Loess geohazards research in China: Advances and challenges for mega engineering projects

Loess is a meta-stable, cemented assemblage of mainly silt and clay-sized particles of low plasticity. When dry it behaves like a brittle material, but when wetted up the fabric rapidly collapses. Unique geomorphological features include extensive surface erosion, soil piping (loess 'karst'), catastrophic landslides, and widespread collapse (hydro-consolidation). The Chinese Loess Plateau is a more or less continuous drape of thick loess covering some 440,000 km(2). It is one of China's regions that is most prone to geohazards. This paper reviews advances in the research related to loess geohazards, drawing particular attention to the need to apply research findings to recent, very large (mega-)construction projects in loess terrain such as the Mountain Excavation and City Construction in Yan'an levelling 78 km(2) for urban expansion, the Lanzhou New District creating 246 km(2) of new level ground for construction, and large engineered interventions in the landscape for gully control and land reclamation such as those in Shaanxi and Gansu generating agricultural land covering an area of some 8000 km(2). These projects are in response to increasing pressures to facilitate expansion of urban centres, their interconnecting infrastructures and their agricultural support systems. It is argued that, where proper application of scientific knowledge for engineering control (e.g. densification, drainage) of these new landscapes is absent, these projects could generate a substantial, and costly geohazard legacy for future generations.