The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
Le Dong - One of the best experts on this subject based on the ideXlab platform.
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estimation of undrained shear strength in moderately oc clays based on field vane test data
Acta Geotechnica, 2017Co-Authors: Kaveng Yuen, Le DongAbstract:The undrained shear strength (s u) of cohesive soils is a crucial parameter for many geotechnical engineering applications. Due to the complexities and uncertainties associated with laboratory and in situ tests, it is a challenging task to obtain the undrained shear strength in a reliable and economical manner. In this study, a probabilistic model for the s u of moderately overconsolidated clays is developed using the Bayesian model class selection approach. The model is based on a comprehensive geotechnical database compiled for this study with field measurements of field vane strength (s u), plastic limit (PL), natural water content (W n), liquid limit (LL), vertical effective overburden stress (\(\sigma_{\nu }^{\prime }\)), Preconsolidation Pressure (\(\sigma_{\text{p}}^{\prime }\)) and overconsolidated ratio (OCR). Comparison study shows that the proposed model is superior to some well-known empirical relationships for OC clays. The proposed probabilistic model not only provides reliable and economical estimation of s u but also facilitates reliability-based analysis and design for performance-based engineering applications.
Helen Ahnberg - One of the best experts on this subject based on the ideXlab platform.
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strength of stabilised soil a laboratory study on clays and organic soils stabilised with different types of binder
2006Co-Authors: Helen AhnbergAbstract:Stabilisation of soft soils by deep mixing with binders is the most frequently used method of ground improvement in Sweden today, and is increasingly being used internationally. The most common binders employed are cement and lime, but a variety of other binders may also be used for stabilisation of soils. For further development of the deep mixing method, there is a need for more extensive research on the undrained and drained strength properties and behaviour of soils stabilised with various types of binders. The overall objective of the study presented in this thesis was to improve the understanding of some of the important aspects of the strength behaviour of stabilised soils. For this purpose, a series of laboratory tests was performed on four soils stabilised with different types of binders. The soils included two types of clay and two types of organic soil. Cement, lime, blastfurnace slag and fly ash in different combinations, alone and together with a number of admixtures, were used as binders. The laboratory testing was focused on the strength properties. However, a number of other basic properties of importance for the understanding of the strength behaviour of stabilised soils were also investigated, such as the density, water content, degree of saturation, permeability and the compression properties. Unconfined compression tests and triaxial tests were used to investigate the strength of the various samples stabilised in the laboratory. The unconfined compressive tests were performed mainly in order to study the effects of different binders on the increase in strength with time after stabilisation. The triaxial tests, conducted both as drained and undrained tests, were performed mainly to study the strength behaviour under various drainage and stress conditions. The influence of different testing procedures, such as different back Pressure and rate of strain, was also studied. Both active and passive undrained triaxial tests were performed in order to investigate the strength anisotropy of the stabilised soils. The results provided illustrative examples of the effects of different binders on the increase in strength of stabilised soils, which may be linked to the chemical reactions taking place after mixing. In addition to the composition of the soil and the binder, a number of other factors also affect the strength of stabilised soil. The results show that the drainage conditions and the stresses acting on stabilised soil may have a considerable influence on the measured strength. A stress dependence of the undrained strength as well as the drained strength is evident from the test results. A quasi-Preconsolidation Pressure, which is governed not only by the stresses applied to the stabilised soil, but also by the cementation taking place during curing, is shown to influence the strength behaviour. An improved strength model is proposed that describes the strength behaviour in the same stress plane commonly used for natural unstabilised soils. It was concluded that although the type of binder may strongly affect the rate of strength increase and the final strength, the general strength behaviour is the same for soils stabilised by the most common binders. The strength and deformation properties of stabilised soils are similar to those of cemented and overconsolidated natural soils. The same set of parameters used to describe the strength of natural soils can also be used for stabilised soils. (Less)
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On the evaluation of undrained shear strength and Preconsolidation Pressure from common field tests in clay
Canadian Geotechnical Journal, 2005Co-Authors: Rolf Larsson, Helen AhnbergAbstract:The undrained shear strength is a key parameter in the estimation of the stability of natural slopes and man-made constructions in soft clay. It is therefore important to develop relevant methods to evaluate the operative strength. Results from an investigation regarding the effect of excavations at slope crests to increase the stability of clay slopes are presented. This study has provided an opportunity to study the effect of overconsolidation on the evaluated parameters from common in situ tests in homogeneous and truly overconsolidated clays. Certain inconsistencies in the commonly used methods of interpretation of field vane tests, cone penetration tests, and dilatometer tests are highlighted, and modified interpretation methods taking the effects of overconsolidation into account are proposed.Key words: clay, overconsolidation, undrained shear strength, cone penetration test, field vane test, dilatometer test.
Kang Cheng - One of the best experts on this subject based on the ideXlab platform.
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experimental investigation into compressive behaviour and Preconsolidation Pressure of structured loess at different moisture contents
Geofluids, 2021Co-Authors: Panpan Guo, Chengwei Zhu, Gang Lei, Kang ChengAbstract: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.
Dalvan Jose Reinert - One of the best experts on this subject based on the ideXlab platform.
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mechanized land preparation in eastern amazon in fire free forest based fallow systems as alternatives to slash and burn practices hydraulic and mechanical soil properties
Agriculture Ecosystems & Environment, 2014Co-Authors: Jose Miguel Reichert, Clovis Moises Priebe Bervald, Miriam Fernanda Rodrigues, Osvaldo Ryohei Kato, Dalvan Jose ReinertAbstract:Abstract Soils of the Brazilian Amazon are particularly fragile due to the inherent soil properties, climate conditions, and the management systems adopted in the region. The aim of this study was to evaluate changes in the mechanical properties and water retention of soils under different tillage systems of secondary vegetation in an area kept fallow for 10 years in Eastern Amazon, Brazil. The treatments consisted of the slash-and-burn of secondary vegetation (SB), slash-and-burn, stump removal and plowing (SBSP), chop-and-mulch of secondary vegetation (CM), and original secondary vegetation (OSV). Undisturbed soil samples were collected immediately, and 15 and 30 days after site preparation (0, 15, and 30 DAP, respectively) to determine bulk density (BD), total porosity (TP) and marcoporosity (Mac), and water retention. Preconsolidation Pressure (σp) and compression index (Cc) were assessed at 0 and 15 DAP, whereas soil penetration resistance (PR) was measured directly in the soil profile. The least BD and greatest Mac and TP and the highest water retention at −30 kPa matric potential were obtained immediately after preparation using the SBSP system. The σp at 0 DAP was lower than the Pressure exerted on the soil surface by the machines used for the CM and SBSP systems, but increased numerically to 15 DAP. The PR differed among the systems until reaching 0.25 cm soil depth. Leaving plant residues from the mulching of secondary vegetation on the soil is not, by itself, an effective practice for maintaining structural soil quality in the short term. Soil tillage in the SBSP system decompacts the upper soil layer, which improves all physical indicators, but only in the short term (less than one month). Soil reconsolidates quickly with the lack or reduced effect of organic matter on soil structure and system equilibrium.
Mohamed Boutouil - One of the best experts on this subject based on the ideXlab platform.
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geotechnical properties of dredged marine sediments treated at high water cement ratio
Geo-marine Letters, 2009Co-Authors: Boubaker Rekik, Mohamed BoutouilAbstract:Cement and lime are widely employed in soil and sediment treatment for an improvement of geotechnical properties, such as an increase in mechanical strength which enables beneficial use in various geotechnical applications. In this study, fine organic-rich dredged harbour sediments of 120% relative water content were treated with dry cement at contents varying between 2% and 10% of bulk sediment wet weight. Tests based on assessments of one-dimensional compression and Atterberg limits were performed on untreated and cement-treated sediments for various curing periods, as well as grain-size, SEM and X-ray diffraction analyses. The results confirm that increasing the cement content improves the geotechnical properties of these harbour sediments. Already in the early phase of curing (first 3 days of curing), particle size increases while sediment plasticity decreases. Changes in the compressibility behaviour include an increase in apparent Preconsolidation Pressure, in the compression index C c and in the primary consolidation coefficient C v, and a decrease in the secondary compression index \( C_\alpha \). This means that the new materials are characterized by a behaviour intermediate between that of fine and that of coarser soils.