汶川地震液化土层类型验证及土性分析

2008年5月12日汶川特大地震中,除在山区引发了大量山体滑坡、崩塌和泥石流外,在成都平原等地液化现象也十分普遍。液化主要分布在含砂、砾石和卵石等的第四系地层。依据地层分布特征和地震烈度,选择6个典型液化点（带）进行现场勘测和试验,以验证液化土层类型、了解液化土层的土性特征,并检验《建筑抗震设计规范》中液化判别方法的适应性。结果表明：(1) 典型液化点土类包含砂、砾石和卵石等,6个验证点中有2个为砂层液化(其中1个为砾砂)、3个为砾石层液化和1个为卵石层液化;(2) 与非液化地层相比,液化地层结构松散,均匀性差,颗粒大小分布曲线较平缓,不均匀系数较大,其中液化砂土级配良好,砾石和卵石级配不良;(3) 依据《建筑抗震设计规范》液化判别方法,将验证点1中砂液化判为非液化,其余5个验证点由于含较多粗颗粒,因无法进行标准贯入试验而无法进行液化判别。     

影响黄土湿陷系数因素的分析

在工程地质勘察及土工试验资料的基础上，分析影响黄土湿陷性的主要因素，应用数理统计方法．系统研究了不同深度黄土湿陷系数随天然含水量和干密度的变化规律：黄土的湿陷系数δs随深度的增加而减小；天然含水量ω和干密度γd与黄土的湿陷系数δs均呈直线负相关关系。通过回归分析建立了黄土湿陷系数与其主要影响因素间的线性回归方程：δs=-0．00038ω-0．1022γd＋0-1839。     

水泥偏高岭土复合稳定粉砂土渗透特性试验研究

水泥稳定粉砂土抗渗性能受粉砂土自身渗透性能、水泥用量、水灰比等因素影响显著,如何在提升其抗渗性能的同时降低水泥用量是提升工程经济效益的关键。通过开展不同水泥偏高岭土掺比、初始用水量、水泥偏高岭土总掺量以及养护龄期条件下的室内渗透试验,研究了上述因素对水泥偏高岭土复合稳定粉砂土抗渗性能的影响规律,探讨了上述因素及无侧限抗压强度与渗透系数之间的经验关系。结果表明：水泥与偏高岭土掺比为5:1时,水泥偏高岭土复合稳定粉砂土抗渗性能最佳,且该掺比不随水泥偏高岭土总掺量的改变而变化;水泥偏高岭土复合稳定粉砂土渗透系数随初始用水量增加呈非线性递增,随水泥偏高岭土总掺量增加和养护龄期发展呈先快后慢降低;基于试验结果归纳提出了4个关于初始用水量、水泥偏高岭土总掺量、养护龄期和无侧限抗压强度的水泥偏高岭土复合稳定粉砂土渗透系数经验模型。研究成果可为水泥稳定粉砂土抗渗性能提升提供理论参考与借鉴。     

砂土地震液化预测的人工神经网络模型

在简要分析BP算法的基础上,应用BP网络的理论与方法,选取烈度、震中距、平均粒径、不均匀系数、地下水埋深、砂层埋深、标贯击数、剪应力比等8个实测指标,建立了砂土液化预测的神经网络模型。通过实例计算与模型评价、验证了该模型的科学性、高效性并较规范法、Seed简化法等传统方法具有更高的预测精度,说明人工神经网络是解决非线性问题的有效方法之一。     

Prolonged Dry Episodes over North America: New Tendencies Emerging During the Last 40 Years

A disproportionate increase in precipitation coming from intense rain events, in the situation of general warming (thus, an extension of the vegetation period with intensive transpiration) and an insignificant change in total precipitation could lead to an increase in the frequency of potentially serious type of extreme events: prolonged periods without precipitation (even when the mean seasonal rainfall totals increase). This paper investigates whether this development is already occurring during the past several decades over North America south of 55°N, for the same period when changes in frequency of intense precipitation events are being observed. Lengthy strings of “dry” days without sizeable (>1.0 mm) precipitation were assessed only during the warm season (defined as a period when mean daily temperature is above the 5℃ threshold) when water is intensively used for transpiration and prolonged periods without sizable rainfall represent a hazard for terrestrial ecosystem's health and agriculture. During the past four decades, the mean duration of prolonged dry episodes (20 days or longer in southeastern Canada, 1 month or longer in the Eastern United States and along the Gulf Coast of Mexico and 2 months or longer in the Southwestern United States and Northern Mexico) has significantly increased. As a consequence, the return period of 1 month long dry episodes over the Eastern U.S. has been reduced more than twofold from 15 to 6~7 years. The longer average duration of dry episodes has occurred during a relatively wet period around most of the continent south of 55°N but is not observed over the Northwestern U.S. and adjacent regions of Southern Canada.      

对薄壁金刚石工程钻头研制的几点看法

从帝际应用出发,对薄壁金刚石工程钻头的质量、结构设计、开刃处理、干钻钻头等方面分析探讨,提出了一些看法。     

"疏不干含水层"的辐射井降水技术

现今工程界,对于在—定条件下的“疏不干含水层”用常规的井点或深井不能达到“降水”目的,而辐射井降水技术能有效地解决这—难题。通过工程实例详细介绍了辐射井的概念、在“疏不干含水层”中的设计方法、施工方法及降水效果。     

钻杆接头材料35CrMo硫氮复合处理层的干摩擦学性能研究

应用离子渗氮与离子渗硫技术,在钻杆接头材料35CrMo钢表面制备了硫氮复合处理层。采用M-200环块磨损试验机,对比研究了原始渗氮表面与硫氮复合表面在干摩擦条件下的抗磨损性能。结果表明,在干摩擦的条件下,由于摩擦副的接触表面缺乏润滑,硬度较高的渗氮层会加剧接触表面的磨损。而硫氮复合处理层由于在表面存在一层硫化亚铁固体润滑层,在磨损过程中可以起到一定的润滑作用,因此其在干摩擦条件下具备更好的抗磨损性能。