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在我国北方地区,很多地方的土质N值较高,水位很低。就北京地区来说,上层土壤分布一般是自地表以下依次为:杂填土、亚粘土、粘土、砂土、砂卵石层。地下水位近年来已下降到地表以下15m或更深。因此,钻孔灌注桩干法作业被广泛地应用着。特别是在城区,由于振动与噪声等对环境的污染,打入式预制桩、振动沉桩被限制使用,而无振动、无噪声、效率高的钻孔灌注桩的应用越来越多。但也有不少地区,在地表以下2～7m处存在着上层滞水:个别地区地表下2～3m就见地下水,有的地方虽
In northern China, soil N is high in many places and the water level is very low. For the Beijing area, the upper layer of soil is generally distributed from the ground surface in the following order: miscellaneous fill, sub-clay, clay, sand, sand and pebble layer. Groundwater levels have fallen to 15m or more below the surface in recent years. Therefore, dry drilling of bored piles is widely used. Especially in urban areas, driven-in prefabricated piles and vibratory piles are limited in use due to environmental pollution such as vibration and noise, and there are more and more applications for bored piles without vibration, noise, and high efficiency. However, there are also many areas where there is an upper layer of stagnant water 2 to 7 meters below the surface: In some areas, groundwater is seen 2 to 3 meters below ground surface, and in some places,