Journal Published Online: 05 September 2018
Volume 42, Issue 2

Performance of Fully Grouted Piezometers under Transient Flow Conditions: Field Study and Numerical Results

CODEN: GTJODJ

Abstract

Piezometers can be installed in clay layers using the fully grouted method. This method is said to reduce installation costs and facilitate installation, especially for nested piezometers. The success of a fully grouted installation depends upon the ratio of grout and surrounding soil hydraulic conductivity and upon the grout physical stability. This article presents new results from field tests and numerical simulations regarding the performance of fully grouted piezometers under transient flow conditions. The field observations show that using low-permeability grout for piezometer installation provides precise pore water pressure (PWP) measurements. This confirms previous findings on the fully grouted installation technique. Field observations for a very high-permeability grout that could be more than 1,100 times more permeable than the soil result in PWPs that totally differ from the PWP obtained with a low-permeability grout. Using three scenarios involving transient flow, the numerical results show that hydraulic conductivity ratios between 0.001 and 10 provide an accurate pore pressure response without a significant time lag for soils with a very low permeability (K ≤ 2 × 10−9 m/s). For most practical applications, a hydraulic conductivity ratio of 100 is the upper limit to obtain acceptable pore pressure measurements for these soils. A large hydraulic conductivity ratio may cause a hydraulic short circuit between the fully grouted piezometer and the upper aquifer. For a borehole diameter of 100 mm, the numerical results demonstrate that grout stiffness has no significant impact on the performance of fully grouted piezometers. However, grout stiffness is important for the long-term performance of the fully grouted piezometer. This article also introduces preliminary results regarding a testing program on grout properties. These results confirm pervious findings by others that the preparation of low-permeability grout is not trivial and that grout initial viscosity controls its physical stability and hydraulic conductivity.

Author Information

Marefat, Vahid
Department CGM, École Polytechnique de Montréal, Montreal, QC, Canada Laboratory for Geotechnical and Geoenvironmental Engineering (LG2), École de technologie supérieure, Montreal, QC, Canada
Duhaime, François
Laboratory for Geotechnical and Geoenvironmental Engineering (LG2), École de technologie supérieure, Montreal, QC, Canada
Chapuis, Robert P.
Department CGM, École Polytechnique de Montréal, Montreal, QC, Canada
Borgne, Vincent Le
GKM Consultants, Quebec, Canada
Pages: 24
Price: $25.00
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Stock #: GTJ20170290
ISSN: 0149-6115
DOI: 10.1520/GTJ20170290