盾构施工参数与沉降变形关系模型构建

针对盾构施工参数变化对施工引起的地表变形的重要影响,该文构建了盾构施工参数与地表沉降变形关系模型。以北京市某地铁盾构区间施工过程中的实测数据为基础,分析了不同盾构施工参数与地表沉降变形的关联度和相关性,得到不同参数对沉降变形贡献值的大小;之后,利用多元回归模型方法建立主要影响参数与地表变形的关系模型,并进行模型的合理性检验;最后,利用该模型得到的沉降量与实测数据进行对比分析,结果显示符合性较好。     

兰州市降雨型黄土滑坡灾害空间分布特征

针对兰州市1986—2016年间降雨型滑坡灾害的空间分布特征,该文基于ArcGIS,利用核密度估算方法分析滑坡点,通过多次测试比较确定了估算的最优距离阈值,得到概化程度高、数值变化平滑的栅格密度,并结合研究区内高程、坡度以及地质环境揭示了降雨型黄土滑坡灾害的空间分布特征。研究表明:滑坡点沿着黄河及其支流沿岸分布,密集程度有"两高两低"分布特点,高程、坡度与滑坡多发存在相关性,城关区滑坡点最多且呈环状分布,西固区次之,其他区较少。     

甘肃永靖黑方台4·29罗家坡黄土滑坡的特征

2015年4月29日上午,甘肃省永靖县盐锅峡镇黑方台滑坡高频发区的党川村罗家坡同一斜坡处连续发生了2次大规模黄土滑坡,总体积约65×10~4m~3,最大滑距630 m,摧毁14户居民房屋和3家工厂.通过现场详细调查、取样试验、1∶500地形测量、滑坡影像、视频等资料分析,对灌溉引发的罗家坡黄土滑坡的特征、滑动过程、形成机理进行了探讨.结果表明:第1次滑坡经过近2 a变形过程,整体突然失稳,高速远程滑动;第2次滑坡变形时间仅3 h,分块逐步滑动,滑动历时长而过程复杂,总体为低速远程滑动.高陡的地形和强度低、水敏感性强的土体是滑坡发生的基础,黄土台塬区长期农业灌溉是引发因素,大量水体入渗形成了20余米厚的饱和软弱基座,使抗剪强度降低,导致斜坡失稳滑动.黄土滑坡高速远程滑动的主要原因是滑坡剪出口位置高,滑动势能大,释放条件好,剪出口下部陡坡段为主要加速段;前方有开阔的滑动空间且有一定坡度、平缓的滑道;滑体底部饱和软弱黏性土在滑道上持续产生超孔隙水压力、液化等低摩阻效应,是远程滑动的润滑剂.同时,两次滑体间还存在冲击加速和能量传递作用.     

软土地区地铁道床沉降特征及其诱发因素分析

以上海4条地铁线路道床长期沉降监测资料为基础,分析了地铁隧道的纵向沉降特征;结合该地区地质环境调查资料,深入分析地铁隧道沉降与下卧层地层结构、浅部地下水位变化以及区域地面沉降三个地质环境因素之间的相互作用关系。结果表明,地铁隧道下卧地层结构差异是地铁隧道沉降差异性的重要地质环境因素,深基坑降排水引起降水目的含水层地下水位下降,使得降水目的层以及相邻软黏性土层发生较大的压缩变形,导致以降水目的层上覆软黏性土层为承载体的地铁隧道也随之发生沉降,区域地面沉降也是地铁隧道沉降的重要影响因素。     

城市生活垃圾卫生填埋场沉降变形分析

城市生活垃圾填埋场地基沉降和垃圾堆体沉降受到的影响因素多,现行规范的计算方法直接采用与实际相差较大,为减少不均匀沉降对垃圾防渗层的影响、准确确定垃圾储量和保证垃圾堆体的稳定,开展垃圾填埋场沉降研究具有重要意义。垃圾填埋场沉降变形包括地基沉降和垃圾堆体沉降,垃圾堆体沉降又分为主沉降和次沉降,主沉降完成时间短于次沉降。通过对陕西省宝鸡市垃圾填埋场地基土进行沉降计算,最大沉降差超过100 mm,对垃圾防渗层不利影响较大;而对垃圾堆体沉降计算,修正后的计算值与沉降观测值非常接近。考虑不同地区地层差异和垃圾成分差异,积累沉降观测资料具有重要意义。     

临江污水处理厂深基坑施工中地下水的处理研究

介绍了场地位临长江,地质条件复杂的黄浦路污水处理厂深基坑施工实例。分析了深基坑施工中地下水的危害,论述了对其处理的方法及要点,指出深基坑地下水的处理中,降水不可回避,但周边沉降可以避免。只要处理方案合理,成井质量得到保证,施工操作规范,可以满足坑内干作业的施工要求。     

北京某山坡湿陷性土层地基处理可行性分析与建议

北京市密云区某拟建别墅工程,属于山体边坡地基基础工程,任务要求对湿陷性地基土层进行湿陷性消除,并将其地基土承载力特征值提高到fak≥130 kPa。此外,还需要考虑边坡稳定性及其永久性加固问题。对该项目进行了深入分析、研究,并采用概念设计方法,对其进行设计预演,发现该项目存在工序复杂、不易实施、在永久性使用方面存在一定隐患、并具有责任不当等问题。对该地基基础工程进行了重新分析,建议取消地基处理措施,改用嵌岩桩作为拟建物的基础。     

一株海绵附生芽孢杆菌的抗硅藻附着活性成分的分离鉴定

为寻找天然抗污损活性化合物,以抗硅藻附着活性为导向,采用有机溶剂萃取、半制备高压液相色谱对分离自海绵的芽孢杆菌UST050418-715代谢产物进行分离,纯化抗硅藻附着活性物质,并利用气相色谱-质谱联用仪、核磁共振波谱分析活性物质结构。从菌株UST050418-715代谢产物中分离得到7种具有抗硅藻附着活性的环二肽类化合物,分别鉴定为:(1)环(L-亮氨酸-反式-8-羟基-L-脯氨酸-)、(2)环(L-缬氨酸-L-脯氨酸)、(3)环(D-脯氨酸-L-亮氨酸)、(4)环(L-脯氨酸-D-亮氨酸)、(5)环(甘氨酸-L-脯氨酸)、(6)环(L-苯丙氨酸-顺式-8-羟基-D-脯氨酸-)、(7)环(L-苯丙氨酸-反式-8-羟基-L-脯氨酸-)。说明海绵附生芽孢杆菌UST050418-715代谢产物中存在大量环二肽类化合物,可以帮助宿主海绵实现对硅藻附着的化学防御。     

Geotechnical Hybrid Simulation to Investigate the Effects of the Hydraulic Conductivity on One-Dimensional Consolidation Settlement

Difficulties in the prediction of time-distribution of consolidation settlement will be introduced by using the Murayama test embankment case of Japan. In particular, it will be discussed why the prediction of consolidation rate is difficult in multi-layered soil with complex and variable mechanical properties like organic soil or peat. It can be inferred that uncertainties, which are embedded intricately in the consolidation problem as well as given ground condition, would be major causes for consolidation settlement. After that, the author focused on the movement of pore water under the various conditions of hydraulic conductivity in the soils, and how it can affect the time-distribution of the consolidation settlement. For the applied key methodology on the consolidation settlement problem, we propose the hybrid consolidation simulation controlling the movement of pore water with high accuracy and, finally, the aim of this article is to discuss the methodological approaches obtained by the study, including the basic concept and accurate movement of pore water under various conditions of soil layers and hydraulic conductivity.     

The Effect of Concrete Deformation on Displacement of an Axially Loaded Drilled Shaft

This article presents the settlement of drilled shafts resulting from their structural deformations. Although drilled shafts are widely used as foundations for settlement-sensitive structures such as bridges and high-rise buildings, the structural deformations of drilled shafts are not typically taken into account in the design process. However, if unexpected structural deformations of drilled shafts cause additional settlement to the foundation, the serviceability of the superstructure can be jeopardized. Unfortunately, very few research efforts have been made to quantify the structural deformation of drilled shafts; this needs to be addressed to accurately predict the settlement of drilled shafts. In this study, we investigate the effect of structural deformation on displacement of axially loaded drilled shafts. Finite element analyses were performed to quantify the structural deformation of drilled shafts. The analysis results indicated that the structural deformation of drilled shafts could be quite significant for long drilled shafts. The main factors that affected the structural deformation of drilled shafts were found to be pile length, the material properties of drilled shafts, and the relative humidity of surrounding soil. An approximate equation is proposed to estimate the long-term deformation of drilled shafts.