Geotechnical Investigation at Bakheng WTP, Phnom Penh

On behalf of the Phnom Penh Water Supply Authority (PPWSA), Vinci Construction Grands Projets S.A.S has requested Inros Lackner (Cambodia) to carry out geotechnical investigations for Phase 3 of the Bakheng Water Treatment Plant Project. The investigations were carried out in two parts in June 2023.
- Part I: Ground investigations by Cone Penetration Tests (CPTu)
- Part II: Ground investigations by borehole explorations and laboratory testing.

Cone Penetration Tests with pore water pressure readings were carried out and the investigation depth varied between about 34 and 39 m. During a Cone Penetration Test, a cylindrical steel probe (piezocone) is pushed into the ground at a constant rate. Soil parameters, such as tip resistance, friction on the piezocone sleeve and pore water pressure, are measured. The data are uploaded and displayed in real-time in graphical format on a laptop computer. The data treatment that removes the overburden stress influence with depth, allow to get a comprehensive interpretation of normalized Soil Behaviour Type (SBT), corrected with the pore pressure measured (SBTn), along with about 15 soil parameters such as permeability, Young's Modulus, relative denisty, friction angle, shear strength and others.
In part II, four boreholes were carried out to investigation depths of 43 to 45 m. The investigation program consisted of a combination of in-situ tests (Standard Penetration Tests) and laboratory tests for soil/rock classification and strength.

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