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The first X-band dual polarized phased array weather radar (DP-PAWR), which simultaneously transmits pulses of horizontal and vertical polarized radiation, was developed and installed at Saitama University, Japan, in December 2017. The DP-PAWR uses mechanical and electronic scanning at azimuth and elevation angles, respectively. It provides polarimetric precipitation measurements via 3-D volume scanning with an update rate between 10 and 60 s, for a range of up to 80 km. Here, we describe the initial DP-PAWR observation results. To evaluate the DP-PAWR observation accuracy, we compared the observational data with radar variables derived from Parsivel disdrometer data. In comparison with the disdrometer, the relative observation accuracy for the DP-PAWR radar reflectively factor had a standard deviation of 1.1 dB and mean value of 0.4 dB. We also conducted detailed observations of a developing thunderstorm using a specific differential phase ( $K_{\mathrm {dp}}$ ) column, focusing on the $K_{\mathrm {dp}}$ core during the storm. The $K_{\mathrm {dp}}$ core movements provided useful information about the convection flow during the storm.

Evaluation of the deformation behavior due to drying is crucial in underground construction works. Especially, geological repository for High-Level Radioactive Waste (HLW) shall be carefully selected to act as a natural barrier to prevent radioactive nuclide leaks. Uniaxial Compressive Strength (UCS) is one such governing factors when designing or selecting a suitable location for such underground storage compartments or access tunnels. Since nuclide leakage through geological repositories, intact rocks UCS will vary with the drying conditions. Hence, it is vital to evaluate the behavior of UCS subject to the conditions prescribed. A variety of statistical models has been built to govern the interdependency between UCS and water content. However, there are no significant amount of research have been conducted to emphasize the UCS variation with the degree of saturation under the influence of drying condition. Numerically, Richard’s equation exact solution in Neuman boundary condition has been derived to exploit the degree of saturation with respect to time and position. Experimentally, obtain the UCS variation with the degree of saturation pertaining to the Neogene Tuff in Utsunomiya city, Japan. A best fit statistical model was generated for experimental data between UCS variation and the degree of saturation. Then, the experimental saturation degree was replaced by Richard’s equation exact solution saturation degree values. Surprisingly, produced graphs for experimental data and numerical analysis data for exact solution were perfectly overlapped. Results point out that change of UCS shows similar characteristics, which exponentially decrease, with both experimental saturation values and exact solution saturation values influenced the drying condition. Moreover, it suggests that UCS value can be predicted subject to the time and position in the sedimentary rocks under drying conditions.

In addition to changes in the deformation characteristics of rock masses based on the water content, significant deformation occurs in sedimentary rocks from saturation to drying. In tunnel constru...

This paper is an overview of a project concerned with “Early warning for torrential rainfall/tornado” under “Enhancement of Societal Resiliency against Natural Disasters,” which is one of eleven themes of the SIP (Cross-ministerial Strategic Innovation Promotion Program under the Council for Science, Technology and Innovation, the Cabinet Office, Government of Japan). The characteristics of the project are the development of a multi-parameter phased array weather radar (MP-PAWR) that enables the accomplishment of an accurate three-dimensional model of precipitation over 30 s within a 60 km radius. Various products developed ducts using MP-PAWR and other observations, and numerical predictions, are also discussed, with a demonstration experiment to provide early warnings for torrential rainfall and related disasters. For end users such as local governments and general citizens, the final goal of this project is the social implementation of these products.

Electrostatic motors are promising forms of actuation for future robotic devices. The study of their different implementations should accelerate their adoption. Current models for resonant electrostatic induction motors were found not to be able to properly describe their behavior, namely, with regard to changes with position. This paper reports a new analytical model for these motors, aiming to address this issue. The model is based on identification of all capacitance harmonics, through a simplified method. Using these, equations for different motor parameters, notably, thrust force, were obtained and compared to previous literature. The new equations model position dependent properties, such as force ripple. The outputs of this model were validated through experimentation with a prototype, with the results confirming the new model better describes motor behavior. An analysis into how to decrease this ripple was also discussed and tested. We concluded that the use of a higher number of harmonics resulted in a much more accurate model, capable of adequately characterizing motor outputs with changes in position.

The stability of the tunnel face is a top priority in a tunnel construction. The estimation of the earth pressure acting in front of the face is essential for the stability evaluation of the face, and many model experiments have been conducted to understand the characteristics of face stability. On the other hand, there are many cases in which the stability of the tunnel face is evaluated by limiting analysis assuming a constant slip region by applying the loosening earth pressure derived by Terzaghi as a boundary condition, but the actual slip region is not always constant and expanded progressively accompanying by the collapse of the face. There are few past studies that have considered this phenomenon. In this study, a estimation method of the tunnel face pressure are developed in consideration of the progress of face collapse. The proposed method is a kind of limit equilibrium method. Assuming a slip line with two ellipses with the same center and different radii, the first-order linear differential equation of earth pressure in the tunnel face direction is calculated from the equilibrium for infinitesimal elements in the circumferential direction.

High groundwater flow velocity is a major challenge in many artificial ground freezing (AGF) projects, especially in groundwater control projects. That condition may be unfavorable for the ...

In recent years, the number of cases where tunnels are constructed in sedimentary rock layers has increased. It is essential to investigate the deformation characteristics of sedimentary rocks for predicting tunnel deformation. The mechanical properties of sedimentary rocks are widely varied due to moisture content. The rocks are dried by tunnel excavation and wetted by groundwater gushing or backfilling. It is necessary to grasp the changes of deformation characteristics of sedimentary rocks due to moisture changes. In this study, soaking tests were conducted on Neogene period Japanese tuff sampled at Utsunomiya, Japan. In the test, the cylindrical tuff specimens are air dried by over 240 hours at first. Then the tuff specimens are taken in pure water with measuring deformations in detail. There are no effective stress increases by soaking and only uniform matric suction are acted on the specimen without any restraints. The results demonstrated that strain tensor was reached to stable state for 2 - 3 days, and the value of the normal strain perpendicular to the bedding plane is greater than the other normal components and shear strains are also observed in both cases. Although the orientation of the maximum principal strain is in the near of the bedding orientation at the initial dry state, the orientation are suddenly rotated to the normal orientation of the bedding plane. It means that the principal orientation of anisotropy are rotated due to continuous moisture changes.

Although it is essential for tunnel construction to evaluate the deformation behavior of sedimentary rock due to drying, the reasons for differences in the mechanical properties between dry and wet rock have not yet been clarified. A previous study on Neogene-period anisotropic tuff states that the magnitude correlation of the stiffness in the bedding orientation and its perpendicular one are reversed in the dry and wet states. Although this indicates the rotation of the principal orientation of the anisotropy, the mechanism is unclear. This phenomenon can clarify the stiffness differences between the dry and wet conditions if the deformation characteristics due to drying can be continuously obtained, in detail. In this study, drying tests on Japanese tuff are conducted, and the deformation behavior due to continuous moisture-content variation involving isotropic matric suction are investigated, in detail. The results of two specimens sampled in the bedding orientation and its perpendicular one show anisotropic deformations due to moisture variation. Normal strain in the orientation perpendicular to the bedding plane is dominant and shear strain occurs. Furthermore, principal strain rotation due to moisture variation is detected for the first time. The maximum and minimum principal strain orientations are rotated by approximately 90° from the wet state to dry state. It is determined that the hardest and softest orientations of tuff continuously alternate due to moisture variation.

The authors introduce an experimental method that focuses on the flow-thermal relation and the visual observation of heat distribution around a cooling pipe in sand under the flow condition. This experiment aims to understand the effect of seepage flow on the heat transfer behavior of sand under cooling and freezing conditions due to a vertically buried heat exchanger pipe. This method combines a flow test, cooling or freezing processes, and the visual observations of temperature profiles with saturated Toyoura sand as the heat transfer medium. A vertical copper pipe inserted into the sand medium is used as the thermal exchanger, while an infrared thermograph is used to measure and visualize the surface-temperature profile of the specimen. The heat transfer distribution behavior is investigated by conducting a series of cooling and freezing experiments on the specimens with variation of the flow rate condition, initial condition, and pipe depth. The thermograph observation results show how water f...

In recent years, human-like robots have received a lot of attentions. A musculoskeletal humanoid is an effective approach for making a human-like robot, and many musculoskeletal humanoids have been developed. However, none have been equipped with really human-like bones and muscles, especially shapes and alignments. Formaking really human-like musculoskeletal humanoids, we thought of the “planar muscle” as the key. A planar muscle is an enhanced wiredriven system in which a motor winds a wire. In a prior system, one motor controlled one wire and the linear muscle needed one motor per wire and complex control systems. We therefore developed the planar muscle that controlled several wires simultaneously by using two moving pulley bars and one motor. The planar muscle is suited to musculoskeletal humanoids because they need a lot of motors and complex control systems in the case of using linear muscles. Furthermore, planar muscles are useful for soft skin-like outers that protect external shocks and sense touch. Using the planar muscles, we are developing a new musculoskeletal humanoid that has human-like bones and muscles. In this paper, we show the planarmuscle concept, especially its soft skin-like outer functions, and evaluate its motion with a body trunk model having multiple vertebrae that we developed.

Drying-induced deformations of porous materials are ubiquitous phenomena, but coupled behaviors of moisture content inside the material and deformation, which are difficult to express the behavior as a physical model. This is partly because multiple mechanisms governing drying-induced deformation are involved so that each mechanism may become dominant by respective situations. This article introduces various activities or efforts in some research fields, and retrieves common results in laboratory experiments and in field observations, mainly for sedimentary rocks. Through these processes, future works to be considered are elucidated.

In this study, an attempt has been made to investigate the deformation behaviour of Shirahama sandstone in drying process using small cylindrical samples. A series of comprehensive laboratory experiments was performed in different drying conditions under a no applied load. Saturated cylindrical samples were dried in a climatic chamber while deformation and evaporative water loss were being monitored. The results obtained are reported and further used in linear poroelastic relation in order to derive the matric suction evolution. In addition, mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM) were used for evaluating their pore structure and explained its role on measured strain and estimated matric suction. The results show that virtually no volume change occurs in the samples until half of the saturated water content is evaporated. It also reveals that the maximum dimensional change capacity is independent of drying condition but evaporation rate and strain occurrences are shown to be affected significantly. In addition, the study of pore structure indicates that substantial strain magnitude and high matric suction occurrence are attributed to water loss from small pores in the clay matrix. Throughout the process, the samples displayed neither a likelihood nor tendency of damage or destruction. However, strain magnitude is observed to be higher for the sample saturated with concentrated sodium sulphate solution. The present study sheds light on essential elements in the studies of dimensional changes of clay bearing sandstone to assist in evaluating ground movement, deterioration, fluid flow and isolation properties of underground facilities.

Unsaturated hydraulic property (relation between the water retention curve and hydraulic conductivity function) of soft rock must be properly estimated for analyzing the saturated-unsaturated groundwater flow such as the flow around a tunnel, rock surface and so forth. In this study a practical technique for estimating the unsaturated hydraulic property of soft rock was developed on the basis of the Campbell model and Genetic Algorithm (GA). The major objectives of the present study are the following two; 1) investigation whether or not the Campbell model can be applied to soft rock for approximating the unsaturated hydraulic properties and 2) application of GA technique for estimating two parameters included in the Campbell model. These parameters were estimated through the inverse analysis of the transient change of evaporation rates from a surface of disk shaped specimen of Tertiary sedimentary rock which are sampled from the Rokkasho area, Aomori prefecture. Two transient evaporation experiments under different atmospheric conditions were proposed for the estimation. The Campbell's parameters of 13 soft rock specimens (5 sandstone and 8 tuff breccia specimens) were estimated through those types of experiments. As the results it was clearly found that the transient change of evaporation rates can be well fitted by the Campbell model except for the region of low saturation and this fact implies that the Campbell model can be applied to the soft rock. And also it was found that, the GA is a promising technique for parameters estimation in the inverse solution method. It can be concluded that the techniques are practically for estimating the unsaturated hydraulic properties of soft rock.

Volcanic breccia is a representative heterogeneous rock. As a preliminary study for determining its mechanical properties in laboratory and field experiments, its material properties and structural features were described. Three-dimensional clast-size distribution was also estimated for the study site using the theory of stereology. With this distribution determined, a numerical simulation was performed to investigate the relationship between the volumetric proportion of clasts in a sample and the areal proportion and maximum length of clasts on a lateral surface of the sample. The following observations were made: (1) coefficients of variation for volumetric proportion are dependent on the size of the sample, and became large when the size of the sample is small; (2) samples with a small coefficient of variation can be selected at any size if a restriction is placed on the ratio, Dmax/D0, of the maximum length of clasts to the size of the sample; and (3) the volumetric proportion of clasts in each sample can be estimated from the observed areal proportions within an error range that depends on the whole volumetric proportion.

ダブルコアチューブにより採取された比較的乱れの小さい自然状態の火山角礫岩を用いて圧密非排水試験を実施し, 力学的性質への礫含有率, 供試体寸法および最大礫径の影響を検討した. その結果, 礫含有率約40%以下の礫同士の接触が少ない状態において次のような結論を得た. 20%以上の礫の混入により内部摩擦角が若干大きくなる傾向にあるが, 礫混入の影響は比較的小さい. 弾性係数は礫含有率によって大きく変化せず, Reuss の理論式に沿った傾向を示す. 供試体寸法の影響は直径30cmまでの供試体では顕著に現われないが, 大きな供試体では内部摩擦角が若干低下する傾向にある. また供試体直径と最大礫径の比が1～3程度であっても力学的特性に大きな影響を与えない.

湿潤供試体や不均質な岩石などを対象として, 三軸圧縮試験において供試体の縦横ひずみを計測できるような局所ひずみの計測方法として, 熱収縮チューブ (HST) を利用した方法を提案した. またその検証実験を実施し, 合わせて三軸圧縮試験例を示した. さらに本手法とLDT (Local Deformation Transducer) を用いたひずみ計測を比較すると, 破壊時まで両者はほぼ一致した出力を示した. 本手法は簡便なひずみ計測方法として, 十分使用できるものと考えられる. 提案した手法は, 三軸セルからのゲージ取り出し口さえ準備すれば, 現有のセルをそのまま利用できる利点がある.

レプリカフィルムから画像処理技術によりクラックを抽出するために, 入力画像の獲得方法およびその画像処理・画像解析方法について検討した. その結果, レプリカフィルムからマイクロクラックを認識するための方法としては, 暗視野照明を用いる方法が画像処理に適した濃度差のある画像を獲得できること, およびその画像処理方法としては適応二値化処理が適していることがわかった. 画像解析方法の検討では, 線検出オペレータは直線的なオブジェクトに対して方向依存性をもつことを指摘するとともに, 入力画像を何段階か回転させて線検出オペレータを作用させることにより, この影響を最小限に抑えることができることを示した. これらの検討をもとにクラック抽出に対する画像解析手順を作成した. この手順に従い, 入力画像を3段階に回転させてクラックの長さと方向を計測し, これらを合わせて評価した場合, 10°刻みのクラックの方向分布およびクラック累計長の方向分布をある程度定量的に求めることができた.

稲田花崗岩内の初期マイクロクラック分布について, 岩石薄片からのクラック抽出結果を画像解析することにより検討した. その結果, 薄片レベルにおいてクラックの空間的な分布は非常に不均質であることが明らかとなった. すなわち, 平均粒径が2mmである主構成鉱物が集合して平均間隔5-10mmのクラスター状に分布しているため, 岩石内で主に石英内に密集して分布している比較的長いクラックの分布もクラスター状となる. 稲田花崗岩の石目はクラック方向分布の最頻値の大きさによって特徴づけることができる. rift面を形成するクラックは長いものが多く粒間クラックが発達するが, 方向分布の散布度は小さい. grain面を形成するクラックにも比較的長いものが多いが, rift面を形成するクラックよりは本数が少なく, 散布度が大きい. それらに比べてhardway面を形成するクラックは短く, 本数も少ない. 一方, 各面におけるクラック長さの頻度分布は, 方向によらずほぼ同様の傾向を示す. また, 長さ別の方向分布は計測限界によらず相似形となる. 石切場におけるgrain面の方向とクラックの方向分布とは10-20°ほど異なり, クラック分布という観点から見ると稲田花崗岩は完全な直交異方性材料ではないと考えられる. また, このようにクラック分布が石目の主軸からずれていることが, 三軸圧縮試験時の最終的な破断面形成に大きな役割を果たしていると考えられる.

Four saturated Miocene soft rocks of Japan i.e. Ohya tuff, Yokohama siltstone, Kobe mudstone and sandstone were tested under consolidated-undrained, cyclic loading conditions. The deformation behavior, pore pressure changes and strength mobilization, and contraction/dilation characteristics of these rocks were studied with emphasis on the non-linearity, stress- and strain-dependence of their mechanical properties. A procedure was introduced to locate the yield point, to estimate Young's modulus and to study the deformation behavior of these soft rocks. Deformation modulus was found to depend on plastic straining according to an exponential equation, whose coefficients in turn, depend on confining pressure. In addition, it also depends on the deviatoric stress levels causing hysteresis to occur. Patterns of pore pressure changes and associated failure modes were interpreted in terms of the initiation/propagation of micro- and macro-cracks inside the specimens. Characteristic stress levels were found, based on which the “true” rock strength components — cohesion and internal friction angle — were determined and their mobilization with respect to stress and strain levels was analyzed using a new interpretation method. Volume change tendencies were inferred from pore pressure changes whose rate was related to the contraction/dilation behavior of soft rocks. On that basis the dilation angle was estimated and its variation and stress- and strain-dependence was analyzed. A simple equation was introduced to characterize the variation of both internal friction and dilation angles with plastic straining, whereas their stress-dependence was studied through the variation of fit coefficients with confining pressure.

Changes in the pore pressure during CU (Consolidated-Undrained) cyclic loading triaxial tests on fully saturated specimens of four Miocene soft rocks, i.e. Ohya tuff, Yokohama siltstone, Kobe mudstone and sandstone are analyzed. As a result, three modes of failure, i.e. brittle, brittle-ductile and ductile can be recognized, and other characteristic stress levels e.g. crack initiation stress, plastic flow/gliding stress, dilation stress, etc. identified. The mobilization of the strength of these rocks in terms of cohesion and internal friction angle is then discussed. A procedure for the estimation of the rock cohesion strength is first introduced on the basis of the modified Griffith's failure criterion. The determination of the mobilized friction angle at any state of stress during the tests follows.

Consolidated-undrained, cyclic triaxial tests were performed on four saturated Miocene soft rocks of Japan namely Ohya tuff, Yokohama siltstone, Kobe mudstone and sandstone. Deformation behavior, pore pressure changes and strength mobilization as well as contraction/dilation characteristics of these rocks were studied with emphasis on the non-linearity, stress- and strain-dependence of their mechanical properties. A procedure was introduced to locate the yield point, estimate Young's modulus and study the deformation behavior of these soft rocks. Patterns of pore pressure changes and associated modes of failure were studied. Characteristic stress levels were found, based on which the “true” rock strength components were determined and their mobilization with respect to stress- and strain levels was analyzed. Volume change tendencies were inferred from pore pressure changes. The rate of such changes was related to the contraction/dilation behavior of soft rocks, from which the dilation angle was estimated and its stress- and strain-dependence was studied. The findings were applied to the FEM simulation of triaxial tests on-and of excavation in/on soft rocks.

A new type apparatus for shear-flow coupling test, named coupled shear-flow-visualization apparatus, was developed to investigate the hydromechanical behavior and the fracturing process of intact soft sedimentary rock. With this apparatus, it is possible to simultaneously carry out direct shear test and constant head flow test, and also to observe specimen surface during the experiment. Under controlled shear load, normal load, flow rate and shear displacement can be obtained as raw data. Moreover, fracture area and fracture apertures can be estimated using image-processing techniques. The shear and normal stress capacities of load cells are 4.08 MPa and 3.33 MPa, respectively. The measurable maximum permeability of apparatus is about 5.80×10 −3 cm/s under a hydraulic gradient of 40 cm/cm. According to the observation of visible fractures on specimen surface, the fractures were not completely propagated at the peak of shear stress. The developed testing method with image processing techniques enabled us to analyze the relationships between fracture flow rate, hydraulic aperture and two fracture apertures defined in this study.