The Deformation of Sandy Soils During Densification by Blasting

• Main Authors: Yu, Chang-Hsueh, 余昌學
• Other Authors: Jeng, Fu-Shu
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/22154949010460222617

碩士 === 國立臺灣大學 === 土木工程學研究所 === 88 === The energy released by detonations of explosives in loose-compacted sandy soils destroys the original soil structure and causes the soil particles to rearrange into a denser state. Laboratory tests were conducted to investigate the deformation of the soil layer, especially in the vicinity of the explosive charge. Sand was dyed into different colors for observation of the change of the profile of the soil mass before and after blasting. The influence of the fine-grained soil, depth of charges, and supplementary drainage system on the effectiveness of densification such as ground settlement, increase of relative density of the soil mass after blasting was also investigated. Test results showed that cavities were formed while the explosive charges were detonated. The cavity may collapse when the soil is saturated or remain at the initial place when the soil is partially saturated. Besides, cavity may also tumble due to overburden pressure. The densification mechanism is related to the gas pressure and shock wave that cause liquefaction of the soil layer and destroy the original soil structure. Subsequent resettlement due to drainage of excess porewater pressure causes the soil particles to rearrange into a denser state. Further review of the test results indicates that the fine-grained soil may induce more excess porewater pressure than pure sand. The difference of settlement and increase of relative density were not observed when using different depth of charges or supplementary drainage system. To acquire full-scaled test data and to study the feasibility of blast densification method in Taiwan, a field test was performed. The plan and design of this field test was also listed.