Study Of Model Test Of High-energy Dynamic Compaction For Collapsible Loess Foundation

With the social and economic development, dynamic technology development, many high energy dynamic compaction of engineering practice have been practiced, for example, crushed gravel backfill foundation has reached 16000kN·m which is the highest level,18000～20000kN·m level of dynamic compaction is being tested. On the loess soil, the level of dynamic compaction has reached 12000kN·m which is the highest level,15000～17000kN·m level of dynamic compaction is also being tested.However, the current norm of "Technical code for ground treatment of buildings" (JGJ 79-2002) in which the highest level of dynamic compaction is 8000kN·m and in the current norm of " Code for building construction in collapsible loess regions" (GB 50025-2004)in which the highest level for dynamic compaction is 8500kN·m can not play a guiding role in the high energy level compaction; but many engineer have different opinion about the development of engineering techniques for dynamic compaction,so in the high filling and deep loess and other infrastructure projects, if there is a need for a higher level of dynamic compaction, what about its reinforcement effect and how to reinforce the energy efficiency, all this isn't only the current concern and think about engineering, but also academic urgent subject. At this stage, the study high energy dynamic compaction is main by field test, which has limitations due to schedule constraints and other conditions.In this paper, based on similar principles, a model test device is designed. And 3000kN·m, 5000kN·m,6000kN·m,8000kN·m, 10000kN·m and 12000kN·m level of dynamic compaction have been simulated by the device indoor. By comparative analysis of tamping settlement, dynamic stress, density and displacement of the dynamic compaction,ground reinforcement mechanism was studied. The high-energy dynamic compaction and the general level of dynamic compaction are also analyzed and compared in strengthening mechanism, strengthening energy efficiency reinforcement effect similarities and differences and merits of other aspects. The results show that:the settlement of sub-low energy dynamic compaction can divide into two stages which is primary compression settlement and secondary compression settlement, primary compression compaction of tamping settlement is relatively significant, high energy dynamic compaction only the primary compression; low-energy dynamic compaction have compaction effect in the soil which on both sides of hammer,compaction effects, the high energy dynamic compaction main reinforces the soil beneath the hammer; low-level dynamic compaction work for dynamic compaction by shear wave in the main, high-energy dynamic compaction in compression wave based. As the level of dynamic compaction increases, the compaction increases the effective depth of treatment, but the increasing rate decreases.