Transient foundation solution of saturated soil to impulsive concentrated loading

The transient dynamic response of saturated soil under suddenly applied normal and horizontal concentrated loading is studied in this paper. The behavior of saturated soil is governed by Biot's consolidation theory. The general solutions for Biot equations of equilibrium are derived in terms of displacements and variations of fluid volume, using Laplace–Hankel integral transforms. The solutions in the time domain can be evaluated by numerical inverse Laplace–Hankel transforms. Selected numerical results for displacements, stresses, and pore pressures are presented. Comparisons with existing closed-form solutions for the elastic half-space are made to confirm the accuracy of the present solutions. The solutions can be used to study a variety of transient wave propagation problems and dynamical interactions between saturated soil and structures.     

三原井水位固体潮加卸载响应比的地震异常

讨论了三原井水位在泾阳4．8级地震前的变化特征，重点是泾阳地震前水位对固体潮响应的变化，即固体潮加卸载响应率与加卸载响应比的变化，对水位观测资料的计算分析表明，震前加卸载响应率及响应比有“平稳－升高－恢复”的特征，说明水位固体潮加卸载响应比方法有可能捕捉5级左右近震的前兆信息。     

大震前地下水位异常与应力异常区

利用井口水位对潮汐应力的响应，分析了含水层对强震孕育过程中应力变化的响应。结果显示，当含水层的瞬时应力变化值大于临界值时，水位的异常图像为阶变形态；当含水层的瞬时应力变化值小于临界值，但某一时段的累计值大于临界值时，水位的异常图像为缓变形态。而水位异常图像出现的上升或下降形态，取决于井孔含水层系统在大震孕育过程的应力调整再积累阶段所处的构造部位。水位震前异常的特征，源于地震孕育过程中应力异常区的形成。     

Measuring drop size distribution and kinetic energy of rainfall using a force transducer

The relatively high cost of commercially available raindrop spectrometers and disdrometers has inhibited detailed and intensive research on drop size distribution, kinetic energy and momentum of rainfall which are important for understanding and modelling soil erosion caused by raindrop detachment. In this study, an approach to find the drop size distribution, momentum and kinetic energy of rainfall using a relatively inexpensive device that uses a piezoelectric force transducer for sensing raindrop impact response is introduced. The instrument continuously and automatically records, on a time‐scale, the amplitude of electrical pulses produced by the impact of raindrops on the surface of the transducer. The size distribution of the raindrops and their respective kinetic energy are calculated by analysing the number and amplitude of pulses recorded, and from the measured volume of total rainfall using a calibration curve. Simultaneous measurements of the instrument, a rain gauge and a dye‐stain method were used to assess the performance of the instrument. Test results from natural and simulated rainfalls are presented. Copyright © 2000 John Wiley & Sons, Ltd.     

Sensitivity analysis of EUROSEM using Monte Carlo simulation I: hydrological,soil and vegetation parameters

Knowledge about model uncertainty is essential for erosion modelling and provides important information when it comes to parameterizing models. In this paper a sensitivity analysis of the European soil erosion model (EUROSEM) is carried out using Monte Carlo simulation, suitable for complex non‐linear models, using time‐dependent driving variables. The analysis revealed some important characteristics of the model. The variability of the static output parameters was generally high, with the hydrologic parameters being the most important ones, especially saturated hydraulic conductivity and net capillary drive followed by the percentage basal area for the hydrological and vegetation parameters and detachability and cohesion for the soil erosion parameters. Overall, sensitivity to vegetation parameters was insignificant. The coefficient of variation for the sedigraph was higher than for the hydrograph, especially from the beginning of the rainstorm and up to the peak, and may explain difficulties encountered when trying to match simulated hydrographs and sedigraphs with observed ones. The findings from this Monte Carlo simulation calls for improved within‐storm modelling of erosion processes in EUROSEM. Information about model uncertainty will be incorporated in a new EUROSEM user interface. Copyright © 2000 John Wiley & Sons, Ltd.     

排除油田深水井动态干扰因素的一种方法

为了适应油田地下水动态观测资料的处理，有效地排除干扰，对Weiner滤波方法进行了改进，利用改进后的方法，处理了胜利油田东水-3井的观测资料，结果表明，利用该方法可以较好地消除各种干扰对地下水动态观测的影响。     

地下水物理参量强地震中短期预报方法的检验

应用“九五”子专题“地下水物理参量异常识别标志体系及预报方法研究”的研究思路,预报方法和指标对河北省井网1983年以来的水位观测资料进行了全时程扫描,结果表明“群井群常年频次法”在河北及邻近地区中强地震前有较明显的异常显示,应用效果较好,对该方法进行了预报效能R值评分,评价结果表明漏报率低,虚报率高。     

由井水位资料反演大同-阳高6.1级地震前后应力场的动态演化过程

利用献[1]给出的用井水位资料反演含水层应力变化的方法和井水位动态观测资料，反演了大同－阳高地震前后大区域应力场的动态变化特征。结果表明：应力场的零值线穿过震中区，地震前，震中区周围应力场发生转向，由正应力区变为负应力区，同时正应力的量值逐渐增大。地震发生后应力场呈缓慢变化。     

Torsional response of a rigid circular foundation on a saturated half-space to SH waves

An analytical approach is used to study the torsional vibrations of a rigid circular foundation resting on saturated soil to obliquely incident SH waves. Biot’s poroelastic dynamic theory is considered to characterize the saturated soil below the foundation, which is solved by Hankel transform later. In order to consider the scattering phenomena caused by the existence of the foundation, the total wave field in soil is classified into free-field, rigid-body scattering field and radiation scattering field. According to the classification of wave field and the mixed boundary-value conditions between the soil and the foundation, torsional vibrations of the foundation are formulated in two sets of dual integral equations. Then, the dual integral equations are reduced to Fredholm integral equation of the second kind to be solved. Combining with the dynamic equilibrium equations of the foundation, the expressions for the torsional vibrations of the foundation are obtained. Numerical results are presented to demonstrate the influence of excitation frequency, incident angle, the torsional inertia moment of the foundation and permeability of the saturated half-space on the torsional vibrations of the foundation.     

Constraining Holocene sea levels using U‐Th ages of phreatic overgrowths on speleothems from coastal caves in Mallorca (Western Mediterranean)

Phreatic overgrowths on speleothems (POS) are carbonate formations deposited at the water table of caves in unique karstic coastal settings having morphologies that can be directly related to sea level at the time of formation. The U‐Th ages of calcite and aragonite overgrowths collected from the modern water table in coastal caves on Mallorca (Cova de Cala Varques A and Cova des Pas de Vallgornera) were determined using high‐precision MC‐ICPMS techniques. U‐Th ages indicate that phreatic carbonate deposition occurred between ca 2·8 and at least 0·6 ka BP and are in accord with an archeologically estimated age of 3·7–3·0 ka BP for a drowned prehistoric construction at a depth of 1 m below current sea level in a cave from the same area. Speleothem δ¹³C and δ¹⁸O and chemical composition of cave pools provide supportive evidence that POS reflect mixing between seawater and brackish water table. Copyright © 2010 John Wiley & Sons, Ltd.