金属矿中铜含量滴碘法快速测定

通过调节pH值,加入氟化氢铵消除铁的干扰,用硫代硫酸钠滴定碘,淀粉溶液做指示剂等方法。探讨了快速滴碘法在金属矿中铜含量分析的应用,方法快速易掌握,结果准确。适用于金属矿中铜的测定。     

Combined loading of caisson foundations in cohesive soil: Finite element versus Winkler modeling

The undrained response of massive caisson foundations to combined horizontal, vertical and moment loading is parametrically investigated through a series of 3D finite element analyses. The parameters are: (a) the embedment ratio (D/B), (b) the factor of safety against initial vertical loading (FS_V) and (c) the ratio of the overturning moment to the horizontal force applied at the top of the caisson (M/Q). Emphasis is given on: (i) the identification of all possible failure mechanisms in M–Q–N space, (ii) the developed stress distributions along the caisson walls for various load levels up to complete failure conditions. The results are then used as a feedback for calibrating the parameters of a generalized four-type spring model, originally proposed by Gerolymos and Gazetas (2006), through a genetic algorithm-based optimization procedure. The predictions of the Winkler model compare very well with the FE results, not only at the local response level (in terms of stress distributions along the caisson shafts), but at a global response level (in terms of force–displacement curves and M–Q–N failure envelopes at the top of the caisson) as well. Contrary to established lateral soil resistance theories, it is shown that both the ultimate horizontal soil reaction and resisting moment per unit depth do not solely depend on the strength properties of soil and geometry of the caisson but are also functions of the applied load ratio M/Q and initial soil yielding due to vertical loading. Interesting conclusions are also drawn regarding the transition from the elastic to the ultimate limit state (hardening). Quantifying through analytical expressions the contribution of each of the two basic lateral resisting mechanisms to the response of the caisson, a classification method for embedded foundations is then proposed. The capabilities of the Winkler model are further demonstrated through comparison with FE analysis of the caisson cyclic lateral response.     

滑坡治理中预应力锚索格构梁内力计算方法对比分析

本文结合某一滑坡防治工程实例,对预应力格构锚索工程提出了适合该工程布置方式的格构梁设计计算模型,并将此模型的计算结果与常用的winkler弹性地基梁和倒梁法的计算结果进行对比分析,研究表明此计算模型更加符合格构梁实际受力情况。      

十字交叉格构梁内力分析与优化设计

根据格构锚加固边坡工程的特点,采用Winkler弹性地基梁理论对格构梁的内力进行分析,针对目前设计中将格构梁拆分为单片梁计算的不足,讨论十字交叉格构节点处荷载分配方法,按有限长梁受多个集中力作用推导其内力公式,并编制相应计算程序。通过工程实例讨论间距、截面尺寸和悬臂长度对梁内力的影响,用于指导优化设计。计算结果表明,格构梁设计可取较小间距和较小的截面尺寸,且两端应留有一定的悬臂长度。