Experiments were conducted to measure the suction of a locally available silty soil and commercially available white clay, using a Dewpoint PotentiaMeter ~WP4!. The results were used to develop the soil-water characteristic curves ~SWCCs!, for these soils and evaluating various fitting functions, in high suction ranges. Efforts have also been made to demonstrate the influence of the soil type and dry unit weight on the soil suction. The study brings out the observation that dry unit weight has negligible influence on the soil suction and parameters effecting SWCC.

Parameters affecting soil-water characteristic curves of fine-grained soils

Handbook of Tropical Residual Soils Engineering

Parameter identification for elasto-plastic modelling of unsaturated soils from pressuremeter tests by parallel modified particle swarm optimization

Bibliography Computational GeoMechanics

Loess consists essentially of silt-sized (typically 20–30 μm) primary quartz particles that form as a result of high-energy earth-surface processes such as glacial grinding or cold climate weathering. These processes have resulted in the almost continuous deposit from the North China plain to southeast England, for example, although it is possible to isolate five major regions: North America, South America, Europe including western Russia, Central Asia and China. These loess regions underlie highly populated areas and major infrastructure links, and are prone to collapse causing subsidence. The areas of most widespread concern are concentrated in Eastern Europe and Russia and to a growing extent in China, although serious problems of potential collapse exist wherever loess is found. Natural loess typically has an open structure with a void ratio of 0.8–1.0 or more, and is found in three main forms: sandy, silty or clayey loess. The primary quartz particles are held in this condition by bonding. These bonds break down progressively as increased stresses are applied at the natural water content, but more importantly the structure undergoes immediate and considerable collapse (up to about 15%) if saturated. The structure is therefore metastable in its catural condition. Such collapse has resulted in catastrophic failures that, in some cases, have caused considerable loss of life. More generally, they have proved enormously expensive in countries such as China, the USA, Bulgaria and other eastern European countries, and no less seriously, although less widespread, in countries such as the UK. This chapter will first examine the nature and global distribution of loess, primarily focussing on the main hazards associated with this material and its consequences to the built environment. The main objective of this chapter is to present the state of the knowledge associated with the improvement of metastable loess soils, drawing on the considerable experience from eastern Europe, and in particular Bulgaria. This will be achieved by considering three questions: o 1. What makes the loess problem still significant? 2. What is new in the principle of treatment of the loess base? 3. Which of the methods now being applied seem promising for the future? Case histories, taken from Bulgaria, will be used to examine design and analysis, measurement and post-treatment evaluation of ground improvement projects associated with loess soils. This will highlight the challenges and methods that can be used to overcome them.

Chapter 25 Treatment of metastable loess soils: Lessons from Eastern Europe

A methodology to identify the collapse potential of unsaturated soils is proposed in this paper on the basis of pressuremeter test results associated with independent measurements of the in situ matric suction. A solution combining the expansion of a cylindrical cavity to a modified Cam clay critical state model has been introduced and accommodated to the framework of unsaturated soil behavior. This accounts for changes in soil properties induced by suction changes. Interpretation of pressuremeter tests performed under unsaturated and soaked conditions links the amount of collapse to strength and stiffness changes and provides assessment to the constitutive soil parameters that are necessary to define the yield envelopes of the soil. A comprehensive site investigation program comprising field and laboratory tests carried out in two residual soil sites is discussed in order to validate the proposed methodology. Values of shear strength, in situ stress, and yield pressure derived from both field and laboratory data are used as input parameters of a constitutive model adopted for describing the yield envelopes of these unsaturated residual soil sites.

Unsaturated Constitutive Surfaces from Pressuremeter Tests

https://ascelibrary.org/doi/pdf/10.1061/%28ASCE%291090-0241%282006%29132%3A3%28427%29

Luis Artur Kratz de Oliveira

Papers

Unsaturated Constitutive Surfaces from Pressuremeter Tests

Closure to “Unsaturated Constitutive Surfaces from Pressuremeter Tests” by Fernando Schnaid, Luis Artur Kratz de Oliveira, and Wai Ying Yuk Gehling