有限应变测量的关键原理——摩尔圆

20世纪60年代，在板块理论建立的同时，对变形岩石和矿田构造作定量分析以替代定性分析的有限应变测量方法也建立了起来。定量分析的主要标志是将摩尔圆方法从力学引入到地质学，同时也引入矿田构造分析中，并且得到改进与发展。有限应变摩尔圆为分析岩石大变形而建立，极摩尔圆随后为分析广布于野外岩石中的一般剪切变形而建立。我国著名学者李四光在此之前将应力摩尔圆和库仑准则从力学领域介绍到构造地质学，尔后一些中国学者为改进和发展极摩尔圆方法作出了自己的贡献。本文以浅显的方式解释摩尔圆的基本概念和作图方法，附带做些练习和解答。

Mohr circle:the fundemental principle of finite strain measurements

Finite strain measurement,the quantitative analysis instead of the qualitative analysis of deformed rocks,was founded in studying deformed rocks, and structure of orefield with the foundation of plate tectonic theories in 1960s.The main mark of the quatitative analysis was that the Mohr circle construction was introduced from mechanics into structural geology,and was improved and developed from then on. The finite strain Mohr cirle was established for analysing large deformation problems,and the polar Mohr circle was established later for analysing general shear deformation of rocks which distributed widely in the field.The famous chinese geologist Lee J S was the first people who introduced the stress Mohr circle and the Coulomb criterion from the field of mechanics into structural geology. Some chinese geologists made their contribution in improving and developing the polar Mohr circle method.The basic conceptions and construct methods of Mohr circle were introduced simply and popularily in this paper with some exercises and their explanations.