New Procedure for Saturating Sand Specimens

Abstract

Saturation of sand specimens in laboratory investigations is necessary to provide reliable measurements of volume change and pore pressure. Conventional methods utilize back pressuring or back pressuring with supplemental use of carbon dioxide. If no carbon dioxide is used, back pressures can easily become undesirably large. On the other hand, the percolation of carbon dioxide through the sand to reduce back pressures can lead to unwanted reaction with soil components. To overcome these problems, a new procedure is proposed that utilizes equipment available in almost any geotechnical laboratory. A theoretical and experimental basis is provided as justification. In the new method, an initial vacuum is applied to the sand specimen in such a manner as not to elevate effective stresses. The soil may be dry, saturated, or partially saturated. After the vacuum is held for no more than five minutes, normal back‐pressuring techniques are used. It is found that sands can be effectively saturated at very low values of back pressure. The procedure is especially useful in normally troublesome materials such as cemented sands.