Internal erosion of gravelly mudstone due to drying/wetting and hydraulic pressure cycles in oedometer test.

When disintegrated mudstone due to the slaking, subjected to hydraulic pressure, could lead to internal erosion. To examine the combined effects of slaking and internal erosion of gravelly mudstone in 1D deformation under a constant vertical load, a series of modified oedometer tests and laboratory penetration tests were conducted with drying/wetting and hydraulic pressure cycles. Some loading conditions showed the sever erosion in progressing of the cycle, susceptibility of the internal erosion was evaluated in terms of non-filter and fitter factors coefficient Keywords: Vertical strain, Slaking, Internal-erosion, Particle-breakage.

METHOD FOR PRESENTING THE RESULTS OF OEDOMETER TESTS UNDER A SURVEY OF A PEAT DEPOSIT

The use of the average values of physical and deformation characteristics for the entire extremely heterogeneous peat layer leads to mistakes in estimation a settlement of the embankments set up over it. The results of numerous oedometer tests of peat and empirical equations for calculating the void ratio of peat as a function of its initial value and the load are presented. A new approach to carrying out the geotechnical surveys in a wetland is proposed.

The effect of pH and electrical conductivity of the soaking fluid on the collapse of a silty clay

Different fluids can permeate the soil collapsing at various levels of severity depending on their physicochemical characteristics. This work evaluated the effect of pH and electrical conductivity (ECf) of different soaking fluids on the collapsible behavior of a lateritic silty clay. Double and single oedometer tests were performed using four chemically distinct soaking fluids (water, leachate and two laboratory solutions, one alkaline and one acid). The collapse index (I) was evaluated according to two criteria. In addition, physical-chemical analysis of the soil and measurements of pH and ECf were done. According to the results, the soil is collapsible for the four soaking fluids. No single relationship was found between fluid pH and collapse index, although, the highest values of collapse index were found in the tests soaked with alkaline and acid solutions. Finally, a unique direct relationship was found between the collapse index and the ECf, that is, the higher this parameter, the higher the collapse index value.

Evaluation of the Organic Soil Compressibility from In-Situ and Laboratory Tests for Road Application

Organic soil is characterised by high compressibility and should be improved so that it can be used for construction. The use of every method of soil improvement requires knowledge of the compressibility parameters. One of these parameters is the constrained modulus. The constrained modulus can be determined using laboratory or in-situ tests. In this study, the constrained modulus of organic soil was determined using oedometer and piezocone tests (CPTU). The author analysed subsoil under an approximately 250 m section of a designed road in north-eastern Poland. The constrained modulus of organic soil sampled from four different depths was determined in oedometer tests. Piezocone tests were conducted at 18 points located every 15 m along the length of the section concerned. To determine the constrained modulus based on the cone resistance from CPTU tests, the knowledge of the α and αM coefficients is needed. For the tested soil, the optimal range of the α coefficient from 0.4 to 0.7 was determined. The αM coefficient ranged from 0.4 to 0.8. The value of the constrained modulus of organic soil obtained from the oedometer tests, depending on the effective stress, ranged from approximately 100 kPa to 400 kPa. The constrained modulus of the tested soil decreased with depth, which both research methods proved.

Effects of curing on emulsion cold mix asphalts and their extracted binder

This paper focuses on the physicochemical changes that happen in cold mix asphalts during curing, and more specifically, while and after transitioning to different simulated seasons. Several tests were carried out in order to better grasp the influence of the weather (temperature and humidity) on the curing of such materials. The mechanical behaviour of the mix was assessed using oedometer tests. The physicochemical evolutions of extracted binders, such as oxidation and rheology, were evaluated. The results show stiffening of the mix and ageing of the binder linked to a higher temperature and a lower humidity. A low temperature and high moisture seem to slow down these evolutions. However the binder behaviour does not explain the whole mix behaviour as the kinetics between them are not always similar. Thus other mechanisms are yet to be found and taken into account to fully understand cold mix asphalts behaviour.

Quantification of sample disturbance for soft, lightly over-consolidated, sensitive clay samples

When using initial deformation from oedometer tests to quantify sample disturbance, a correction for false deformation is sometimes needed. A method to determine this false deformation is presented.

Experimental Investigation into Compressive Behaviour and Preconsolidation Pressure of Structured Loess at Different Moisture Contents

This paper investigates the influence of the structured property of loess on its compressive behaviour and proposes a new method for determining the preconsolidation pressure of structured loess soil. A series of oedometer tests were carried out on undisturbed and remoulded loess samples prepared at various moisture contents. The effects of moisture content on the structured yield stress, the preconsolidation pressure, and the structural strength were also captured. It was found that the influence of the structured property of loess on the compression behaviour is divergent between undisturbed and remoulded loess samples. The discrepancy before and after structural yielding is more remarkable for the undisturbed soil. The Casagrande method realized through the MATLAB program can effectively eliminate human factors and accurately calculate the corresponding preconsolidation pressure for undisturbed soil. The effects of moisture content on the method for determining the preconsolidation pressure considering the structured property of loess were discussed. The determination method can accurately evaluate the loess consolidation state in loess regions. The influencing rules which the moisture content exerts on the structured yield stress, the preconsolidation pressure, and the structural strength all conform to exponential functions. The study is of great significance to correctly differentiating the foundation consolidation states and calculating the ground settlement in loess regions.

Compression and consolidation behaviors of lime-treated dredging slurry under vacuum pressure

Dredging slurry is treated by a combination of lime treatment and vacuum preloading. However, the mechanical characteristics and consolidation mechanics of lime-treated slurry under vacuum loading is not fully understood, making it difficult to predict slurry settlement. In this study, we develop a laboratory model of lime-treated slurry and subject it to vacuum preloading to investigate the compression and consolidation behaviors. The results demonstrate the reduction of the risk of clogging around the prefabricated vertical drains, the increase in soil permeability, and the improvement of vacuum preloading upon lime treatment. log (1 + e)-log p curves for soils with different percentages of lime content are obtained through a series of modified oedometer tests. Based on these curves, an analytical solution for lime-treated slurry settlement under vacuum preloading was derived and validated through laboratory tests. The solution can be used to predict lime-treated slurry settlement under vacuum pressure effectively.

High compressibility caused by particle breakage: a DEM investigation

This paper summarises the numerical and experimental studies of brittle, hollow, cylindrical particles, called shells. It addresses the influence of shell properties both at the particle and assembly scales. Extreme compressibility has been recorded in the oedometer tests. Due to the large internal porosity of the shell, the breakage phenomena lead to highly compressive deformations with a significant stress dissipation. Using the Discrete Element Method (DEM), we have investigated in depth the micro-mechanical phenomena governing this macroscopic response. By quantifying the breakage and separating the double-porosity of the material, the foundations of a future constitutive model have been established throughout a simple prediction model applicable to the engineering practice.