In order to express time dependence actions, such as secondary consolidation, creep, and strain rate dependence, much elasto-viscoplastic constitutive models are proposed until now. However, in these constitutive models based on a viscoplasticity theory, the time dependence action from an overconsolidation domain to a normal consolidation domain cannot be expressed continuously. Moreover, Pc-effect by secondary consolidation cannot be evaluated quantitatively, either. In this paper, the elasto-viscoplastic model in consideration of Pc-effect by secondary consolidation is proposed. Moreover, the simulations of shear test and consolidation test were carried out and the validity and applicability of this constitutive model were examined.
Development of technique which can restrain the progress of desertification sustainably and voluntary is taken place by using valuable herbal plant licorice (Glycyrrhiza uralensis). Firstly, prehension about geo-environment included weather condition around the study areas is needed to succeed the technique. This paper indicates the results of geo-environmental survey were held in the arid area where licorice lives natively and doesn't live. And this paper also shows the consideration about difference between habitat and non-habitat of licorice, and relationships between physical properties and chemical properties in the ground. The experimental results are concluded that 1) The arid ground in Bogd soum and Baatsagaan soum in Bayanhongor province, Mongolia, the ground was heterogeneous whose grain size properties are between sand and silt within the depth of 1 ~ 2 m. 2) Water content in the ground which licorice could be lived was at least more than 5 %, and keeping groundwater level and ground moisture could be important for bringing up seedlings of licorice. 3) The silty layers has relatively higher available moisture than the sandy layers, and calcium carbonate (CaCO3) accumulated in the silty layers, so that they had higher pH and EC values than sandy layer.
Slope stability analysis is one of the classical problems in the geotechnical engineering, while it is still in research and development of optimization problem of a multimodal function. Especially, in a natural slope stability analysis, a function to solve a safety factor become the multimodal function due to its scale or complex stratal architecture. In this paper, a calculation method of safety factor by efficient search algorithm using noncircular slip surface based on force equilibrium referred by Spencer method. The proposed method was applied to several slope models with previously calculated safety factors for the verification. Consequently, the proposed method is efficient to compare its computational accuracy and speed.
In order to predict the long-term deformation of shield tunnels located in soft clayey ground and conduct their long-term management, this paper investigates the calculation method of long term tunnel deformation due to the consolidation settlement of surrounding ground. Although it is required to take into account of the non-linear behavior caused by the generation of cracks within the tunnel lining and their enlargement, it is difficult to employ the sophisticated segment-ring model for tunnel lining because of calculation time and memory. Therefore, this paper proposes the empirical modeling method of the reduction of stiffness due to the generation and the enlargement of cracks and combines it with the soil-water-coupling analysis of tunnel deformation. The proposed method was verified and validated by the comparison between the calculation results and the field measurement results.
In order to investigate the calcium leaching mechanism of cement-treated soil under marine environment, leaching test was conducted. Artificial seawater, NaCl, MgCl2, MgSO4 solutions were used in the test. As a result, it was observed that calcium ion in cement-treated soil is leached by the salt containing magnesium ion in seawater. Specifically, calcium hydroxide in cement-treated soil turns into soluble form such as calcium chloride and calcium sulfate by reacting with magnesium ion, and this reaction reduces the pH value in cement-treated soil. Therefore, the mechanical and chemical characteristics of cement-treated soil immersed in seawater was investigated by micro cone penetration test and chemical component analysis. It was verified that the deterioration progress was based on calcium leaching under the influence of magnesium ion in seawater.
This paper examines the compatibility of volcanic cohesive soil as a material for use in foamed mixture lightweight soil. Since the physical and mechanical properties of volcanic cohesive soil are influenced by its allophane content, eight types of volcanic cohesive soil with different allophane contents were prepared. The results showed that the liquidity, lightweight properties, and unconfined compressive strength of the foamed mixture lightweight soil are also influenced by the allophane content. Based on these results, an equation for estimating the unconfined compressive strength in terms of the sand-cement ratio, foam-cement ratio, and allophane content is proposed.
A practical method to calculate a seismic residual displacement of slope exhibiting complicated critical slip surface has not been established. Moreover, only a horizontal component of seismic motion was considered in the design, not vertical component. Therefore, a calculation method to obtain the seismic residual displacement was presented in this paper, and the seismic residual displacement was calculated with various phase differences between horizontal and vertical components of seismic motion. Simple slope models exhibiting circular and plain slip surfaces were used for the verification. Consequently, the seismic residual displacement become larger with certain combination of horizontal and vertical component in seismic motion.
It is a crucial problem for maintainance of castle masonry walls to establish a stability evaluation method under seismic loads. Hence, in the present study, techniques to predict the seismic deformation and evaluate the dynamic stability of castle masonry walls were examined. Simulations of the deformation characteristics of castle masonry walls during shaking table tests to investigate the applicability of the distinct element method to seismic deformation predictions were conducted after deciding appropriate input parameters for each component(stone, cobble, and ground). As a result, it is confirmed that displacements and deformation modes of the castle masonry wall in the tests were well reproduced by analyses. Finally, proposals to evaluate analytical results by using a bulging index (ratio of bulging amount to masonry height) were shown for the inspection of the dynamic stability of castle masonry walls should be inspected.