Possible explanations on the formative processes of the Tsugaru-Juniko landslide, northern Japan

<p>Identification of complex surficial and internal sedimentological characteristics of landslide deposits can provide insights into the emplacement mechanisms of mass movements. In this study, deposits of the Tsugaru-Juniko landslide, which was historically recorded triggered by an earthquake in 1704 (Imamura, 1935), in Aomori Prefecture, Japan were investigated. This landslide extended about 2 km from east to west with a volume of about 10<sup>8</sup> m<sup>3 </sup>(Furuya et al., 1987), of which deposit is represented by irregular topography and several lakes on and around the rim of it. We conducted field geological and geomorphological surveys and made geomorphological and geophysical analyses using a 1-m resolution LiDAR-DEM and 2D electrical resistivity tomography (ERT) measurement (10 m spacing of electrodes) over a 450 m wide landslide deposit. In plain view, the landslide deposit exhibits quite different features between its northern and southern parts, and each shows a clear sequential distribution of various features. At the northern part, the translation zone is characterized by hummocks and debris lobes containing mixtures of poorly sorted, angular, blocky rock debris of andesitic tuff. Prominent features on the debris lobes are debris-flow-ridges with lobate-shaped aprons extending NW to the downslope. In the accumulation zone, slope surface upheavals of compression origin and radial cracks are observed in the front part of the landslide. At the southern part, as compared to those features observed at the northern part, the slope is commonly marked by transverse ridges, oriented NE-SW, with prevalent steep cliffs on both sides, but generally steeper on the east. The ridges are separated from one another by trenches, elongated across the slope. Based on the distributions of these features, possible explanations on the formative processes of the landslide are complex associated with flowing and sliding at northern and southern parts, respectively. However, geological evidences from its internal structures are rare, ERT survey at the northern part of the landslide deposit reveals that up to 30-m-deep high-resistivity anomaly is associated with the landslide deposit, and low-resistivity anomaly with the bedrock consisting of pumice tuff, as also confirmed in the field. This may result from the high porosity of landslide deposit, because the displaced material deposited loosely.</p>

Sorption Behavior of Nickel and Palladium in the Presence of NH3(aq)/NH4+

ABSTRACTIt is necessary to assess the impact of nitrate salts and their reduction products (e.g. NH3(aq)/NH4+) contained in low-level radioactive waste generated from nuclear reprocessing process for the safety assessment of geological disposal of the waste. In the present study, sorption behavior of Ni and Pd on pumice tuff was investigated in the presence of NH3(aq)/NH4+. Under various NH3(aq)/NH4+ concentration, pH and ionic strength conditions, distribution coefficient (Kd) of Ni and Pd on pumice tuff was determined by a batch experiment. For Ni system, the Kd values showed no significant dependence on initial NH4+ concentration ([NH4+]ini < 1 M) in neutral pH region, which agreed with the prediction from thermodynamic data. For Pd system, the Kd values decreased with an increase of [NH4+]ini, suggesting the formation of stable ammine complexes (Pd(NH3)m2+ (m: 1 – 4)). The obtained Kd values for Ni and Pd were analyzed using a surface complexation model. By taking complexes predicted by thermodynamic data into account, sorption behavior of Ni and Pd in the presence of NH3(aq)/NH4+ were well explained.

Gas Transport Properties of Pumice Tuff for Performance Assessment of LLW Disposal Facility

In Japan, some of the radioactive waste with a relatively higher radioactivity concentration from nuclear facilities is to be packaged in rectangle steel containers and disposed of in sub-surface disposal facilities, where normal human intrusion is unlikely to occur. If dissolved oxygen in pore water is consumed by steel corrosion after the closure of the facility, hydrogen gas will be generated from the metallic waste, steel containers and concrete reinforcing bars largely by anaerobic corrosion. If the generated gas accumulates and the gas pressure increases excessively in the facility, the facility’s barrier performance might be degraded by mechanical influences such as fracturing of surrounding rock and cementitious materials or plastic deformation of the bentonite buffer. In this study laboratory experiments for gas and water transport properties of the rock were performed to evaluate gas flow through the rock mass (pumice tuff) around a facility for low level waste disposal. Based on the experimental results two-phase flow properties were evaluated by means of an inverse analysis method. The pumice tuff was subjected to hydraulic conductivity tests, water retention (moisture characteristic) tests, and gas injection tests. Non-linear properties such as relative permeability and water retention curve and hydraulic conductivity as a function of confined stress obtained from these tests are discussed. It was possible to estimate the intrinsic permeability, the relative permeability for gas and water and the water retention curve by applying an inverse analysis method using the multi-phase flow analysis code GETFLOWS and universal sensitivity analysis code UCODE_2005 to the gas injection tests. It was found from this study that gas flow in the pumice tuff is reasonably well described by classical two-phase flow concepts and that the two-phase flow properties can be applied to performance assessment of the facility with regard to the influence of gas generation and migration.