Research On The Mechanical Response Characteristic Of Muck Soil Under Impact Loading

The Static-Dynamic Drainage Consolidation Method(SDDCM) is more and more used in the ultra-soft clay ground as well as other poor ground, one of which mechanical response characteristics of muck soil under the impact loading are getting special attention in the industry. With the research of this paper, strengthening mechanism of the static-dynamic drainage consolidation method is known and understood more deeply, providing guidance and basis for the construction method and design optimization.Research reviews of muck soil mechanical response characteristics under the impact load, the constitutive model and model test are summarized firstly. Secondly, static-dynamic consolidation model tests (1:30 similarity ratio) are performed on the muck soil in which different drainage system were installed using a self-developed high-energy electromagnetic impact testing system in order to research the accumulation and dissipation of pore pressure, earth pressure and impact energy transfer processes under the impact loading, and having a understanding of muck soil mechanical response characteristics under the impact loading by simulating field engineering; And using the SPAX-2000 (modified) static and dynamic triaxial testing system, static-dynamic drainage consolidation method is simulated. Through triaxial impact test of muck soil, the mechanical responses of muck soil under the action of different impact loading frequency(1Hz,8Hz and 16Hz), different confining pressure(250kPa, 300kPa and 350kPa) and different intermediate principal stress(250kPa,300kPa and 350kPa) is investigated to further study mechanical response characteristics of muck soil under the impact loading under the action of different intermediate principal stress, confining pressure and different frequencies; By last in view of the modified Cap model and finite characteristic ratio model, the model results and the test results were analyzed, the main achievements are as followings:Firstly, the study of static-dynamic drainage consolidation model test show that the pore pressure more easily dissipate, and larger settlement more easily take place in the vertical drains dense area; When drainage body spacing encryption 33%, settlement increases 25%. This shows that drainage setting is necessary, but should maintain a reasonable density. The more dense drains, with the number of impact passes increase, the greater the proportion of the energy distribution in the deep soft ground, and the proportion becomes the largest in final impact; more obvious trend of the main compression zone moving downward is showed.Secondly, the triaxial test:1. At the same frequency, confining pressure and intermediate principal stress, with the increase of impact load(30kPa,60kPa and 90kPa), body energy increment(additional body stress incrementxcorresponding body strain increment) decreases; When the impact load increase 50%(from 60kPa increase to 90kPa), the corresponding body energy increment reduceds 38% at most. This illustrates that the energy of soil absorbing tends to be saturated. This provides a theoretical explanation for preventing the rubber soil. This once again demonstrates the importance of strengthening principle of static-dynamic drainage consolidation method "less hit more times, energy added step by step".2. At the same impact load, confining pressure and intermediate principal stress, with the increase of impact frequency(1Hz,8Hz and 16Hz), axial strain and body energy increment decreases gradually, the corresponding axial strain and body energy increment under the impact frequency of 8Hz can be reduced 75% and 45% at most than under 1Hz, 16Hz can be reduced 69% and 62% at most than under 8Hz. Above indicate that impact load with low frequency plays a greater role than high frequency in energy transfer and absorption. This provides an important reference value for ground treatment with low frequency in practical projects.3. At the same impact load and impact frequency of 1Hz, the presence of the intermediate principal stress on the strain of soft soil had a significant influence:with the increase of intermediate principal stress(250kPa,300kPa and 350kPa), cumulated axial strain and cumulated volume strain decreases gradually, the corresponding cumulated axial strain and cumulated volume strain under 300kPa are respectively reduced by 44% and 27% than under 250kPa,350kPa are respectively reduced by 46% and 19% than under 300kPa.Thirdly, in view of the modified Cap model and finite characteristic ratio model, the model results and test results were analyzed. It can be found that the calculated values which based on finite characteristic ratio model is accord with experimental values, so the description of soft soil mechanics response with finite characteristic ratio model is precise.