A new simple system for measuring volume changes in unsaturated soils

2002 ◽  
Vol 39 (3) ◽  
pp. 757-764 ◽  
Author(s):  
C W.W Ng ◽  
L T Zhan ◽  
Y J Cui
Keyword(s):  
Volume Change ◽  
Unsaturated Soils ◽  
Volumetric Strain ◽  
Apparent Volume ◽  
Differential Pressure ◽  
Simple System ◽  
Measuring System ◽  
Volume Changes ◽  
Ambient Temperatures ◽  
Triaxial Apparatus

A new simple system for accurately measuring overall total volume changes in unsaturated soil specimens with a triaxial apparatus is introduced in this paper. The basic principle of the measuring system is to record changes in the differential pressure due to changes in the water level inside an open-ended, bottle-shaped inner cell caused by volume change in the specimen and inside a reference tube using an accurate differential pressure transducer. Several important steps were taken to improve the accuracy and sensitivity of the measuring system. Detailed calibrations were carried out to account for apparent volume changes as a result of changes in cell pressure, fluctuation in the ambient temperatures, creep in the inner cell wall, and relative movement between the loading ram and the inner cell. The calibration results demonstrate that the measuring system is reasonably linear, reversible, and repeatable. The estimated accuracy of the measuring system is in the order of 32 mm3 (or 0.04% volumetric strain for a triaxial specimen 38 mm in diameter and 76 mm in height) once the system is properly calibrated.Key words: unsaturated soils, volume-change measurement, open-ended, bottle-shaped, inner cell, differential pressure, calibration.

Constitutive relations for volume change in unsaturated soils

1976 ◽  
Vol 13 (3) ◽  
pp. 261-276 ◽  
Author(s):  
D. G. Fredlund ◽  
N. R. Morgenstern
Keyword(s):  
Volume Change ◽  
Unsaturated Soils ◽  
Soil Structure ◽  
Constitutive Relations ◽  
Water Volume ◽  
Engineering Practice ◽  
State Variables ◽  
Volume Changes ◽  
Stress Changes ◽  
Measured Volume

Volume change constitutive relations for unsaturated soils are proposed from a semi-empirical standpoint. One equation describes the deformation of the soil structure and a second equation defines the volume of water present in the element. Each equation can be viewed as a three-dimensional surface with two independent stress state variables forming the abscissas.Uniqueness is tested by measuring volume changes resulting from stress changes in two orthogonal directions and comparing predicted and measured volume changes resulting from a stress change in a third direction. Samples of undisturbed Regina Clay and compacted kaolin showed good agreement between the predicted and measured volume changes for monotonic deformation of the soil structure. The agreement was not as close for the water phase. The variation was attributed to difficulties in measuring water volume changes over a long period of time. The laboratory results indicate that the proposed constitutive equations are of the appropriate form for use in engineering practice.

Pore-water pressure and water volume change of an unsaturated soil under infiltration conditions

2005 ◽  
Vol 42 (6) ◽  
pp. 1509-1531 ◽  
Author(s):  
Inge Meilani ◽  
Harianto Rahardjo ◽  
Eng-Choon Leong
Keyword(s):  
Pore Water ◽  
Volume Change ◽  
Unsaturated Soils ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Volumetric Strain ◽  
Confining Pressure ◽  
Matric Suction ◽  
Water Volume ◽  
Infiltration Tests

Triaxial shearing–infiltration tests were conducted to study the pore-water pressure and volume change of unsaturated soils subjected to infiltration conditions. A modified triaxial apparatus with three Nanyang Technological University (NTU) mini suction probes along the specimen height was used for the experimental program. Elastic moduli were obtained for the soil structure with respect to changes in net confining pressure (E) and matric suction (H). Water volumetric moduli associated with changes in net confining pressure (Ew) and matric suction (Hw) were also obtained from the shearing–infiltration tests. Water volumetric strain and pore-water pressure during the shearing–infiltration tests were computed based on volume change theory. This paper presents the significance of obtaining the parameter Hw from an appropriate scanning curve of a soil-water characteristic curve (SWCC) for the computation of water volumetric strain and pore-water pressure changes during a shearing–infiltration test. The appropriate scanning curve should be obtained from the wetting curve of the SWCC at the matric suction where the infiltration test commences.Key words: infiltration, matric suction, triaxial, unsaturated soils, pore-water pressure, water volume change.

Experimental investigation of the effect of compliant pores on reservoir rocks under hydrostatic and triaxial compression stress states

2019 ◽  
Vol 56 (7) ◽  
pp. 983-991
Author(s):  
Hua Yu ◽  
Kam Ng ◽  
Dario Grana ◽  
John Kaszuba ◽  
Vladimir Alvarado ◽  
...  
Keyword(s):  
Pore Pressure ◽  
Triaxial Compression ◽  
Matrix Material ◽  
Volumetric Strain ◽  
Confining Pressure ◽  
Differential Pressure ◽  
Sandstone Sample ◽  
Stress States ◽  
Rock Springs ◽  
Stage 1

The presence of compliant pores in rocks is important for understanding the stress–strain behaviors under different stress conditions. This paper describes findings on the effect of compliant pores on the mechanical behavior of a reservoir sandstone under hydrostatic and triaxial compression. Laboratory experiments were conducted at reservoir temperature on Weber Sandstone samples from the Rock Springs Uplift, Wyoming. Each experiment was conducted at three sequential stages: (stage 1) increase in the confining pressure while maintaining the pore pressure, (stage 2) increase in the pore pressure while maintaining the confining pressure, and (stage 3) application of the deviatoric load to failure. The nonlinear pore pressure – volumetric strain relationship governed by compliant pores under low confining pressure changes to a linear behavior governed by stiff pores under higher confining pressure. The estimated compressibilities of the matrix material in sandstone samples are close to the typical compressibility of quartz. Because of the change in pore structures during stage 1 and stage 2 loadings, the estimated bulk compressibilities of the sandstone sample under the lowest confining pressure decrease with increasing differential pressure. The increase in crack initiation stress is limited with increasing differential pressure because of similar total crack length governed by initial compliant porosity in sandstone samples.

Volume Change Associated to Carbon Partitioning from Martensite to Austenite

2012 ◽  
Vol 706-709 ◽  
pp. 2290-2295 ◽  
Author(s):  
M. J. Santofimia ◽  
Lie Zhao ◽  
Jilt Sietsma
Keyword(s):  
Volume Change ◽  
Chemical Potential ◽  
Theoretical Models ◽  
Carbon Partitioning ◽  
Volume Changes ◽  
Measured Volume

Annealing of martensite/austenite microstructures leads to the partitioning of carbon from martensite to austenite until the chemical potential of carbon equilibrates in both phases. This work calculates the volume change associated with this phenomenon using theoretical models for the carbon partitioning from martensite to austenite. Calculations are compared with experimentally determined volume changes. This comparison reveals that in the case of steels with higher contents of austenite-stabilizing elements, reported volume changes are satisfactory predicted assuming a low mobilily martensite/austenite interface. In the case of a steel with lower additions of austenite-stabilizing elements, experimentally measured expansions are considerably larger than predicted ones. The large measured volume expansions probably reflect the decomposition of the austenite.

A novel non-contacting laser displacement transducer technique for volume change measurements of unsaturated soils

2010 ◽  
pp. 751-756 ◽  
Author(s):  
X Zhang ◽  
M Mavroulidou ◽  
M Gunn ◽  
Z Cabarkapa ◽  
J Sutton
Keyword(s):  
Volume Change ◽  
Unsaturated Soils ◽  
Displacement Transducer
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