青藏高原东北部观赏地被植物马蔺根系固土护坡效应研究

为了进一步丰富青藏高原东北部地区植被护坡工程植物选择,推动区内植被护坡工程实用性和观赏性兼顾发展。该项研究以青藏高原东北部观赏地被植物马蔺为研究对象,以青海省大通县朔北藏族乡至东峡镇之间区域为研究区,在野外植物分布特征和生长特征调查的基础上,结合单根拉伸试验和重塑根-土复合体三轴压缩试验,定量评价了野生马蔺植株和根系生长特征、单根抗拉特性以及根系对土体抗剪强度的增强效应。试验结果表明：马蔺主要分布在研究区内洪积扇、坡积裙和河漫滩等地貌单元,立地条件包括上述地貌单元内的林下坡地、田间、道旁、湿地、荒地等;通过选取两处试验区开展调查可知,马蔺平均株高、冠幅和植株密度分别为75.22±11.40 cm、106.09±25.62 cm和1.51±0.55 株/m2;马蔺标准株根系分布深度可达50 cm,主要分布在0~30 cm深度范围内,根幅约40~50 cm;马蔺根径为0.20～0.70 mm,单根抗拉力、抗拉强度和延伸率平均值分别为7.94±2.91 N,46.30± 11.06 MPa和54.17%±17.08%,随着根径的增大,单根抗拉力和单根抗拉强度分别呈幂函数增大和幂函数降低关系,单根极限延伸率随着根径的增大呈逐渐增大变化趋势,但二者之间未表现出相对显著性的关系;马蔺根系对土体黏聚力和内摩擦角均有增强作用,可分别显著增强0~30 cm和0~10 cm深度范围内土体黏聚力和内摩擦角,且对土体黏聚力的增强作用较为显著。该项研究成果对于选用观赏地被植物马蔺进行研究区坡面水土流失、浅层滑坡等地质灾害现象的生态防护工作,具有理论研究价值和实际指导意义。     

Efficient stochastic analysis of unsaturated slopes subjected to various rainfall intensities and patterns

Rainfall infiltration poses a disastrous threat to the slope stability in many regions around the world. This paper proposes an extreme gradient boosting (XGBoost)-based stochastic analysis framework to estimate the rainfall-induced slope failure probability. An unsaturated slope under rainfall infiltration in spatially varying soils is selected in this study to investigate the influences of the spatial variability of soil properties (including effective cohesion c′, effective friction angle φ′ and saturated hydraulic conductivity k_s), as well as rainfall intensity and rainfall pattern on the slope failure probability. Results show that the proposed framework in this study is capable of computing the failure probability with accuracy and high efficiency. The spatial variability of k_s cannot be overlooked in the reliability analysis. Otherwise, the rainfall-induced slope failure probability will be underestimated. It is found that the rainfall intensity and rainfall pattern have significant effect on the probability of failure. Moreover, the failure probabilities under various rainfall intensities and patterns can be easily obtained with the aid of the proposed framework, which can provide timely guidance for the landslide emergency management departments.     

Centrifuge modelling of landslides and landslide hazard mitigation: A review

Landslides are serious geohazards that occur under a variety of climatic conditions and can cause many casualties and significant economic losses. Centrifuge modelling, as a representative type of physical modelling, provides a realistic simulation of the stress level in a small-scale model and has been applied over the last 50 years to develop a better understanding of landslides. With recent developments in this technology, the application of centrifuge modelling in landslide science has significantly increased. Here, we present an overview of physical models that can capture landslide processes during centrifuge modelling. This review focuses on (i) the experimental principles and considerations, (ii) landslide models subjected to various triggering factors, including centrifugal acceleration, rainfall, earthquakes, water level changes, thawing permafrost, excavation, external loading and miscellaneous conditions, and (iii) different methods for mitigating landslides modelled in centrifuge, such as the application of nails, piles, geotextiles, vegetation, etc. The behaviors of all the centrifuge models are discussed, with emphasis on the deformation and failure mechanisms and experimental techniques. Based on this review, we provide a best-practice methodology for preparing a centrifuge landslide test and propose further efforts in terms of the seven aspects of model materials, testing design and equipment, measurement methods, scaling laws, full-scale test applications, landslide early warning, and 3D modelling to better understand the complex behaviour of landslides.     

JGN型耐高温建筑结构胶抗震加固性能研究

为有效增强建筑结构的抗震性能、提高建筑抗震水平,对JGN型耐高温建筑结构胶抗震加固性能展开研究。将高活性酚醛胺(T－31)作为主固化剂、聚酰胺树脂(PA)为辅助固化剂,结合气相白炭黑、超细石英砂、石棉纤维、纳米材料、环氧树脂等材料,制备JGN型耐高温建筑结构胶。在高温环境下,使用万能试验机分析不同配比条件对结构胶抗震加固性能的影响。测试主要以拉伸强度、压缩强度以及压缩弹性模量为指标。测试结果表明：当固化剂质量比为45∶15、气相白炭黑掺量为4.5%、超细石英砂掺量为10%、石棉纤维掺量为10.5%、纳米SiO₂掺量为3.5%、纳米CaCO₃掺量为2.5%时,JGN型耐高温建筑结构胶的拉伸强度和压缩强度更大,压缩弹性模量得到优化,结构胶的抗震加固性能达到最佳状态。     

主余震作用下高强钢筋混凝土框架的易损性分析

为研究主余震作用下配置高强钢筋的RC框架结构的抗震性能,根据相同设计指标和"等强代换"的原则,设计了三榀六层四跨的钢筋混凝土框架,纵向受力钢筋的强度等级分别为HRB400、HRB500和HRB600。通过OpenSees平台进行有限元建模,将最大层间位移角作为结构损伤指标,反应地震作用的结构响应。选取15条地震加速度时程,通过重复法构造人工主余震序列并进行IDA分析,得到结构在不同强度的主余震序列作用下的地震易损性曲线。结果表明:主震PGA越大,余震的最大层间位移角越大,结构达到各极限状态的概率越高。对比配置不同钢筋强度的三榀框架的计算结果,可知"等强代换"原则下,相同主余震序列作用时,钢筋强度的提高对结构抗倒塌性能有不利影响,但影响有限。     

鄂西宜昌斜坡带五峰组—龙马溪组页岩优势岩相及其生气潜力

【研究目的】不同页岩岩相的矿物组分、含气性和可压性等的差异,决定不同岩相的开发潜力不同,页岩岩相的划分及评价对找寻页岩气勘探开发甜点具有重要指导意义。【研究方法】基于钻井、岩心和分析测试资料,综合利用地质理论结合硅质矿物-黏土矿物-碳酸盐矿物含量三端元图解,对鄂西宜昌斜坡带上奥陶统五峰组—下志留统龙马溪组下段含气页岩岩相进行划分,结合有机碳含量、含气量、岩心镜下特征等划分优势岩相。优选有机质丰度、硅质矿物含量、黏土矿物含量3项指标与页岩含气量进行相关性分析,建立了五峰组—龙马溪组含气页岩优势岩相的分级标准。【研究结果】研究区优势岩相均为II类优势岩相,II₁类（最优）优势岩相为S-2混合硅质页岩相和S-3含黏土硅质页岩相,位于龙马溪组一亚段和五峰组上段,厚6 m;II₂类（次优）优势岩相为S硅质页岩相,位于五峰组下段,厚4 m。【结论】宜昌斜坡带和涪陵地区具有相似的岩相垂向演化序列,优势岩相均位于五峰组—龙马溪组一亚段,但同一岩相组合的页岩厚度和品质差异较大,发生在鲁丹阶早期的湘鄂西水下隆起和鲁丹阶晚期的水下隆起是造成宜昌地区优势岩相的厚度和品质均要差于涪陵地区的主要原因。创新点：建立五峰组—龙马溪组含气页岩优势岩相的分级标准,提出龙马溪组一亚段和五峰组是优势岩相发育层位。     

煤巷弱胶结顶板稳定性分析与变形控制技术

煤层顶板为弱胶结岩体时稳定性差,常在煤炭回采过程中或巷道掘进时发生大变形或失稳等现象,维护难度较大。针对煤巷弱胶结粉砂岩顶板力学特征与变形控制等问题,以广西林场煤矿煤巷弱胶结粉砂岩顶板支护工程为工程背景,采用现场调研、实验室试验、理论分析等方法进行研究。通过现场调研,发现研究巷道有顶板岩层自承能力差、受水环境影响、支护结构失效率高、底板受水影响底鼓量大、受采动影响等特征;顶板岩石点荷载试验表明,其单轴抗压强度仅为1.9～ 2.3 MPa,采用电镜扫描发现,弱胶结粉砂岩以粗粒矿物为骨架;在普氏理论的基础上,推导了巷道顶板和两帮承压极限表达式,提出了提高巷道围岩整体强度和承载能力、确定合理的锚杆支护参数、顶板设计锚索加强支护等弱胶结巷道围岩控制要点。依据试验分析与理论研究成果,提出了以注浆加固为基础,锚杆和锚索联合支护的控制方案,并在林场煤矿进行了工业性试验。现场监测数据表明,设计的支护方案可以有效地控制煤巷弱胶结粉砂岩顶板变形。     

突变理论在边坡工程应用的研究进展

突变理论是非线性科学领域中的一个重要分支,作为一种数学工具已经在众多领域得到广泛应用,在边坡工程中的应用尤为活跃。首先简述了突变理论的发展概况和基本原理,然后分别从3个方面详细论述了突变理论在边坡工程应用中的研究进展,即基于尖点突变法的边(斜)坡稳定性分析、基于突变级数法的边(斜)坡稳定性评价和基于灰色理论、模糊数学的尖点突变预测模型对滑坡时间预报,重点讨论了相应的理论模型、应用方法和实际效果,最后结合目前存在的问题探讨突变理论在边坡工程的发展趋势。     

Extremely slow slope movements influencing the stability of Spis Castle,UNESCO site

Spis Castle, a monument included in the UNESCO World Heritage Site list (Eastern Slovakia) is built on a travertine mound overlying soft Paleogene rocks. Lateral spreading resulting from the subsidence of strong upper travertine into soft claystone strata has fractured and separated the castle rock into several cliffs. The differential movement of individual cliff faces is the primary influence on the stability of the monument. In order to monitor and quantify the movement, two techniques were adopted: a mechanical-optical TM-71 crack gauge and a demec gauge (demountable mechanical—SOMET type crack gauge). This paper presents the results and interpretation of medium and short-term monitoring at the site.     

天山北坡城市群空间组织形态的识别研究

 正确认识天山北坡城市群的空间组织结构以及空间发展形态,对于完善绿洲城市群的发展理论和规划具有重要意义。以天山北坡城市群为研究对象,通过资源环境承载力的分析,总结出未来城市群发展面临的客观制约因素;通过中心性分析、断裂点理论修正的Voronoi多边形等方法识别出城市群的中心城市及各自的辐射范围城市;通过引力模型识别出城市之间的社会经济联系强度。据此,利用多维尺度分析的方法,可视化地展现了天山北坡城市群发展的空间组织形态。经调查了解：（1）乌鲁木齐市与克拉玛依市是未来城市群发展的两个中心城市,五家渠市、阜康市、昌吉市、石河子市周边目前属于乌鲁木齐市的辐射范围城市,奎屯市,乌苏市属于克拉玛依市的辐射范围城市;（2）城市群内部的城市之间的联系比较松散,特别是两个中心城市之间联系较弱;（3）城市群的空间发展形态为串珠式,是一种特殊的走廊式空间形态。