The Destruction of Stabilized Expansive Clays Due to Frost Action

The chapter discusses changes in geotechnical properties of expansive soil stabilized with cement, which occurred as a result of regular freezing. The purpose of stabilization was winter protection of substrate of a very big and open excavation for foundation. Substrate of the building consisted of Neogene clays of the Poznań series; in order to protect them, a minimum 40-cm layer was stabilized with cement under geotechnical supervision, which remained under special cover during winter period. Values of clay swelling parameters under natural conditions (hard-plastic state I_L = 0.13, clay fraction content f_i = 32.5%) amounted to: swelling index V_P = 7.6–11.3%, swelling pressure p_c = 99.5–170 kPa. The groundwater level of pressure character was stabilizing 0.50 m below the excavation bottom level. Multiple winters freezing caused full destruction of the expansive clay-cement composite layer, disabling scheduled performance of foundation works on the subsoil prepared in this way. The chapter also describes phenomena and reasons of frost and water destruction affecting expansive clay subsoil. The author summarized ineffective performance of insulation layers and protective zone of stabilized clay zone in the excavation for foundation during the winter and spring periods.