Rigid Inclusion Quality Control and Performance Verification Using Drilling Parameters: A Streamlined Approach

Rigid inclusions are a ground improvement technique that provides soil reinforcement and settlement mitigation using drilled displacement elements. Rigid inclusion installation typically uses a Monitoring While Drilling (MWD) electronic logging system that captures data such as torque, downward thrust, rotary speed and grout take with depth and time. Installation of each rigid inclusion can be considered data from a large-scale in-situ test consisting of penetration of a rotating probe into the ground. Automatically generated graphic logs are typically reviewed visually by members of a project team for quality control during and after installation. This workflow underutilizes the valuable data provided by these MWD systems. This paper discusses the use of MWD installation data integrated with cone penetration test (CPT) data and static load test results to develop a streamlined and robust quality control workflow for rigid inclusions. A compound parameter designated the Penetration Resistance Index (PRI) is computed using soil-tool interface mechanics principles for each production element. The PRI, when plotted with depth, can be correlated with CPT data so that changes in soil profile can be detected as production elements are installed across the site. When the PRI is integrated over element length below the neutral plane, the resulting Integrated Resistance Index (IRI) value can be compared with the IRI of load test elements to rapidly assess element suitability. Use of the PRI and the IRI can help improve quality and efficiency of Rigid Inclusions systems by detecting potential areas where geotechnical conditions are sufficiently different or have improved significantly as production installation progresses. This information allows designers to determine whether optimization of the intended element lengths is possible or where a more intense treatment may be necessary. This quality control workflow can be performed in near-real time.