Satoshi Nishimura

A fully coupled thermo-hydro-mechanical (THM) finite element (FE) formulation is presented that considers freezing and thawing in water-saturated soils. The formulation considers each thermal, hydraulic and mechanical process, and their various interactions, through fundamental physical laws and models. By employing a combination of ice pressure, liquid pressure and total stress as state variables, a new mechanical model has been developed that encompasses frozen and unfrozen behaviour within a

The paper reports the shear strength anisotropy of the natural, highly overconsolidated, London Clay from Heathrow Terminal 5 as established by comprehensive hollow cylinder apparatus (HCA) testing. Multiple high-quality block samples from 5·2 m and 10·5 m below ground level provided samples for suites of undrained stress-path shear tests performed after consolidation to effective stress states similar to those estimated in situ. The direction of the major principal stress axis, α (or of the pri

Although microtubules are involved in various pathological conditions of the heart including hypertrophy and congestive heart failure, the mechanical role of microtubules in cardiomyocytes under such conditions is not well understood. In the present study, we measured multiple aspects of the mechanical properties of single cardiomyocytes, including tensile stiffness, transverse (indentation) stiffness, and shear stiffness in both transverse and longitudinal planes using carbon fiber-based system

Towards the development of a mechanical model that can be part of multi-physical analysis of frozen soils, a program of systematic frozen-unfrozen parallel triaxial tests at different temperatures and strain rates was conducted. The mechanical behavior of the reconstituted high-plasticity clay samples was investigated and interpreted through a state concept based on Ladanyi and Morel’s (1990) postulate on the unique relationship between the inter-particle “effective” stress and the strain path.

The cross-anisotropic elasticity parameters were experimentally determined for six sedimentary clays of different ages and origins at both natural and reconstituted states by using high-precision triaxial apparatus. All the parameters and their dependency on the effective stress are satisfactorily described by a simple, conventional power-law model. The patterns of the inherent anisotropy exhibited close agreement between the natural and reconstituted states, suggesting that the development of n

The volume change behaviour of fine-grained soils under repeated freeze–thaw cycles was investigated in context of artificial ground freezing, in which relatively quick freezing is achieved under confinement. Laboratory cyclic freeze–thaw tests with large freezing rates were performed on two clays in two different laboratory set-ups, either with isotropic pressure or with one-dimensional configuration. After freeze–thaw cycles, soils appear to reach residual states unique to each stress level, a

Frozen soils are characterised by the co-existence of ice and unfrozen liquid water in the pores, engendering complex interactions between thermal, hydraulic and mechanical processes within a coupled system. The consequence is reflected in the peculiar features seen in frozen soils' deformation behaviour and strength. This study applies a re-interpretation to a constitutive modelling framework for frozen soils originally proposed by Nishimura and co-workers in 2009 and demonstrates its expedienc

The field-induced refractive index change of an InGaAs/InAlAs MQW waveguide is examined for various wavelengths and TE/TM modes using a MZ modulator. The quadratic EO coefficients in the MQW waveguide for both TE and TM modes due to quantum confined Stark effect (QCSE) is on the order of 10/sup -18/ (m/sup 2//V/sup 2/), which is dominant compared with the linear EO effect. An effective linear EO effect, however, is significant because of the bias field arising from the built-in potential. This e

Infrastructure in cold regions is vulnerable to the potential degradation of permafrost under a warming climate. Meanwhile, the accumulation of meteorological data and the refinement of AOGCMs in recent years have improved the confidence in future global air temperature predictions. A reliable scheme is now desired that converts these climate predictions into future geocryological predictions relevant to geotechnical engineering and risk assessment. This paper describes a multidisciplinary appro

A new model is proposed for describing freeze-thaw-induced plastic volume changes in saturated clays based on microscopic inhomogeneities inherent in the soil structure and the pore water transfer between them. It is shown through a simple inhomogeneous mesostructure model that the equilibrium state reached after freezing serves as an important reference state for interpreting the volumetric behaviour. The soil state evolution towards this freeze equilibrium state describes many features seen in

This paper reports an attempt to accurately quantify one-dimensional compressibility of stiff, cement-treated high-water-content clays by using a constant-rate-of-strain (CRS) oedometer equipped with an image-based strain measurement system. The errors in stiffness measurements due to imperfect specimen–platen bedding and apparatus compliances, significant factors when stiff soils are tested, were avoided by directly observing movements of the specimen's lateral surface over a transparent confin