Evaluation of excavation damaged zones(EDZs)in Horonobe Underground Research Laboratory(URL)

Excavation of underground caverns,such as mountain tunnels and energy-storage caverns,may cause the damages to the surrounding rock as a result of the stress redistribution.In this influenced zone,new cracks and discontinuities are created or propagate in the rock mass.Therefore,it is effective to measure and evaluate the acoustic emission(AE)events generated by the rocks,which is a small elastic vibration,and permeability change.The authors have developed a long-term measurement device that incorporates an optical AE(O-AE)sensor,an optical pore pressure sensor,and an optical temperature sensor in a single multi-optical measurement probe(MOP).Japan Atomic Energy Agency has been conducting R&D activities to enhance the reliability of high-level radioactive waste(HLW)deep geological disposal technology.In a high-level radioactive disposal project,one of the challenges is the development of methods for long-term monitoring of rock mass behavior.Therefore,in January 2014,the long-term measurements of the hydro-mechanical behavior of the rock mass were launched using the developed MOP in the vicinity of 350 m below the surface at the Horonobe Underground Research Center.The measurement results show that AEs occur frequently up to 1.5 m from the wall during excavation.In addition,hydraulic conductivity increased by 2e4 orders of magnitude.Elastoplastic analysis revealed that the hydraulic behavior of the rock mass affected the pore pressure fluctuations and caused micro-fractures.Based on this,a conceptual model is developed to represent the excavation damaged zone(EDZ),which contributes to the safe geological disposal of radioactive waste.

GRIMSEL现场的气体渗透试验(英文)

自 1976 年以来,日本核废料管理基金会与研究中心(RWMC)一直在进行核废料处置的研究。最近,RWMC非常关注核废料处置库的监测、遥控以及现场勘查技术等重要的社会公众与技术问题。其中,处置库溢出气体是一项重要的安全可靠性评估项目。这项名为“工程屏障的气体渗透试验”(GMT)的研究是在瑞士 Nagra 的 Grimsel现场实验室进行的。GMT 集中研究在粮仓形的处置库中由核废料产生的气体在工程屏障中的渗透问题。在 Grimsel现场,一个按比例缩小的工程屏障库由一个具有透气孔的混凝土仓和砂–膨润土缓冲材料组成,缓冲材料被放置在一个专门建造的洞室中。混凝土仓直径为 2.5 m,高为 2.5 m,放置在直径为 4 m 的从上到下开挖而成的竖井中。在工程屏障饱和及水渗透试验之后,气体分两个阶段被注入地窖中。气体第一次被注入之后,重复进行水渗透试验,以便观察工程屏障库的变化。第二次气体注入的时候,在工程屏障及岩石圈中采用一种可以多点取样的鸡尾酒气体跟踪器。在气体注入之后,小心挖掘出工程屏障库,然后用各种方法来进行鉴定,并采用实验室以及建模程序来进行现场的模拟研究。

Development of a validation technique for road surface profile applicable to point cloud data

In recent years,various information and communication technology(ICT)devices measuring three-dimensional(3D)point cloud data have been developed and widely used for the application of pavement surface investigation.However,ICT devices have generally been developed not only for measuring road surface profiles but for various geo-reference point clouds.In this background,the validation of surface profiles acquired with ICT devices fulfils an important role in proving the reliability of measurement result composed by point clouds.This study proposes a wavelet transform agreement(WTA)which involves a normalization factor of profile amplitude for further improvement in the wavelet-based coherence technique.The WTA analysis allows evaluating similarity/dissimilarity of two profiles considering both the location and wavelength simultaneously.For this purpose,a terrestrial laser scanner(TLS),a mobile mapping system(MMS),and an unmanned aerial vehicle(UAV)are employed to prove the advantage of WTA in practical applications.As a result,the advantages of WTA analysis are clearly recognized in the optimization for the measurement interval of TLS,the multi-line measurement of MMS for ride quality improvement of a pavement,and the efficient operation of UAV in terms of the flight altitude.This paper also shows the identification of aging development for surface roughness over time in terms of locations and wavelengths.These findings help not only to guarantee the accuracy of profile measurements but to realize the sophisticated way of using 3D point clouds acquired with ICT devices.The outcomes of this study contribute to the increase of productivity for pavement works with improving the quality of surface profile measurement.

Evaluation of seismic behavior of box culvert buried in the ground through centrifuge model tests and numerical analysis

Japan has yet to establish a seismic design for road box culverts(RBCs)because past major earthquakes did not damage them.In recent years,structures with enlarged sectional dimensions(the purpose of which is to optimize the internal space in RBCs)have become common.However,the unknown seismic strength of such large RBCs makes RBC seismic designs increasingly necessary.Several seismic design methods have been developed for and applied to rectangular underground structures,e.g.,cut-and-cover tunnels,which are structurally similar to RBCs.Although these methods are applicable to RBCs,it is uncertain whether they can be applied directly because there are currently no evaluation results from model tests on RBCs,which have unique structural features,e.g.,no haunch at the bottom of the sidewalls.Therefore,we verify a seismic behavior of an RBC and develop a method for evaluating it in order to establish a seismic design for RBCs.We conducted centrifuge model tests subjected to seismic force and a numerical analysis using an elastoplastic finite analysis method,in addition,we validated this analysis by comparing the test and analytical results.The test results show RBCs will most likely develop rocking rotation when the ground strain exceeds approximately 0.08%.A comparison of the numerical and experimental results shows that this analysis can estimate the shear deformation behavior with approximately 90%accuracy in square cross-section cases.Meanwhile,this analysis has tendency to underestimate the axial forces in each case and to overestimate the bending moments of some members in the case of wide cross-sections.

Decreasing inhaled contaminant dose of a factory worker through a hybrid Emergency Ventilation System:Performance evaluation in worst-case scenario

Air pollution is detrimental to human health,causing several human illnesses.The industrial microenvironment generates high levels of indoor airborne pollutants,becoming a pervasive issue for workers.It is essential to im-prove the indoor air quality in this workplace by applying enhanced ventilation systems to minimize inhalation risk.Displacement ventilation is used in industrial buildings because of its stratified air distribution and low cost.However,in case of accidental pollutant release,an enhancement is needed to minimize inhalation exposure.This study proposes a hybrid emergency ventilation system using localized push-pull ventilation to improve the installed displacement ventilation system of a representative workshop.Computational fluid dynamics was ap-plied to calculate steady-state indoor air flow and volume-averaged pollutant concentration.System performance was evaluated in terms of source position;a computer simulated person was integrated to the building to confirm effectiveness against personal inhalation.Results showed marked improvement in performance when push-pull technique was used:room-averaged concentration diminished up to 91%while ventilation rate only increased 4%.Inhaled pollutant mitigation was achieved but performance dependence against leakage source and personal position was confirmed.

Temporal variation in modal properties of a base-isolated building during an earthquake

Temporal variation of dynamical modal properties of a base-isolated building is investigated using earthquake records in the building. A batch processing least-squares estimation method is applied to segment-wise time-series data. To construct an input-output system,an auto-regressive model with exogenous input (ARX) of second-order including a forgetting coefficient as a weighting coefficient is used for the estimation of modal parameters. The fundamental and second natural frequencies and the damping ratios of the fundamental and second natural modes of the base-isolated building are identified in the time domain. The identified results are consistent with the results obtained from the micro-tremor vibration data,forced-vibration test data and earthquake records in the present base-isolated building in the case of taking into account the amplitude-dependency of the isolators and viscous dampers. It is finally pointed out that several factors,e.g.,amplitude dependency of the isolator and damper system and special characteristics of the series-type viscous damper system,may be related complicatedly with the temporal variation in modal properties of the above-mentioned system.