变热流工况土壤导热系数对热恢复特性的影响研究

土壤热恢复特性是土壤源热泵长期稳定高效运行的决定性因素之一.土壤导热系数是土壤热物性最重要的参数之一,对土壤的热恢复特性具有决定性意义.利用ANSYS有限元分析模型,模拟研究在变热流工况下,土壤的导热系数对土壤热恢复特性的影响.     

Cadmium in agricultural soils,vegetables and rice and potential health risk in vicinity of Dabaoshan Mine in Shaoguan,China

Soil cadmium （Cd） contamination resulted from mining and smelting is a major environmental concern,and health risk associated with Cd exposure to multi-media through muti-pathway is increasing.Cd concentrations in soils,vegetables and paddy rice were investigated,and potential non-carcinogenic and carcinogenic health risks exposure to Cd were estimated at six villages around the Dabaoshan Mine,South China.A total of 87 soil samples were found to exceed the China＇s maximum permission level （MPL） for Cd,while the highest value of 4.42 mg/kg was found near irrigation ditch associated with Hengshi River in Xinyi （XY） Village.Cd contents in vegetables and rice exceeded the maximum permissible concentration by more than five times in every village.Cadmium accumulation in plants is in the order of celery 〉 lactuca sativa L 〉 Chinese cabbage 〉 Romaine lettuce 〉 asparagus lettuce 〉 mustard 〉 cabbage mustard 〉 cabbage.The mean hazard quotient （HQ） of all villages is in the range of [5.29,25.75],and the mean values of cancer risk for investigated areas are more than 10 times greater than the USEPA （2009） threshold limit value of 10-4.Moreover,human non-carcinogenic and carcinogenic risks are mainly attributable to paddy rice intake,followed by vegetables intake,soil ingestion,inhalation,and dermal contact.The results indicate that Cd has a huge potential risk on human health for the local residents.     

Influence of thinning on acidic deposition in Chinese fir plantations简

Acidic deposition,which is mainly caused by atmospheric pollution,is one of the global environmental problems.Thinning is an effective management to improve the tree productivity,reduce the wildfire risk and maintain a healthy forest.Since thinning may reduce the effect of acidic deposition,the effect of thinning on acidic deposition was estimated.The biomass,soil properties,pH value of runoff and groundwater in both unthinned and thinned Chinese fir plantations were measured and compared over a 5-year period（2-6 years after thinning）.The results indicated that acidic deposition in the Huitong State Ecosystem Research Station was serious,and it got worse with time.Forest thinning resulted in a huge change in biomass and soil properties.During the 5-year monitoring period,biomasses of understory and litter,plant species richness,coverage of undergrowth plant layer were significantly higher in thinned site than in unthinned site.Moreover,higher soil fertility as well as lower amounts of runoff and groundwater were found in thinned site.It was suggested that thinning could improve the structure of forest,leading to restoring the effluent（runoff and groundwater） pH to the normal value.     

填料级配对筋土界面特性的影响

不同填料级配对筋土界面特性的影响直接关系到工程的稳定性.通过室内大型直剪试验,研究了颗粒级配、密实度、筋材种类等对于界面强度的影响,深入了解筋土界面抗剪强度以及界面剪胀特性.试验结果表明,粗颗粒和细颗粒土分别与筋材的界面强度要明显大于级配较好的标准砂与筋材的界面强度.密实砂土界面强度具有类似混凝土材料强度高韧性低脆性破坏的特性.对于土工格栅,粗颗粒砂粒由于粒径较大达到峰值强度需要较大的剪切位移.     

非饱和膨胀土渗透性室内模拟试验

以广西南宁强膨胀土为实验对象,对比分析了膨胀土室内渗透试验结果和土体裂隙性指标。结果表明:土样初始渗透系数与表面裂隙率之间具有较好的相关性,其相关关系可以反映土体表层裂隙的发育情况;而在渗透试验中,当渗透系数收敛到1E-6 m/s时所用的时间,可定义为裂隙闭合时间,这一时间数据与土样表面裂隙率表现出较好的相关性。其关系可以从侧面反映出现场场地大气剧烈影响深度范围内的膨胀土裂隙开展状态。分析表明:渗透试验的方法可以间接描述膨胀土的裂隙发育。     

离子选择电极在水土流失养分监测中的应用

水土流失径流养分监测通常采用野外采集后进行实验室分析的方法,操作复杂。为验证离子选择电极这种可快速测量养分的方法在水土流失监测中的可靠性,以氨氮离子选择电极为例,与传统纳氏试剂分光光度法进行比较,在准确度、抗离子干扰及坡面径流迁移规律等方面进行实验。结果表明:电极法测定范围最大值为1000 mg/L,分光光度法测定范围最大值为2 mg/L;用幂函数模型模拟坡面径流氨氮迁移规律时,电极法测定值的拟合系数为0.9537,分光光度法的为0.9305。在95%的置信水平上,两方法结果并无显著性差异,而电极法的标准偏差小,其结果更接近标准值。     

软上地基上加筋碎石垫层工作性状试验研究

通过模型试验研究了加筋和不加筋碎石垫层在软土地基上的承载特性,分析了垫层厚度、加筋材料、加筋层数、筋体布置位置等因素对垫层承载特性的影响。结果表明：垫层厚度对地基沉降影响明显,合理的垫层厚度能有效地降低地基的沉降;加筋后的碎石垫层对降低地基沉降的效果更明显,同等条件下,土工格室的加筋效果优于土工格栅;加筋层数及筋体布置位置对加垫碎石垫层承载特性有一定影响,层数越多加筋效果越好,将筋体布置在垫层下部时效果最好;加垫层能在一定程度上提高地基基床系数,其中土工格室加筋碎石垫层对提高地基基床系数效果最好。     

圆砾改良膨胀土膨胀性试验研究

针对陕南旬阳地区某电厂工程在地基处理过程中遇到的膨胀土问题,结合场址附近圆砾资源丰富的地质条件,提出了一种新的改良方法——在膨胀土中掺入圆砾.根据土工试验规程进行重型击实试验,分别按照掺加圆砾比例为0%、20%、30%、40%、45%和55%开展试验.研究结果表明:改良试样的最大干密度从1.84g·cm-3提高到2.05g·cm-3,最优含水量从18.76%降低到11.32%;对改良试样进行膨胀量试验,掺加圆砾比例为45%时膨胀性改良效果最好,浸水膨胀达到稳定的时间约为600min.而未掺加圆砾的试样在2 160min还未达到膨胀稳定状态.     

不锈钢,铜和铝合金酸性土壤腐蚀行为研究

研究了1Cr13,1Cr18Ni9Ti,H62黄铜和Ly11铝合金在酸性土壤中的腐蚀行为,结果表明,Ly11铝合金的腐蚀率比不锈钢的腐蚀率约大50倍,发现Ly11铝合金在不同种的酸性土壤中的腐蚀率与其腐蚀产物的相结构有一定的对应关系     

区域土壤腐蚀试验数据分布特征研究——Ⅱ位置分布特征表述

将区域腐蚀试验数据看作是连续、光滑变化 的土壤腐蚀性-位置函数具体数值，用三次样条函数处理塔里木地区库尔勒-库车公路沿线土 壤腐蚀试验数据，得到插值公式并计算最高腐蚀性土壤的位置和腐蚀分区边界等.同样思路 也适用二维位置分布研究，但复杂得多.本文还介绍三角网格线性插值和绘制平面等值线图 等一般方法.