- 學位論文
砂質土壤炸震夯實之研究
The study of blasting densification effects on sandy soil
摘要
土壤液化通常發生在排水性差的鬆散飽和土壤，如粉土質砂、鬆散細砂或不排水的礫石層，經由外力動態荷重反覆震盪，如地震，鬆散沙的土壤體積減少，土壤孔隙水壓力增加，因此剪切強度下降，也就是有效應力下降。土地開發前的地盤改良可減少往後發生液化的風險。 在台灣關於土壤液化的地盤改良方法有很多種，而炸震夯實法在國內是比較少見的，本研究設置一個現地試驗，在接近飽和的砂土中埋設炸藥，利用爆炸所產生的爆震波當成震動的來源，觀察土壤對於不同爆震波所受到的不同反應。 在砂質土壤中飽和度是引發土壤液化的一個關鍵原因，而土壤孔隙間的飽和度最主要就是土壤含水量的多寡，不同含水量的土壤對於土壤遭受爆震波時有不同的反應，不同間距、深度的炮孔設置所產生的爆震波強度對於炸震前後土壤含水量變化有不同的影響。 由本實驗結果可以得知炸震夯實工法能有效改良土壤炮孔周圍的土壤性質，受到的炸藥的能量越大，土壤改善的效果越明顯，距離炮孔越遠的土壤改良的效果越少，炸震實驗可以改變土壤的乾密度、含水量、孔隙率和土壤的飽和度，而改良的成效深度較深的土壤比深度較淺的土壤明顯。
並列摘要
Liquefaction is more likely to occur in loose to moderately saturated granular soils with poor drainage, such as silty sands or loose sands and gravels capped. During wave loading, usually cyclic undrained loading, e.g. seismic loading, loose sands tend to decrease in volume, which produces an increase in their pore water pressures and consequently a decrease in shear strength, i.e. reduction in effective stress. Soil improvement can reduce the risk of liquefaction. In Taiwan, there are many methods of soil improvement to improve liquefaction, blasting densification is relatively rare. It set an in-place test and use blast wave to shock soil in the nearly saturated sand, Observe the soil for different blast waves produced different responses. Degree of saturation of sandy soil is an important factor in soil liquefaction, degree of saturation means water in soil pore space, which can range from 0 to the value of the soils' porosity at saturation. different water contents in soil have different reactions by shock wave. The variation of water content was affected by blasting shock wave that occurred by different distance and depth of blasting hole. By the experimental results that blasting densification can effectively improve the soil characteristics surrounding blast hole, if the energy of explosive is stronger, the result of soil improvement will be better, if the distance of blasting hole is farther, the result of soil improvement will be worse. It can change dry unit weight, water content, porosity, and degree of saturation by blasting densification, results of soil improvement in deep soil layers are found better than in shallow soil layers.