Experimental Study Under Compression On The Push-extend Multi-under-reamed Pile Of Large Scale Real Pile Of The Field

The Push-extend Multi-under-reamed Pile is developed on the basis of ordinary pile, it is a new type of pile, that after drilling, stretching specialized squeezed hydraulic equipment into the hole, according to the requirements of bearing capacity and the distribution of strata distribution, in the design part of pile squeezed out expanding cavity, then putting into the steel cage, pouring concrete, finally formed the pile, expanding bearing disk and pile end together to bear force. It has lots of characteristics like high capacity, small settlement, low cost and so on, reflecting the significant economic and social benefits.At present, the Push-extend Multi-under-reamed Pile has been widespread concern in engineering field, a lot of experimental study have been done by many domestic scholars based on load transfer mechanism, bearing capacity, failure mechanism. Arrangement of bearing enlarging disk make soil around pile complex, the failure mechanism is also different, therefore, to determine failure state of surrounding soil of the Push-extend Multi-under-reamed Pile is very important. However, the test methods currently applied exist certain limitations, such as: on-site static load test is limited to applying a static load on such as: on-site static load test is limited to applying a static load on the top of the pile to record the force-displacement curve, laying rebar strain gauges to measure load transfer rules, this tradition method has the disadvantage that only the test data, but can not see changes of soil. Laboratory model tests, while having flexible design, easy to operate, cost savings and other characteristics, however, there are differences inevitable in test materials, the proportion of the model, the soil actual situation and other aspects compared with the actual situation, makes the test data information exists a certain deviation.Inspired by Qian Yongmei professor’s small scale half pile model test, the group proposed a new research method of the Push-extend Multi-under-reamed Pile, namely test of a large scale real piles with half face. This test method can reflect the interaction of pile and soil in the state of compression, the whole process of soildestruction can be observed and recorded clearly. Combining this test method, this paper will make depth study on stress mechanism of the type of pile and failure condition of soil around pile under pressure, and validate theoretical results available.At the same time, summed and perfect test equipment, test methods and test process to form a complete test program, so that it has universal applicability and promotion,thus promoting research and more widely used squeezed pile, so that it has universal applicability and promotion, thus promoting research and application widely of the Push-extend Multi-under-reamed Pile.