Earth and rockfill dam core wall hydraulic fracture test device

Abstract

The invention relates to an earth and rockfill dam core wall hydraulic fracture test device. Specifically, a water inlet hole is additionally arranged on a base of an ordinary triaxial apparatus pressure chamber corresponding to the test sample center position, a vertical sleeve with threads is fixed on the water inlet hole, a rotary hollow cylindrical steel member with the barrel wall is positioned in the sleeve, a water spray hole is previously arranged at the certain position between the sleeve and the barrel wall of the member, hydraulic pressure can be injected through the water inlet hole additionally arranged on the base, and a fracture water head is arranged at the position of the water spray hole. The earth and rockfill dam core wall hydraulic fracture test device overcomes the defects of presently using a hollow test sample directly to carry out hydraulic fracture tests, solves the problem that centrifugal hydraulic fracture tests are not obvious in soil arch effect, reasonably reflects hydraulic fracture conditions and action methods, and is suitable for determine earth and rockfill dam core wall hydraulic fracture tests and fracture water heads.

Description

technical field [0001] The invention relates to a hydraulic splitting test device for testing the core wall of an earth-rock dam. Background technique [0002] At present, the commonly used model tests for indoor testing of hydraulic splitting of earth-rock dam core walls include static model tests and centrifugal model tests. Static model tests usually include ordinary triaxial hydraulic splitting tests and true triaxial hydraulic splitting tests. Generally, a hole or slit is opened in the center of a cylindrical or cuboid sample, and then water is injected into the hole or slit through the bottom of the sample until The sample is split. [0003] The hydraulic splitting test is carried out by directly opening a hole in the center of the sample. The method is simple, easy to operate, and widely used. However, there are some problems as follows: ① Firstly, a hole or a slit is directly opened in the center of the sample. During the test, under a certain stress state, the def...

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Problems solved by technology

However, there are some problems as follows: ① Firstly, a hole or a slit is directly opened in the center of the sample. During the test, under a certain stress state, the deformation of the hole will affect the deformation and strength of the sample, which will directly cause the soil ②Furthermore, when water is injected from the bottom of the sample to the opening or slot, seepage will occur at the contact surface between the bottom of the sample and the base of the pressure chamber, which changes the boundary conditions of the test bottom and further affects the test. ③Secondly, the radial pressure generated when injecting water into the cylindrical opening of the sample causes the sample to be pulled on the chord and crack along the vertical direction, which is the main performance of vertical cracks in the hydraulic splitting test ④ In addition, according to the common concept, the "arch effect" caused by the modulus difference between the core wall and the dam shell rockfill is one of the fundamental reasons for the possible occurrence of hydraulic splitting

However, ① some studies have shown that when the centrifugal test was used to simulate the failure of the Teton Dam in the United States, the results showed that the hydraulic splitting did not occur in the core wall, which was completely contrary to the analysis results of the Teton Dam impoundment accident in 1976, which indicated that the centrifugal test The results are sometimes unreliable; ② During the practice of the centrifugal test, it was found that the arching effect produced by adjusting the contact conditions of the soil column sides is not obvious, and the hydraulic splitting of the soil column often does not occur

It can be seen that the hydraulic splitting analysis of the centrifuge test has uncertain results, and sometimes even conclusions that are contrary to the actual situation, and it is not enough to use it to judge and predict the hydraulic splitting of the core wall, and it needs to be further improved in engineering applications

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