This research deals with seasonal change of salt weathering and XRD analysis of salts for the stone caves, called “yagura, ” built in Kamakura, central Japan, during the Kamakuraera, about A. D. 1200 to 1300. The detected salts are gypsum, epsomite, thenardite and calcite. Among these salts, the soluble epsomite and thenardite occur from winter to early spring, while insoluble gypsum and calcite are observed through the year. In order to consider this observation result, we measured temperature and humidity in stone caves and also performed solution experiment using rocks of the same lithologies with the yagura stones. Consequently, the seasonal change in salt precipitation is shown to be correlated well with that in humidity change, and considerable quantity of salt-forming ions are shown to dissolve out from the rock samples into water.
Salts are considered to precipitate on rock surfaces through evaporation of solutions made by water-rock interaction, especially during dry season of winter. Three types of collapse are recognized for rock surfaces of yagura's; (1) salts pulverize rock surfaces into powder (“powder-type”), (2) salts form crusts on rock surfaces, and crusts fall down together with thin films of host rocks (“crust-type”), and (3) salts grow inside cracks and fracture them into blocks (“blocktype”). Salt weathering is well known as weathering process in arid/semi-arid areas. This research shows that salt weathering is also important in humid areas like Japan in case dry and wet seasons occur. Gypsum is reported from many ruins of other areas, while the seasonal change of soluble epsomite and thenardite causes the “powder-type” collapses and considerably affects yagura's.

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Mineralogical studies on two types of Miocene sedimentary rocks (shale and siliceous shale) in the Oga Peninsula, northern part of Japan indicate that (1) weathered shale contains gypsum, while weathered siliceous shale does not, and (2) carbonates are abundant in unweathered shale, but they are poor and feldspar is abundant in unweathered siliceous shale.
The calculations on the change in groundwater chemistry due to the dissolution of calcite and feldspar indicates that gypsum is formed by the calcite dissolution but it is difficult to be formed by the feldspar dissolution. The mineralogical studies and the dissolution calculations suggest that the mineralogical composition of original sedimentary rocks is important factor controlling gypsum formation, together with pyrite abundance in the original rocks and humidity.

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The markov matrix and information entropy have been used for analyzing successions of sedimentary rock and modeling of hydrogeological environment in wide groundwater basin. In this study, these techniques were applied to evaluate recognizable pattern of a fracture distribution using boreholes data. The changing pattern of fracture frequencies along boreholes were calculated by using the markov matrix and Information entropy. As a result of the calculations, it was found that the fracture frequencies could be well described by using these techniques, and the thickness of low fracture frequency zone was estimated.

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It is supposed that the running water such as infiltration water/groundwater/surface water in floodplain is affected to an old river channel or old low-water channel. In Nagata district at Tama River, we investigated the situation of running water in a floodplain. The observations were different when a study was carried out on the running water flow during a construction work for strengthening a pier of bridge over the river against earthquake. In this study, we showed a change of running water by this pier. And we discussed causes of change by using field measurement and available topographic maps and aerial photographs. As a result the following things were shown.
1) It was understood that the running water environment in the floodplains of Tama River was complicatedly influenced by the old river channel. The bridge pier is situated over the old low-water channel, which used to be the low-water channel during the 1940s. For this reason the groundwater level dropped down significantly and the ponds near bydried up after the pier strengthening work was started.
2) The electrical conductivity and level of groundwater at some points are higher than those of the groundwater at the peripheral points. The reason for the difference is regarded as the influence of topographic features of the riverbed during the 1970s. The water quality in/near the zone of high electrical conductivity was changed during a pier construction work.
3) We grasped the topography of old river channel utilizing former edition topographic map, an ancient map and old aerial photograph. It is shown that this technique is important means to elucidate behavior of running water in the present floodplain.
4) The works related to river channel improvement have been started since 2001 spring. By this improvement work, it will be easier to understand the actual cause of influence on the flow of subsurface water and the ecosystem in a floodplain.

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The appearance of mud islands, termed mudlumps, is well known in the Mississippi River delta mouths. A similar phenomenon occurred at the mouth of the Iinashi River in 1991. Although several theories have been proposed to explain the formation processes of these phenomena, there are many unclear points in the deformation behavior of soft ground from the accumulation of sandy sediments during the formation of mudlumps. However, due to advances in both constitutive equations which can explain mechanical behavior of soil and reasonable soil parameters, as well as advent of new generations of powerful computers, it has become possible to predict the deformation behavior of soft ground using finite element method.
This paper presents finite element analysis of mudlump formation caused by sand accumulation using an elastoviscoplastic model. The formation process of mudlumps is explained quantitatively by comparing results of finite element analysis with information based on sedimentary environments such as key layers. Finally, this study demonstrates the importance of integrated studies of sedimentary environments and geotechnical engineering of natural phenomenon where little information on deformation behavior exists.

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