Comparison of diaphragm wall movement prediction and field performance for different construction techniques

Abstract

The demand for deep excavation for basement construction is growing rapidly in Bangkok due to the limited availability of land. Recently, the maximum depth of excavation has increased up to approximately −25 m. Deep excavation in Bangkok subsoils requires consideration of the soil conditions and the real piezometric level of ground water. In general, Bangkok subsoil consists of 13~16 m of thick, dark grey soft-to-medium clay, followed by stiff, silty clay, before the first sand layer at 21~30 m. The piezometric level of ground water has risen to −13 m from its previous level of −23 m due to the control of deep well pumping for twenty years by the Thai Government. A diaphragm wall is normally used as a soil retaining structure. The behavior and performance of a diaphragm wall is usually predicted by the finite element method (FEM) using Mohr–Coulomb soil modeling as failure criteria, with the soil modulus parameters for soft and stiff Bangkok clay from the self-boring pressuremeter test. This paper presents a comparison between the diaphragm wall movements from FEM analysis predictions and field measurements for two projects, the new Bank of Thailand head office and the Rosewood Hotel, which were constructed with different techniques. The predicted movement agreed well with the field measurements.