Influence of Matric Suction on the Results of Plate Load Tests Performed on a Lateritic Soil Deposit

Abstract

The performance of foundation systems on unsaturated soil deposits is considerably influenced by variations of the negative pore-water pressure (i.e., matric suction) distribution within the soil mass due to local microclimate conditions. Although significant understanding has been gained in the last few decades on the behavior of unsaturated soils, the use of unsaturated soil mechanics concepts in the interpretation of field tests has not been incorporated into the state-of-practice. As a consequence, conservative foundation engineering principles are used in practice in regions where unsaturated soil conditions prevail. For example, direct use of field test results (e.g., from plate load tests) obtained during a dry season in unsaturated soil deposits may lead to the selection of unconservatively high design parameters at the site. On the other hand, ignoring altogether the beneficial impact of matric suction on the bearing capacity of soils may lead to unnecessarily expensive foundation systems in tropical, arid climates. This paper investigates the influence of soil suction on the results of plate load tests conducted at a depth of 1.5 m on a structured, naturally occurring lateritic soil. Ten tests were carried out under different soil suction conditions. Matric suction was monitored during plate load testing using tensiometers installed at the bottom of the testing pit up to a depth equal to one plate diameter (0.80 m), which is generally recognized as the influence zone in which significant stress variation occurs (Terzaghi and Peck 1948). The results provide insight into the influence of soil matric suction on ultimate bearing capacity and settlement rate of plate load tests performed on lateritic soils.

Modelling the applied vertical stress and settlement relationship of shallow foundations in saturated and unsaturated sands

“…Second, there is a lack of a valid framework to interpret bearing capacity and settlement behaviour of unsaturated soils. Steensen-Bach et al (1987), Oloo et al (1997), Costa et al (2003), Mohamed and Vanapalli (2006), Rojas et al (2007), and demonstrated that the bearing capacity of unsaturated soils is significantly influenced by matric suction from their investigations on model footing or in situ plate load tests. Recently, Vanapalli and Mohamed (2007) provided a framework to both interpret and predict the variation of bearing capacity of unsaturated soils with respect to matric suction using saturated shear strength parameters (i.e., c', f 0 ) and the soil-water characteristic curve (SWCC).…”

Bearing Capacity of Shallow Foundations on Unsaturated Silty Soils

“…where B is the width of the foundation; L is the length of the foundation; and N unsat is the UBC factor in unsaturated soils, which was obtained using back analysis by Oh and Vanapalli (2013) [18]. In addition, for the estimation of the UBC of foundations on coarse-grained unsaturated soils under drained loading conditions, equations based on the modification of the UBC equation (Equation ( 4)) proposed by Terzaghi (1943) [1] for strip foundations on saturated soils is available in the literature [12,13,15,26,29,30,32,34].…”

“…Therefore, research on the behavior of unsaturated soils has been prioritized over the last ten years. In the literature, experimental studies have been conducted under both drained and undrained conditions [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]. In general, research in this area has aimed to improve understanding of the mechanical behavior of unsaturated soils and to develop appropriate methods for assessing the bearing capacity of unsaturated soils.…”

Experimental Evaluation of Stiffness Properties of a Quicklime-Stabilized Clay Subgrade Using a Resistivity Plate Loading Testing Device

“…Many research studies have covered several of these problems (11)(12)(13)(14)(15)(16)(17), including programs to establish the mechanical, strength, and physical properties of soils (12,(18)(19)(20), relationships between various physical and mechanical test methods (15,(21)(22)(23), variables affecting different test methods (24)(25)(26)(27)(28)(29), design philosophies (30), quality control and assurance in construction (25,31), and so forth. Soil stabilization with lime is widely accepted for improving problematic soils like clay in subgrade engineering (32)(33)(34).…”