Mobile Advanced Geotechnical Laboratory

BGC has provided support for the Pueblo Viejo Project in the central Dominican Republic from 2001 through to the present.  Our services have ranged from conceptual design through prefeasibility, feasibility, construction and operations.

As part of these efforts, BGC carried out a comprehensive program of advanced laboratory testing to characterize the strength, compressibility and permeability of the native foundation saprolite, as well as the low permeability fill (LPF) used in the core of the tailings dams.  Given the challenges associated with transporting soil samples over great distances and across international borders, BGC developed a state-of-the-art mobile advanced geotechnical laboratory for on-site testing.  This facility has served to minimize sample disturbance during transport and has greatly reduced the turnaround time of testing.

The project included a number of unique testing programs, three of which are highlighted below:

• High pressure triaxial testing of LPF – Conventional triaxial equipment allows testing to confining pressures of up to 1 MPa.  The anticipated stresses at the base of the largest tailings dam were significantly larger. BGC developed a high pressure triaxial system and conducted a series of tests in the mobile laboratory to evaluate the performance of the saprolite at confining stresses of up to 5 MPa
• Anisotropic triaxial testing- BGC developed an apparatus which allowed triaxial tests to be carried out under anisotropic stress conditions.  Servo-controlled triaxial equipment is commercially available which allows testing along any stress path.  However, this equipment is very expensive and requires advanced training and routine oversight.  Given the remote nature of the mobile laboratory, a more practical apparatus was required which was simple to use and produced reliable results.  BGC developed equipment that allowed an additional dead load to be applied to the sample throughout the test.  This equipment, which was fabricated for only 5% of the cost of a servo-controlled system, has been used successfully to evaluate the shear strength of samples of foundation saprolite and LPF consolidated to a wide range of stress ratios
• Direct residual shear tests – BGC carried out direct residual shear tests to evaluate the residual shear strength of foundation saprolite.  Tests were carried out on undisturbed specimens trimmed from larger block samples and on cored samples recovered from geotechnical boreholes using a Mazier core barrel