一、挖孔桩在碎石土、粘土、砂及砂夹卵石层较厚,承载力低,而桥墩(台)基底必须埋置到较深层的地层时,如果采用明挖或沉井,则土方及圬工工程数量颇大,速度也慢。为了节约工程数量及加快施工速度,同时在地下水较小时,可以采用挖孔桩基础。挖孔桩基础能节约大量土方和圬工工程,例如施工10个墩(台)基础(深度10m～19m),挖孔桩总长547m,仅挖土方2236m~3,灌注混凝土1807m~3(承台数量已包括在內)。如用明挖则一个墩(台)的土方将达到或超过10个墩(台)挖孔桩的土方总数量。如用沉井则2～3个墩(台)的圬工将达到或超过上述10个 First, digging piles in the gravel soil, clay, sand and sand pebble thick, low bearing capacity, and the pier (Taiwan) basement must be buried deeper strata, if using open cut or caisson, then Earthworks and masonry works are quite large and slow. In order to save the project quantity and speed up the construction speed, at the same time when the groundwater is small, the foundation of digging hole piles can be used. Digging pile foundation can save a lot of earthwork and mortar works, for example, construction of 10 pier foundation (depth 10m ~ 19m), digging pile total length 547m, digging only 2236m ~ 3, pouring concrete 1807m ~ 3 The number has been included). If you use the next digging a pier (Taiwan) earthwork will reach or exceed the total number of earthwork of 10 pier (Taiwan) digging pile. As with caisson 2 to 3 piers (Taiwan) will meet or exceed the above 10 workers