Analysis of shaft resistance of jacked piles in sands

In recent years, pile jacking has become a viable alternative installation method for displacement piles. Pile jacking produces minimal noise, vibration and air pollution during installation. In addition, it is possible, at the end of jacking, to have a good estimate of the ultimate static capacity of the pile. In this paper, the shaft resistance of piles jacked into sand is studied using one‐dimensional finite element analysis. The finite element simulations, using a two‐surface plasticity model, demonstrate the effects of relative density and confinement on the unit shaft resistance of piles jacked in sand. The impact of the number of jacking strokes on the unit shaft capacity is also assessed. Based on the numerical results, we developed equations for shaft resistance quantifying the effects of relative density, initial confinement and number of jacking strokes. Predictions using these equations are compared with data obtained from centrifuge tests and field tests. Copyright © 2010 John Wiley & Sons, Ltd.     

超高层建筑GPS实时动态监测技术研究

在特高等级精密工程的测量范畴内,实现对超高层建筑的施工监测是一个非常重要的工作内容,GPS实时动态监测技术在监测中发挥着不可忽视的作用。本文首先对GPS监测技术做简要阐述,并分析了超高层建筑的特点;然后指出了GPS监测技术在施工监测中所发挥的作用;最后结合案例,具体分析了GPS监测技术在超高层建筑中的应用,以期为超高层建筑GPS实时动态监测技术的相关研究提供部分参考意见。     

Geological control factors of micro oil distribution in tight reservoirs

Understanding the oil distribution characteristics in unconventional tight reservoirs is crucial for hydrocarbon evaluation and oil/gas extraction from such reservoirs. Previous studies on tight oil distribution characteristics are mostly concerned with the basin scale. Based on Lucaogou core samples, geochemical approaches including Soxhlet extraction, total organic carbon (TOC), and Rock-Eval are combined with reservoir physical approaches including mercury injection capillary pressure (MICP) and porosity-permeability analysis, to quantitatively evaluate oil distribution of tight reservoirs on micro scale. The emphasis is to identify the key geological control factors of micro oil distribution in such tight reservoirs. Dolomicrites and non-detrital mudstones have excellent hydrocarbon generation capacity while detritus-containing dolomites, siltstones, and silty mudstones have higher porosity and oil content, and coarser pore throat radius. Oil content is mainly controlled by porosity, pore throat radius, and hydrocarbon generation capacity. Porosity is positively correlated with oil content in almost all samples including various lithologies, indicating that it is a primary constraint for providing storage space. Pore throat radius is also an important factor, as oil migration is inhibited by the capillary pressure which must be overcome. If the reservoir rock with suitable porosity has no hydrocarbon generation capacity, pore throat radius will be decisive. As tight reservoirs are generally characterized by widely distributed nanoscale pore throats and high capillary pressure, hydrocarbon generation capacity plays an important role in reservoir rocks with suitable porosity and fine pore throats. Because such reservoir rocks cannot be charged completely. The positive correlation between hydrocarbon generation capacity and oil content in three types of high porosity lithologies (detritus-containing dolomites, siltstones, and silty mudstones) supports this assertion.     

China’s rural revitalization and development: Theory,technology and management

Journal of Geographical Sciences - The urban-rural transformation from dichotomy to integration is a gradual process. Like rural areas in many countries, Chinese rural society is experiencing a...     

区域可持续发展能力的能值与(火用)耦合分析模型构建

可持续发展能力评价方法是识别人地协同规律、支撑科学决策的重要工具和热点需求。通过文献回顾与理论分析框架构建,耦合能值及?方法,提出自组织能力指数（SO）、生态压力指数（EP）、可持续发展能力指数（SC）构成的,基于热力学理论的可持续发展能力分析模型,利用文献荟萃法筛选17个典型发达国家1985年状态值计算SO与EP阈值,划分了4个阶段。利用中美两国1985-2015年特征对比验证,结果显示：① 2005年以前中国属“低自组织能力、低生态压力”阶段,之后进入“低自组织能力、高生态压力”阶段,存在低生态效率、规模扩张驱动特征;美国一直属“高自组织能力、高生态压力”阶段,存在高生态效率驱动、经济与生态脱钩特征,与全球生态足迹网络和世界自然基金会等的研究结果一致,模型具有较好适应性和可靠性。② 模型利用“获得?量/输入能值量”表达经济社会生态效率、“经济社会?损耗量/生态系统年产?量”表达生态压力,连接了经济社会对生态基底的熵化路径,可识别区域所处可持续发展阶段、分析水平变化和驱动因素。③ 模型以人类与生态并重的视角,从深度上反映经济社会的生态效率、从广度上评价生态空间被占用比例,具有宏观规模与微观效率分析相结合的优势,是对经典方法的补充。     

建筑物侧面轮廓线约束的高分辨率遥感影像建筑物高度估算方法

针对现有利用阴影长度法提取建筑物高度时存在的阴影间相互遮挡问题,提出了一种基于建筑物侧面轮廓线进行建筑物高度估算的新方法。首先,利用RPC模型计算建筑物像点位移的方向与卫星成像角度,再将遥感影像进行旋转,使建筑物像点位移沿水平方向;然后,利用Canny算法进行轮廓检测,并构建一定长度的矩形形态学结构元素,对轮廓图像进行形态学开运算,以提取侧面轮廓线,再利用Hough变换与建筑物角点约束,对所提取的轮廓线进一步筛选;最后,根据卫星侧视成像时建筑物高度与像点位移的几何关系进行建筑物的高度估算。利用实际的高分辨率卫星影像对本文方法进行了验证,并与阴影法估算建筑物高度进行了对比。试验结果证明,利用建筑物侧面轮廓线进行建筑物高度估算平均误差可以达到0.7 m,且实际精度优于使用阴影法进行建筑物高度估算。     

乐山市水资源承载力分析及开发潜力研究

水资源的供需关系已演变为限制经济社会不断发展的一个关键障碍,所以对水资源承载力展开探究,以支撑经济和社会的不断发展,将会具有现实意义和至关重要的影响,本文从水资源负载指数和承载指数模型出发,根据当前乐山市水资源情况现状,对当地水资源承载力进行分析。     

Experimental study on a sampling technique based on a freeze-sediments valve for deep-sea microorganism

Deep-sea microorganism research has become a hot topic in life science, owing to its special value in high pressure and low temperature environment. If not kept the in-situ low temperature and high pressure, it will cause the microorganism to lose its activity and lead to a waste of resources. A freeze-sediments valve presents a promising solution to maintain the low temperature and high pressure in situ, improve the success rate of sampling and shorten the sampling time. A series of experiments were conducted to characterize the freeze-sediments valve, including the sampling time without leakage, adaptation to different sediments and the effect of the length, etc. Most important of all, temperature change of sediments is observed in all experiments. Experimental results indicated that the freeze-sediments valve was formed in 5 min without leakage and the freeze-sediments valve could be applied to different sediments without limitations on sediments type and mineral content. Considering the pressure retaining capacity and formation time of freeze-sediments valve, it was found that the freeze-sediments valve with a length of 60–80 mm has good pressure retaining capacity whose value was 41.3–48.4 Mpa and short formation time which was 5 min. Precooling the sampler could be used to shorten the sampling time in the actual environment application. This sampling technique can play a vital role in maintaining in-situ low temperature at −2 to −4 ° Celsius in all the experiments. According to the tests, the sampling technique based on the freeze-sediments valve had the potential to solve the problem of keeping in-situ temperature, low sampling success rate and long sampling time in the future.     

钙质土中重力串锚水平承载力特性有限元研究

目前没有规范给出串锚的水平承载力计算公式,为了利用有限元法研究串锚水平承载力特性,采用相关理论计算以及室内试验的方法来验证有限元法模拟计算的可靠性。实践证明,有限元法具有较高的计算精度。利用有限元分析软件ABAQUS建立了串锚-土体模型,模拟串锚在水平荷载作用下破坏过程,研究了串锚在水平荷载作用下破坏机理,从而得到了串锚水平承载力特性。在相同的工况条件下,串锚的水平承载力与其锚链长度有关,在一定范围内,增加锚链的长度可以提高串锚的水平承载力;串锚的水平承载力不是相应的单个锚的水平承载力相加,其水平承载力小于相应的单个锚水平承载力之和,在进行串锚水平承载力设计计算时应给与相应的考虑。