Unified numerical study of shallow foundation on structured soft clay under unconsolidated and consolidated-undrained loadings     

Santosh Kumar Yadav  Guan-lin Ye  Usama Khalid 《Marine Georesources & Geotechnology》2020,38(4):400-416

Abstract

Based on a new elasto-plastic constitutive model, this paper presents a soil–water coupled numerical prediction of the bearing capacity for shallow foundation constructed on Ballina soft clay for unconsolidated undrained (UU) and consolidated undrained (CU) conditions. This elasto-plastic constitutive Shanghai model has an advantage of describing the mechanical behaviour of over-consolidated and structured soil under different loading and drainage conditions, by using one set of material parameter. In this paper, the Shanghai model used for both UU and CU conditions has the same initial parameters obtained from laboratory test results. The loading conditions and consolidation stages vary based on construction details. The predicted bearing pressure-settlement responses for UU and CU, approves the field observation. The phenomenon of gaining the bearing capacity due to consolidation is captured and explained by the use of soil–water coupled numerical analysis with a new elasto-plastic model. The stress strain behaviour, stress paths and the decay of the structure of elements at different depths presented in this study, reveal the mechanism for the difference between UU and CU conditions to understand the foundation behaviour. Effect of the initial degree of soil structure on the bearing capacity is also addressed. Overall, this approach provides the integrated solution for the shallow foundation design problems under short and long-term loadings.  相似文献   

Analysis of shaft resistance of jacked piles in sands     

Rodrigo Salgado 《国际地质力学数值与分析法杂志》2011,35(15):1605-1635

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.  相似文献   

测斜技术原理与作业要点探讨     

侯金波  李更召  陈潇  朱俊鹏 《测绘与空间地理信息》2016,(6)

深层水平位移监测(即测斜)能直接反映土体或支护结构的变形特征,是高风险建筑基坑工程安全的重要保证。本文对测斜技术原理进行了阐述,并根据工程实践经验对测斜监测的作业要点进行了探讨与总结。  相似文献   

变形监测技术在基坑施工中的应用     

邸彦彬  张涛 《测绘与空间地理信息》2016,(3)

深基坑工程是地下工程施工中内容比较丰富且富有变化的领域。为了确保基坑工程施工安全顺利进行,在复杂的地质条件下进行变形监测,及时发现和预报异常现象。对有效控制基坑变形、指导施工、保证施工质量具有重要意义。  相似文献   

Characteristics of the Asian–Pacific Oscillation in Boreal Summer Simulated by BCC_CSM with Different Horizontal Resolutions     

Yazhou Zhang  Zhijie Liao  Yaocun Zhang  Feng Nie 《大气科学进展》2016,33(12):1401-1412

The summer Asian–Pacific Oscillation(APO) is a major teleconnection pattern that reflects the zonal thermal contrast between East Asia and the North Pacific in the upper troposphere. The performance of Beijing Climate Center Climate System Models(BCC CSMs) with different horizontal resolutions, i.e., BCC CSM1.1 and BCC CSM1.1(m), in reproducing APO interannual variability, APO-related precipitation anomalies, and associated atmospheric circulation anomalies, is evaluated.The results show that BCC CSM1.1(m) can successfully capture the interannual variability of the summer APO index. It is also more capable in reproducing the APO's spatial pattern, compared to BCC CSM1.1, due to its higher horizontal resolution. Associated with a positive APO index, the northward-shifted and intensified South Asian high, strengthened extratropical westerly jet, and tropical easterly jet in the upper troposphere, as well as the southwesterly monsoonal flow over North Africa and the Indian Ocean in the lower troposphere, are realistically represented by BCC CSM1.1(m), leading to an improvement in reproducing the increased precipitation over tropical North Africa, South Asia, and East Asia, as well as the decreased precipitation over subtropical North Africa, Japan, and North America. In contrast, these features are less consistent with observations when simulated by BCC CSM1.1. Regression analysis further indicates that surface temperature anomalies over the North Pacific and the southern and western flanks of the Tibetan Plateau are reasonably reproduced by BCC CSM1.1(m), which contributes to the substantial improvement in the simulation of the characteristics of summer APO compared to that of BCC CSM1.1.  相似文献   

多普勒雷达观测在北京7.21暴雨数值模拟中的三维变分同化研究     

汤鹏宇  何宏让  钱贞成  缪子青 《气象科学》2016,36(3):349-357

基于背景误差的特征长度理论,研究调整背景误差水平分辨率对多普勒雷达资料三维变分同化的影响。首先利用NMC方法针对暴雨落区统计不同水平分辨率的背景误差协方差,分析两种不同分辨率的背景误差的结构特征,研究水平分辨率对背景误差特征长度的影响。将其应用于雷达资料同化中,研究背景误差水平分辨率变化对雷达资料同化的影响。结果表明:背景误差水平分辨率由27 km提高到3 km时,在大气低层体现出更细致的动力场信息,其动力场水平特征长度按水平分辨率的二次根递减,而温度场与水汽场水平特征长度变化不明显。在将不同分辨率的背景误差用于三维变分同化时,更高分辨率的背景误差可以在分析场增量中体现更细致的中小尺度信息,能够明显改善雷达径向速度资料同化效果,并在随后的暴雨数值模拟中雨量及其分布形态更接近实况。  相似文献   

附有物理量和气象条件约束的光学卫星国土观测有效覆盖率评估     

巫兆聪  巫远  张熠  杨帆 《测绘学报》2016,45(7):841-849

传统光学卫星国土观测覆盖评估建立在卫星对地理想覆盖的基础上,并未考虑卫星存储、星地数据传输、观测时长等物理量及观测区域气象因素对于覆盖性能的影响。本文针对光学遥感卫星的国土观测需求.建立国土观测有效覆盖能力评估指标体系,根据卫星数据存储能力、星地数据传输能力、卫星单圈最大观测时长、卫星观测太阳高度角等性能参数,提出了基于物理性能约束下的有效覆盖计算方法。根据气象台站历年气象数据,提出了气象约束因子的计算方法。综合考虑卫星物理性能约束与观测区域气象约束,计算光学遥感卫星对地观测有效覆盖能力。最后根据专家设计的光学遥感卫星国土观测有效覆盖能力评估指标权重,利用层次分析法(AHP)评估光学遥感卫星系统对于国土观测的需求满足程度。试验结果表明,本文方法对于国土观测有效覆盖的估算和评价结果更加精确,更接近于国土观测的实际应用需求,为对地观测有效覆盖能力评估提供了一种更为精确的可行方案。  相似文献   

Development and Utilization of the World’s and China’s Bulk Mineral Resources and their Supply and Demand Situation in the Next Twenty Years   总被引：1，自引：0，他引：1  

ZHANG Zhaozhi  JIANG Guangyu  WANG Xianwei  ZHANG Jianfeng 《《地质学报》英文版》2016,90(4):1370-1417

Bulk mineral resources of iron ores, copper ores, bauxite, lead ores, zinc ores and potassium salt play a pivotal role on the world’s and China’s economic development. This study analyzed and predicted their resources base and potential, development and utilization and their world’s and China’s supply and demand situation in the future 20 years. The supply and demand of these six bulk mineral products are generally balanced, with a slight surplus, which will guarantee the stability of the international mineral commodity market supply. The six mineral resources(especially iron ores and copper ores) are abundant and have a great potential, and their development and utilization scale will gradually increase. Till the end of 2014, the reserveproduction ratio of iron, copper, bauxite, lead, zinc ores and potassium salt was 95 years, 42 years, 100 years, 17 years, 37 years and 170 years, respectively. Except lead ores, the other five types all have reserve-production ratio exceeding 20 years, indicative of a high resources guarantee degree. If the utilization of recycled metals is counted in, the supply of the world’s six mineral products will exceed the demand in the future twenty years. In 2015–2035, the supply of iron ores, refined copper, primary aluminum, refined lead, zinc and potassium salt will exceed their demand by 0.4–0.7 billion tons(Gt), 5.0–6.0 million tons(Mt), 1.1–8.9 Mt, 1.0–2.0 Mt, 1.2–2.0 Mt and 4.8–5.6 Mt, respectively. It is predicted that there is no problem with the supply side of bulk mineral products such as iron ores, but local or structural shortage may occur because of geopolitics, monopoly control, resources nationalism and trade friction. Affected by China’s compressed industrialized development model, the demand of iron ores(crude steel), potassium salt, refined lead, refined copper, bauxite(primary aluminum) and zinc will gradually reach their peak in advance. The demand peak of iron ores(crude steel) will reach around 2015, 2016 for potassium salt, 2020 for refined lead, 2021 for bauxite(primary aluminum), 2022 for refined copper and 2023 for zinc. China’s demand for iron ores(crude steel), bauxite(primary aluminum) and zinc in the future 20 years will decline among the world’s demand, while that for refined copper, refined lead and potassium salt will slightly increase. The demand for bulk mineral products still remains high. In 2015–2035, China’s accumulative demand for iron ores(crude steel) will be 20.313 Gt(13.429 Gt), 0.304 Gt for refined copper, 2.466 Gt(0.616 Gt) of bauxite(primary aluminum), 0.102 Gt of refined lead, 0.138 Gt of zinc and 0.157 Gt of potassium salt, and they account for the world’s YOY(YOY) accumulative demand of 35.17%, 51.09%, 48.47%, 46.62%, 43.95% and 21.84%, respectively. This proportion is 49.40%, 102.52%, 87.44%, 105.65%, 93.62% and 106.49% of that in 2014, respectively. From the supply side of China’s bulk mineral resources, it is forecasted that the accumulative supply of primary(mine) mineral products in 2015–2035 is 4.046 Gt of iron ores, 0.591 Gt of copper,1.129 Gt of bauxite, 63.661 Mt of(mine) lead, 0.109 Gt of(mine) zinc and 0.128 Gt of potassium salt, which accounts for 8.82%, 13.92%, 26.67%, 47.09%, 33.04% and 15.56% of the world’s predicted YOY production, respectively. With the rapid increase in the smelting capacity of iron and steel and alumina, the rate of capacity utilization for crude steel, refined copper, alumina, primary aluminum and refined lead in 2014 was 72.13%, 83.63%, 74.45%, 70.76% and 72.22%, respectively. During 2000–2014, the rate of capacity utilization for China’s crude steel and refined copper showed a generally fluctuating decrease, which leads to an insufficient supply of primary mineral products. It is forecasted that the supply insufficiency of iron ores in 2015–2035 is 17.44 Gt, 0.245 Gt of copper in copper concentrates, 1.337 Gt of bauxite, 38.44 Mt of lead in lead concentrates and 29.19 Mt of zinc in zinc concentrates. China has gradually raised the utilization of recycled metals, which has mitigated the insufficient supply of primary metal products to some extent. It is forecasted that in 2015–2035 the accumulative utilization amount of steel scrap(iron ores) is 3.27 Gt(5.08 Gt), 70.312 Mt of recycled copper, 0.2 Gt of recycled aluminum, 48 Mt of recycled lead and 7.7 Mt of recycled zinc. The analysis on the supply and demand situation of China’s bulk mineral resources in 2015–2035 suggests that the supply-demand contradiction for these six types of mineral products will decrease, indicative of a generally declining external dependency. If the use of recycled metal amount is counted in, the external dependency of China’s iron, copper, bauxite, lead, zinc and potassium salt will be 79%, 65%, 26%, 8%, 16% and 18% in 2014, respectively. It is predicted that this external dependency will decrease to 62%, 64%, 20%,-0.93%, 16% and 14% in 2020, respectively, showing an overall decreasing trend. We propose the following suggestions correspondingly.(1) The demand peak of China’s crude steel and potassium salt will reach during 2015–2023 in succession. Mining transformation should be planned and deployed in advance to deal with the arrival of this demand peak.(2) The supply-demand contradiction of China’s bulk mineral resources will mitigate in the future 20 years, and the external dependency will decrease accordingly. It is suggested to adjust the mineral resources management policies according to different minerals and regions, and regulate the exploration and development activities.(3) China should further establish and improve the forced mechanism of resolving the smelting overcapacity of steel, refined copper, primary aluminum, lead and zinc to really achieve the goal of "reducing excess production capacity".(4) In accordance with the national strategic deployment of "One Belt One Road", China should encourage the excess capacity of steel, copper, alumina and primary aluminum enterprises to transfer to those countries or areas with abundant resources, high energy matching degree and relatively excellent infrastructure. Based on the national conditions, mining condition and geopolitics of the resources countries, we will gradually build steel, copper, aluminum and lead-zinc smelting bases, and potash processing and production bases, which will promote the excess capacity to transfer to the overseas orderly.(5) It is proposed to strengthen the planning and management of renewable resources recycling and to construct industrial base of renewable metal recycling.(6) China should promote the comprehensive development and utilization of paragenetic and associated mineral species to further improve the comprehensive utilization of bulk mineral resources.  相似文献   

基于挟沙力的三峡水库泥沙淤积形态分析          下载免费PDF全文

李文杰  李娜  杨胜发  王涛 《水科学进展》2016,27(5):726-734

三峡水库蓄水运用后,泥沙淤积主要分布在常年库区的宽谷和弯道,峡谷则无累积性淤积。基于实测资料计算了三峡成库前（2001年）和成库后（2003-2011年）的挟沙力,结果表明挟沙力随着不同运行阶段坝前水位的抬高而逐步降低,宽谷河段降低幅度较大,峡谷河段降低幅度较小,泥沙淤积比率逐步增大。宽谷河段挟沙力普遍降至含沙量以下而发生淤积,峡谷河段挟沙力仍大于含沙量而无累积性淤积。流量越大,宽谷河段的挟沙力越小于含沙量,而峡谷河段的挟沙力越大于含沙量,表明宽谷河段淤积主要发生在汛期,而峡谷河段汛期以冲刷为主。由于细颗粒泥沙絮凝沉降以及黏性淤积物难以冲刷,恢复饱和系数淤积取1、冲刷取0.01得到的沿程淤积量计算值与实测值吻合较好。弯道河段计算的淤积量与实测值差异较大,表明弯道河段二维特征明显,利用一维的挟沙力计算淤积量不能适用。  相似文献   

北京某山坡湿陷性土层地基处理可行性分析与建议          下载免费PDF全文

刘伍  樊金桂  张贺 《探矿工程》2016,43(11):75-79

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。  相似文献