Freezing Technology: Challenges and Prospects for Sustainable Development in Urban Infrastructure

Ground freezing has been broadly applied to construction and maintenance works of infrastructures because of its environmental friendliness. Since freezing technology represented by ground freezing can improve the strength of soil as well as its water-tightness, it becomes an essential technology for construction and maintenance of urban infrastructures where the use of space in underground has already been highly integrated. In this paper, overview of the freezing technology is introduced with some important characteristics of freezing soil for practical application. In addition, freezing technology is used for interesting works which could not be completed without freezing, and the state of the arts in freezing technology is presented. A pipe-in-pipe, now the authors are developing, is an example to utilize the potential of frozen sand, and the effect of freezing is explained with experimental results

Effect of Elemental Shape and Modeling of Mixed Hybrid FEM on Numerical Solution

AbstractMixed Hybrid Finite element method, MHF, is known to be an efficient and powerful analyzing technique with satisfactory accuracy when differentiated variables should be evaluated, such as flow velocity based on velocity potential theory or stress calculated from displacement. On the other hand, it is known that the calculation accuracy and efficiency are affected by elemental shape and modeling. The aim of this study is to confirm the efficiency and accuracy of MHF by comparing it with FEM, and to discuss optimum elemental shapes and modeling. MHF, unlike FEM, evaluates the velocity potential and the flux on the element boundaries not at the element nodes; consequently, the material or mass balance of each element due to flow-in and flow-out through the boundaries can be strictly estimated. The flow velocity within an element, however, should be interpolated by those values on the boundaries, and a distinctive shape function, known as the Raviart-Thomas shape function, becomes necessary. The authors established the MHF formulation for arbitrary shaped elements with 3 and 4 boundaries, and numerically investigated its efficiency and accuracy with various shapes of elements. Through this study, it was confirmed that MHF can evaluate accurate flow velocity with a fewer number of elements than those of FEM. In addition, the effect of shape and modeling of elements on the numerical results were discussed to obtain better accuracy even if the total number of the elements is kept constant

An Incarcerated Colon Inguinal Hernia That Perforated into the Scrotum and Exhibited an Air-Fluid Level

There are few reports of a transverse colon inguinal hernia; furthermore, an inguinal hernia perforating the scrotum is rare. Here we report the case of a 79-year-old man who died after developing an incarcerated colon inguinal hernia that perforated the scrotum and exhibited an air-fluid level. The patient was referred to our hospital in November 2011 with a complaint of inability to move. Physical examination revealed an abnormally enlarged left scrotum and cold extremities. He reported a history of gastric cancer that was surgically treated more than 30 years ago. His white blood cell count and C-reactive protein level were elevated. Abdominal and inguinal computed tomography revealed that his transverse colon was incarcerated in the left inguinal canal. Free air and air-fluid level were observed around the transverse colon, suggestive of a perforation. The patient and his family refused any surgical intervention; therefore, he was treated with sultamicillin tosilate hydrate and cefotiam hydrochloride. However, he succumbed to panperitonitis 19 days after admission. The findings from this case indicate that the transverse colon can perforate into an inguinal hernia sac

Development of Pipe-in-Pipe Filled with Granular Material for Flexible and Ductile Bending Performance

AbstractThe pipe-in-pipe which the authors propose in this paper is an innovative structural material to exert a more flexible and ductile bending performance than usual steel pipes. It consists of double thin wall pipes with granular materials such as sand between the outer and inner pipes to transmit their interactive stresses within a cross section. If a single hollow pipe is subjected to bending moment, the curvature of the pipe increases with the growth in magnitude of bending moment. Upon increasing of the bending moment, the pipe finally failed by local failure, and an oval-shaped deformation of cross section was observed. This failure is known as the Brazier Effect, a kind of local buckling. However, the major parts of the pipe still keep its original strength except for the failure portion. The sand filled between the outer and inner pipes of the pipe-in-pipe prevent this local failure by transmitting the interactive stresses between the pipes. As a result, smooth and flexible bending deformation is realized even under large bending moments. The purposes of our study are to clarify the mechanism of this system and to construct the model for design of this structure

The mechanism of spontaneous corrugation on the snowy and icy roads produced by the moving vehicles in cold regions

Abstract Traffic safety in cold regions is seriously affected by the snow and ice brought by the extreme climate. The snowy and icy road cannot provide enough friction for the safe operation of vehicles due to its smooth and uneven surface. In this research, we are going to focus on the uneven corrugation occurred on snowy and icy roads and to investigate the formation mechanism of this spontaneous corrugation which can seriously threaten the traffic safety. According to field observations, we found that the corrugation phenomenon generated by moving vehicles is a complicated thermal–mechanical coupled process. In order to simplify this complicated process, we are going to focus on the mechanical process of the formation of spontaneous corrugation only at this stage. Field observation by time-lapse cameras has been conducted to disclose its forming process directly. Then, we adopted sand as the material to reproduce the spontaneous corrugation in the laboratory which can eliminate the influence of the thermal process. By considering the compressibility and mobility of the surface material comprehensively, a numerical model has been successfully constructed for imitating the forming process of corrugation. Then based on this proposed numerical model, a preliminary discussion on the influence of natural frequency on the number of the corrugation has been conducted. The relationship between the natural frequency which is decided by the vehicle itself and the corrugation is promising to be utilized in optimizing the vehicle design to improve the performance on the snowy and icy roads

Fundamental study on spontaneous corrugation pattern on dry sand due to moving vehicle

On unpaved or snowy icy roads, it is known that corrugation pattern on road surface spontaneously emerges due to the repetition of loading by vehicle, and this phenomenon is named washboard road. Washboard road on snowy icy road causes serious problem on the driving of vehicles because the braking performance deteriorates due to lack of friction between road surface and tires. The authors developed an indoor experimental device to reproduce similar phenomenon in a laboratory. As the first step of the study, we chose fine dry sand as a surface material and we successfully reproduced the corrugation on the track. After scrutinizing the growing process of corrugation, we found that the running velocity of the track and the natural frequency of the oscillator are the most important factors for the growth. However, the frequencies of the corrugation converge to some specific value which is different from the natural frequency of the oscillator. Further, we adopted different road materials such as saturated sand, artificial snow and natural snow. This paper introduces interesting findings on formation process of washboard road