某锡矿地下采场爆破参数优化研究

云南省某锡矿由于爆破参数不合理,导致炸药单耗过高,并且大块较多,在一定程度上对矿山的经济效益造成影响。为通过优化爆破参数,改变此现状,基于利文斯顿爆破漏斗原理,在该矿1660中段某采场按照不耦合装药的形式,进行单孔爆破漏斗试验、变孔距爆破漏斗试验、斜面台阶爆破漏斗试验。得到该种锡矿的最佳炸药单耗爆破漏斗最大体积、最佳爆破漏斗半径、最小抵抗线和最佳孔间距。基于爆破漏斗理论对采场爆破参数进行优化,最终得出采场的合理爆破参数、孔间距和排距。按照此参数在该矿山进行应用,取得了良好的效果。     

Particle swarm optimization model to predict scour depth around a bridge pier

Scour depth around bridge piers plays a vital role in the safety and stability of the bridges. The former approaches used in the prediction of scour depth are based on regression models or black box models in which the first one lacks enough accuracy while the later one does not provide a clear mathematical expression to easily employ it for other situations or cases. Therefore, this paper aims to develop new equations using particle swarm optimization as a metaheuristic approach to predict scour depth around bridge piers. To improve the efficiency of the proposed model, individual equations are derived for laboratory and field data. Moreover, sensitivity analysis is conducted to achieve the most effective parameters in the estimation of scour depth for both experimental and filed data sets. Comparing the results of the proposed model with those of existing regression-based equations reveal the superiority of the proposed method in terms of accuracy and uncertainty. Moreover, the ratio of pier width to flow depth and ratio of d50 (mean particle diameter) to flow depth for the laboratory and field data were recognized as the most effective parameters, respectively. The derived equations can be used as a suitable proxy to estimate scour depth in both experimental and prototype scales.     

Multi-approach analysis of maximum riverbed scour depth above subway tunnel

When subway tunnels are routed underneath rivers, riverbed scour may expose the structure, with potentially severe consequences. Thus, it is important to identify the maximum scour depth to ensure that the designed buried depth is adequate. There are a range of methods that may be applied to this problem, including the fluvial process analysis method, geological structure analysis method, scour formula method, scour model experiment method, and numerical simulation method. However, the application ranges and forecasting precision of these methods vary considerably. In order to quantitatively analyze the characteristics of the different methods, a subway tunnel passing underneath a river was selected, and the aforementioned five methods were used to forecast the maximum scour depth. The fluvial process analysis method was used to characterize the river regime and evolution trend, which were the baseline for examination of the scour depth of the riverbed. The results obtained from the scour model experiment and the numerical simulation methods are reliable; these two methods are suitable for application to tunnel projects passing underneath rivers. The scour formula method was less accurate than the scour model experiment method; it is suitable for application to lower risk projects such as pipelines. The results of the geological structure analysis had low precision; the method is suitable for use as a secondary method to assist other research methods. To forecast the maximum scour depth of the riverbed above the subway tunnel, a combination of methods is suggested, and the appropriate analysis method should be chosen with respect to the local conditions.     

渭河下游河道冲淤规律及断面形态变化研究

渭河具有水沙异源的特性,水量主要来自于咸阳以上干流,沙量主要来源于支流泾河。在天然水沙断面资料分析及实体模型试验研究的基础上,根据平滩水位变化情况等,将泾、渭河洪水分为4类组合,分析了典型年份不同水沙组合条件下渭河下游河道的冲淤规律及主槽形态的变化特点。结果表明:1975年以渭河为主的大洪水,对扩大主槽形态、提高主槽输水输沙能力具有明显作用,而1992年以泾河为主的大洪水的作用却不明显;河道萎缩条件下的1995年小水大沙使主槽严重淤积、变得更为宽浅,断面面积减小。     

On stability of MHD flows located on the surface of axisymmetric torus

The erosion process of a cohesive sediment after consolidation was studied experimentally in a closed conduit system.The test samples investigated in this study are mixtures of sand and clay with variable compositions and different consolidation times.The main concern of this study is the effects of the dry density of the consolidated sediment on scour rate.A scour rate formula is derived and further interpreted based on the experimental results.     

漏斗结构平移模型下房屋龙卷风荷载的分析

基于龙卷风的漏斗结构模型以及Rankine涡平移模型的理论,对房屋进行漏斗结构平移模型下的龙卷风荷载分析,得出较Rankine涡平面模型更为真宴的房屋龙卷风荷载,对房屋的风吸力及扭转荷载作用力进行了分析,得出风吸力的大小随龙卷凤的高度而变化,对低矮房屋的作用力最大。     

试析荆江四口建闸控制对江湖冲淤的影响

应用一维悬移质数学模型 ,对三峡工程建成后长江中下游干流和洞庭湖区冲淤变化进行了联合计算 ,在此基础上研究了荆江松滋口和藕池口的建闸调度方案对江湖冲淤和三口分流分沙的影响。结果表明 :建闸控制后 ,三口分流分沙量减少 ;松滋口减幅最大 ;长江干流河道冲淤变化较小 ;松滋口分流道淤积 ,洞庭湖区淤积量明显减少     

NUMERICAL SIMULATION OF MOVING SCOUR BOUNDARY AND TURBULENCE FLOW AROUND SUBMARINE PIPELINES

A two dimensional vertical mathematical model is proposed in this paper for simulating the equilibrium profile of local scour around submarine pipelines. The current model is composed of a new k-ε turbulence model, fitting moving boundary with pre-meshed grid lines and incipient criterion of shear stress for sediments. Employing the proposed model, an instance is carried out numerically and compared with experiments. The calculation results agree well with the experiments. It shows that the improved two equation turbulence model, adopted in this paper is appropriate to simulating the turbulent flow ficld around submarine pipelines, fitting moving boundary with pre-mcshed grid lines method is efficient for moving boundary problems in a multiply connected domain and the stability evaluation method for seabed with critical shear stress based on log-wall law is a reliable choice.     

水布垭水利枢纽导流隧洞水力学试验研究

水布垭导流隧洞具有水头高,流量大,洞线长,地质环境差等特点,因而技术问题较多,难度较大。为此,进行了大量的试验研究。主要试验成果有：泄流能力及影响泄流能力的主要因素,压力特性及改善压力特性措施,出口消能防冲措施的比较等。这些试验成果为工程优化设计提供了科学依据。     

黄河宁蒙河段洪水冲淤规律分析

分析了1973—2005年宁蒙河段汛期场次洪水的冲淤特性、冲淤效率与下河沿断面水沙量之间的关系。结果表明:当下河沿断面洪水平均含沙量大于7 kg/m3时,宁蒙河段以淤积为主;当下河沿断面洪水平均含沙量小于7 kg/m3时,宁蒙河段以冲刷为主,且流量为2 200～2 500 m3/s时冲刷效率最大,此时洪水总水量应大于25亿m3。