Estimation of in situ viscoelastic parameters of weak floor strata by plate-loading tests

Summary This paper explores an approach to estimation of the viscoelastic parameters of weak floor strata using plate-loading tests. Mathematical equations are derived to describe deformation-time history for the standard Burgers model under three-dimensional stress-strain conditions, which are verified with a finite element model. A number of time-dependent in-mine plate-loading tests were conducted and the values of the viscoelastic parameters were estimated based on the derived equation. It is shown that large discrepancies between the parameter values estimated from the plate-loading tests and those acquired from the in-mine convergence data are the results of neglecting adjacent pillar interaction. Finite element modelling was conducted to investigate the effects of adjacent pillar interactions upon the pillar settlement. Based on the finite element analyses, a correction curve was developed to adjust the viscoelastic parameter values to take into account the interaction between adjacent pillars. With the correction, the parameter values estimated from the plate-loading tests compared favourably with those acquired from the in-mine convergence results.     

Stability analysis of rock wedges with multiple sliding surfaces

Summary Although wedge and plane sliding stability analyses are well established in the geotechnical literature, certain geologic environments produce blocks which cannot be adequately modelled as either wedges or plane slides. An example is blocks forming in cylindrically folded sedimentary rocks, where the surface of sliding is neither a single plane nor a double plane but is curved. This type of block may be idealized as a prismatic block with multiple sliding planes, all with parallel lines of intersection. If the sliding planes number three or more, the distribution of normal forces, and hence the factor of safety, is indeterminate. A new analytical model for sliding stability analysis is described in which the distribution of normal forces on the contact planes is chosen to minimize the potential energy of the system. The classic wedge and plane solutions are shown to be special cases of this more general model, which allows determination of the safety factor for any shape of prismatic contact surface. An example from Tennessee concerning a block with a curved sliding surface is described and the factor of safety compared with the standard wedge analysis. It is shown that with three or more contact planes, the safety factor may be significantly lower than that calculated from the wedge model, which provides an upper limit on stability.     

夯扩桩半模夯扩试验及夯扩机理探讨

设计了夯扩桩半模夯扩试验，采用读数显微镜直接测读上体质点位移，获得了不同密度的均匀砂土中砂粒的位移，由此确定土体的位移场和密度场。借鉴魏西克（Ｖｅｓｉｃ）球形孔穴膨胀理论和梅耶霍夫（Ｍｅｙｅｒｈｏｆ）塑性剪切理论，结合模型试验成果，对夯扩机理作了探讨，并定性地提出了夯扩机理模式。     

内蒙古科尔康油田沙海组储集层的岩石学特征

根据碎屑岩铸体薄片和扫描电镜观察分析资料，研究了科尔康油田沙海组储集层的岩石学特征。科尔康油田沙海组储集层的岩石类型主要为岩屑砂岩和岩屑砂砾岩。碎屑岩的岩性特征对沙海组储集层的成岩作用具有显著的影响作用。     

Study of the liquefaction resistance of a saturated sand reinforced with Geosynthetics

This article presents various tests using a cyclic triaxial instrument, on samples of saturated Hostun RF sand, reinforced with circular sheets of geosynthetic material. Tests performed with different types of geosynthetics of different compressibility, rigidity and roughness characteristics indicate a significant increase in liquefaction resistance for samples reinforced with compressible, non-woven geotextiles. The undrained behaviour of saturated Hostun RF sand reinforced with non-woven geotextiles is analysed on the basis of different test series. This analysis highlights the influence of reinforcement compressibility on interstitial pressure distribution in the sample, thus showing the role of this type of inclusion in the increase in liquefaction resistance.     

华北地区煤的显微组分结焦性热台试验

为探讨煤的显微组分的结焦性，对不同变质程度煤的镜质组、壳质组和惰性组分别进行了显微镜热台加热试验．在加热过程中，活性组分经历了３个明显不同的变化阶段，即变形阶段、胶质体形成阶段以及固化阶段．随煤变质程度的增加，镜质组的初变温度和胶质体形成时的温度逐渐增大，而固结温度变化规律不明显；壳质组在低变质阶段因受热而挥发掉，但随煤级增高其变形程度减弱；半镜质组在受热过程中也有变形和少量胶质体形成，而惰性组只发生微弱变化．在低变质阶段，活性显微组分形成的焦炭显微结构以各向同性为主；随变质程度的增高，焦炭显微结构中各向异性成分比例增大     

对近年来地震危险区预测效果的评估

采用R值评分方法，对中国地震局地球物理研究所2001—2004年度划定的全国地震危险区进行了评估，2001—2004年度的R值分别为0．265、0．182、0．293、0．404。近两年的R值相对高些，为了排除随机成分，做了相应的随机预报试验检验，并对地震落入危险区的随机概率作了估计。结果表明，4个年度的R值明显高于随机预报，除2002年度外，地震随机落入危险区的概率很低，不到2％。这说明中国地震局地球物理研究所实际地震危险区划分取得了一定的效果，且逐年提高。     

悬吊式钢混结构体系抗震试验与分析

悬吊式钢混结构体系是一种新型结构体系，通过一榀1／2比例此种框架的拟静力试验，研究了这种结构在低周反复水平荷载作用下的受力特点、变形和耗能能力以及破坏机理等，试验表明此种框架与传统异形柱框架的性能不同，为此种结构体系的应用提供了试验基础。     

结构动力模型试验相似理论及其验证

通过几何比尺为2的两个有机玻璃模型的结构动力试验，验证了结构动力模型试验的弹性相似律和弹性力一重力相似律。得到了以下结论：(1)大小模型频率符合相似律，一阶频率误差为2．7％、4．1％，二阶频率误差为O、6．05％。弹性相似律比弹性力一重力相似律更适合于频率预测的试验。(2)大小模型的加速度、应变符合相似律，弹性相似律的加速度误差为-1．55％～8．75％，应变误差为O．377％～7．297％。弹性力-重力相似律的加速度误差为3．07％～4．158％，应变误差为6．849％～12．959％。(3)不同相似律大小模型的时问比尺吻合很好。加速度与应变时程曲线的波形一致，既无漏峰也无错峰。     

Evaluation of soil liquefaction in the Chi-Chi, Taiwan earthquake using CPT

During the 1999 Chi-Chi, Taiwan earthquake, many sand boiling phenomena were observed in central Taiwan, which caused severe ground settlement and structure damages. According to the installed accelerograms, the peak ground surface horizontal accelerations in the liquefaction-affected areas range from 774.42 to 121.3 gal. The writers carried out an extensive investigation of soil liquefaction in this earthquake. In this paper, we present results of the CPT exploration and post-earthquake liquefaction analysis. Two hundred and seventy five (275) cone penetration test data were collected from the liquefaction-affected areas, and 46 liquefaction case histories and 88 non-liquefaction case histories were derived that can be used to evaluate the accuracy of existing liquefaction evaluation models. In addition, the strength of the liquefied soils after earthquake and the implication of its liquefaction potential in the future event are discussed.