True triaxial loading apparatus and its application to coal outburst prediction

Two generations of true triaxial loading (TTAL) apparatuses are presented. First generation apparatuses were intended primarily for true stress state imitation in rock or mineral specimens. Advanced second-generation installations are designed to provide precise measurements in any stress and simulation of rock outburst at sudden relief of one sample face. Both TTAL apparatuses can apply pressure up to 250 MPa corresponding to earth depth about 10,000 m independently along each of three axes. Experimental results are given on effect of absorbed water on ultimate state in coal as well as adsorbed methane influence on simulated coal outbursts.     

大直径灌注桩的静载试验研究

静载试验依然是目前确定桩基极限承载力最可靠的方法 ,对某工程大直径灌注桩的静载试验的Q s曲线、轴力、侧阻应力和端阻应力进行了详细分析 ,并得出了一些有益的结论 ,可以为以后同类型工程的设计和施工提供参考。     

国际GGP计划和武汉超导重力仪观测

介绍了近年来应用部分超导重力仪观测研究地球动力学研究方面的成果 ,包括精密测定地球潮汐常数 ,研究大气和海洋潮汐信号 ,确定地球自由核章动参数和检测地球自由振荡等内容。     

中国地壳运动观测网络基准站倾斜固体潮观测中的海潮负荷信号改正问题

利用最新的全球海潮模型（Csr3.0,Fes95.2,Tpxo2,Csr4.0和Scw80)和中国近海海潮资料，基于标准地球模型负荷格林函数，采用Agnew的积分格林函数方法研究了倾斜固体潮观测中的海潮负荷效应。文章计算了中国地壳运动观测网络25个基准站8个主要潮流的倾斜负荷，数值结果说明对某一潮波而言，倾斜负荷振幅达10^-9弧度，沿海地区达10^-8弧度或更多。文章构制了北京和上海等8个主要台站的倾斜负荷随时间变化。     

铅—橡胶阻尼器的试验研究

通过4种外径相同但铅芯直接不同的8个铅－橡胶阻尼器的低周往复水平荷载试验，研究影响铅－橡胶阻尼器性能的主要因素，得到了这种阻尼器的初始刚度，屈服刚度和等效阻尼比的变化规律。试验结果还表明，铅－橡胶阻尼器即使在很小的剪切变形下也具有较高的耗能能力。     

基桩极限荷载的确定及其预测

由基桩静载试验数据建立目标函数，用非线性最小二乘法求解该目标函数的极小值，从而得到基桩极限荷载值。这一方法不仅可用于对单桩极限荷载的精确确定，也可用于对单桩极限荷载的预测，计算实例表明，该方法是很有效的，具有较大的实用价值。     

Constraints on the dynamics of mantle plumes from uplift of the Hawaiian Islands

The ∼0.2 mm/yr uplift of Hawaiian islands Lanai and Molokai and Hawaiian swell topography pose important constraints on the structure and dynamics of mantle plumes. We have formulated 3-D models of mantle convection to investigate the effects of plume-plate interactions on surface vertical motions and swell topography. In our models, the controlling parameters are plume radius, excess plume temperature, and upper mantle viscosity. We have found that swell height and swell width constraints limit the radius of the Hawaiian plume to be smaller than 70 km. The additional constraint from the uplift at Lanai requires excess plume temperature to be greater than 400 K. If excess plume temperature is 400 K, models with plume radius between 50 and 70 km and upper mantle viscosity between 10²⁰ and 3×10²⁰ Pa s satisfy all the constraints. Our results indicate that mantle plume in the upper mantle may be significantly hotter than previously suggested. This has important implications for mantle convection and mantle melting. In addition to constraining plume dynamics, our models also provide a mechanism to produce the observed uplift at Lanai and Molokai that has never been satisfactorily explained before.     

Cyclic shear behaviour of steel box girders: experiment and analysis

An experimental investigation of the cyclic shear behaviour of steel box girders was conducted on one‐quarter scale models, comprising of two specimens with longitudinally unstiffened webs and one specimen with longitudinally stiffened webs. All the specimens exhibited ductile behaviour. The tests evidenced significant increases in the shear strength and energy dissipation capacity regarding the use of thicker webs and the provision of longitudinal web stiffeners. The web stiffeners also enhanced the stable hysteresis behaviour without substantial degradation in the energy dissipation due to pinching. The test results are compared with the shear behaviour simulated by inelastic large deformation analysis incorporated with a sophisticated constitutive model. The hysteresis behaviour, peak cyclic shear stresses, energy dissipation, and deformation shapes of the three specimens are satisfactorily predicted by the analysis. It is verified that the presented analytical method can be used precisely for further investigations of box girders in shear. Copyright © 2002 John Wiley & Sons, Ltd.     

Time domain dynamic analysis of piles under impact loading

In this paper, time domain dynamic analysis of piles under impact loading is presented. For this purpose a hybrid boundary element technique is implemented. Linear beam column finite elements are used to model the piles and resulting governing equations are solved using an implicit integration scheme. The continuum is assumed to be elastic and an efficient step-by-step time integration scheme is implemented by using an approximate half space integral formulation. By enforcing displacement equilibrium conditions at each time step, a system of equations is generated which yields the solution. Results of this time domain formulation under linear material behavior are compared with Laplace domain results to validate the methods.     

GPS measurements of ocean loading and its impact on zenith tropospheric delay estimates: a case study in Brittany, France

 The results from a global positioning system (GPS) experiment carried out in Brittany, France, in October 1999, aimed at measuring crustal displacements caused by ocean loading and quantifying their effects on GPS-derived tropospheric delay estimates, are presented. The loading effect in the vertical and horizontal position time series is identified, however with significant disagreement in amplitude compared to ocean loading model predictions. It is shown that these amplitude misfits result from spatial tropospheric heterogeneities not accounted for in the data processing. The effect of ocean loading on GPS-derived zenith total delay (ZTD) estimates is investigated and a scaling factor of 4.4 between ZTD and station height for a 10° elevation cut-off angle is found (i.e. a 4.4-cm station height error would map into a 1-cm ZTD error). Consequently, unmodeled ocean loading effects map into significant errors in ZTD estimates and ocean loading modeling must be properly implemented when estimating ZTD parameters from GPS data for meteorological applications. Ocean loading effects must be known with an accuracy of better than 3 cm in order to meet the accuracy requirements of meteorological and climatological applications of GPS-derived precipitable water vapor. Received: 16 July 2001 / Accepted: 25 April 2002 Acknowledgments. The authors are grateful to H.G. Scherneck for fruitful discussions and for his help with the ocean loading calculations. They thank H. Vedel for making the HIRLAM data available; D. Jerett for helpful discussions; and the city of Rostrenen, the Laboratoire d'Océanographie of Concarneau, and the Institut de Protection et de S?reté Nucléaire (BERSSIN) for their support during the GPS measurement campaign. Reviews by C.K. Shum and two anonymous referees significantly improved this paper. This work was carried out in the framework of the MAGIC project (http://www.acri.fr/magic), funded by the European Commission, Environment and Climate Program (EC Contract ENV4-CT98–0745). Correspondence to: E. Calais, Department of Earth and Atmospheric Sciences, Purdue University, West Lafayette, IN 47907-1397, USA. e-mail: ecalais@purdue.edu Tel. : +1-765-496-2915; Fax:+1-765-496-1210