Engineering geological properties of Miocene hard clays along the middle line of the North–South Diversion Water Project in China

Miocene hard clays are widely distributed in eastern China and are associated with extensive damage to engineering structures. This paper presents the engineering geological properties of Miocene hard clays along the middle line of the North–South Diversion Water Project (NSDWP), including areas of the Nanyang Basin as well as the Fangcheng-Baofeng and Handan-Yongnian regions. Results of laboratory testing show that beneath the weathering zone the Miocene hard clays have similar engineering geological properties, including a high clay fraction with significant montmorillonite, high physico-chemical activity, high water content and high to very high shrink/swell. The effects of wetting and drying cycles on the swelling potential of the hard clays are summarized and attention drawn to the importance of these when considering excavation and construction.