大学课件_《岩土力学》chpt6土压力.ppt

1、岩土工程研究所第六章第六章 土压力土压力Chapter 6 Earth Pressure岩土工程研究所第一节第一节 概述概述 Introductionn土压力概念土压力概念 What is earth pressure?n土压力种类：土压力种类：Types of earth pressuren静止土压力：静止土压力：Earth pressure at rest岩土工程研究所nWhat is earth pressure?第一节第一节 概述概述 IntroductionEarth pressure:Earth pressure:The pressure applied on The pressu

2、re applied on a retaining wall from soil a retaining wall from soil 岩土工程研究所第一节第一节 概述概述 Introduction主动土压力主动土压力 Active earth pressure被动土压力被动土压力 Passive earth pressure静止土压力静止土压力 Earth pressure at restnTypes of earth pressure?岩土工程研究所第一节第一节 概述概述 Introduction主动土压力主动土压力 Active earth pressure:The wall moves

3、 away from the supported soil,and the horizontal soil pressures are refereed to as active pressure.The soil is in active state.被动土压力被动土压力 Passive earth pressure:The wall is caused to move towards the soil being supported,and the horizontal soil pressures are refereed to as passive pressure.The soil

4、is in passive state.静止土压力静止土压力 Earth pressure at rest:The wall is rigid and does not yield,that is there is no movement taking place,the horizontal soil pressures are said to be at-rest pressure.The soil is in at-rest state.nTypes of earth pressure?主动极限平衡状态主动极限平衡状态:Active state:plastic equilibrium w

5、ith lateral expansion taking place.被动被动极限平衡状态极限平衡状态:Passive state:plastic equilibrium with lateral compression taking place.静止平衡状态静止平衡状态:At-rest state:elastic equilibrium with no lateral strain taking place.岩土工程研究所第一节第一节 概述概述 IntroductionUnder natural conditions of deposition,with semi-infinite exte

6、nt,there is a negligible amount of horizontal strain,the soil is said to be in an at-rest state(or K0 state),and the horizontal effective stress is:Where K0=coefficient of earth pressure at rest.nAt-rest earth pressure?The resultant thrust is equal to the area of the pressure distribution diagram,I.

7、e.岩土工程研究所第二节第二节 朗肯土压力理论朗肯土压力理论Rankines theory nActive earth pressure in cohesionless soils Smooth vertical back,horizontal surface The wall moves away from the earthfill,Vertical stress is major principal stress Soil in state of plastic equilibriumKa is coefficient of active earth pressure岩土工程研究所第二节

8、第二节 朗肯土压力理论朗肯土压力理论Rankines theorynActive earth pressure in cohesionless soils Pressure distributionA uniform surcharge load(q)is applied over the whole surface The wall moves away from the earthfill,Vertical stress is major principal stress 岩土工程研究所第二节第二节 朗肯土压力理论朗肯土压力理论Rankines theorynActive earth pr

9、essure in cohesionless soils The resultant thrust is equal to the area of the pressure distribution diagram,I.e.the area of trapezia The line of action of Pa passes through the center of the area of the trapezia 岩土工程研究所 The wall moves towards the earthfill,Vertical stress is minor principal stress第二

10、节第二节 朗肯土压力理论朗肯土压力理论Rankines theorynPassive earth pressure in cohesionless soils H/3Kp is coefficient of passive earth pressurePassive earth pressure岩土工程研究所 Vertical stress is minor principal stress第二节第二节 朗肯土压力理论朗肯土压力理论Rankines theorynPassive earth pressure in cohesionless soils Kp is coefficient of

11、passive earth pressureThe resultant thrust is equal to the area of the pressure distribution diagram The line of action of Pp passes through the center of the area of the pressure distribution diagram 岩土工程研究所第二节第二节 朗肯土压力理论朗肯土压力理论Rankines theorynActive earth pressure in cohesive soils Assuming:Tensio

12、n crack depth:Total passive resistance force:岩土工程研究所第二节第二节 朗肯土压力理论朗肯土压力理论Rankines theorynActive earth pressure in cohesive soils Assuming:Tension crack depth:(c)(d)If Z00,then case(c);岩土工程研究所第二节第二节 朗肯土压力理论朗肯土压力理论Rankines theorynActive earth pressure in cohesive soils(c)(d)If Z00,then case(c);If Z00,

13、then case(d);PaPa岩土工程研究所第二节第二节 朗肯土压力理论朗肯土压力理论Rankines theorynPassive earth pressure in cohesive soils 岩土工程研究所第二节第二节 朗肯土压力理论朗肯土压力理论Rankines theorynPassive earth pressure in cohesive soils 岩土工程研究所nActive earth pressure in case of ground water 第二节第二节 朗肯土压力理论朗肯土压力理论Rankines theoryThe resultant horizonta

14、l thrust:岩土工程研究所第二节第二节 朗肯土压力理论朗肯土压力理论Rankines theorynActive earth pressure in stratified soil12Layer 1Layer 2岩土工程研究所 谢谢谢谢！Thank You!-结束 The END-岩土工程研究所总结总结 SummarynToday,in the following hours I am going to introduce chapter 6 using English.My spoken English is not so good.This is the first time that I have had a class in English.It is really a challenging task for both you and me.I am not sure whether I can success,but I will do my best to make you understand what I mean.I hope all of you support me.