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This research aims to propose the use of spectral analysis of surface wave (SASW) tests along with in-situ suction measurements for non-destructive determination of shrinkage cracks. The underlying principle behind this proposed method is that, while suction and the small-strain shear modulus are positively correlated for intact samples, this is not the case for cracked ground. A series of SASW tests were performed on a clay embankment at different periods, during which the suction, modulus, and shrinkage crack depth varied seasonally. The soil water retention curve (SWRC) of the undisturbed sample collected from the cracked zone was determined, which related the suction-to-moisture content and void ratio of the soil. A free-free resonant frequency (FFR) test in the lab was conducted to determine the small-strain shear modulus (G0) at various moisture contents. The small-strain moduli from the SASW tests on the intact ground were generally higher than those from the FFR tests due to the effect of confining stress. A drop in the small-strain modulus determined using the SASW test was observed as an increase in suction-induced cracks and it relieved the horizontal stress. The crack depth measured in the field was then modelled using a semi-empirical procedure that can be used to predict crack depth relative to suction.

The present study attempted estimations of watershedscale storage changes at two mountainous watersheds in northern Thailand to understand the behaviors of watershedscale storage under the 2011 Chao Phraya River flood. For this purpose, we applied a methodology that separates an hourly hydrograph into several discharge sub-components, and formulized watershed-scale storage-discharge relationships. The results showed that (1) this methodology was applicable to sub-tropic watersheds, (2) there were five different discharge sub-components, that correspond to the number of dominant rainfall-runoff processes, in two mountainous watersheds in northern Thailand, (3) the peak total storage in 2011 was estimated to occur in October because of strongly seasonal slower discharge subcomponents, whereas the maximum total discharge was observed in June, (4) the sum of watershed-scale maximum storages of all the discharge sub-components in the upper Yom and Nan River watersheds were respectively estimated to be 135 mm and 405 mm, and the difference might be explained by the existence of the active fault running northsouth in the upper Nan River watershed, and (5) the estimated storage with the recession time constants of 111 h at the beginnings of rainy seasons could explain the risk of slope failure occurrences within a watershed.

ABSTRACT:In recent years, surface penetration has attracted attention as a repair method for concretes structures. Silicate based penetration materials have been used in this method. In this study, visual appearance, water permeability, water absorption, water-vapor permeability, neutralization (carbonation) and chloride ion penetration testing of a silicate based surface penetration material are performed. The protection and waterproofing effects of a silicate based surface penetration material are evaluated based on the results. The silicate based surface penetration material penetrates deeply into the concrete surface, shows self-repair functionality, is effective to the neutralization (the carbonation) of the concrete and improves the performance of waterproofing. The penetration depth of the silicate based surface penetration materials plays an important role in the surface penetration method. Therefore, permeability testing of a mortar specimen, penetration depth testing of the mortar specimens with various silicate based surface penetration materials, viscosity testing of the materials and modelling of the one dimensional penetration into the mortar specimens are performed. The results of viscosity testing and coefficient of permeability suggest that these silicate based surface penetration materials will perform well surface penetration materials.

Chemical grouting techniques are used as ground improvement methods to obtain stable ground. In this method, soft sandy soils are solidified by injecting liquid solidification agents into the soils to prevent liquefaction as well as to increase strength. In this study, liquid glass grouting agents containing liquid glass with a higher polymerization degree (No. 5 liquid glass grouting agents) are being developed and discussed while focusing on the liquid agents to be used for chemical grouting techniques. Specifically, the solidification properties of No. 5 liquid glass grouting agents and the influence of the molar ratio of liquid glass to the strength and shrinkage characteristics of sand-gel and homo-gel are experimentally studied. As a result, the sand-gel made of No. 5 liquid glass grouting agents is superior in strength and has smaller shrinkage ratios after gelation, and therefore, is superior in soil improvement.

Landslide is a natural disaster which occurs very often in mountainous areas. Climate is an important determinant on the amount of moisture in the ground, which is a key to the stability of soil slope. Therefore, climate change due to the global warming may affect the intensity of rainfall and the evaporation in the future and influences situation of slope stability in a long time. The purpose of this study is to propose a method for assessing the effect of climate change on slope stability using general circulation model (GCM). A method for predicting climate change impact on slope stability is to link the antecedent precipitation index (API), hydrological model, obtained through downscaling GCM to critical antecedent precipitation model. The GCM is downscaled using a dynamical technique to derive regional climate models. Then a statistical correlation is used to adjust for the basis of the regional climate model. The GCM used in this study is the ECHAM4/OPYC3 model. The analysis found that the trend of susceptibility to slope failure depends on the pattern of simulated rainfall and the recession constant of the antecedent precipitation index.