Investigation on the Effect of Curing Time on Uni-Axial Strength of Clayey Soils Strengthened by Saturated Lime Solution
This paper describes some of the main results of an investigation on the effect of passing saturated lime solution with different curing time on the clayey soil. Six series of laboratory tests had been set up, on lean clay samples, to investigate simultaneously the effect of volume of solution and curing time. The samples were classified based on average volume of passing. Three categories were considered, 19Vv, 28Vv and 40Vv. The volume of the saturated solution was fixed and all of the samples were held in a chamber with desired condition of temperature and humidity for different curing period, followed by a mechanical and chemical test. The findings released from the tests indicated that the length of curing period and volume of saturated lime solution at which curing took place had an important influence on the amount of strength developed. An exponential evolution was found for the uni-axial strength as a consequence of the curing time. Especially after 28 days. Calcium ion consumption after 28 days and also exponential evolution for uni-axial strength demonstrated the threshold value of curing period of 28 days for treatment of soil by saturated lime solution.
Increase in basin sediment yield from landslides in storms following major seismic disturbance
The landslide area along the Tachia River catchment of central Taiwan was investigated using the remote sensing images of various typhoon and earthquake events taken from 1996 to 2004 and the sediment discharge measured at hydrometric stations. Our findings indicate that 88% of the coseismic landslides triggered by the 1999 Chi-Chi earthquake were first-time occurrences. After the Chi-Chi earthquake, 59% of the landslide area was reactivated during typhoon Toraji and 66% during typhoon Mindulle. The landslides prone to reactivation were on the formations with closely spaced discontinuities. It is suggested that further rock-mass defects in the formations were added or opened by the earthquake, and that the landslide areas continued to extend until the end of 2004. Post-1999 rainstorms delivered large amounts of colluvial sediment into the main channel, leading to a 2-fold increase in post-seismic sediment discharge while the precipitation was only half that of the pre-earthquake rate.
Soft subgrades' stabilization by using various fly ashes
Abstract This publication presents the results of research involving different types of self-cementing fly ashes (without any other activators) for the stabilization of four different types of soft subgrades from various road sites in Wisconsin, USA. The strength approaches were applied to estimate the optimum mixture design and to determine the thickness of the stabilized layer. The stabilized soil samples were prepared by mixing fly ash at different contents at varying water contents. The performance of fly ash stabilized subbase depends both on the specific source of fly ash and the engineering properties of soils. It is suggested that the performance analysis of fly ash should be based upon the laboratory tests such as index properties, compaction, unconfined compressive strength and CBR tests of a specific site. This is suggested rather than using the study of the physical properties and chemical composition of fly ash and soil. As disclosed in the literature, the strength gain due to stabilization depends mainly upon three factors; ash content, molding water content and compaction delay. The samples were subjected to unconfined compression strength and California bearing ratio (CBR) tests after 7 days curing time to develop water content–strength relationship. To evaluate the impact of compaction delay that commonly occurs in the field during construction, the sets of samples were compacted 2 h later after mixing with water. The unconfined compression strength and CBR tests were performed and used to determine the thickness of the stabilized layer in pavement design. All of these factors were taken into account throughout this research.