PHYSICAL MODEL TESTS OF COAL GANGUE FOUNDATION UNDER DYNAMIC COMPACTION LOADS
ZHANG Qingfeng1,WANG Dongquan2
(1. School of Environmental and Civil Engineering,Jiangnan University,Wuxi,Jiangsu 214122,China;2. School of Mechanics and Architecture Engineering,China University of Mining and Technology,Xuzhou,Jiangsu 221008,China)
Abstract:In order to study reinforcement effect in coal gangue foundation improved by dynamic compaction,the distribution and rules of the dynamic stress at different depths,effective strengthening depths under different impact loadings,a serial of physical model tests are carried out. The dynamic strain gauge DH5939 is used to record the induced dynamic stress of different tamping energies,different blows and different measuring points. It is shown that the single blow settlement decreases with the increase of the number of tamping and increases with the increase of tamping energy under the same blows. The dynamic stress has mainly a single peak,no obvious second crest,acts in a very short time and the time that dynamic stress reaches peak is less than the decay time. It has a significant decay to reach the peak under the impact loadings along the depth of the hammer. For the same depth,with increasing of tamping energy and compaction number,the dynamic stress increases correspondingly. In addition,the physico-mechanical properties of the coal gangue foundation such as degree of compaction and cohesion have greatly improved after dynamic compaction;and they increase with the increasing of tamping energy,the distance from the rammer point is more near,the increasing amplitude is more obvious under the same tamping energy. It is concluded that the best tamping energy is about 3 000 kN•m and the best blow count is 7–9 blows for meeting the actual engineering. The results are suitable for coal gangue foundations improved by dynamic compaction. These results also have a certain reference value for other loose friable media such as construction wastes.
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