固体潮与矿井坍崩事故

矿井是人类的重要资源和环境。从矿井内的宏观前兆、象力理论和引潮力的影响讨论了矿井灾害的预测问题。     

声发射/微震监测煤岩瓦斯复合动力灾害的研究现状

煤岩瓦斯复合动力灾害是深井开采面临的一种由冲击地压和煤与瓦斯突出共同作用的新的灾害表现形式.微破裂前兆是煤岩瓦斯复合动力灾变过程显现的共性本质特征,具有微震和声发射活动性.笔者在收集和阅读大量国内外煤岩瓦斯复合动力灾害资料的基础上,对煤岩瓦斯复合型动力灾害的监测技术进行了研究.研究结果表明:声发射监测技术和微震监测技术的原理相同,不同的是频谱范围有差异.煤岩瓦斯复合动力灾变过程要经历从微小破裂萌生→扩展→集结和从无序到有序的发展过程,声发射和微震监测技术可以很好的对灾变的整个过程进行监测,是研究煤岩瓦斯复合动力灾害的重要手段,对研究煤岩瓦斯复合动力灾害机制和前兆辨识具有重要意义.     

煤矿采掘过程中煤岩体电磁辐射特征及应用

运用研制的KBD5矿用本安型电磁辐射监测仪测试了煤矿采掘过程中工作面煤岩体的电磁辐射，分析了电磁信号与采掘工艺及煤岩动力灾害危险性等的关系。研究表明，煤矿采掘过程伴随产生电磁辐射，电磁辐射是煤岩体受到采动影响后应力重新分布或变形破裂趋向新平衡的结果；有煤与瓦斯突出和冲击地压危险时，有明显的电磁异常前兆；采取防治措施后，电磁辐射显著下降。电磁辐射技术在煤矿可以用于预测煤与瓦斯突出、冲击地压等煤岩动力灾害。     

地电和三临前兆产生机理及一种新的短临预报方法（谐振预报法）

研究了地电短临震兆机理，在此基础上给出了引潮力触发地电短临前兆模式。据此从理论上分析了地电临震震兆特征，并以唐山７．８级大震为例，从实际观测中检出具有模式特征的震兆，从而验证了所提模式理论的客观存在的可能性。     

引潮力对显著地震触发作用与大震关系及在雅江地震预报中的应用

大地震的孕育和发生是震源区及其附近地壳应变能的积累和快速释放过程。当地震孕育到后期, 震源区及其附近应变能高度积累, 处于极不稳定的临界状态。因此, 地震短临预报方法必须基于临界状态的特点。临界状态的最重要特点是触发因素将起重要作用。固体潮的引潮力是一种重要的触发因素。笔者改进了过去仅用月亮固体潮引潮力的地方平太阴时方法, 而用月亮与太阳整个固体潮引潮力作为触发因素, 显然这样更为科学和合理。研究表明, 大地震前震源区及其附近发生的几次显著地震易受固体潮引潮力某个方位附近触发。并应用这一现象结合其他地震前兆方法成功预报了2001年2月23日四川雅江6. 0级地震。     

地声

早在邢台地震时,我们最敬爱的周总理就明确地指出“地震是有前兆的,可以预测的,可以预防的。”今天几经大震后,我们对地震前兆现象有了进一步的认识。在各种物理前兆现象中,“地声”越来越被人们所重视,正在广泛研究地声的发射机制及其与地震的有机联系。     

成组地震的应力场变化与前兆关系

综述了成组地震以及地震静应力触发方面的研究现状，并在此基础上讨论了：如何应用震后静应力变化研究成组地震前兆；如何区分地震组的前兆和组中单个地震的前兆。     

地震震游的前兆系统和不均匀性及非线性对系统的影响

研究了地震震源前兆系统的几个特点。震源和前兆是在应力应变场不同分量作用下发育成的。不均匀性和非线性因素对震源和前兆有强烈的影响。讨论了介质和应力应变场不均匀性对地震震源形成和地震前兆影响的差别。在不同的应力场中，前兆的非线性关系首先在应变灵敏性上显示出来。应变灵敏性的不完备导致了“错误预测”和“漏报”这类预测错误。由地震前兆形成的条件可以得出复杂的前兆分布以及前兆相对震中转移规律的结论。研究了前兆信号曲线组成的几个特点，这些特点可以使地震短期前兆的区分更有根据。     

西南地区6级以上强震的综合预测总结

通过对地震预测实践过程中成功和失败的震例总结，提练出一套预报6级以上强震的综合预测决策判据：根据突变异常的数量和分布范围预测震级；根据突变异常的准同步涌现和某些外部触发因素预测发震时间；根据综合前兆异常相对集中区中地震活动性异常与前兆异常、宏观异常与微观异常配套出现来预测地震危险区。     

地震前兆统计检验的地震学问题：对目前地震预测问题争论的评述（之二）

在目前前于地震预测的争论中,地震前兆的统计检验是一人重要的问题。我们指出,这个问题不是一个纯粹的统计学问题,而首先是一个地震学问题。通过引入前兆的“分辩率”的概念和讨论地震前兆的统计检验,我们澄清了前兆检验中的“边缘问题”即落在预测区边缘附近的地震究竟是否应当算预测成功的问题。     

青藏块体东北缘潜在强震震源研究

依据单一力源模型的基本原理 ,利用青藏块体东北缘多年来水准观测垂直位移资料 ,反演该区 2 0a来中强地震的潜在震源力学参数与未来可能的危险区域 ,得到 :①如果确定所选研究区仅有一个等价强震力源 ,反演的强震力源与实际震中符合度较好 ,这对中强地震地点的预测有一定的参考价值 ;②在青藏块体东北缘6级左右的地震 ,比较合理的可研究范围一般为震源有效半径的 1 0倍 ,对应的等价力源的量级约为 1 0 1 1 N ;③从 1 995～ 2 0 0 0年的分区模拟结果看 ,在祁连的中段存在一个潜在的等价强震力源 (1× 1 0 1 1 N) ;另外 ,在青海与甘肃南部交界处存在一个潜在的等价强震力源 ,该力源深度为 5km ,大小达到 5× 1 0 1 1 N。     

Numerical simulation of incipient particle motion

A two-dimensional(2 D) computational model for simulation of incipient sediment motion for noncohesive uniform and non-uniform particles on a horizontal bed was developed using the Discrete Element Method(DEM).The model was calibrated and verified using various experimental data reported in the literature and compared with different theories of incipient particle motion.Sensitivity analysis was done and the effects of relevant parameters were determined.In addition to hydrodynamic forces such as drag,shear lift and Magnus force,the particle-particle interaction effects were included in the model.The asymptotic critical mobility number was evaluated for various critical particle Reynolds numbers(R*) in the range of very small and very large R*.The obtained curve is classified into four regions.It was found that in the linear region,the drag force has the principal role on the initiation of motion.Moreover,the critical mobility number is independent of particle diameter.A procedure for estimating the critical shear velocity directly from the information on particle diameter and roughness height was developed.Finally,the mechanism of incipient motion for the different regions was studied and the effect of different forces on the incipient particle motion was obtained.It was found that the maximum effects of lift and Magnus forces were,respectively,less than ten and twenty percent of the total force.The drag force,however,was typically the dominant force accounting for majority of the net hydrodynamic force acting on sediment particles at the onset of incipient motion.     

The tidal force function and tidal torques

Summary The tidal force function of the two-body system is defined. It is formed by two parts, reflecting the direct, as well as, the indirect tidal effects. It enables deriving the tidal torques due to both the tidal effects independently of density distributions. The Stokes parameters of both bodies, the Love numbers and phase lag angles are sufficient for the solution.     

已建立交桥结构地震反应上限研究

本文利用积函数极值法，从地震作用的角度出发，推导并建立了已建立交桥桥墩的基底剪力的表达式。将立交桥结构简化为多自由度的空间杆系，研究了基底剪力的计算方法。已建立交桥在强烈地震作用下，结构可能进入非线性阶段，本文探讨了怎样利用积函数极值法分析结构的非线性问题的途径。     

位移换能型加速度计中电子力与机械力的比例设计

分析了力平衡式加速度计中机械平衡力与电子反馈力之间的比例关系；阐明了加速度计系统参数的设计方法。     

Deciphering seismic and normal-force fluctuation signatures of debris flows: An experimental assessment of effects of flow composition and dynamics

Debris flows are gravity-driven mass movements that are common natural hazards in mountain regions worldwide. Previous work has shown that measurements of ground vibrations are capable of detecting the timing, speed, and location of debris flows. A remaining question is to what extent additional flow properties, such as grain-size distribution and flow depth can be inferred reliably from seismic data. Here, we experimentally explore the relation of seismic vibrations and normal-force fluctuations with debris-flow composition and dynamics. We use a 5.4 m long and 0.3 m wide channel inclined at 20°, equipped with a geophone plate and force plate. We show that seismic vibrations and normal-force fluctuations induced by debris flows are strongly correlated, and that both are affected by debris-flow composition. We find that the effects of the large-particle distribution on seismic vibrations and normal-force fluctuations are substantially more pronounced than the effects of water fraction, clay fraction, and flow volume, especially when normalized by flow depth. We further show that for flows with similar coarse-particle distributions seismic vibrations and normal-force fluctuations can be reasonably well related to flow depth, even if total flow volume, water fraction, and the size distribution of fines varies. Our experimental results shed light on how changes in large-particle, clay, and water fractions affect the seismic and force-fluctuation signatures of debris flows, and provide important guidelines for their interpretation.     

How hydrological factors initiate instability in a model sandy slope

Knowledge of the mechanisms of rain‐induced shallow landslides can improve the prediction of their occurrence and mitigate subsequent sediment disasters. Here, we examine an artificial slope's subsurface hydrology and propose a new slope stability analysis that includes seepage force and the down‐slope transfer of excess shear forces. We measured pore water pressure and volumetric water content immediately prior to a shallow landslide on an artificial sandy slope of 32°: The direction of the subsurface flow shifted from downward to parallel to the slope in the deepest part of the landslide mass, and this shift coincided with the start of soil displacement. A slope stability analysis that was restricted to individual segments of the landslide mass could not explain the initiation of the landslide; however, inclusion of the transfer of excess shear forces from up‐slope to down‐slope segments improved drastically the predictability. The improved stability analysis revealed that an unstable zone expanded down‐slope with an increase in soil water content, showing that the down‐slope soil initially supported the unstable up‐slope soil; destabilization of this down‐slope soil was the eventual trigger of total slope collapse. Initially, the effect of apparent soil cohesion was the most important factor promoting slope stability, but seepage force became the most important factor promoting slope instability closer to the landslide occurrence. These findings indicate that seepage forces, controlled by changes in direction and magnitude of saturated and unsaturated subsurface flows, may be the main cause of shallow landslides in sandy slopes. Copyright © 2013 John Wiley & Sons, Ltd.     

Real‐time force control for servo‐hydraulic actuator systems using adaptive time series compensator and compliance springs

Servo‐hydraulic actuators have been widely used for experimental studies in engineering. They can be controlled in either displacement or force control mode depending on the purpose of a test. It is necessary to control the actuators in real time when the rate‐dependency effect of a test specimen needs to be accounted for under dynamic loads. Real‐time hybrid simulation (RTHS) and effective force testing (EFT) method, which can consider the rate‐dependency effect, have been known as viable alternatives to the shake table testing method. Due to the lack of knowledge in real‐time force control, however, the structures that can be tested with RTHS and EFT are fairly limited. For instance, satisfying the force boundary condition for axially stiff members is a challenging task in RTHS, while EFT has a difficulty to be implemented for nonlinear structures. In order to resolve these issues, this paper introduces new real‐time force control methods utilizing the adaptive time series (ATS) compensator and compliance springs. Unlike existing methods, the proposed force control methods do not require the structural modeling of a test structure, making it easy to be implemented especially for nonlinear structures. The force tracking performance of the proposed methods is evaluated for a small‐scale steel mass block system with a magneto‐rheological damper subjected to various target forces. Accuracy, time delay, and resonance response of these methods are discussed along with their force control performance for an axially stiff member. Overall, a satisfactory force tracking performance was observed by using the proposed force control methods.     

智能型压电-摩擦耗能器

本文利用压电陶瓷驱动器的电致形变特征和摩擦耗能器的紧固力决定摩擦力大小的特性,提出了智能型压电－摩擦复合耗能器。文中首先提出了叠层压电陶瓷驱动器与Ｐａｌｌ摩擦耗能器复合的基本结构;其次,提出了压电－摩擦耗能器可调紧固力的计算方法,分析了耗能器形状参数的影响;最后,具体设计了可调摩擦耗能型和拟粘滞型两种压电－摩擦耗能器。