Dynamic Compressive Testing And Mechanical Behavior Of Limestone And Fiber-reinforced Concrete

Split Hopkinson Pressure Bar (SHPB) test technique which is a basic method of researching the mechanics properties of material is applied extensively. Surrounding the dynamic compression mechanical properties of material,a series of tests and researches is carried on the limestone and fiber concrete. The primary research achievement is as following:(1) Because of the dynamic compression test characteristic of the brittle material (such as rock and concrete) and meeting the test assumption of one dimension and uniform, getting the effective test data, the SHPB is improved on the basis of traditional testing system, and the precise data is gained by using the gimbal device ,shaper and wrapping bandage.(2) Based on the improved technique, the intact limestone and damaged limestone are collected and processed according to effective rang determined in field which blasting excavation damages the bottom parallel hole and side direction breaks. A series of tests is carried on the intact and damaged limestone by four kinds strain rate, and the result indicate that the limestone has obvious brittleness and the strain rate influents obviously the mechanics properties of limestone, and at the same loading the strain rate of intact limestone is higher than the damaged limestone, and the ultimate failure stress of the complete limestone is higher 30% than the damage limestone. So the blasting damage effect should be sufficiently thought during stability evaluation and support design of wall rock.(3) Using the engineering graduation, the dynamic compression test is conducted in the concrete and the steel fiber reinforced concrete and the polypropylene fiber concrete with different loading rate. The rule which the dynamic compressive strength and elastic ratio change with strain-rate. The dynamic compression test is carried on the concrete of different type fiber and different the mixture quantity. The result shows that the strength raising of the high mixture quantity is slower than the low mixture quantity with the strain rate raising. However the higher mixture quantity of steel fiber is not better.(4) The impairment of fiber concrete which is affected by continuous load is described by damage variance. The test indicates that there is a compacted procession during the damage. The compare is made between engineering concreteand model concrete, and the result is that the stress and strain model concrete of is higher. If the dynamic compression mechanics properties is applied at engineering, the reduction factor should be used.(5) Based on the test results, a BP neural network is presented in this paper. The simulation about the graph stress and strain is done, and the result is anastomotic between the model and the test graph.