| 词条 | Expansive clay |
| 释义 |
Expansive clay is a clay soil that is prone to large volume changes (swelling and shrinking) that are directly related to changes in water content.[1] Soils with a high content of expansive minerals can form deep cracks in drier seasons or years; such soils are called vertisols. Soils with smectite clay minerals, including montmorillonite and bentonite, have the most dramatic shrink-swell capacity. The mineral make-up of this type of soil is responsible for the moisture retaining capabilities. All clays consist of mineral sheets packaged into layers, and can be classified as either 1:1 or 2:1. These ratios refer to the proportion of tetrahedral sheets to octahedral sheets. Octahedral sheets are sandwiched between two tetrahedral sheets in 2:1 clays, while 1:1 clays have sheets in matched pairs. Expansive clays have an expanding crystal lattice in a 2:1 ratio; however, there are 2:1 non-expansive clays.[2] Mitigation of the effects of expansive clay on structures built in areas with expansive clays is a major challenge in geotechnical engineering. Some areas mitigate foundation cracking by watering around the foundation with a soaker hose during dry conditions. This process can be automated by a timer, or using a soil moisture sensor controller. Even though irrigation is expensive, the cost is small compared to repairing a cracked foundation. Admixtures can be added to expansive clays to reduce the shrink-swell properties, as well.[3] One laboratory test to measure the expansion potential of soil is ASTM D 4829. See also
References1. ^Hobart king, "Expansive Soil and Expansive Clay: The hidden force behind basement and foundation problems". Geology.com. Accessed March 19, 2015. 2. ^Science.gov clay related articles 3. ^Biswas, Rajdip, and Nemani Kriscna. “Effect of fly ash on strength and swelling aspect of an expansive soil.“ Department of Civil Engineering National Institute of Technology. Visited on November 19th, 2015. 4 : Types of soil|Soil mechanics|Soil physics|Sediments |
| 随便看 |
开放百科全书收录14589846条英语、德语、日语等多语种百科知识，基本涵盖了大多数领域的百科知识，是一部内容自由、开放的电子版国际百科全书。