Test study on the characteristics of mudcakes and in situ soils around bored piles

Abstract

Constructing a bored pile produces a disturbed zone of soil adjacent to the pile, referred to as a “mudcake.” The physical properties of the mudcake are different from those of the surrounding soil. This paper reports research on bored piles in silt, clay, and sandy silt layers in Hangzhou, China. Laboratory tests were performed on samples of in situ soil, mudcake, and mudcake mixed with cement grout. The test results showed that mudcakes have a higher water content, higher void ratio, higher compressibility, lower friction, and lower shear strength than in situ soils. They also showed that mudcake properties could be improved by the addition of cement grout. Mudcakes form a weak, thin layer between a pile and a borehole wall, which can lead to a decrease in bearing capacity and an increase in settlement of the pile. Grouting improves the characteristics of mudcakes remarkably, thereby increasing the bearing capacity of piles, which is demonstrated by the case history in this paper.