真空联合堆载预压加固长江漫滩相软基孔压测试分析

结合长江江苏镇江段某码头堆场地基采用真空联合堆载预压法加固处理工程,通过现场钻孔埋设孔隙水压力计,对长江漫滩相软土地基加固过程中孔隙水压力的发展变化过程进行了测试分析。结果表明:真空预压区,加固30d后地基中孔隙水压力变化基本稳定,且土中超静孔隙水压力的消散受该深度排水板中真空荷载的影响十分显著;排水板中真空荷载随深度衰减,衰减速率与排水板周围土层性质密切相关;通过现场测试得到排水板周围为长江漫滩相淤泥质粉质黏土时,真空荷载沿排水板深度衰减速率约为3kPa/m。     

钢板组合PEC柱-削弱截面钢梁组合框架抗震试验研究

为深入研究PEC柱-钢梁组合框架结构体系的抗震性能,设计了1榀两层单跨钢板组合截面PEC柱-削弱截面钢梁组合框架1∶2缩尺试件,并对其进行了低周往复荷载抗震试验。根据实测数据整理,得到了试验滞回特征曲线,并结合试验过程现象记录,分析了试件滞回特性、抗侧刚度退化规律、节点连接性能、耗能与延性和试件破坏模式等力学性能。研究结果表明:试件结构具有较高的承载力和较大的抗侧刚度;采取梁端截面削弱方式可实现梁端塑性铰位置远离节点区,且端板对穿螺栓连接能有效将梁端受拉翼缘拉力转化为对应边对节点区的压力,使得节点区形成了混凝土斜压带传力模式,提高了节点区抗震性能;试件滞回曲线较为饱满,在梁翼缘与端板连接焊缝存在施工缺陷情况下,其整体侧移、延性系数和等效黏滞阻尼比分别达到3.50%(推)/4.50%(拉)、2.92(推)/3.21(拉)和0.306,且承载力仍未下降至其极限承载力的85%,即试件结构具有良好的变形、抗震延性与耗能能力;该试件在循环往复荷载下呈现的破坏模式为梁削弱截面部位和PEC柱脚相继形成塑性铰的塑性机构。     

浅埋衬砌隧道-邻近建筑地震动力相互作用IBEM模拟

采用高精度间接边界元方法(IBEM)考察地震波入射下隧道-邻近建筑物二维地震动力相互作用的规律。结果表明:建筑物与邻近隧道存在着明显的相互作用,整体动力反应规律取决于隧道,建筑物之间的空间位置关系、隧道埋深、入射波的频率和角度等因素。隧道位于建筑物正下方时,刚性衬砌隧道(相对围岩)对上部结构主要表现为隔震效应;隧道位于建筑物两侧时,隧道对建筑顶部位移有明显放大效应,最大可放大约40%。同时隧道应力也明显增大,最大可放大约43%。因此实际中需根据隧道-建筑物的空间位置关系,适当调整衬砌隧道与沿线建筑物的抗震设防水平。     

Distribution and assessment of mercury (Hg) in surface sediments of Futian mangrove forest,China

Environmental Geochemistry and Health - To investigate the distribution of mercury (Hg) in Futian mangrove wetland, surface sediments from land to sea were collected, including Kandelia obovata,...     

Contamination characteristics of trace metals in dust from different levels of roads of a heavily air-polluted city in north China

Concentrations of eight trace metals (TMs) in road dust (RD) (particles?<?25 μm) from urban areas of Xinxiang, China, were determined by inductively coupled plasma mass spectrometry. The geometric mean concentrations of Zn, Mn, Pb, As, Cu, Cr, Ni and Cd were 489, 350, 114, 101, 60.0, 39.7, 31.6, and 5.1 mg kg^?1, respectively. When compared with TM levels in background soil, the samples generally display elevated TM concentrations, except for Cr and Mn, and for Cd the enrichment value was 69.6. Spatial variations indicated TMs in RD from park path would have similar sources with main roads, collector streets and bypasses. Average daily exposure doses of the studied TMs were about three orders of magnitude higher for hand-to-mouth ingestion than dermal contact, and the exposure doses for children were 9.33 times higher than that for adults. The decreasing trend of calculated hazard indexes (HI) for the eight elements was As?>?Pb?>?Cr?>?Mn?>?Cd?>?Zn?>?Ni?>?Cu for both children and adults.     

Structural and technological determinants of carbon intensity reduction of China’s electricity generation

Environmental Science and Pollution Research - Electricity generation is the largest sector with decarbonization potential for China and the world. Based on the new emission factors, this paper...     

Protective effects of dietary betaine on intestinal barrier function and cecal microbial community in indigenous broiler chickens exposed to high temperature environment

Environmental Science and Pollution Research - High temperature environment causes reduction in productivity in broilers by disrupting the intestinal barrier function. This study aimed to...