, and a first variable-head box and a second variable-head box which are positioned at two sides of the model box and have adjustable heights; the middle part of the model box is horizontally provided with a baffle plate for dividing the model box into an upper cover layer model box and a lower karst cave model box; clay blocks are evenly paved in the cover layer model box; the first water outlet pipe is communicated with the first water changing head box, the second water outlet pipe is communicated with the second water changing head box, and the third water outlet pipe is communicated with the rainfall device; therefore, on one hand, the invention can provide a brand-new technical means for researching the osmotic deformation generated by the soil layer in the rainfall process, karst collapse caused by dominant flow and the like, and also reproduces and reveals the causative mechanism of the karst collapse process, thereby providing a certain reference value for the prevention and prediction work of the karst collapse.
Description
Technical Field
The invention relates to the technical field of karst collapse, in particular to an experimental method of a karst collapse experimental device containing a dominant channel based on an upper cover layer.
Background
In nature, the soil often generates holes due to plant root penetration, small animals move to form channels and cavities, part of areas generate densely distributed dry shrinkage joints due to low water content of the soil, and the soil finger-shaped penetration channels are formed due to unstable wetting fronts, and the channels existing in the soil are called dominant channels.
The process of water and solute passing through the porous medium through the dominant channels is called dominant flow, and the dominant flow is used as water to move in one part of the soil and is faster than the reflection form of the phenomenon of other parts, so that the soil profile has irregular wetting degree. An important feature of the preferred flow is that the peak portion of the moisture content can rapidly propagate to a certain depth when wet, while surrounding most of the matrix pore space, with migration velocities far outside the predicted range of the richard equation. Another important feature of the dominant stream is its own imbalance, i.e. the dominant stream acts as a flow path in which the infiltration does not have sufficient time to equilibrate with other parts of the slow migration of the soil matrix, but is unbalanced.
For the karst area with the upper covering layer containing the dominant channel, during rainfall, in the process that rainwater gradually enters deep karst through the upper covering layer, the dominant channel serves as a flow path, in the path, insufficient time for infiltration is kept in balance with other slowly moving parts in the soil matrix, at the moment, rapid water flow can bring soil tiny particles into the deep karst channel together, and under the combined action of the infiltration force, the soil gravity and the possible negative pressure effect, the karst collapse phenomenon is further accelerated.
As karst collapse has the characteristics of concealment in space, burst in time and the like, great difficulty is brought to the analysis of the mechanism of the karst collapse, and the like, and the method is one of the currently important scientific research problems for preventing, controlling and reducing the disaster. Therefore, the development of karst collapse research is of great significance.
At present, the prediction and forecast of karst collapse mainly adopts a karst dangerous area dividing method based on a GIS technology, the method mainly carries out evaluation analysis on influence factors of the karst collapse, gives different weights to the influence factors, and adopts functions of GIS superposition analysis and the like to realize the division of karst dangerous grades. The prediction method has a good effect on the prediction and prediction of karst collapse of a macroscopic region, but has great subjectivity in the aspects of selection of evaluation factors, weight assignment and the like, and quantitative prediction and evaluation can not be carried out on the collapse range of a specific karst region, so that the engineering management of karst disasters can not be effectively guided. Simulation experiments based on the similarity theory bring possibility for researching analysis of karst collapse microscopic cause mechanism, and also guide direction for quantitative prediction and evaluation of karst collapse.
The prior karst collapse simulation device can not develop effective research aiming at the karst collapse type with the upper covering layer containing the dominant channel. Based on the above, a karst collapse experiment device and an experiment method with an upper cover layer containing a dominant channel are studied, and the collapse phenomenon can be effectively simulated through a physical model test.
Disclosure of Invention
The invention provides a karst collapse experimental device and an experimental method for an upper covering layer containing a dominant channel, which can intuitively understand the whole process of karst collapse of the upper covering layer containing the dominant channel under rainfall conditions.
The technical scheme adopted by the invention is as follows: an experimental method of a karst collapse experimental device based on an upper covering layer containing a dominant channel,
the karst collapse experiment device comprises a model box made of organic glass, a rainfall device 2 positioned above the model box, a water supply tank 3 positioned below the model box, a first water changing head box 41 and a second water changing head box 42 which are positioned at two sides of the model box and have adjustable heights;
a non-contact video displacement measuring instrument 5 is arranged right in front of the model box;
the middle part of the model box is horizontally provided with a baffle plate 11 for dividing the model box into an upper cover layer model box 12 and a lower karst cave model box 13; the partition plate 11 is uniformly provided with water permeable holes, and the middle part of the partition plate 11 is provided with more than two simulation holes 111 with adjustable hole areas; clay blocks 112 are uniformly paved in the cover layer model box 12, a dominant channel 113 and a soil pressure sensor 114 are buried in each clay block 112, the dominant channel 113 is a plastic film pipeline, and the soil pressure sensor 114 is connected with a soil pressure data acquisition device;
the side wall of the karst cave model box 13 is provided with pressure measuring holes, and each pressure measuring hole is connected with a water pressure data acquisition device through a water pressure sensor 131;
the outlet of the water supply tank 3 is communicated with three water outlet pipes, the first water outlet pipe is communicated with a first water changing head tank 41 through a first water pump 31, the second water outlet pipe is communicated with a second water changing head tank 42 through a second water pump 32, the third water outlet pipe is communicated with a rainfall device through a third water pump 33, and a water outlet valve 34 is arranged on the third water outlet pipe;
the first water changing head box 41 is communicated with the covering layer model box 12 through a first water injection pipeline 411, and the second water changing head box 42 is communicated with the karst cave model box 13 through a second water injection pipeline 421;
the experimental method specifically comprises the following steps:
step (1): the preparation of the advantageous channel 113 is carried out,
preparing a pair of circular iron rings and more than two iron wires, wherein two ends of each iron wire are respectively welded on the pair of circular iron rings to form a pipeline supporting framework, covering a plastic film layer outside the pipeline supporting framework, and uniformly punching holes in the plastic film layer;
step (2): the preparation of the clay mass 112 is carried out,
preparing a cube model box, paving metal meshes in the model box, filling clay into the model box, and burying the soil pressure sensor 114 and the dominant channel 113 in the model box while filling so that two ports of the dominant channel 113 are positioned at different heights in the clay block 112;
after clay is filled in the model box, compacting to form a clay block 112, attaching a metal mesh to the outer surface of the clay block 112 to form a metal mesh layer, and forming more than two leakage holes in the metal mesh layer;
step (3): the clay blocks 112 are laid out so that,
step (4): opening one simulated hole 111 on the partition 11, and adjusting the opening position and opening degree of the simulated hole 111;
step (5): the second water pump 32 is turned on, the height of the second variable water head box 42 is adjusted, so that the water supply box 3 can feed water into the second variable water head box 42, the second variable water head box 42 can feed water into the karst cave model box 13 through the second water injection pipeline 421, the water level in the karst cave model box 13 gradually rises, and after a certain time, the karst cave model box 13 has a certain water level, namely, a simulated karst cave has a stable underground water level;
step (6): the first water pump 31 is turned on, the height of the first variable water head box 41 is adjusted, so that the water supply tank 3 supplies water into the first variable water head box 41, the first variable water head box 41 supplies water into the cover layer model box 12 through the first water injection pipeline 411, the water level in the cover layer model box 12 gradually rises, and after a certain time, the cover layer model box 12 has a certain water level, namely, the simulated upper cover layer has a stable underground water level;
step (7): opening the third water pump 33 and controlling the opening of the water outlet valve 34 to enable the water supply tank 3 to feed water to the rainfall device, and enabling the rainfall device to leak water downwards uniformly, namely simulating rainfall on a karst area;
s1: the influence of rainfall and karst cave opening size on karst collapse is studied,
the steps (1), (2), (3), (5) and (6) are kept unchanged,
adjusting the opening position and the opening degree of the simulated hole 111 in the step (4), or adjusting the opening degree of the water outlet valve 34 in the step (7);
the soil pressure data acquisition device, the water pressure data acquisition device and the non-contact video displacement measuring instrument 5 record and read information respectively;
s2: the influence of the underground water level fluctuation and the karst cave opening size on karst collapse is studied,
the steps (1), (2), (3) and (6) remain unchanged, (7 deleted, no rainfall)
Closing the third water pump 33 and screwing the water outlet valve 34, and adjusting the opening position and the opening degree of the simulated hole 111 in the step (4), or adjusting the height of the second variable head tank 42 in the step (5), so that a vacuum negative pressure state is generated between the water level of the karst cave model tank 13 and the partition plate 11.
The soil pressure data acquisition device, the water pressure data acquisition device and the non-contact video displacement measuring instrument 5 record and read information respectively;
further, the rainfall device 2 comprises a rainfall box 21 and a rainfall conduit 22, wherein the rainfall box 21 is horizontally arranged right above the model box through rainfall box brackets 23 arranged on four corners of the bottom surface, and water leakage holes are uniformly formed in the bottom surface of the rainfall box 21;
the rainfall conduit 22 is horizontally arranged at the upper part of the rainfall box 21, and one end of the rainfall conduit 22 is communicated with the third water outlet pipe.
Further, the first variable head tank 41 and the second variable head tank 42 have the same structure and comprise a tank body and a tank body bracket 7 with adjustable height, wherein the tank body bracket 7 is arranged at the bottom of the tank body, a vertical partition plate 71 perpendicular to the bottom surface of the tank body is arranged in the tank body, the height of the vertical partition plate 71 is lower than the height of the tank body, and the vertical partition plate 71 divides the tank body into a water inlet tank and a water outlet tank;
the water inlet tank of the first variable head tank 41 is respectively communicated with the water supply tank 3 and the cover layer model tank 12 through a first water pump 31 and a first water injection pipeline 411, and the water outlet tank of the first variable head tank 41 is communicated with the water supply tank 3 through a pipeline;
the water inlet tank of the second variable head tank 42 is respectively communicated with the water supply tank 3 and the karst cave model tank 13 through the second water pump 32 and the second water injection pipeline 421, and the water outlet tank of the second variable head tank 42 is communicated with the water supply tank 3 through a pipeline.
Further, 3 simulated holes 111,3 simulated holes 111 are formed in the middle of the partition plate 11, and are uniformly formed along the length direction of the partition plate 11;
each simulated hole 111 is provided with an adjusting mechanism 6, the adjusting mechanism 6 comprises a pair of circular baffles 61 and four arc plates 62, the pair of circular baffles 61 are fixedly arranged at intervals up and down, and the middle of each circular baffle is provided with a round hole with the same aperture corresponding to the simulated hole 111;
each arc-shaped plate 62 is movably arranged between a pair of circular baffle plates 61 in a matching way through a key slot;
when the corresponding ends of the four arc plates 62 are combined or separated, a pair of round holes on the pair of round baffles 61 are closed or opened, so that the corresponding simulated holes 111 are closed or opened.
The beneficial technical effects of the invention are as follows:
(1) The karst collapse experimental device with the upper cover layer containing the dominant channels takes karst collapse cases with the upper cover layer containing the dominant channels in the nature as research objects, indoor experiments can be completed by means of the device, different groundwater supply and change conditions can be simulated by the rainfall device and the variable head box, experimental data of the whole process can be collected by the soil pressure, water pressure and displacement data collecting device, therefore, the generation and development processes of dominant flows in the upper cover layer under rainfall conditions can be clearly and intuitively displayed, water level fluctuation or change is displayed to cause erosion, deformation and stable states of the lower bottom plate of the upper cover layer at different times, and the whole karst collapse development process can be reappeared.
(2) According to the experimental method of the karst collapse experimental device with the upper cover layer containing the dominant channels, the clay blocks are prepared and paved during use, the rainfall device, the water changing head box and the simulated holes are controlled to reasonably combine influencing factors, and the data acquisition device can collect and read data to a computer in real time, so that experimental data and experimental rules have great reference values. The experimental data and the experimental rules are very beneficial to analyzing and researching the essential relation between different groundwater supplies and changes and karst collapse geological disasters, on one hand, the method provides good basic conditions for further researching the whole karst region destabilization collapse process of the upper covering layer containing the dominant channels, especially provides a novel technical means for researching karst collapse caused by dominant flows, and on the other hand, the causative mechanism of the karst collapse whole process of the upper covering layer containing the dominant channels under the mutual influence of seepage fields, stress fields and displacement fields can be reproduced and revealed. The invention can be implemented indoors and has the advantages of visual phenomenon, short period, low cost, convenient movement and the like. The invention has the advantages of repeatability of experimental phenomenon, reliable and real data, extremely high degree of coincidence with engineering reality and the like.
(3) The method can provide a new thought for researchers in the field to explore karst collapse causes and mechanisms in complex areas, solves the difficulty of quantitative and visual research in the karst collapse research field to a certain extent, and provides a new method for predicting and forecasting the karst collapse.
Drawings
FIG. 1 is a schematic structural view of a karst collapse experiment device with a dominant channel based on an upper cover layer.
Fig. 2 is a schematic structural view of the rainfall device of the present invention.
FIG. 3 is a schematic view of the structure of the overlay model box of the present invention.
Fig. 4 is a state diagram of the arc plate involution in the adjusting mechanism of the invention.
Fig. 5 is a view showing a state in which the arc plate is unscrewed in the adjusting mechanism of the present invention.
FIG. 6 is a schematic view of a karst cave mold according to the present invention.
Fig. 7 is a schematic view of the structure of the water supply tank of the present invention.
FIG. 8 is a schematic view of the clay block according to the present invention.
Fig. 9 is A-A view of fig. 8.
Wherein: the device comprises an 11 partition plate, a 111 simulated hole, 112 clay blocks, 113 dominant channels, 114 soil pressure sensors, a 12 covering layer model box, a 13 karst cave model box, a 131 water pressure sensor, a 2 rainfall device, a 21 rainfall box, a 22 rainfall conduit, a 23 rainfall box support, a 3 water supply box, a 31 first water pump, a 32 second water pump, a 33 third water pump, a 34 water outlet valve, a 41 first water changing head box, a 411 first water injection pipeline, a 42 second water changing head box, a 421 second water injection pipeline, a 5 non-contact video displacement measuring instrument, a 7 box support, a 71 vertical partition plate, a 6, an adjusting mechanism, a 61 pair of circular baffles and 62 arc plates.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the detailed description is presented by way of example only and is not intended to limit the invention.
Examples
Referring to fig. 1, an experimental method of a karst collapse experimental apparatus based on a dominant channel contained in an upper cover layer,
the karst collapse experiment device comprises a model box made of organic glass, a rainfall device 2 positioned above the model box, a water supply tank 3 positioned below the model box, a first water changing head box 41 and a second water changing head box 42 which are positioned at two sides of the model box and have adjustable heights;
a non-contact video displacement measuring instrument 5 is arranged right in front of the model box;
the middle part of the model box is horizontally provided with a baffle plate 11 for dividing the model box into an upper cover layer model box 12 and a lower karst cave model box 13; the partition plate 11 is uniformly provided with water permeable holes, and the middle part of the partition plate 11 is provided with more than two simulation holes 111 with adjustable hole areas; clay blocks 112 are uniformly paved in the cover layer model box 12, a dominant channel 113 and a soil pressure sensor 114 are buried in each clay block 112, the dominant channel 113 is a plastic film pipeline, and the soil pressure sensor 114 is connected with a soil pressure data acquisition device;
the first water changing head tank 41 is communicated with the covering layer model tank 12 through a first water injection pipeline 411, and the second water changing head tank 42 is communicated with the karst cave model tank 13 through a second water injection pipeline 421.
The first variable head tank 41 and the second variable head tank 42 have the same structure and comprise a tank body and a tank body bracket 7 with adjustable height, wherein the tank body bracket 7 is arranged at the bottom of the tank body, a vertical partition plate 71 which is vertical to the bottom surface of the tank body is arranged in the tank body, the height of the vertical partition plate 71 is lower than the height of the tank body, and the tank body is divided into a water inlet tank and a water outlet tank by the vertical partition plate 71;
the water inlet tank of the first variable head tank 41 is respectively communicated with the water supply tank 3 and the cover layer model tank 12 through a first water pump 31 and a first water injection pipeline 411, and the water outlet tank of the first variable head tank 41 is communicated with the water supply tank 3 through a pipeline;
the water inlet tank of the second variable head tank 42 is respectively communicated with the water supply tank 3 and the karst cave model tank 13 through the second water pump 32 and the second water injection pipeline 421, and the water outlet tank of the second variable head tank 42 is communicated with the water supply tank 3 through a pipeline.
Referring to fig. 2, the rainfall device 2 includes a rainfall box 21 and a rainfall conduit 22, the rainfall box 21 is horizontally installed right above the model box through rainfall box brackets 23 arranged on four corners of the bottom surface, and water leakage holes are uniformly formed on the bottom surface of the rainfall box 21;
the rainfall conduit 22 is horizontally arranged at the upper part of the rainfall box 21, and one end of the rainfall conduit 22 is communicated with the third water outlet pipe.
Referring to fig. 3, 3 simulated holes 111,3 simulated holes 111 are formed in the middle of the partition 11, and are uniformly formed along the length direction of the partition 11;
referring to fig. 4 and 5, each simulated hole 111 is provided with an adjusting mechanism 6, the adjusting mechanism 6 comprises a pair of circular baffles 61 and four arc plates 62, the pair of circular baffles 61 are fixedly arranged at intervals up and down, and the middle of each circular baffle is provided with a round hole with the same aperture corresponding to the simulated hole 111;
each arc-shaped plate 62 is movably arranged between a pair of circular baffle plates 61 in a matching way through a key slot;
when the corresponding ends of the four arc plates 62 are combined or separated, a pair of round holes on the pair of round baffles 61 are closed or opened, so that the corresponding simulated holes 111 are closed or opened.
Referring to fig. 6, the side wall of the karst cave model box 13 is provided with pressure measuring holes, and each pressure measuring hole is connected with a water pressure data acquisition device through a water pressure sensor 131; the bottom of the karst cave model box 13 is provided with a water drain hole, and the water drain hole is communicated with the water supply tank 3 through a pipeline.
Referring to fig. 7, the outlet of the water supply tank 3 is connected with three water outlet pipes, the first water outlet pipe is connected with a first water changing head tank 41 through a first water pump 31, the second water outlet pipe is connected with a second water changing head tank 42 through a second water pump 32, the third water outlet pipe is connected with a rainfall device through a third water pump 33, and a water outlet valve 34 is arranged on the third water outlet pipe;
referring to fig. 8 and 9, the soil pressure sensor 114 and the dominant channel 113 are buried in the clay block 112 such that both ends of the dominant channel 113 are located at different heights in the clay block 112;
the outer surface of the clay block 112 is adhered with a metal net layer, and more than two leakage holes are formed in the metal net layer.
The experimental method specifically comprises the following steps:
step (1): the preparation of the advantageous channel 113 is carried out,
preparing a pair of circular iron rings and more than two iron wires, wherein two ends of each iron wire are respectively welded on the pair of circular iron rings to form a pipeline supporting framework, covering a plastic film layer outside the pipeline supporting framework, and uniformly punching holes in the plastic film layer;
step (2): the preparation of the clay mass 112 is carried out,
preparing a cube model box, paving metal meshes in the model box, filling clay into the model box, and burying the soil pressure sensor 114 and the dominant channel 113 in the model box while filling so that two ports of the dominant channel 113 are positioned at different heights in the clay block 112;
after clay is filled in the model box, compacting to form a clay block 112, attaching a metal mesh to the outer surface of the clay block 112 to form a metal mesh layer, and forming more than two leakage holes in the metal mesh layer;
step (3): the clay blocks 112 are laid out so that,
paving clay blocks 112 in the cover layer model box 12, wherein the paving height of the clay blocks 112 is 0.5-1.5 times of the height of the karst cave model box 13;
step (4): opening one simulated hole 111 on the partition 11, and adjusting the opening position and opening degree of the simulated hole 111;
step (5): the second water pump 32 is turned on, the height of the second variable water head box 42 is adjusted, so that the water supply box 3 can feed water into the second variable water head box 42, the second variable water head box 42 can feed water into the karst cave model box 13 through the second water injection pipeline 421, the water level in the karst cave model box 13 gradually rises, and after a certain time, the karst cave model box 13 has a certain water level, namely, a simulated karst cave has a stable underground water level;
step (6): the first water pump 31 is turned on, the height of the first variable water head box 41 is adjusted, so that the water supply tank 3 supplies water into the first variable water head box 41, the first variable water head box 41 supplies water into the cover layer model box 12 through the first water injection pipeline 411, the water level in the cover layer model box 12 gradually rises, and after a certain time, the cover layer model box 12 has a certain water level, namely, the simulated upper cover layer has a stable underground water level;
step (7): opening the third water pump 33 and controlling the opening of the water outlet valve 34 to enable the water supply tank 3 to feed water to the rainfall device, and enabling the rainfall device to leak water downwards uniformly, namely simulating rainfall on a karst area;
s1: the influence of rainfall and karst cave opening size on karst collapse is studied,
the steps (1), (2), (3), (5) and (6) are kept unchanged,
adjusting the opening position and the opening degree of the simulated hole 111 in the step (4), or adjusting the opening degree of the water outlet valve 34 in the step (7);
the soil pressure data acquisition device, the water pressure data acquisition device and the non-contact video displacement measuring instrument 5 record and read information respectively;
s2: the influence of the underground water level fluctuation and the karst cave opening size on karst collapse is studied,
the steps (1), (2), (3) and (6) remain unchanged, (7 deleted, no rainfall)
Closing the third water pump 33 and screwing the water outlet valve 34, and adjusting the opening position and the opening degree of the simulated hole 111 in the step (4), or adjusting the height of the second variable head tank 42 in the step (5), so that a vacuum negative pressure state is generated between the water level of the karst cave model tank 13 and the partition plate 11.
The soil pressure data acquisition device, the water pressure data acquisition device and the non-contact video displacement measuring instrument 5 record and read information respectively.
It will be readily appreciated by those skilled in the art that the foregoing description is merely a preferred embodiment of the invention and is not intended to limit the invention, but any modifications, equivalents, improvements or alternatives falling within the spirit and principles of the invention are intended to be included within the scope of the invention.
Claims (4)
1. An experimental method of a karst collapse experimental device based on an upper covering layer containing a dominant channel is characterized by comprising the following steps:
the karst collapse experiment device comprises a model box made of organic glass, a rainfall device (2) positioned above the model box, a water supply tank (3) positioned below the model box, a first water changing head box (41) and a second water changing head box (42) which are positioned at two sides of the model box and are adjustable in height;
a non-contact video displacement measuring instrument (5) is arranged right in front of the model box;
the middle part of the model box is horizontally provided with a baffle plate (11) for dividing the model box into an upper cover layer model box (12) and a lower karst cave model box (13); the partition board (11) is uniformly provided with water permeable holes, and the middle part of the partition board (11) is provided with more than two simulated holes (111) with adjustable hole areas; clay blocks (112) are evenly paved in the cover layer model box (12), each clay block (112) is embedded with an advantage channel (113) and a soil pressure sensor (114), the advantage channels (113) are plastic film pipelines, and the soil pressure sensors (114) are connected with a soil pressure data acquisition device;
the side wall of the karst cave model box (13) is provided with pressure measuring holes, and each pressure measuring hole is connected with a water pressure data acquisition device through a water pressure sensor (131);
the outlet of the water supply tank (3) is communicated with three water outlet pipes, the first water outlet pipe is communicated with a first water changing head tank (41) through a first water pump (31), the second water outlet pipe is communicated with a second water changing head tank (42) through a second water pump (32), the third water outlet pipe is communicated with a rainfall device through a third water pump (33), and a water outlet valve (34) is arranged on the third water outlet pipe;
the first water changing head box (41) is communicated with the covering layer model box (12) through a first water injection pipeline (411), and the second water changing head box (42) is communicated with the karst cave model box (13) through a second water injection pipeline (421);
the experimental method specifically comprises the following steps:
step (1): the preparation of the dominant channel (113),
preparing a pair of circular iron rings and more than two iron wires, wherein two ends of each iron wire are respectively welded on the pair of circular iron rings to form a pipeline supporting framework, covering a plastic film layer outside the pipeline supporting framework, and uniformly punching holes in the plastic film layer;
step (2): the preparation of clay blocks (112),
preparing a cube model box, paving metal meshes in the model box, filling clay into the model box, and burying a soil pressure sensor (114) and a dominant channel (113) in the model box while filling so that two ports of the dominant channel (113) are positioned at different heights in a clay block (112);
compacting to form a clay block (112) after clay filling in the model box is completed, attaching a metal mesh to the outer surface of the clay block (112) to form a metal mesh layer, and forming more than two soil leakage holes on the metal mesh layer;
step (3): paving clay blocks (112),
paving clay blocks (112) in the cover layer model box (12) so that the paving height of the clay blocks (112) is 0.5-1.5 times of the height of the karst cave model box (13);
step (4): opening a simulation hole (111) on the partition plate (11), and adjusting the opening position and the opening degree of the simulation hole (111);
step (5): the second water pump (32) is turned on, the height of the second variable water head box (42) is adjusted, so that the water supply tank (3) feeds water into the second variable water head box (42), the second variable water head box (42) feeds water into the karst cave model box (13) through the second water injection pipeline (421), the water level in the karst cave model box (13) gradually rises, and after a certain time, the karst cave model box (13) has a certain water level, namely, a simulated karst cave has a stable underground water level;
step (6): the first water pump (31) is turned on, the height of the first variable water head box (41) is adjusted, so that the water supply tank (3) feeds water into the first variable water head box (41), the first variable water head box (41) feeds water into the cover layer model box (12) through the first water injection pipeline (411), the water level in the cover layer model box (12) gradually rises, and after a certain time, a certain water level is arranged in the cover layer model box (12), namely, a simulated upper cover layer has a stable underground water level;
step (7): opening a third water pump (33) and controlling the opening of a water outlet valve (34) to enable the water supply tank (3) to feed water to a rainfall device, wherein the rainfall device uniformly leaks water downwards, namely, rainfall on a karst area is simulated;
s1: the influence of rainfall and karst cave opening size on karst collapse is studied,
the steps (1), (2), (3), (5) and (6) are kept unchanged,
adjusting the opening position and the opening degree of the simulated hole (111) in the step (4), or adjusting the opening degree of the water outlet valve (34) in the step (7);
at the moment, the soil pressure data acquisition device, the water pressure data acquisition device and the non-contact video displacement measuring instrument (5) record and read information respectively;
s2: the influence of the underground water level fluctuation and the karst cave opening size on karst collapse is studied,
the steps (1), (2), (3) and (6) are kept unchanged,
closing a third water pump (33) and screwing a water outlet valve (34), and adjusting the opening position and the opening degree of the simulated hole (111) in the step (4), or adjusting the height of the second variable head tank (42) in the step (5) so that a vacuum negative pressure state appears between the water level of the karst cave model tank (13) and the partition plate (11);
at the moment, the soil pressure data acquisition device, the water pressure data acquisition device and the non-contact video displacement measuring instrument (5) record and read information respectively.
2. The experimental method of the karst collapse experiment device based on the dominant channel in the upper covering layer according to claim 1, wherein the experimental method comprises the following steps: the rainfall device (2) comprises a rainfall box (21) and a rainfall conduit (22), wherein the rainfall box (21) is horizontally arranged right above the model box through rainfall box brackets (23) arranged on four corners of the bottom surface, and water leakage holes are uniformly formed in the bottom surface of the rainfall box (21);
the rainfall guide pipe (22) is horizontally arranged at the upper part of the rainfall box (21), and one end of the rainfall guide pipe (22) is communicated with the third water outlet pipe.
3. The experimental method of the karst collapse experiment device based on the dominant channel in the upper covering layer according to claim 1, wherein the experimental method comprises the following steps: the first variable water head tank (41) and the second variable water head tank (42) have the same structure and comprise a tank body and a tank body bracket (7) with adjustable height, wherein the tank body bracket is arranged at the bottom of the tank body, a vertical partition plate (71) perpendicular to the bottom surface of the tank body is arranged in the tank body, the height of the vertical partition plate (71) is lower than that of the tank body, and the tank body is divided into a water inlet tank and a water outlet tank by the vertical partition plate (71);
the water inlet tank of the first variable head tank (41) is respectively communicated with the water supply tank (3) and the cover layer model box (12) through a first water pump (31) and a first water injection pipeline (411), and the water outlet tank of the first variable head tank (41) is communicated with the water supply tank (3) through a pipeline;
the water inlet tank of the second water changing head tank (42) is respectively communicated with the water supply tank (3) and the karst cave model box (13) through a second water pump (32) and a second water injection pipeline (421), and the water outlet tank of the second water changing head tank (42) is communicated with the water supply tank (3) through a pipeline.
4. The experimental method of the karst collapse experiment device based on the dominant channel in the upper covering layer according to claim 1, wherein the experimental method comprises the following steps: 3 simulated holes (111) are formed in the middle of the partition plate (11), and the 3 simulated holes (111) are uniformly formed along the length direction of the partition plate (11);
each simulation hole (111) is provided with an adjusting mechanism (6), each adjusting mechanism (6) comprises a pair of circular baffles (61) and four arc plates (62), the pair of circular baffles (61) are fixedly arranged at intervals up and down, and the middle of each circular baffle corresponds to the simulation hole (111) and is provided with a round hole with the same aperture;
each arc-shaped plate (62) is movably arranged between a pair of circular baffle plates (61) in a matching way through a key slot;
when the corresponding ends of the four arc plates (62) are combined or separated, a pair of round holes on a pair of round baffles (61) are closed or opened, so that the corresponding simulated holes (111) are closed or opened.
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| AU2020103048A4 (en) * | 2019-12-16 | 2020-12-24 | Guilin University Of Technology | Anti-floating simulation device of subways in karst areas |
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