深厚土层散体材料桩桩体竖向承载力计算

Bearing Capacity Calculation of Granular Column Pile Body in Deep Soft Layer

散体材料桩处理软弱地基有较好的效果及经济效益,因而应用广泛。在深厚土层中,桩体无法穿透上覆软弱土层而达到下部较稳定层,此时增强体竖向承载力主要来自于桩体与桩周一定范围内土体的相互作用。散体材料桩竖向极限承载力大都采用桩周土体最大侧向约束力乘以被动土压力系数来计算,介绍了若干计算方法后,提出了一种基于天然地基土荷载-变形曲线的散体材料桩竖向极限承载力计算方法。该方法是假定桩周土体侧向变形达到某一既定值时,该值在天然地基土荷载-变形曲线上对应的土压力值即为桩周土对桩的最大侧向约束力。考虑到成桩作用对土体的强化作用,引入系数λ,表征桩周土体较天然土体的强化程度。考虑到地基土的成层性,推荐采用旁压试验(PMT)或扁铲侧胀试验(DMT)获取荷载-变形曲线。

With the good results and economic benefits,the granular column is widely used in the soft foundation treatment.Considering that the pile body is unable to penetrate the upper soft soil layer and reach the lower stable layer in the thick soil layer,the vertical bearing capacity of reinforcement mainly comes from the interaction between pile body and pile circumference within certain scope.Generally,the vertical ultimate bearing capacity of granular column is calculated by multiplying the maximum lateral binding force of pile circumstance body by the coefficient of passive earth pressure.After introducing several computational methods,the author will put forward a kind of computational method for the vertical ultimate bearing capacity on the granular column on the basis of the foundation soil load-deformation curve of natural earth.In this method,it is supposed that the lateral deformation on the pile circumference body has reached a certain value,at this moment,the pressure value exerted by the certain value on the natural foundation soil load-deformation curve is called as the maximum lateral binding force on the pile body exerted by the pile circumference soil.In consideration of the reinforcement effect on the soil body exerted by pile,the reinforcement degree between the pile soil and natural soil body will be embodied by the incoming coefficientsλ.In view of the foundation soil stratification,it is recommended to carry out the pressure-meter test(PMT)or flat dilatometer test(DMT)to get the load-deformation curve.