QA/QC for deep-mixed ground: current practice and future research needs

Abstract

The quality of deep-mixed soil (improved soil by in situ mixing) depends upon a number of factors including the type and condition of native soil, the type and amount of binder, and the production process. The quality assurance/quality control (QA/QC) practice which focuses upon the quality of deep-mixed soil was originally established in Japan and Nordic countries and has been accepted worldwide for more than three decades. It comprises a laboratory mix test, field trial installation, monitoring and control of construction parameters during production and the verification by measuring the engineering characteristics of deep-mixed soil either by unconfined compression tests on core samples or by sounding. Diversification of application, soil type and execution system, together with the improved understanding on the behaviour of deep-mixed ground in the past two decades make it necessary for our profession to review the current QA/QC practice. Based on the literature review and the International collaborative study, the authors discussed the similarity and differences in the QA/QC procedures employed in different parts of the world and proposed the future research needs in a keynote lecture at Okinawa 2009 Deep Mixing Symposium. The current paper is a summary of this keynote address.