tailieunhanh - Soil and Environmental Analysis: Physical Methods - Chapter 9

Dẻo là các tài sản đó cho phép đất bị biến dạng không bị nứt trong một căng thẳng áp dụng. Một đất có thể biểu hiện dẻo, và do đó được đắp, trên một loạt các nội dung nước, lần đầu tiên xác định số lượng các nhà khoa học Thụy Điển Atterberg (1911, 1912). Trên phạm vi này, đất hoạt động như một chất lỏng, trong khi bên dưới nó, nó cư xử như một chất rắn dễ vỡ và cuối cùng gãy xương ở phản ứng với căng thẳng áp dụng ngày càng tăng. Giới hạn trên. | 9 Liquid and Plastic Limits Donald J. Campbell Scottish Agricultural College Edinburgh Scotland I. INTRODUCTION Plasticity is the property that allows a soil to be deformed without cracking in response to an applied stress. A soil may exhibit plasticity and hence be remolded over a range of water contents first quantified by the Swedish scientist Atterberg 1911 1912 . Above this range the soil behaves as a liquid while below it it behaves as a brittle solid and eventually fractures in response to increasing applied stress. The upper limit of plasticity known as the liquid limit is at the water content at which a small slope forming part of a groove in a sample of the soil just collapses under the action of a standardized shock force. The corresponding lower limit the plastic limit is at the water content at which a sample of the soil when rolled into a thread by the palm of the hand splits and crumbles when the thread diameter reaches 3 mm. By convention both water contents are expressed gravimetrically on a percentage basis. The numerical difference between the liquid and plastic limits is defined as the plasticity index. Remarkably these simple empirical tests have been used essentially unchanged for nearly a century by soil engineers and soil scientists BSI 1990 . Engineers found the limits particularly the plastic limit to be useful in the design and control testing of earthworks and soil classification Dumbleton 1968 as a result of the development by Casagrande of apparatus to measure the limits Casagrande 1932 . Although his apparatus was based on that of Atterberg Casa-grande appreciated the need where empirical tests were concerned to specify closely every detail of the test procedure so that both the repeatability of the test by one operator and the reproducibility between operators were optimized Sherwood 1970 . Consequently the Casagrande tests became widely adopted as the Copyright 2000 Marcel Dekker Inc. Table 1 Relation Between Potato Harvesting .