Use of Real-Time Monitoring Data to Interpret Variable Subsurface Conditions and Validate Construction for a Large Deep Mixing Scheme Using Cutter Soil Mixing to Support MSE Walls at Kitimat LNG, BC, Canada

The cutter soil mixing (CSM) technique was used to construct an extensive deep mixing scheme for foundation support of mechanically stabilized earth (MSE) walls at the Kitimat Liquefied Natural Gas (LNG) facility in Bish Cove, British Columbia, Canada. Using real-time monitoring from the Bauer B-tronic system, the performance of CSM in highly variable subsurface conditions that consisted of thick deposits of fine-grained soils overlying granular soils was assessed, and the data used to develop a set of termination criteria for deep mixing using the CSM technique that would achieve the ground improvement design requirements. Real-time monitoring data was also used for interpretation of highly variable subsurface conditions, identifying areas where modifications to the deep mixing design was required, allowing fine-tuning of the termination criteria used for problematic areas that included dense granular till, thick organic layers, and obstructions, and identifying areas where increased in-situ wet grab and/or post-installation core sampling and testing would be most appropriate for quality control (QC) and quality assurance (QA). The merits of using real-time monitoring data as part of the engineering decision-making process including the development of “inferred torque” based on pressures at the cutter wheels to develop a simplified termination criteria in highly variable soil conditions is presented.