饱和土的大气张力郎肯土压力

蒙理明

(海口市城市规划设计研究院，海口 570105)

摘要：该文总结了饱和土的大气张力郎肯土压力算法。其计算要点有：饱和度系数、自由水通道率、膜的抗剪强度贡献、大气张力郎肯土压力。算例分析表明，按大气张力郎肯土压力，饱和粘土的自由水通道率折减不大，相对自由水压力通过一定厚度后衰减为零，其结果与水土合算的接近。饱和土的大气张力郎肯土压力算法，接近我国规范，对砂性土宜按水土分算计算,对粘性土宜按水土合算计算。表层为较硬的饱和粘土的基坑，按经典郎肯土压力，基坑上部主动土压力为负值,表示土体拉住支护，处理为零，这是错误的；而按大气张力郎肯土压力，表示坑内支护上的大气压强能抵抗主动土压力，扶住支护。

关键词：饱和土的大气张力郎肯土压力；相对自由水压力衰减；主动土压力负值；扶住支护

doi:10.3963/j.issn.1674-6066.2015.04.022

Abstract:This paper summarizes the algorithm of the atmospheric tension Rankine's earth pressure of saturated soil. The calculation point is, saturation coefficient, the rate of free water channel, the shear strength of membrane contribution, atmospheric tension Rankine's earth pressure. Example analysis shows that，according to the atmospheric tension Rankine's Earth pressure, reduction of free water channel rate of saturated clay is not large, relatively free water pressure through a certain thickness attenuation is zero, the result with water and soil economical approach. Algorithm of the atmospheric tension Rankine's earth pressure of saturated soil,close to the specification in our country, the sand soil should calculate by Soil and water points algorithm, the cohesive soil should be calculated by water and soil economical approach.For the foundation pit as the surface is a hard saturated clay，according to the classical Rankine's earth pressure,the upper active earth pressure is negative, saying the soil pull in support, handling is zero, that is wrong; and according to the atmospheric tension Rankine's earth pressure, saying the atmospheric pressure on the pit supporting can resist active earth pressure, hold support.

收稿日期：2015-06-17.

作者简介：蒙理明(1955-),教授级高工.E-mail:66229258mlm@163.com

Atmospheric Tension Rankine's Earth Pressure of Saturated Soil

MENGLi-ming

(Urban Planning & Design Institute of Haikou, Haikou 570105,China)

Key words:atmospheric tension Rankine's earth pressure of saturated soil；relatively free water pressure attenuation；active earth pressure negative；hold support

太沙基1923年提出了饱和土中的有效应力原理。在计算饱和土的郎肯土压力时，太沙基公式表达的是水土分算法。我国建筑地基基础设计规范[1]的9.3.3条：作用于支护结构的土压力和水压力，对砂性土宜按水土分算计算；对粘性土宜按水土合算计算，也可按地区经验确定。方玉树和李广信曾对水土分算与水土合算问题进行了充分的讨论[2-5]。

笔者在2008年提出了自由水通道率表达式。意思是在水土合算和水土分算之间，即在粘土到砂类土之间，自由水通道率是一个由0到1的连续过程，是以t=lgK(渗透系数)为自变量的分段连续函数[6]。……