Shunji Kanie

Effect of Tensile Strength on Ice Lens Initiation Temperature

Conditions of ice lens segregation when a new one is start to grow is explored in experimental approach in this paper. Two consecutive open-system frost heave tests have conducted with the same Diluvial Silt of which mean tensile strength is 0.75MPa. Four predominant ice lenses have segregated in 114.2mm high specimen during the first heave test. Then, applying positive temperature to pedestals: i.e. thawing, the second heave test has conducted under the same test condition as the first one. Ice lenses have appeared exactly the same location as the first test. Therefore, it is revealed that ice lens initiation takes place where lower tensile strength remains. The temperature of ice lens initiation during the second frost heave test which have been interpolated by the boundary temperatures have found to be higher than those of the first ones. The difference is almost the same as 0.95 o C. Expected pore ice pressure at the initiation calculated with generalized Clausius-Clapeyron Equation using the temperature difference is 1.05MPa. The calculated pore ice pressure is little higher than the sample tensile strength. Therefore, it is expected that pore ice is pushing structure of mudstone against its tensile strength and overburden pressure to fracture via unfrozen film water.

A Practical Method for Three-Dimensional Frost Heave Simulation based on Takashi's Equation

Various models have been proposed for frost heave estimation. However, a practical evaluation method for multi-dimensional deformation has not yet been established. This study aimed to discuss the possibility of expanding the existing evaluation method into three dimensions based on previous experience on simulating interactive behavior between a chilled gas pipeline and frost heave. Takashis equation was adopted among several frost heave models considered; this model has been used to estimate one-dimensional frost heave according to the Japanese Geotechnical Standard. A new three-dimensional frost heave apparatus was developed to apply Takashis equation to multi-dimensional heave, and a modified equation was proposed based on the experimental results. Considering the effect of anisotropic properties on frost heave, this proposal was adopted for a simulation program by coupling the heat transfer calculation and mechanical equilibrium analysis in a finite element method (FEM) model. The simulation results are presented in this paper as an example to confirm the proposed models applicability.

Interactive Behavior between Frost Bulb and Chilled Pipe by an Axially-Symmetric Freezing Experiment

It is known that chilled gas pipelines buried at a boundary between permafrost and non-permafrost are subject to severe bending deformation since they are held tightly in the permafrost whereas the growth of frost bulbs in the non-permafrost region causes frost heave of the pipes. However, the flexural rigidity and the behavior of the pipeline and the surrounding frost bulb as a composite structure have not yet been studied, although they are important factors in evaluating structural safety and stability. The purpose of this study is to experimentally determine the interactions between a chilled gas pipeline and a frost bulb under the simplified condition of axial symmetry, and also to evaluate the adfreeze strength of the frost bulb and its dependence on boundary stress and temperature.

Dynamics of washboard road formation driven by a harmonic oscillator

Granular surfaces subjected to forces due to rolling wheels develop ripples above a critical speed. The resulting pattern, known as washboard or corrugated road, is common on dry, unpaved roads. We investigated this phenomenon theoretically and experimentally, using laboratory-scale apparatus and beds of dry sand. A thick layer of sand on a circular track was forced by a rolling wheel on an arm whose weight and moment of inertia could be varied. We compared the ripples made by the rolling wheel to those made using a simple inclined plow blade. We investigated the dependence of the critical speed on various parameters, and describe a scaling argument which leads to a dimensionless ratio, analogous to the hydrodynamic Froude number, which controls the instability. This represents the crossover between conservative, dynamic forces and dissipative, static forces. Above onset, wheel-driven ripples move in the direction of motion of the wheel, but plow-driven ripples move in the reverse direction for a narrow range of Froude numbers.Granular surfaces subjected to repeated passage often spontaneously develop a corrugated pattern. In this study, we scrutinized the growth dynamics of surface corrugation in a self-rotating sand bed that is traced by the edge of a vertically oscillating arm. We found that both the rotation velocity and the frequency of the oscillator strongly affect the occurrence rate of corrugation as well as the time evolution in the corrugation pattern, due to the intermittent collision between the oscillator and sand bed. We also discovered that the growth dynamics involves two distinct collective modes that describe the translational motion of the corrugation pattern on the sand bed.

Numerical Analysis of Pipe-in-Pipe Filled with Various Materials

The pipe-in-pipe proposed in this paper is an innovative structural material with more flexible and ductile bending performance than that shown by usual steel pipes. A pipe-in-pipe structure comprises double thin-walled pipes with granular material such as sand filled between the outer and inner pipes. The filling material prevents local failure known as the Brazier effect by transmitting the interactive stress between the pipes. As a result, smooth and flexible bending deformation is realized even under a large bending moment. In addition, when the sand filled in the pipe is frozen, the flexural rigidity of the pipe increases, but the pipe maintains its high ductility. To adopt such a pipe-in-pipe as a practical pipeline material, a numerical method must be established to evaluate the elastoplastic bending behavior. This paper proposes numerical methods for the bending behaviors of pipe-in-pipes and examines the difference in bending behaviors due to the filling materials using the proposed models.

Frost Heave Induced Pipe Strain of an Experimental Chilled Gas Pipeline

A full-scale chilled gas pipeline experiment was conducted in Fairbanks, Alaska to develop the design criteria for pipeline construction in arctic regions. The test pipeline had a length of 105 m and a diameter of 0.9 m. One-third of the pipeline was located in permafrost and the remaining was in non-permafrost. The monitoring data were collected from December 1999 to January 2005 including both freezing and thawing phases. In the transition zone between frozen and unfrozen soil, the foundation material experienced a vertical movement caused by differential frost heave. The test results indicated that the bending action was the main factor for the circumferential and longitudinal strain distribution in the pipeline. The circumferential strain ranged from about 100 to 500 during freezing. The maximum tensile and maximum compressive strains along the pipeline were approximately located at the edges of the transition zone.

Experimental and Practical Evaluation Method of Three-dimensional Frost Heave of Frozen Soil

Various models have been proposed for frost heave estimation. However, a practical evaluation method for multi-dimensional deformation has not yet been established. This study aimed to discuss the possibility of expanding an existing evaluation method into three dimensions based on previous experience on simulating interactive behavior between an underground structure and frost heave. Takashi’s equation was adopted among several frost heave models considered; this model has been used to estimate one-dimensional frost heave according to the Japanese Geotechnical Standard. However, it is applicable only for one-dimensional frost heave. The authors developed a new apparatus to measure three-dimensional frost heave to apply Takashi’s equation to multi-dimensional heave, and a modified equation was proposed based on the experimental results. Considering the effect of anisotropic properties on frost heave, this proposal was adopted for a simulation program by coupling the heat transfer calculation and mechanical equilibrium analysis in a finite element method (FEM) model. The fundamental simulation results are presented in this paper as an example to confirm the proposed model’s applicability.

STUDY ON RELATIONSHIP BETWEEN WAVE FORCE ACTING ON FIXED-SUBMERGED STRUCTURE AND ITS SECTIONAL SHAPE

Recently, completely submerged structure resting on piles is expected as a new alternative structure to bridge and/or immersed tunnel for relatively shallow-water crossing. In case of those structures, no change in buoyancy can be expected and only pile must resist against external wave force. As a result, the piles should have enough length to exert their friction strength against pulling out force due to wave. Since high safety factor for pulling out is required, reducing vertical force acting on piles becomes important for economical design. This study aims to evaluate the effect of sectional shape on the wave force and to introduce the relationship between sectional shape and vertical wave force acting on supporting structure.

EFFECT OF TENSION LEG ARRANGEMENT ON DYNAMIC CHARACTERISTICS OF SUBMERGED FLOATING STRUCTURE

For a type of “perfectly underwater” structures moored by tension legs like Submerged Floating tunnel, dynamic behaviors of the floating body are expected to involve many severe design and computational problems. In addition, motions induced by some external forces like strong waves and earthquakes may be very complex and it is difficult to explain the mechanisms of the behavior accurately. Especially, dynamic characteristics in consideration of elasticity coupling caused by restoring force of tension leg arrangement have not been clear so far. When elasticity coupling can arise, restoring forces of tension legs associated with the rotation show some bad influences on the dynamic behaviors. From this point of view, we focus on the effect of tension leg arrangement on dynamic characteristics of submerged floating structure in this study.