In Situ Test Protocols for Quality Assessments of Deep Mixing Columns

Deep mixing (DM) technology involves the mixing of soils extending to large depths with cement, or lime, or other types of stabilizers for raising the strength of soft and compressible soils, reduction of settlements of roads, embankments, and enhancing the stability of excavation supports and slopes. Quality assurance (QA) of deep mixing methods used in the construction projects must be addressed to evaluate the effectiveness of DM treatment methods adapted in the field. If not addressed, columns with deficient strength and stiffness properties will induce damage to infrastructures built on them. Several in situ testing protocols for QA studies were developed as a part of a research study conducted for the National Deep Mixing Program. This protocol development was based on extensive literature reviews, documented case study information and surveys with practitioners associated with the in situ methods. This paper provides comprehensive details on three testing protocols of standard penetration test, cone penetration test and pressuremeter test. The protocols covered both step by step testing methodologies on soil columns, and interpretation methods for strength and stiffness properties. A case study example utilizing SPT protocol is presented to illustrate the steps in QA studies.