Mechanical behavior of Malan loess under unconfined compression conditions

Abstract

Loess landslides result in heavy casualties and economic losses. Among them, toppling is one of the predominant failure modes in Malan loess. Loess toppling failure normally arises from deep vertical cracks, which tend to develop in the shoulder areas of loess slopes and extend to a depth of several meters. Under natural conditions, loess’ static lateral pressure coefficient is low and the loess mass within a 2 m horizontal depth from the slope surface approximates an unconfined compression stress state. In this work, we sought to further examine this unconfined compression state using acoustic emission monitoring and in situ computed tomography scans to investigate the mechanical behavior of Malan loess. Results indicated that Malan loess failed under compression-induced tension in unconfined compression condition. It exhibited the brittle failure with an abrupt release of elastic energy. The failure plane was at large angles and occurred nearly along the loading axis. This result coincided well with the vertiloess structure, which is characterized by vertically aligned strong units and weak segments. The above failure mode supports the formation of vertical cracks in the loess strata and consequently the toppling and crack sliding slope failures, as well as the formation of loess walls and columns.