This paper describes the characteristics of shear modulus at small strain in a normally consolidated region of peat and organic clay. When the seismic response of the ground is analyzed, the shear modulus at small strain (G0) of soil is an important parameter. However, previous studies on peat in this area are fewer than on inorganic soils such as sand and clay. Therefore, it is impossible to obtain a highly accurate G0 for peat. Due to the above, although some large earthquakes in Hokkaido, Japan, have caused great damage to earth structures on peat, the results of seismic response analysis cannot be expected to be highly credible under the current conditions. Therefore, a series of cyclic torsional shear tests were conducted on normally consolidated samples with a wide range of physical properties, from organic clay to fibrous peat, and the influence of effective confining pressure and physical index on G0 was studied.

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The Old Alluvium (OA) in Singapore is a quartenary alluvial deposit consisting of mainly medium to very dense cemented clayey quatzo-feldspathic sands and fine gravels with some coarse gravel and lenses of silt and clay (Pitts, 1984). Previous attempts to define the engineering properties of the OA from soil tests have met with limited success due to the vast scatter in the results resulting conservative assumptions of soil parameters for design of earth retaining structures. Consequently, the observed performance of recent deep excavations works in the OA shows a significant deviation from the predicted performance. Amongst the various reasons that could account for the deviation of actual field performance, one major factor was inability of conventional testing methods to derive stress-strain behaviour of soil at smaller strain level. In this paper, the ensuing investigations to measure the small strain stiffness behaviour of the Singapore OA soils from laboratory and field tests are presented. PS suspension logging tests are conducted to interpret the small strain stiffness of the soil in the field in-situ. Bender element tests in triaxial set up are conducted on undisturbed samples to determine the small strain stiffness of soil in the laboratory.

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To meet the high demand of land resources due to rapid development in Macau, reclamation is the major solution. As the reclamation projects are usually located on seabed of soft marine deposits, the engineering behavior of such material is crucial to the performance of the reclaimed lands. This study mainly investigates the influence of long term consolidation on the shear wave velocity (V_s) of the Macau marine clay (MMC). The small strain shear modulus or shear wave velocity plays a very important role in construction design. Many correlations have been developed relating the small strain shear modulus or shear wave velocity to the current stress state (isotropic or anisotropic), stress history (OCR), and void ratio, but the shear wave velocity is usually determined at the end of primary consolidation, and its variation in the secondary consolidation process due to creep has rarely been taken into account. In this study, a series of consolidation tests with reconstituted and undisturbed samples were conducted over more than half year with shear wave velocity measured by piezoelectric bender elements in a modified oedometer. From the results of consolidation tests and the simultaneously acquired (Vs), variation of (Vs) during the consolidation process was closely monitored. It is found that the increase of shear wave velocity is linearly dependent on the average degree of consolidation and the time lag after the primary consolidation in the consolidation process. Based on the testing results, correlation equations for the shear wave velocity in the consolidation process were developed and possible explanations were provided.

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In tropical volcanic countries such as Indonesia, residual soil covers most of the islands; as the weathering process of igneous, sedimentary and metamorphic rocks is still actively undergone due to the tropical climate. The objective of this paper is presented the effect of drying-wetting cycle’s repetition on the static and dynamic properties of three natural residual soils. The laboratory and field test results from three residual soils show that, the void ratio decreased with clay content, the cohesion were increase with clay content. Drying-wetting cycle’s repetition reduces void ratio, negative pore-water pressure, cohesion and internal friction angle of soils. On the other hand, the unit weight of soil and shear modulus (GUBE) increase with the number of cycles. The cohesion after the sixth cycle reduce 8,70%, 9,09% and 1,5% respectively. Shear modulus (GUBE) after the sixth cycle for all undisturbed residual soils increase 25,46%, 24,15% and 11,25% respectively. As the soil densities and void ratio were increase, the soil cohesion were decrease.

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Soil erodibility is almost always determined and regarded as a constant parameter that does not change with the climate change. Indonesia has dry and wet seasons which may greatly affected the soil properties. Most erosion models and sediment prediction have been developed based on the soil erodibility factor (K) determined from Weischmeier Nomograph; although soil physical changes due to drying and wetting cycles were neglected. This proposed paper presents the Weischmeier soil erodibility factors affected by the soil properties’ change on the drying and wetting cycles. For this particular purpose, the effect of drying-wetting cycle’s repetition on undisturbed soil from Manting Basin Mojokerto had been studied. The drying-wetting cycle’s processes were repeated 6 times; the properties of the soil specimens were investigated at 1, 2, 4 and 6 cycle. During the drying process, the soil specimens were naturally and gradually air dried; while in the wetting process, the soil specimens were gradually wetted up to their fully saturated condition. The soil properties such as: water content (wc), degree of saturation (Sr), void ratio (e), suction and dry unit weight were measured at every desired conditions. The Weischmeier soil erodibility factors were then determined using Weischmeier Nomograph. The results shows that the soil erodibility factors were almost insignificantly unchanged on the dry condition up to around 90% degree of saturation; but then they were decreased rapidly up to 100% degree of saturation. This is thought to be due that the permeability coefficient greatly increase at nearly saturated condition; this condition change the permeability level from very slow to slow to moderate in the Weischmeier Nomograph.

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Basement construction has been developed for many years by using either top-down construction method or bottom-up technique. Recent, deep basement construction in Bangkok City becomes complicated as it may trigger damage to sensitive surrounding structure. Central Embassy department store project is the luxury department store and hotel located in the Central Business District (CBD). There are 5-6 basement floors which required excavation to 24.2 meter below ground level. The excavation is closed to Bangkok Mass Transit System (BTS) sky train foundation at the front and the British Embassy at the back. Various depth and size of diaphragm wall were carefully analyzed and designed based on many obstruction. Fully instrument scheme including inclinometer, piezometer and stress transducer were installed in diaphragm wall and soil for monitoring of walls and their effect. The field measurement agrees with FEM prediction. The basement construction was completed without any effect to BTS sky train foundation and British Embassy.

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According to the design code of construction for port and harbor facilities in Japan, ground that has sand size content between 50% and 80% is called intermediate soils, because of its intermediate behavior between sand and clay. Though intermediate soils with low plasticity are likely to be under partially drained conditions, stability analysis and evaluation of the shear strength for intermediate soil has been carried out based on undrained conditions. The drainage characteristics of the soil were estimated; that is, it was estimated whether the ground is under fully undrained conditions or partially drained conditions using CPTU data. The partially drained shear strength was estimated from the analysis of the distribution characteristics of CPTU based shear strength between the undrained shear strength line and the fully drained shear strength line, which was ranged approximately from ϕ´=5º to ϕ´=15º, similar to ranges of back analysis for the estimation of replacement depths.

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