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为了防止塌方,保证操作安全,大直径人工挖孔桩大多采取分段挖土、分段护壁的方法施工。分段现浇混凝土护壁厚度,一般取受力最大处,即地下最深段护壁所承受的土压力及地下水的侧压力由计算确定,设混凝土护壁厚度为t,则可按下式计算:t≥KN/f_c或t≥KpD/2f_c式中N——作用在护壁截面上的压力(牛/米~2),N=PD/2;p——土和地下水对护壁的最大侧压力(牛/米~2);当挖孔无地下水时,p=γHtg~2
In order to prevent landslides and ensure the safety of operation, large-diameter manual excavation piles are mostly constructed by segmental excavation and staged retaining. The thickness of the segmented cast-in-place concrete wall is generally taken to be the maximum force, that is, the earth pressure and ground pressure of the underground deepest retaining wall are determined by calculation. If the thickness of the concrete retaining wall is t, the following formula can be used: t≥ KN/f_c or t≥KpD/2f_c where N - the pressure acting on the wall section (N/m ~ 2), N = PD/2; p - the maximum lateral pressure of the soil and groundwater on the wall (Cattle / m~2); When digging holes without groundwater, p=γHtg~2