Research On The Application Of Dynamic Compaction Method To The Soft Subgrade Of Expressway

For the time being, highway construction in our country is undergoing a rapid development process. During this construction process, it is inevitable to encounter various unfavorable geological conditions. Therefore, it is a consequential subject for us to study how to handle such adverse sections both economically and reasonably. The dynamic compaction has many superiorities on the unfavorable ground treatment, and it is appropriate applying it to foundations with different geological conditions. The facilities for dynamic compaction are easy-operating and the construction speed is fast. There are many advantages of dynamic compaction such as effectively improve the bearing capacity, almost diminish the liquefaction of sand, have no restriction of the climate and seasons and have a salient economic results. Hence it is one of the main technologies in the field of highway foundation treatment.Based on the collapsible loess foundation treatment on the highway from Yulin to Jiaxian in Shaanxi Province, study the application of dynamic compaction on the collapsible loess foundation treatment along the expressway high embankment section. The main contents of the research are as follows:(1) In combination with the research status at home and abroad, the mechanisms of dynamic consolidation, the blast theory, was summarized. By analyzing the divergent functions on soil reinforcement through compression wave, shear wave and Rayleigh wave, the basic principles about saturated and unsaturated soil mass were presented.(2) Factors which influence the effectiveness of dynamic compaction were systematically analyzed. And the designing methods pertain to the parameters such as tamping energy, times and frequency of tamping, arrangement of tamping position, effective consolidation depth and sphere, tamping interval, and so on.(3) Illustrated as the collapsible loess foundation treatment on the highway from Yulin to Jiaxian in Shaanxi Province, study the application of dynamic compaction. In the test area, it was double intermittent tamped with a major tamping and minor tamping of2000kN·m and1000kN·m, respectively, which reflected single point tamping energy. Then impose a full tamping of1000kN·m for one time. The tamping positions were quincunx-arranged with8single-point-tamping. The effectiveness of dynamic compaction was validated from both the laboratory test as well as in-situ test, and the bearing capacity was even after the treatment:the minimum bearing capacity was235kPa and the minimum critical edge load was497.55kPa. A striking increment compared with before and it met the request of load ratings of the expressway high embankment. Thus it was proved to be reliable and efficient on the collapsible loess foundation treatment.(4) The emerged problems and apropos solutions were presented in the thesis. It was vindicated effective via in-situ construction and it is referable to similar projects.