On the basis of the test results of three-point bending creep fracture, the fracture toughness K1c and creep fracture toughness K1cc are obtained in this paper for amphibole-plagioclase granite in ship lock zone of the Three Gorges Project. Further- more,the fracture test of four-point bending 1–11 mixed mode provides the experimental data of stress intensity factor K1 and K11. According to these tests, the empirical formula for critical fracture criterion is obtained and compared with the theories of maximum tension stress and maximum tension strain.
The permanent ship lock of the Three Gorges Project,which has double lanes with five stages, is one of the biggest ship locks in the world, the total length is 1607m. The high slope that comes to 170m after excavated is an important component of the permanent ship lock. The exposed foundation rock of the permanent ship lock of the Three Gorges Project is made of amphibole-plagioclase granite in pre-sinian, In which there are some schist dotted and there are several groups of big obliquity faultage as well as large number of joints. The joints are mainly NNW, NE-NEE, NNE and NW near EW in direction. 74 percent of them are steep, 19 Surface of most joints is smooth, straight, and rather coarse. The rock with a little weathered isn't filled or filled by epidote. A few joints are filled by calcic and wolframite. There are only 1 to 2 sets of joints developed in the same area. The joints with small dip angle didn't develop at the area. The results from numerical analysis of several typical sections in permanent shiplock indicates that there exists a wide range of tension stress area in the upside of the high slope, on the top of the isolated rockmass and its sidewall (Xu et al. 1998, Xia et al. 1996). As a part of the structure of the locking room, if the rock was excavated, the stress would redistribute, which would lead to the extending of slope rock in different degree, especially to the jointed rockmass under tension stress. Four-point bending test (1- II mixed mode) and creep fracture.
Most of the rock materials have obvious time effect in the mechanical properties. Creep fracture tests Were conducted to investigate whether the jointed rock reduced its ability to resist fracture when loaded for a long time, i.e., If the fracture toughness K1c has time effect.
Because of the long time to accomplish a creep test, the results are greatly affected by environment such as electricity, temperature, and humidity. In order to reduce the time for test, we designed and processed 4 experimental equipments. The equipment has simple structure, and it can prevent the tests for creep fracture from being affected by environment. The creep fracture test integrates the methods of three-point bending fracture and creep tests. During the test, two loading methods are adopted: One is loading and measurement step by step.
