Method for determining the position of landslide slip-surface with a typical inclinometric curves

In the actual monitoring of deep hole displacement,the identification of slip surfaces is primarily based on abrupt changes observed in the inclinometric curve.In conventional identification methods,inclinometric curves exhibiting indications of sliding can be categorized into three types:B-type,D-type,and r-type.The position of the slip surface is typically determined by identifying the depth corresponding to the point of maximum displacement mutation.However,this method is sensitive to the interval of measurement points and the observation scale of the coordinate axes and suffers from unclear sliding surfaces and uncertain values.Based on the variation characteristics of these diagonal curves,we classified the landslide into three components:the sliding body,the sliding interval,and the immobile body.Moreover,three different generalization models were established to analyze the relationships between the curve form and the slip surface location based on different physical indicators such as displacement rate,relative displacement,and acceleration.The results show that the displacement rate curves of an r-type slope exhibit a clustering feature in the sliding interval,and by solving for the depth of discrete points within the step phase,it is possible to determine the location of the slip surface.On the other hand,D-type slopes have inflection points in the relative displacement curve located at the slip surface.The acceleration curves of B-type slopes exhibit clustering characteristics during the sliding interval,while the scattered acceleration data demonstrate wandering characteristics.Consequently,the slip surface location can be revealed by solving the depth corresponding to the maximum acceleration with cubic spline interpolation.The approach proposed in this paper was applied to the monitoring data of a landslide in Yunnan Province,China.The results indicate that our approach can accurately identify the slip surface location and enable computability of its position,thereby enhancing applicability and reliability of the deep-hole displacement monitoring data.

Asymmetric Relationship between the Meridional Displacement of the Asian Westerly Jet and the Silk Road Pattern

In previous work, a significant relationship was identified between the meridional displacement of the Asian westerly jet （JMD） and the Silk Road Pattern （SRP） in summer. The present study reveals that this relationship is robust in northward JMD years but absent in southward JMD years. In other words, the amplitude of the SRP increases with northward displacement of the jet but shows little change with southward displacement. Further analysis indicates that, in northward JMD years, the Rossby wave source （RWS） anomalies, which are primarily contributed by the planetary vortex stretching, are significantly stronger around the entrance of the Asian jet, i.e., the Mediterranean Sea-Caspian Sea area, with the spatial distribution being consistent with that related to the SRP. By contrast, in southward JMD years, the RWS anomalies are much weaker. Therefore, this study suggests that the RWS plays a crucial role in inducing the asymmetry of the JMD-SRP relationship. The results imply that climate anomalies may be stronger in strongly northward-displaced JMD years due to the concurrence of the JMD and SRP, and thus more attention should be paid to these years.

Recasting theory of elasticity with micro-finite elements

In the classical theory of elasticity,a body is initially modeled as a homogeneous and dense assemblage of constituent ＂material particles＂.The kernel concept of elastic deformation is the displacement of the particle that associates the current configuration with the reference one.In this paper,we exploit an alternative constituent ＂micro-finite element＂,and use the stretch of the element as the essential quality to recast the theory of elasticity.It should be realized that such a treatment means that the elastic body can be modeled as a finite covering of elements and consequently characterized by a manifold.The recasting of the elasticity theory becomes more feasible for dealing with defects and topological evolution.

Experimental study on a pre-damaged scaled tunnel model strengthened with CFRP grids

The effectiveness of carbon fiber reinforced polymer（CFRP） grids as the strengthening materials for a pre-damaged scaled tunnel model is experimentally investigated. First, the bond performances between the CFRP grid and the concrete under different types of adhesive and surface treatment were tested. The most efficient anchoring system was adopted for the subsequent scaled tunnel strengthening. Test results show that when the epoxy structural adhesive was used as the bonding material, the failure mode was CFRP grids rupturing,and the anchorage performance was optimal. When the polymer mortar was used as the adhesive, the surface treatments with anchored bolts and grooves can improve the bond performance, and the failure mode was sliding failure with the polymer mortar peeled off. After strengthening with CFRP grids, both the stiffness and the load capacity of the pre-damaged scaled tunnel model were improved. Additionally,the results obtained by fiber bragg grating（FBG） sensors indicate that the strains across tunnel segments were reduced,and the overall performance of the tunnel was improved.

Imaginary displacement method for analysis of multi-fingered robot hands grasping stability

Gives an overview of the present status of researches on grasp stability of multi fingered dexterous robot hands,presents the imaginary displacement method for evaluating the grasp stability, which is easy to realize on computer,and has no limit on contact points for each finger. Analyses for grasping stability with single contact point of typical objects with different curvature proved the effectiveness of the method proposed and optimal grasp examples are given as well.

基于广义估计方程评价正畸治疗对牙周病致前牙移位患者牙槽骨、CGRP水平及微环境改建的影响

目的探讨广义估计方程评价正畸治疗对牙周病致前牙移位患者牙槽骨、降钙素基因相关肽(CGRP)水平及微环境改建的影响。方法选取2019年8月至2022年8月期间于我院就诊的牙周病致前牙移位患者286例,按照随机数字表法将患者分为对照组(n=143,采用牙周基础治疗)和观察组(n=143,采用口腔正畸治疗),比较两组患者的临床资料及治疗前后CGRP水平、前牙覆盖距离、牙周袋深度、牙槽骨高度、出血指数、肿瘤坏死因子-α(TNF-α)、白细胞介素-6(IL-6)、白细胞介素-2(IL-2)水平,并构建广义估计方程(GEE)分析患者正畸治疗后CGRP水平与牙槽骨及微环境改建的关联;运用Spearman分析CGRP水平与前牙覆盖距离、牙周袋深度、牙槽骨高度、TNF-α、IL-6、IL-2水平的相关性。结果与治疗前相比,两组牙周病致前牙移位患者治疗后30d和治疗后1年的CGRP水平上升、前牙覆盖距离缩小、牙周袋深度减小、牙槽骨高度减小、出血指数降低、炎症因子TNF-α、IL-6、IL-2分泌减少,且观察组前牙移位患者的以上指标明显优于对照组前牙移位患者(P<0.05)。通过Spearman相关性分析发现,血清CGRP与前牙覆盖距离、牙周袋深度、牙槽骨高度、出血指数、TNF-α、IL-6、IL-2呈显著负相关(P<0.05)。GEE分析结果显示,治疗后观察组的前牙覆盖距离、牙周袋的深度、牙槽骨的高度、出血的指数、TNF-α、IL-6、IL-2优于对照组,差异具有统计学意义(P<0.05)。结论CGRP水平与牙周病致前牙移位患者正畸治疗中牙槽骨及微环境改建的密切相关,可以依据CGRP水平与牙周病致前牙移位患者正畸治疗中牙槽骨及微环境改建的相关性判断出患者的治疗效果是否良好,在口腔治疗中起着重要作用。

Nonlinear Modeling and Identification of Structural Joint by Response Control Vibration Test

Components of mechanical product are assembled by structural joints,such as bolting,riveting,welding,etc.Structural joints introduce nonlinearity to some engineering structures,and the nonlinearity need to be modeled precisely.To meet serious quality requirements,it is necessary to detect and identify nonlinearity of mechanical products for structural optimization.Modal test to acquire a dynamic response has been applied for decades,which provides reliable results for finite element(FE)model updating.Here response control vibration test for identification of nonlinearity is presented.A nonlinear system can be regarded as linearity for particular steady state response,and classical linear analysis tool is applicable to extract modal data for particular response.First,its applicability is illustrated by some numerical simulations.Subsequently,it is implemented on experimental setup with structural joints by shaking table.The stiffness and damping function dependent of relative displacement are fitted to describe its inherent nonlinearity.The spring and damping forces are identified by harmonic balance method(HBM)to predict output response.Based on the identified results,the procedure is recommended that it allows a reliable measurement of nonlinearity with a certain accuracy.

APPROACH FOR LAYOUT OPTIMIZATION OF TRUSS STRUCTURES WITH DISCRETE VARIABLES UNDER DYNAMIC STRESS, DISPLACEMENT AND STABILITY CONSTRAINTS

A mathematical model was developed for layout optimization of truss structures with discrete variables subjected to dynamic stress, dynamic displacement and dynamic stability constraints. By using the quasi-static method, the mathematical model of structure optimization under dynamic stress, dynamic displacement and dynamic stability constraints were transformed into one subjected to static stress, displacement and stability constraints. The optimization procedures include two levels, i.e., the topology optimization and the shape optimization. In each level, the comprehensive algorithm was used and the relative difference quotients of two kinds of variables were used to search the optimum solution. A comparison between the optimum results of model with stability constraints and the optimum results of model without stability constraint was given. And that shows the stability constraints have a great effect on the optimum solutions.

Coseismic gravity and displacement changes of Japan Tohoku earthquake(Mw 9.0)

The greatest earthquake in the modern history of Japan and probably the fourth greatest in the last 100 years in the world occurred on March 11, 2011 off the Pacific coast of Tohoku.Large tsunami and ground motions caused severe damage in wide areas, particularly many towns along the Pacific coast. So far, gravity change caused by such a great earthquake has been reported for the 1964 Alaska and the 2010 Maule events. However, the spatial-temporal resolution of the gravity data for these cases is insufficient to depict a co-seismic gravity field variation in a spatial scale of a plate subduction zone. Here, we report an unequivocal co-seismic gravity change over the Japanese Island, obtained from a hybrid gravity observation（combined absolute and relative gravity measurements）. The time interval of the observation before and after the earthquake is within 1 year at almost all the observed sites, including 13 absolute and 16 relative measurement sites, which deduced tectonic and environmental contributions to the gravity change. The observed gravity agrees well with the result calculated by a dislocation theory based on a self-gravitating and layered spherical earth model. In this computation, a co-seismic slip distribution is determined by an inversion of Global Positioning System（GPS） data. Of particular interest is that the observed gravity change in some area is negative where a remarkable subsidence is observed by GPS, which can not be explained by simple vertical movement of the crust. This indicated that the mass redistribution in the underground affects the gravity change. This result supports the result that Gravity Recovery and Climate Experiment（GRACE） satellites detected a crustal dilatation due to the 2004 Sumatra earthquake by the terrestrial observation with a higher spatial and temporal resolution.

Maximum Relative Displacement of Adjacent Buildings During Ground Motions

In order to give the reasonable width of seismic gaps to prevent the structural pounding during ground motions,the maximum relative displacement of adjacent structures is studied in this paper.The factors that may have effects on the maximum relative displacement are discussed.As for multi-degree-of-freedom(MDOF) systems,they can be equivalent to single-degree-of-freedom(SDOF) systems with the influences of high modes neglected.The results show that the period ratio,height ratio and peak ground acceleration are the main factors that have great effects on the maximum relative displacement of adjacent structures.The maximum relative displacement of MDOF systems can be obtained from calculating the maximum relative displacement of the equivalent SDOF systems.

A Straightforward Direct Traction Boundary Integral Method for Two-Dimensional Crack Problems Simulation of Linear Elastic Materials

This paper presents a direct traction boundary integral equation method(DTBIEM)for two-dimensional crack problems of materials.The traction boundary integral equation was collocated on both the external boundary and either side of the crack surfaces.The displacements and tractions were used as unknowns on the external boundary,while the relative crack opening displacement(RCOD)was chosen as unknowns on either side of crack surfaces to keep the single-domain merit.Only one side of the crack surfaces was concerned and needed to be discretized,thus the proposed method resulted in a smaller system of algebraic equations compared with the dual boundary element method(DBEM).A new set of crack-tip shape functions was constructed to represent the strain field singularity exactly,and the SIFs were evaluated by the extrapolation of the RCOD.Numerical examples for both straight and curved cracks are given to validate the accuracy and efficiency of the presented method.

Quantitative prediction of oil saturation of unconsolidated sandstone reservoir based on time-lapse seismic “relative difference method”: Taking Zeta oil field in West Africa as an example

In view of the disadvantage that the absolute difference of time-lapse seismic(the difference between monitoring data and base data) is not only related to the change of oil saturation, but also closely related to the thickness of reservoir, a time-lapse seismic "relative difference method"(the ratio of monitoring data to base data) not affected by the thickness of reservoir but only related to the change of fluid saturation, is proposed through seismic forward modeling after fluid displacement simulation. Given the same change of fluid saturation, the absolute difference of time-lapse seismic conforms to the law of "tuning effect" and seismic reflection of "thin bed", and the remaining oil prediction method based on absolute difference of time-lapse seismic is only applicable to the reservoirs with uniform thickness smaller than the tuning thickness or with thickness greater than the tuning thickness. The relative difference of time-lapse seismic is not affected by reservoir thickness, but only related to the change of fluid saturation. It is applicable to all the deep-sea unconsolidated sandstone reservoirs which can exclude the effect of pressure, temperature, pore type and porosity on seismic. Therefore, the relation between the relative difference of time-lapse seismic and the change of fluid saturation, which is obtained from seismic forward modeling after Gassmann fluid displacement simulation, can be used to quantitatively predict the change of reservoir water saturation and then the distribution of the remaining oil. The application of this method in deep sea Zeta oil field in west Africa shows that it is reasonable and effective.

Seismic Isolation of Reactor Assembly for a Fixed Base Accelerator Driven System Reactor Building

In the SILER （Seismic-Initiated events risk mitigation in LEad-cooled Reactors） Project, it is interesting to apply seismic isolation technology for the reactor assembly of the fixed base reactor building for ADS （Acceleration Driven System） heavy liquid reactor MYRRHA （Multipurpose Hybrid Research Reactor for High-Tech Application） which contains the most critical safety related components, such as reactor vessel, safe shutdown and control rod mechanisms, primary heat exchangers, primary pumps, spoliation target assembly and fuel assemblies, etc. The purpose of this paper is to investigate the possibility of an application of a partial seismic isolation to the safety critical components only, here, the reactor assembly. This paper presents the preliminary analysis results of the isolated reactor assembly and compares these with those of seismic isolated ADS reactor building. The analysis results show the reduction of the seismic acceleration response but the increase of the relative displacement for the reactor assembly. Some safety issues, especially, coolant＇s incapable covering the reactor core make difficult to apply for the partial seismic isolation of the ADS reactor assembly due to large relative displacement occurring the partial isolation system. Further study on the partial seismic isolation application of the critical safety components are also discussed.

Calculation of reverse-fault-related parameters using topographic profiles and fault bedding

Fault-related parameters are critical for studying tectonic evolution, deformation character- istics, active tectonism, and seismic hazards. A new method of calculating reverse-fault- related parameters has been developed, which uses systematic analysis of the geometrical characteristics of normal and reverse scarps of reverse faults together with measurements of topographic profiles and fault bedding. The results show that the most suitable method of calculating fault parameters heavily relies on the specific type of fault scarp. For a reverse scarp, the size of the vertical displacement （VD） of the fault, the vertical separation （VS） of the hanging wall and the footwall, and the fault scarp height （SH）how the relationship VD ≥VS ≥ SH; conversely, for normal scarps, VD ≤ VS ≤ SH. The theoretical equations were used to study fault deformation in the Southwest Tianshan Mountain foreland basin. The results showed that, for every fault, VD ≥ VS ≥SH, which is consistent with our predicted relationship. This finding demonstrates that this method is suitable to explore structural information of reverse faults. In the study area, the vertical displacement is 1.4 times the horizontal displacement, suggesting that fiexural-slip faults may play an important role in transferring local deformation from horizontal shortening to vertical uplift. Therefore, one of the most important steps in correct calculation of reverse-fault-related parameters is selection of the proper equations by identifying the specific type of fault scarp and the corresponding calculation method.

冻融环境下泡沫混凝土的单轴压缩特性

为了解冻融环境下泡沫混凝土的单轴压缩特性,分别对4种密度(500、600、800和1 000 kg/m3)的泡沫混凝土进行了变加载速率(10~100 N/s)的试验研究,并基于X-CT重构了冻融环境下泡沫混凝土的孔隙结构模型。在此基础上,研究了单轴压缩过程荷载-位移曲线的特征及其影响因素,并借助回归分析和灰关联理论分析了泡沫混凝土密度、冻融循环次数及加载速率与抗压强度的关联程度。结果表明:冻融循环后泡沫混凝土单轴压缩过程荷载-位移曲线的切线模量大幅减小,非线性特征加强;冻融循环后试件孔隙率增大,孔径分布离散化程度加强。冻融环境下泡沫混凝土抗压强度与密度等级之间始终保持指数关系,相关系数均在0.9以上;泡沫混凝土密度等级与抗压强度联系最为紧密,其次是冻融循环次数和加载速率,灰关联度均在0.65以上。

A destructive field study on the behavior of piles under tension and compression

This paper involves a series of destructive full-scale load tests on long bored piles instrumented with strain gauges along the shafts,including two compression and two tension loading tests.The load-displacement response,axial force,skin friction,and the thresholds of the slip displacement for fully mobilizing the skin resistances in different soils are discussed.Moreover,the theoretical solution for estimating the pile tip settlement under compression was adopted to analyze the test results.It was found that the measured skin frictions for the piles under compression were about 6% to 42% higher than the estimated values of the cone penetration tests(CPTs),whereas the measured skin frictions in the uplift cases were about 16% to 50% smaller than the estimated values.In addition,the average limited skin frictions for the tension piles were about 0.36 to 0.78 times the average ultimate skin frictions for the piles under compression.It also can be indicated that the skin friction along the pile depth approached the limited state,and decreased from a peak value with increasing loads.

锚定板位移-荷载关系近似解析算法

首先,通过适当的假设,基于弹性地基梁理论,提出了黏性土中锚定板位移-荷载关系的近似解析算法。其次,基于6个不同尺寸方形锚定板位移-荷载关系的数值模拟结果,获得了土体水平基床系数的比例系数与锚定板水平位移关系式中的两个拟合参数。然后,用锚定板现场抗拔力试验结果验证了理论分析方法的可行性。最后,讨论了土的黏聚力及内摩擦角对锚定板抗拔承载力的影响。研究结果表明,在某一深度范围内方形锚定板位移-荷载关系近似解析算法是可行的。

Analysis of stress and failure in rock specimens with closed and open flaws on the surface

The influence of closed and open surface flaws on the stress distribution and failure in rock specimens is investigated.Heterogeneous finite element models are developed to simulate the compression tests on flawed rock specimens.The simulated specimens include those with closed flaws and those with open flaws on the surface.Systematic analyses are conducted to investigate the influences of the flaw inclination,friction coefficient and the confining stress on failure behavior.Numerical results show significant differences in the stress,displacement,and failure behavior of the closed and open flaws when they are subjected to pure compression;however,their behaviors under shear and tensile loads are similar.According to the results,when compression is the dominant mode of stress applied to the flaw surface,an open flaw may play a destressing role in the rock and relocate the stress concentration and failure zones.The presented results in this article suggest that failure at the rock surface may be managed in a favorable manner by fabricating open flaws on the rock surface.The insights gained from this research can be helpful in managing failure at the boundaries of rock structures.

低硬度橡胶隔震支座基本力学性能及恢复力特性

本研究对低硬度橡胶隔震支座的材料性能 (主要包括力学性能 )进行了系统的试验开发及理论研究。研究用低硬度橡胶隔震支座包括天然橡胶隔震支座及铅芯橡胶隔震支座两大类 18种规格总计近 30个大直径隔震支座。研究内容涉及橡胶隔震支座竖向刚度、水平刚度及阻尼等基本力学性能 ;压缩界限 ,屈曲及极限剪切变形等界限性能 ;温度、压力、剪切变形、老化和徐变等相关性及长期特性 ;同时还对橡胶材料其他性能进行了系统的试验研究。本文主要介绍低硬度天然橡胶隔震支座及铅芯橡胶隔震支座的基本力学性能 ,如竖向。

想象动作中动态脑电的信息熵研究

想象动作可以引起脑电信号的特异性变化,如何通过提取脑电特征参数来识别想象动作的发生是目前脑-计算机接口(BCI)系统设计的技术关键之一。本研究使用两种信息熵(功率谱熵和小波熵)作为特征参数,对手部想象动作执行前后的动态脑电信号进行分析,并与目前常用的mu节律事件相关去同步(ERD)参数进行比较,以寻找特异性更强的动态参数。结果显示在想象动作对侧的运动感觉区域中,功率谱熵和小波熵均表现出与mu节律强度变化具有明显锁时关系的改变,且区分错误率得到明显降低。而在中顶部位置mu节律强度无明显变化处,熵参数对左右手想象动作的响应也具有明显的不同。结论,功率谱熵和小波熵具有良好的时域分辨能力和更准确的区分效果,可以作为特征参数用于在线BCI系统。