CN110716028A - Centrifugal model test simulation method and system for damming dam - Google Patents

Abstract

A centrifugal model test simulation method for a damming dam comprises the steps of simulating a damming body by using a mixture material of broken stones and sand in a model box, randomly arranging potassium nitrate powder in the damming body, placing the model box in a basket of a centrifugal machine, injecting water into the model box after centrifugal acceleration is stable at a set value, dissolving the potassium nitrate powder, forming a pore structure in the damming body in uneven distribution, and simulating uneven deformation; the invention also provides a centrifugal model test simulation system of the damming dam, aiming at the characteristics that the damming dam material has complex characteristics, the inside of the damming dam often has unevenly distributed large pore structures and the damming dam is unevenly deformed, and the unevenly distributed pore structures of the damming dam are simulated in the geotechnical centrifuge.

Description

A quake dam centrifugal model test simulation method and system

technical field

The invention belongs to the technical field of dam model tests, in particular to a dam dam centrifugal model test simulation method and system.

Background technique

Barriers are often caused by geological disasters and are widely distributed in mountainous areas around the world. The existence of dams poses a huge threat to the safety of life and property of the downstream people, and if not handled properly, it will cause devastating disasters. The dam is mainly composed of two types of structures: the "natural" dam body formed by the landslide and the "artificial" anti-seepage body designed and constructed, and are significantly affected by the dam foundation and the bank slope where it is located. The environment in which the barrier dam is located is complex and changeable, and it also has functions such as water retention and flood discharge. Therefore, it experiences the coupling effect of multiple processes such as frequent stress changes, deformation, damage, and seepage. Reasonable consideration should be given to dams with a level of 100 meters. Coupling responses at multiple scales such as volume, meter-level impermeable structure, centimeter-level structural surface, and even millimeter-level cracks. At present, the stress, deformation, seepage characteristics and stability analysis of dams are mainly based on the theoretical methods of earth-rock dams. The evolution of properties is difficult to be reasonably considered by the existing analytical theoretical methods, and it is urgent to study the multi-body and multi-process interaction characteristics of dams and the evolution mechanism of long-term working properties.

The geotechnical centrifuge can make the model and the prototype have the same stress and similar deformation by applying a centrifugal force field equivalent to the gravity field on the model. The geotechnical centrifugal model test has obvious advantages in studying the deformation and failure mechanism of the dam slope. Due to the complex material properties of dams, there are often unevenly distributed pore structures during the formation process, resulting in uneven large deformations. At present, there is no centrifugal model test simulation technology for dams, and the important role of geotechnical centrifugal model tests in the study of the deformation and failure characteristics of dams cannot be played well.

SUMMARY OF THE INVENTION

In order to overcome the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a centrifugal model test simulation of a dam dam for the complex characteristics of the dam material, the non-uniformly distributed macropore structure, and the occurrence of non-uniform deformation. Method and system for simulating the unevenly distributed pore structure of a damming dam in a geocentrifuge

In order to achieve the above object, the technical scheme adopted in the present invention is:

A method for simulating a centrifugal model test of a damming dam. In a model box, a damming body is simulated with a mixed material of gravel and sand, and potassium nitrate powder is randomly arranged in the model box. After the acceleration is stabilized at the set value, water is injected into the model box to dissolve the potassium nitrate powder, and an unevenly distributed pore structure is formed in the damming body to simulate the generation of uneven deformation.

Preferably, in the simulation experiment, the gradation of gravel and sand is adjusted according to the actual situation and the scaling effect of the geotechnical centrifuge.

Preferably, in the simulation experiment, the potassium nitrate powder is arranged at the position where the pores are to be formed in the damming body, and the density of the potassium nitrate powder is controlled to make it similar to the strength of the damming body material. By adjusting the content of the potassium nitrate powder , arrangement location and arrangement quantity, thereby controlling the shape, location and quantity of pores in the damming body.

Preferably, in the simulation experiment, the simulated damming body is provided with a simulated anti-seepage structure composed of gypsum mixture, and the simulated anti-seepage structure is set at a central position along the width direction of the simulated damming body, penetrating from top to bottom , the gypsum mixture is formed by mixing water, gypsum, sand, and calcium carbonate, and is configured according to the mixing ratio that meets the test strength requirements.

The present invention also provides a dam centrifugal model test simulation system, including a model box 1, wherein a vertical water-permeable partition 2 is arranged in the model box 1 to divide the box into two chambers, one of which is A water outlet is opened on the side wall of the chamber, and a simulated damming body 3 mainly composed of gravel, sand and potassium nitrate powder 8 is arranged in the chamber. One end of the simulated damming body 3 is in contact with the permeable baffle 2, and the other One end is in contact with the inner side wall of the mold box 1 , and a water inlet 4 and a pressure port 5 are opened on the side wall of the other chamber.

Preferably, in the simulation experiment, the simulated damming body 3 is provided with a simulated anti-seepage structure 6 composed of gypsum mixture, and the simulated anti-seepage structure 6 is set at the central position along the width direction of the simulated damming body 3, from top to bottom The bottom penetrates down, the bottom is fixed at the bottom of the model box 1 through the groove structure, the simulated anti-seepage structure 6 is installed with strain gauges, and the gypsum mixture is formed by mixing water, gypsum, sand and calcium carbonate. mix configuration.

Preferably, in the simulation experiment, the water inlet 4 is connected to an external water storage system, the water storage system includes a water tank, a solenoid valve and a water delivery pipe, wherein the water tank is fixed on the rotating arm of the centrifuge near the main shaft, Store enough water before the start of the test for use during the test; the switch of the water tank is controlled by a solenoid valve to realize the supply of water flow during the operation of the centrifuge, and the water is delivered to the other through the water inlet 4 through the water pipe Chamber.

Preferably, in the simulation experiment, the permeable baffle 2 is composed of a wire mesh and a semi-permeable cloth bonded together, and the water permeability of the semi-permeable cloth satisfies that the water inside the other chamber will not seep out under the action of centrifugal force. It can seep out after a certain air pressure.

Preferably, in the simulation experiment, different positions of the wire mesh are bonded with semi-permeable cloths with different water permeability, and the position of the seepage water is controlled by controlling the magnitude of the applied air pressure, thereby forming a specific dam pore generation sequence.

Preferably, in the simulation experiment, on the premise that the water in the other chamber will not seep out before the acceleration of the centrifuge reaches a stable value, the water permeability of the semi-permeable cloth selected at the position where the pores are expected to be formed first is better than that in the In anticipation of the water permeability of the semi-permeable cloth selected at the positions where the pores will be formed, the impermeable cloth is selected in the area other than the simulated damming body 3 .

Compared with the prior art, the beneficial effects of the present invention are:

1) The centrifugal model test simulation of the uneven large pores of the dam and the uneven settlement of the dam body can be realized, which lays a foundation for further revealing the deformation and failure characteristics of the dam.

2) Different dam pore distribution forms and pore formation sequences can be realized, and a variety of working conditions can be simulated, with a wide range of applications.

3) The simulation of the seepage prevention structure of the dam in the centrifugal model test can be realized.

4) The test cost of the present invention is low, the operation is simple and the control of each system is simple.

Description of drawings

FIG. 1 is a schematic view of the structure of the present invention (perspective view 1).

Figure 2 is a schematic view of the structure of the present invention (perspective view 2).

Figure 3 is a schematic structural diagram (top view) of the present invention.

Figure 4 is a schematic structural diagram (sectional view) of the present invention.

Detailed ways

The embodiments of the present invention will be described in detail below with reference to the accompanying drawings and examples.

The idea of the present invention is to construct a simulated damming body with a certain gradation of mixed materials of crushed stone and sand, and randomly arrange potassium nitrate powder in it. The potassium nitrate powder was dissolved to form an unevenly distributed pore structure in the damming body, simulating the generation of uneven deformation.

1, 2, 3 and 4, the simulation system of the present invention includes a model box 1, and a vertical water-permeable partition 2 is arranged in the model box 1 to divide the box into two chambers, one of which is There is a water outlet on the side wall of the chamber, and a simulated damming body 3 mainly composed of crushed stone, sand and potassium nitrate powder is arranged in the chamber. One end of the simulated damming body 3 is in contact with the permeable baffle 2, and the other end Once in contact with the inner side wall of the mold box 1, a water inlet 4 and a pressure port 5 are opened on the side wall of the other chamber.

A specific structure of the present invention is as follows:

1. Damping body simulation system

That is, the simulated damming body 3 is mainly composed of a mixture of gravel and sand, which is arranged in the "one chamber" of the model box 1. At the same time, a certain amount of potassium nitrate powder is arranged in the position where the pores are to be formed in the simulated damming body 3, and the density of the potassium nitrate powder is controlled to make it similar to the strength of the simulated damming body 3 material. According to the design of the experimental scheme, the content, arrangement position and arrangement quantity of potassium nitrate powder can be adjusted to control the shape, position and quantity of pores in the damming dam.

2. Anti-seepage structure simulation system

That is, for the simulated anti-seepage structure 6 constructed with gypsum mixture, by adjusting the proportion of the mixture, a suitable simulated material that can satisfy the similar conditions of the model can be obtained. The simulated anti-seepage structure 6 is poured before the test sample preparation, and its height and thickness can be adjusted according to the actual situation of the project and the scaling effect of the geotechnical centrifuge.

3. Water storage system

Including water tank, solenoid valve, water pipe. The water tank is fixed on the rotor arm of the centrifuge near the main shaft to store enough water before the start of the test for use during the test. The switch of the water tank is controlled by a solenoid valve, which can realize the supply of water flow during the operation of the centrifuge, and transport the water to the dam pore control system through the water pipe.

4. Dam pore control system

The main body is a cuboid hollow aluminum box 7, which is the above-mentioned "another chamber", one of which is a permeable partition 2 composed of barbed wire and semi-permeable cloth, and the other five sides are welded by aluminum plates. The barbed wire is also connected by welding. The bottom of the steel plate facing the barbed wire is provided with a water inlet 4 and a pressure port 5. The water inlet 4 and the pressure port 5 can also be set on several other steel plates, but the effect is not as good as setting Conspicuous on the opposite side. The dam pore control system is placed in the model box 1 behind the simulated dam body 3 , and the permeable diaphragm 2 is in contact with the simulated dam body 3 . Before the test, the inside of the aluminum box is filled with water. In the test, a semi-permeable cloth with suitable water permeability can be selected, so that the water inside the aluminum box will not seep out under the action of centrifugal force, but can seep out after a certain air pressure is applied. In addition, semi-permeable cloths with different water permeability can be bonded at different positions, and the position of seepage water can be controlled by controlling the magnitude of the applied air pressure, thereby forming a specific damming dam pore generation sequence.

5. Drainage control system

Water outlets are respectively provided at the bottom of the box walls on both sides of the model box 1, so that the water seeping out from the dam pore control system can be discharged from the box in time.

According to the above system structure, the concrete steps of the present invention to carry out the simulation test are as follows:

(1) Preparation of anti-seepage structure simulation system

The anti-seepage structure simulation material is a gypsum mixture formed by mixing water, gypsum, sand and calcium carbonate. Adjust the quality mix ratio of the four materials, and conduct a pre-test to measure the compressive strength of the material, and prepare according to the mix ratio that meets the test strength requirements. Gypsum mix is ready for use. Adjust the shape and size of the casting mold according to the shape and size of the anti-seepage structure in the design of the test plan, and cast the pre-prepared gypsum mixture into the mold according to the set mixing ratio. After the gypsum mixture is cured to the set strength, the casting mold is opened, the simulated anti-seepage structure 6 is taken out, and strain gauges are installed in appropriate positions. The prepared simulated anti-seepage structure 6 is placed in a set position in the model box 1, and the bottom of the simulated anti-seepage structure 6 is fixed to the bottom of the model box 1 through the groove structure.

(2) Prepare the dam pore control system

According to the stable centrifuge acceleration of the centrifuge, the shape of the dam, the formation sequence of the dam pores and other factors, select the appropriate semi-permeable cloth to bond on the wire mesh surface of the dam pore control system. On the premise of ensuring that the water in the dam pore control system will not seep out before the centrifuge acceleration reaches a stable value, select a semi-permeable cloth with better water permeability at the position where pores are expected to be formed first, and select a semi-permeable cloth at the position where pores are expected to be formed later. Select a semi-permeable cloth with poor water permeability, and select an impermeable cloth in the area other than the simulated damming body 3. The dam pore control system bonded with the semi-permeable cloth is placed at the rear of the model box 1 .

(3) Preparation of damming body simulation system

The simulation material of the damming body is composed of a mixture of gravel and sand, and the gradation of the material is determined according to the actual situation of the project. In order to reduce the friction between the simulated damming body 3 and the side wall of the model box 1, before filling the simulated damming body 3, apply Vaseline on the side wall of the model box 1, and then formulate it with the design gradation and density as the control index. The simulated materials of the damming body are filled in layers on both sides of the simulated anti-seepage structure 6 respectively. During the filling process of the simulated damming body 3, according to the pore position and pore size in the experimental design, an appropriate amount of potassium nitrate powder with similar strength to the simulated damming body material was filled in the positions where the pores were to be generated. The prepared dam body simulation system and the anti-seepage structure simulation system together form the dam model. On the side of the model, a pin is used to embed an appropriate amount of white foam fragments, so that the centrifugal field non-contact displacement measurement system can work, and the fragments are randomly arranged.

(4) Place the model in the basket of the centrifuge, connect the water inlet of the dam pore control system to the water storage system, install the water inlet air intake control solenoid valve, and control the water inlet solenoid valve to make the dam dam pore control system Fill it with water and close the water inlet.

(5) Start the centrifuge and load step by step until stable acceleration.

(6) Open the air intake control solenoid valve and gradually increase the applied air pressure value, so that the water seepage in the dam pore control system gradually seeps out from the most easily seeped position until all the semi-permeable cloths begin to seep out. Stop increasing the air pressure when water seeps out and let it stabilize for a while. If the water volume in the dam pore control system is insufficient, close the intake solenoid valve, open the water intake solenoid valve, and supplement the water source for the dam pore control system through the water storage system. As the water in the dam pore control system entered the dam model, the potassium nitrate powder in the dam material was rapidly dissolved and discharged from the drainage control system, resulting in a large pore structure at the corresponding position. After the potassium nitrate powder is completely dissolved, close the water inlet solenoid valve.

(7) According to the experimental design, load is applied to simulate specific working conditions.

(8) Turn off the centrifuge, and the test ends.

Claims (10)

1. a damming dam centrifugal model test simulating method, is characterized in that, in the model box, simulate the damming body with gravel and sand mixed material, and potassium nitrate powder is randomly arranged therein, and the model box is placed in the centrifugal After the centrifugal acceleration is stabilized at the set value, water is injected into the model box to dissolve the potassium nitrate powder and form an unevenly distributed pore structure in the damming body to simulate the generation of uneven deformation. 2. The method for simulating the centrifugal model test of a dam dam according to claim 1, wherein the gradation of the gravel and the sand is adjusted according to the actual situation and the scaling effect of the geotechnical centrifuge. 3. quake dam centrifugal model test simulation method according to claim 1, is characterized in that, described saltpetre powder is arranged in the position where pore is to be formed in the damming body, controls the density of saltpetre powder, makes it and damming The strength of the bulk material is similar, and the shape, position and number of pores in the damming body can be controlled by adjusting the content, arrangement position and arrangement quantity of potassium nitrate powder. 4. The quake dam centrifugal model test simulation method according to claim 1, wherein the simulated dam body is provided with a simulated anti-seepage structure composed of gypsum mixture, and the simulated anti-seepage structure is arranged along the simulated weir. The central position in the width direction of the plug body runs through from top to bottom. The gypsum mixture is formed by mixing water, gypsum, sand and calcium carbonate, and is configured according to the mixing ratio that meets the test strength requirements. 5. A damming dam centrifugal model test simulation system, comprising a model box (1), characterized in that a vertical water-permeable baffle (2) is provided in the model box (1) to divide the box into two a chamber, wherein a water outlet is opened on the side wall of one chamber, and a simulated damming body (3) mainly composed of crushed stone, sand and potassium nitrate powder (8) is arranged in the chamber, and the simulated damming body is arranged One end of (3) is in contact with the water permeable baffle (2), the other end is in contact with the inner side wall of the model box (1), and a water inlet (4) and a pressure port (5) are opened on the side wall of the other chamber . 6. The quake dam centrifugal model test simulation system according to claim 5, wherein the simulated dam body (3) is provided with a simulated anti-seepage structure (6) composed of a gypsum mixture, and the simulated anti-seepage structure (6) is provided. The structure (6) is arranged at the central position along the width direction of the simulated damming body (3), penetrates from top to bottom, and the bottom is fixed to the bottom of the model box (1) through the groove structure, and the simulated anti-seepage structure (6) is installed There are strain gauges, and the gypsum mixture is formed by mixing water, gypsum, sand, and calcium carbonate, and is configured according to the mixing ratio that meets the test strength requirements. 7. The dam centrifugal model test simulation system according to claim 5, wherein the water inlet (4) is connected with an external water storage system, and the water storage system comprises a water tank, a solenoid valve and a water delivery pipe, The water tank is fixed on the rotating arm of the centrifuge near the main shaft, and before the start of the test, enough water is stored for use in the test process; the switch of the water tank is controlled by a solenoid valve to realize the supply of water flow during the operation of the centrifuge, and Water is delivered to the other chamber via the water inlet (4) by means of a water delivery pipe. 8. The dam centrifugal model test simulation system according to claim 5, characterized in that, the water permeable baffle (2) is composed of a wire mesh and a semi-permeable cloth bonded together, and the water permeability of the semi-permeable cloth meets the requirements of the The water inside the other chamber will not seep out under the action of centrifugal force, but can seep out after a certain air pressure is applied. 9. The dam centrifugal model test simulation system according to claim 8, wherein the semi-permeable cloths with different water permeability are bonded at different positions of the wire mesh, and the position of the seepage water is controlled by controlling the size of the applied air pressure , so as to form a specific dam pore generation sequence. 10. The dam centrifugal model test simulation system according to claim 8, characterized in that, on the premise that the water in the other chamber will not seep out before the acceleration of the centrifuge reaches a stable value, it is expected that the water in the other chamber will not seep out. The water permeability of the semi-permeable cloth selected at the position of the pores is better than that of the semi-permeable cloth selected at the positions where the pores are expected to be formed, and the impermeable cloth is selected in the area other than the simulated damming body (3).

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