In thermal-related engineering such as thermal energy structures and nuclear waste disposal, it is essential to well understand volume change and excess pore water pressure buildup of soils under thermal cycles. However, most existing thermo-mechanical models can merely simulate one heating–cooling cycle and fail in capturing accumulation phenomenon due to multiple thermal cycles. In this study, a two-surface elasto-plastic model considering thermal cyclic behavior is proposed. This model is based on the bounding surface plasticity and progressive plasticity by introducing two yield surfaces and two loading yield limits. A dependency law is proposed by linking two loading yield limits with a thermal accumulation parameter nc, allowing the thermal cyclic behavior to be taken into account. Parameter nc controls the evolution rate of the inner loading yield limit approaching the loading yield limit following a thermal loading path. By extending the thermo-hydro-mechanical equations into the elastic–plastic state, the excess pore water pressure buildup of soil due to thermal cycles is also accounted. Then, thermal cycle tests on four fine-grained soils (natural Boom clay, Geneva clay, Bonny silt, and reconstituted Pontida clay) under different OCRs and stresses are simulated and compared. The results show that the proposed model can well describe both strain accumulation phenomenon and excess pore water pressure buildup of fine-grained soils under the effect of thermal cycles.
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Cheng Wei Chen Ren-peng Hong Peng-yun Cui Yu-jun Pereira Jean-Michel 《Acta Geotechnica》2020,15(10):2741-2755
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To achieve accurate positioning of autonomous underwater vehicles, an appropriate underwater terrain database storage format for underwater terrain-matching positioning is established using multi-beam data as underwater terrain-matching data. An underwater terrain interpolation error compensation method based on fractional Brownian motion is proposed for defects of normal terrain interpolation, and an underwater terrain-matching positioning method based on least squares estimation (LSE) is proposed for correlation analysis of topographic features. The Fisher method is introduced as a secondary criterion for pseudo localization appearing in a topographic features flat area, effectively reducing the impact of pseudo positioning points on matching accuracy and improving the positioning accuracy of terrain flat areas. Simulation experiments based on electronic chart and multi-beam sea trial data show that drift errors of an inertial navigation system can be corrected effectively using the proposed method. The positioning accuracy and practicality are high, satisfying the requirement of underwater accurate positioning. 相似文献
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对华南对流云中过冷云水-飞机积冰的直接气象因子的中尺度数值预报试验 总被引：6，自引：2，他引：6
利用“海峡两岸及临近地区暴雨试验”（HUAMEX）加密观测资料和MM5湿物理显式方案模拟研究了1998.5.23-24自粤北移向南海海岸冷锋前对流云团中的云物理过程，给出了造成飞机积冰的直接气象因子-云中过冷水的空间分布和随时间演变及其与水汽、冰相（冰晶、霰、雪）、垂直气流的相互关系。结果显示，当对流较强因而产生冰相后，由于冰粒子与过冷水间的碰并及过冷水滴蒸发，过冷水迅速减少；当对流较弱因而只有液相云水而无冰相加入时，过冷云水维持。模拟试验显示具有完善湿物理显式方案的高分辨非静力平衡中尺度数值模式MM5可用于对飞机积冰的直接气象因子-云中过冷水的数值预报。 相似文献
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在华南暴雨试验中，采用了多种先进的探测系统，不同探测系统采用测量原理不同，资料的时空分辨率及探测精度有差异，为资料的集成带来一定的难度。针对华南暴雨试验的资料，提出多种资料集成和显示方案。多种探测资料的集成处理包括了对资料的预处理、反演、坐标归一化等，并在其基础上建立了互联网上的气象数据动态查询、站网雷达基数据的处理显示系统，利用可以管理和分析大型多维动态复杂数据集的微机可视化系统PC-Vis5D，实现了单部雷达资料、中尺度数值模式输出结果与观测真实数据的动态集成分析显示。 相似文献
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北京西山下苇甸中寒武统张夏组生物丘发育特征及其地质意义 总被引：2，自引：0，他引：2
北京西山下苇甸剖面寒武系地层出露完整,中寒武统张夏组底部和顶部发育两期生物丘地层.通过野外观察及薄片鉴定发现,张夏组底部发育的生物丘为凝块石生物丘,顶部发育的为叠层石生物丘,两期生物丘的造丘生物主要为藻类.凝块石生物丘生长在低能的潮下带环境,而叠层石生物丘则形成于海水能量较高的潮间带或潮下带上部.不同的沉积环境造成了两期生物丘内部结构的差异,主要体现在造丘生物的排列方式上.根据该剖面两期生物丘的特征,总结了生物丘的发育模式,并对其地质意义进行了探讨. 相似文献
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建筑拥挤度是评价城市人居环境的一个重要方面,对城市规划具有重要的理论和实践意义,它具有复杂和模糊的特性,如何从定量化的角度来描述是一个亟待解决的问题。本文将统计学的离散系数,描述遥感影像空间域的形状因子引入到城市建筑拥挤度研究,丰富和完善了评价指标体系。以Google Earth为数据源,选取了新疆库尔勒市四个典型样区进行了实证研究,结果表明,各评价指标能够较好地反映建筑物拥挤度。本文方法可以为城市环境相关研究提供理论和技术方法支持。 相似文献
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