Strength Development in Cement Admixed Bangkok Clay: Laboratory and Field Investigations

Abstract

The in-situ deep mixing technique has been established as an eŠective means to eŠect columnar inclusions into soft Bangkok clay to enhance bearing capacity and reduce settlement. In this paper, an attempt is made to identify the critical factors governing the strength development in cement admixed Bangkok clay in both the laboratory and theˆeld. It is found that clay-water/cement ratio, wc/C is the prime parameter controlling the laboratory strength development when the liquidity index varies between 1 and 2. Based on this parameter and Abrams' law, the strength prediction equation for various curing times and combinations of clay water content and cement content is proposed and veriˆed. This will help minimize the number of trials necessary to arrive at the quantity of cement to be admixed. Besides the wc/C, the strength of deep mixing column is controlled by the execution and curing conditions. For low strength improvement (laboratory 28-day strength less than 1,500 kPa), theˆeld strength of the deep mixing columns, quf, made up from both dry and wet mixing methods is higher than 0.6 times the laboratory strength, qul. The quf/qul ratios for the wet mixing columns are generally higher than those for the dry mixing columns. This higher strength ratio is due to the dissipation of the excess water in the column (consolidation) caused by theˆeld stress. The water to cement ratio, W/C, of 1.0 is recommended for the wet mixing method of the soft Bangkok clay. A fast installation rate was shown to provide high quality for low strength columns. Suggestions are made for improving the deep mixing of soft Bangkok clay, which are very useful both from economic and engineering viewpoints.

Strength and Microstructure of Cement Stabilized Clay

“…The field mixing effect such as installation rate, water/cement ratio and curing condition on the strength development of cemented soil was investigated by Nishida et al (1996) and Horpibulsuk et al (2004cHorpibulsuk et al ( , 2006Horpibulsuk et al ( and 2011b. Based on the available compression and shear test results, many constitutive models were developed to describe the engineering behavior of cemented clay (Gens and Nova, 1993;Kasama et al, 2000;Horpibulsuk et al, 2010a;Suebsuk et al, 2010 and2011).…”

Rapid field evaluation of the strength of cement-stabilized clayey soil

“…With the rapid economic development of Shanghai, many underground facilities, such as metro tunnels and deep excavations, are constructed in the soft deposits of Shanghai (Shen et al 2006(Shen et al , 2014Xu et al 2012b). In order to improve safety during underground construction, Portland cement is often used as an additive in many ground improvement techniques, such as deep mixing (Han et al 2007;Shen et al 2003Shen et al , 2008Chen et al 2013;Horpibulsuk et al 2011;Sukmak et al 2013) and jet grouting (Tan and Wei 2012;Tan and Wang 2013a, b;Shen et al 2013a, b, c;Wang et al 2013).…”

Sustainable Measures for Mitigation of Flooding Hazards: A Case Study in Shanghai, China

“…Numerous coastal mega-cities around the world have experienced hazards due to global warming. These hazards include increased demand for groundwater due to temperature rise [3][4][5][6], ocean acidification, and the collapse of ecosystems worldwide on land and at sea [7][8][9][10]. Moreover, rising temperatures and rising sea levels due to global warming tend to increase the probability of heavy rainfall risks, particularly in coastal cities [11,12].…”