Analytical solution to rock pressure acting on three shallow tunnels subjected to unsymmetrical loads

According to the interaction of three shallow tunnels with large section, the analytical solution to rock pressure has been derived and discussed. The load model is given when the bilateral tunnels are excavated. According to the model, the stresses of three tunnels and single tunnel are calculated and compared to analyze the distribution characteristics, where the stresses are influenced by controlling factors of clear distance, covering depth and inclination angle of ground surface. The results show that, in general, the bias distribution is more serious. Therefore, it is significant to settle down the load model of three shallow tunnels so as to determine the measure of reinforcement and design the structure of support. The model and results can be used as a theoretical basis in designation and further research of the three shallow tunnels.     

北京和河北地区生鲜乳中重金属铅含量的风险监测

目的:调查北京和河北地区生鲜乳和牧场投入品中重金属污染情况。方法:针对北京和河北地区养殖场分布情况,采集这两个地区35家牧场的生鲜乳样和北京地区3家规模牧场中饲料、生产用水等投入品样,开展铅污染状况的风险监测。结果:北京地区3家牧场的52份饲料样品铅的含量未超出标准限量要求,6份用水样品未检出铅的含量,饲料和用水合格率均为100%;北京和河北地区奶牛养殖场35份生鲜乳合格率为100%。结论:北京地区牧场投入品的安全性较好,北京和河北地区的生鲜乳无明显受重金属铅的污染,通过本文不仅了解北京和河北地区生鲜乳中铅污染水平,同时也为制修订标准、风险预警和风险评估提供了参考数据。     

隧道明挖施工与并行地铁区间相互影响分析

考虑基坑开挖导致邻近既有地铁区间产生内力重分布及附加位移,以实际工程为例,结合FLAC3D有限差分计算软件,对明挖法隧道基坑开挖支护与既有隧道相互作用进行数值分析,提出施工过程中的指导性措施,控制施工风险.