Installation Effects of Controlled Modulus Column Ground Improvement Piles on Surrounding Soil

Abstract

The installation of foundations and ground improvement systems alters soil stresses affecting their soil-structure interaction and behavior under vertical loading. The installation effects have been investigated for several foundation types, especially for driven piles; however, experimental full-scale investigations of drilled displacement piles are very limited. This paper focuses on investigating the short-term installation effects of controlled modulus columns (CMCs) using an instrumented full-scale field test unit. The soil was instrumented using push-in pressure sensors (PS) and shape acceleration arrays (SAAs) to monitor the evolution of soil horizontal stresses, pore water pressures, and lateral displacements during installation and vertical load test. These sensors were installed at approximately 1D, 2D, 3D, and 4D from the outside surface of the CMC shaft, where D is the diameter of the CMC. The measurements presented in this paper clearly show that the soil experienced an increase of horizontal stresses and lateral movement throughout the CMC installation. During mandrel advancement, the horizontal stresses gradually increase until the mandrel reaches the location (depth) of the pressure sensors, which was followed by a horizontal stress decrease. The measurements presented in this paper indicate that the zone affected by the CMC installation extend to 2 to 3D from the outer surface of the CMC shaft.