TY - CHAP

T1 - Soil compactibility and compressibility

AU - Peth, Stephan

N1 - Publisher Copyright: © 2011, Springer Netherlands. All rights reserved.

PY - 2011

Y1 - 2011

N2 - Determination of soil compressibility is crucial for estimating the impact of field traffic or animal trampling on soil porosity and related soil physical functions. The Compressibility index Cc is derived from compression curves obtained from standard oedometer tests (CCT) allowing to calculate volumetric soil deformation that may be expected when Pc is exceeded by a certain stress value. The index is determined under static loading conditions meaning that the slope reflects a loaded stress situation. While this stress condition is a realistic assumption for many geotechnical problems, where permanent loads are applied (e.g., building foundations), for arable land permanent loads do seldom occur. Instead soils are usually loaded for a short time (seconds) in the incidence of field traffic and then subsequently unloaded again. During unloading elastic rebound recovers a part of the plastic deformation which unfortunately is not quantified by applying standard CCT procedures. On the other hand soils are repeatedly loaded during long term land use and also on a short term basis by multiple axle machines. Concerning long term field traffic, especially in intensive cropping systems, the subsoil may be exposed to hundreds of load applications. Considering the cumulative soil compression associated with this repeated loading the assumption of full elasticity in the re-compression stress range is not valid. Cyclic compressibility (Cn) of subsoils for estimated expected mean stresses of employed farm machinery should additionally be determined by repeated (cyclic) loading tests. Soil compression depends on multiple interrelated factors where especially loading time, pore water pressure, stress path and stress state affect the parameters obtained from soil mechanical tests. Derivation of soil compressibility indices requires an adaption of the boundary conditions in soil mechanical laboratory testing to a more realistic representation of in situ stress paths, i.e., short loading time; short and long term repeated loading. Finally, due to the coupling of hydraulic and mechanical stresses in the course of loading, it is indispensible to standardize initial soil pore water pressure and measure its change during the loading process.

AB - Determination of soil compressibility is crucial for estimating the impact of field traffic or animal trampling on soil porosity and related soil physical functions. The Compressibility index Cc is derived from compression curves obtained from standard oedometer tests (CCT) allowing to calculate volumetric soil deformation that may be expected when Pc is exceeded by a certain stress value. The index is determined under static loading conditions meaning that the slope reflects a loaded stress situation. While this stress condition is a realistic assumption for many geotechnical problems, where permanent loads are applied (e.g., building foundations), for arable land permanent loads do seldom occur. Instead soils are usually loaded for a short time (seconds) in the incidence of field traffic and then subsequently unloaded again. During unloading elastic rebound recovers a part of the plastic deformation which unfortunately is not quantified by applying standard CCT procedures. On the other hand soils are repeatedly loaded during long term land use and also on a short term basis by multiple axle machines. Concerning long term field traffic, especially in intensive cropping systems, the subsoil may be exposed to hundreds of load applications. Considering the cumulative soil compression associated with this repeated loading the assumption of full elasticity in the re-compression stress range is not valid. Cyclic compressibility (Cn) of subsoils for estimated expected mean stresses of employed farm machinery should additionally be determined by repeated (cyclic) loading tests. Soil compression depends on multiple interrelated factors where especially loading time, pore water pressure, stress path and stress state affect the parameters obtained from soil mechanical tests. Derivation of soil compressibility indices requires an adaption of the boundary conditions in soil mechanical laboratory testing to a more realistic representation of in situ stress paths, i.e., short loading time; short and long term repeated loading. Finally, due to the coupling of hydraulic and mechanical stresses in the course of loading, it is indispensible to standardize initial soil pore water pressure and measure its change during the loading process.

UR - http://www.scopus.com/inward/record.url?scp=84865985961&partnerID=8YFLogxK

U2 - 10.1007/978-90-481-3585-1_146

DO - 10.1007/978-90-481-3585-1_146

M3 - Contribution to book/anthology

AN - SCOPUS:84865985961

T3 - Encyclopedia of Earth Sciences Series

SP - 742

BT - Encyclopedia of Earth Sciences Series

PB - Springer Netherlands

ER -