Uplift capacity of pile group anchors

Experimental investigations on model single pile anchor and pile group anchors of configuration 2 × 2 subjected to uplift loads were conducted on dry Ennore sand, obtained from Madras, India. The embedment length to shaft width ratios, L/d = 20 and L/d = 30, and enlarged base width to shaft width ratios, B/d = 1,2,3, center to center spacing of pile anchors in the groups, 3d, 4d, 6d and 8d were used. The load displacement response, ultimate resistance and variation of group efficiency with L/d, B/d and spacing have been studied quantitatively and qualitatively. For short pile group anchors (L/d = 20), the isolation spacing appears to be at a spacing of about 4d to 6d and 8d for B/d = 1 and B/d = 2 and 3, respectively. For long pile group anchors (L/d = 30), the isolation spacing appears to be at a spacing of about 4d, 6d and 8d for B/d = 1, 2 and 3, respectively. The analytical model of limit equilibrium method has been proposed to predict the net uplift capacity of pile group anchors. The predicted results compare reasonably well with the experimental results.     

地下河洞穴发育的系统演化

本文运用系统科学理论的某些基本原理和洞穴发育模拟实验研究成果，在我国南方喀斯特区多年研究实践的基础上，把一个地下流域看作一个物质与能量的输入─输出系统。将这一系统的洞穴发育分为流入（输入）洞穴，流出（输出）洞穴和含水层洞穴三大部分。分析和讨论了它们的发育机制、基本特征、相互关系及整体系统有序化的演化过程。     

我国高精度地心坐标转换参数的建立

本文介绍了为高精度获得地心坐标而建立的ＧＰＳ－ＫＴＩＳ系统的原理、方法和精度。与《ＤＸ－２》不同，ＧＰＳ－ＫＴＩＳ的动态变换特性（即模型的动态性、解算过程的区域性和已知数据的现势性）使转换参数能反映大地网的局部形变并能体现最新空间大地测量成果的影响。试算结果表明，ＧＰＳ－ＫＴＩＳ转换参数的转换精度比我国当前应用的《ＤＸ－２》转换参数提高了７０％，这标志着我国新一代地心坐标转换参数的建立。     

新疆天山未来十年强震危险区判定的初步研究

根据新疆天山活断层新活动特征、卫星影象显示的线性构造与地震活动显示的网络构造,确定出天山可能发生强震的警戒断层有:独山子——安集海活断层、清水河子与精河——阿什里活断层、卡克博河与特克斯河活断层、兴地活断层和北轮台活断层。综合分析判定出5个未来十年可能发生强震的危险区:沙湾西南强震危险区、乌鲁木齐西南新生强震危险区、新源西新生强震危险区、库尔勒东强震危险区和轮台北新生强震危险区。研究结果表明,天山地区全新世活断层新活动颇为强烈,某些活断层具有控震作用。预测今后十年新疆天山地区有发生多个6.5级以上地震的可能。     

用有限元法补偿系统误差的光束法平差

本文介绍了一种被称作有限元法的补偿系统误差方法,即将每张象片的象主点坐标和象点的“焦距”作为待定的补偿参数参予全区整体平差。实例计算表明,方法不但可行。而且有效地提高了加密精度,特别是高程精度。     

Performance of clay masonry veneer in wood‐stud walls subjected to out‐of‐plane seismic loads

This paper presents the findings of shaking‐table experiments conducted to examine the out‐of‐plane seismic performance of masonry veneer walls. Seven wall assemblies were tested, each consisting of a clay masonry veneer anchored to a wood‐stud backing. Design variables include the type of veneer ties, tie spacing, and presence or absence of mortar joint reinforcement and window opening. The walls were designed and constructed in accordance with current US code provisions. Results of the experiments show that failure of the corrugated ties is governed by pullout of the nails from the wood studs, while failure of the rigid ties is governed by detachment from the mortar joints or pull‐through of the screw heads through fastener holes. Both types of ties show satisfactory performance under ground motions corresponding to Design Basis and Maximum Considered Earthquakes representative of Seismic Design Category E. Although the rigid ties were stronger than the corrugated ties, they had wider vertical spacing and failed at a slightly higher seismic load. Observed extraction capacities of the nails show high variability, which merits attention. Joint reinforcement did not show any noticeable effect on the out‐of‐plane behavior of the veneer. Results of an analytical study have shown that the detachment of a veneer from the backing system is preceded by veneer cracking, which influences the distribution of tie forces, and that the vertical tie spacing influences the cracking load for the veneer. Copyright © 2010 John Wiley & Sons, Ltd.     

紫坪铺水利枢纽引水发电洞进水口边坡锚索预应力损失分析

四川岷江紫坪铺水利枢纽工程引水发电洞进水口边坡布置了大量预应力锚索进行加固,并安装了13台锚索测力计进行监测。本文在对锚索测力计监测资料整理分析的基础上,重点分析了锚索预应力随时间变化的关系、预应力损失情况及预应力损失的原因,对锚索预应力损失的控制有重要的借鉴意义。     

剪切波分裂分析系统SAM(2007)——区域地震台网资料应用实例

通过对云南、辽宁、福建遥测地震台网的波形资料分析实例,介绍了"剪切波分裂系统分析方法"软件SAM(2007)的用法。通过对区域台网资料的处理分析,表明SAM(2007)是研究剪切波分裂的一个比较实用的软件,能够有效的处理快、慢剪切波识别的问题,研究地壳介质的地震各向异性问题,能普遍用于分析国内区域地震台网资料。     

首都圈地区震源机制解综合研究

对首都圈地区2002年1月～2010年6月619个ML≥2.0地震的震源机制解的基本特征进行了统计分析,并且依据区域构造特征将首都圈划分为3个区域,用聚类统计方法中的最长距离法对各分区的机制解进行了聚类分析,研究了各分区的构造应力张量特征。研究结果表明,首都圈地区震源机制解P轴方位的优势分布为NNE-NEE向,T轴方位的优势分布为NNW-NWW向,绝大多数地震震源处的应力场以水平作用为主,破裂以水平走滑为主。首都圈西部最大主压应力方位为NE75°,中部最大主压应力方位为NE62°,东部最大主压应力方位近EW向,区域构造应力场以水平向挤压为主要特征。