Numerical study on maximum rebound ratio in blasting wave propagation along radian direction normal to joints

1 INTRODUCTION For one dimensional wave, such as seismic wave, passing across single joint or multiple parallel joints, combining the theory of displacement discontinuities and the method of characteristics, solutions in terms of magnitudes of the reflection ratio and the transmission ratio have been obtained by several researchers[1?6] for P-wave and S-wave respectively. However, for a practical dynamic problem in a rock mass involving blasting wave propagation from a tunnel or borehole,…     

Transmission ratio （Tn） in the radian direction normal to joints in 2-D compressional wave propagation in rock masses

The transmission ratio along the radian direction normal to the joints was studied in the Universal Distinct Element Code （UDEC）. The variation of the transmission ratio with the ratio of joint spacing to wavelength was generalized into a general curve, which was determined by two critical points. The relationship between the two critical points and the affecting factors, quantity of joints and the normalized normal stiffness of joints, were obtained. A prediction model of the transmission ratio in the radian direction normal to the joints was proposed. The proposed model was applied to a field explosion test. The estimated values of the peak particle velocity from the prediction model were compared with the field records. The comparisons showed that the prediction model of the transmission ratio in the direction normal to the joints in the process of 2-D compressional wave propagation through multiple parallel joints is reliable.     

爆破振动作用下邻近埋地混凝土管道动力响应特性

为保证埋地混凝土管道在爆破施工过程的安全性,采用现场监测和动力有限元数值模拟相结合的研究方法,对超浅埋地铁站通道爆破开挖邻近埋地混凝土管道的动力响应进行研究.通过建立管道拉应力峰值和振动速度峰值的函数关系,由最大拉应力强度理论得到管道的爆破控制振速.由管道不同断面最大振速与对应位置管道正上方地表振速之间关系,提出保证管道安全的地表爆破控制振速.结果表明:空管状态下,掌子面后方,管道断面底部和中部振速较为接近,顶部振速最小;掌子面前方,管道断面质点振速呈现出底部最大、中部次之、顶部最小的振动特征;沿着管道轴线方向,质点振速最大的位置出现在掌子面前方3 m管道断面底部位置.管道在空管和满水两种状态下质点振动特征基本一致,管道中水的存在能降低管道质点振速,最大降低幅度为7.3%.管道的爆破控制振速为10.84 cm/s,保证管道安全的地表爆破控制振速为4.53 cm/s.确定的爆破控制振速可以指导现场爆破施工.     

Blast-induced ground vibration prediction in granite quarries: An application of gene expression programming,ANFIS, and sine cosine algorithm optimized ANN

Blasting of rocks has intrinsic environmental impacts such as ground vibration, which can interfere with the safety of lives and property. Hence, accurate prediction of the environmental impacts of blasting is imperative as the empirical models are not accurate as evident in the literature. Therefore, there is need to consider some robust predictive models for accurate prediction results. Gene expression programming(GEP), adaptive neuro-fuzzy inference system(ANFIS), and sine cosine algorithm optimized artificial neural network(SCA-ANN) models are proposed for predicting the blast-initiated ground vibration in five granite quarries. The input parameters into the models are the distance from the point of blasting to the point of measurement(D), the weight of charge per delay(W), rock density(q), and the Schmidt rebound hardness(SRH) value while peak particle velocity(PPV) is the targeted output. 100 datasets were used in developing the proposed models. The performance of the proposed models was examined using the coefficient of determination(R2) and error analysis. The R2 values obtained for the GEP, ANFIS,and SCA-ANN models are 0.989, 0.997, and 0.999, respectively, while their errors are close to zero. The proposed models are compared with an empirical model and are found to outperform the empirical model.     

MATLAB在开采沉陷预计参数求取中的应用

提出了基于实测资料,根据不同地质条件选择合适的预计公式的方法.利用MATLAB软件中非线性最小二乘拟合函数求取概率积分法预计参数,预计地表上任意点的移动和变形值,为求取预计参数提供了一种新的思路,实现了地表移动变形预计的可视化.     

一种建筑工程场地参数VS30的外推模型修正方法

为提高覆盖土层较浅工程场地上钻孔的外推V_S30值精度,选取日本KiK-net台站中符合一定条件的钻孔数据,利用相关系数矩阵排除共线性问题以确定可用于回归的3个体现钻孔剖面特性的参数,通过最优子集法建立常数外推V_S30残差与这3个参数的优选函数关系,利用调整后R²、贝叶斯信息准则和k倍交叉验证3种特征选择方法确定其中的最优关系。根据修正后预测V_S30与实际观测V_S30间残差均值和标准差的分布给出推荐的常数外推模型修正函数。结果表明,该V_S30的外推模型能够较好提高底部常速度模型的预测精度,并且在新疆地区具有一定适用性。提出的方法可以对中国不同地区的场地V_S30经验估计模型建立提供参考。     

Development and experimental validation of a one-dimensional dynamic hygrothermal modeling based on air humidity ratio

A modified one-dimensional transient hygrothermal model for multilayer wall was proposed using air humidity ratio and temperature as the driving potentials. The solution for the governing equations was obtained numerically by implementing the finite-difference scheme. To evaluate the accuracy of the model, a test system was built up to measure relative humidity and temperature within a porous wall and compare with the prediction of the model. The prediction results have good agreement with the experimental results. For the interface close to indoor side, the maximum deviation of temperature between calculated and test data is 1.87 K, and the average deviation is 0.95 K; the maximum deviation of relative humidity is 11.4%, and the average deviation is 5.7%. For the interface close to outdoor side, the maximum deviation of temperature between prediction and measurement is 1.78 K, and the average deviation is 1.1 K; the maximum deviation of relative humidity is 9.9%, and the average deviation is 4.2%.     

逐层回弹法评定火灾后混凝土抗压强度的试验研究

目的研究火灾后混凝土抗压强度与混凝土不同深度处的平均回弹值之间的关系，建立逐层回弹法评定火灾后混凝土抗压强度的专用测强曲线和计算公式．方法通过采用逐层回弹法对不同火灾温度条件下的混凝土试块进行逐层切割回弹试验。得到火灾后混凝土不同深度处的回弹数据，利用分层回弹数据的变化趋势和混凝土的实测强度来拟合火灾后混凝土的专用测强曲线和计算公式．结果表明按逐层回弹法建立的火灾后混凝土测强曲线和计算公式具有良好的精度。同时该方法考虑了不同深度处的回弹值与混凝土强度之间的相关关系，使得本文提出的测强曲线更接近实际．结论逐层回弹法可以应用于火灾后混凝土的强度评定。该法满足工程精度的要求．可以为火灾后混凝土结构的检测鉴定提供新的依据．     

混沌序列优化预测模型研究

混沌是一种普遍的非线性动力学行为,大多数情况下是有害的。针对混沌时间序列的难以预测和控制的问题,提出了基于趋势的混沌预测模型,用改进的最优化方法来估计模型的参数,在其相空间中对时序的未来值进行预测。算例表明,选取最佳的模型阶数能增加预测的准确程度,预测效果比统计方法好。     

楔形桩极限承载力提高机理研究

为研究楔形桩相对等截面桩极限承载力提高机理及楔形桩承载力特性,根据楔形桩承载机理,将楔形桩承载过程分为弹性变形及挤土塑性破坏两个阶段.假定桩侧土体发生破坏时应力状态服从Mohr-Coulomb强度准则,建立了楔形桩承载力分析模型并提出了楔形桩极限承载力增大系数.通过与已有模型试验分析对比验证了本文解答的合理性.在此基础上,分析了承载力增大系数随桩-土界面摩擦系数、楔形角、静止土压力系数等的变化规律.结果表明:本文理论方法能够较为合理地预测楔形桩的极限承载力;楔形桩承载力增大系数随着土体内摩擦角增大而增大,但随着静止土压力系数和桩-土界面摩擦系数增大而减小,同时存在特定的楔形角使得承载力增大系数最大.     

Rock parameters inversion for estimating the maximum heights of two failure zones in overburden strata of a coal seam

In order to enter effective parameters of rock mass in a numerical model, the relationships between mechanical parameters of rock and rock mass were obtained by an inversion method and an orthogonal test, given our measurements of the maximum heights of two failure zones in the Longdong coal mine.Using the maximum heights of the caving zone and the water-conducting fractured zone as test indices the modulus of elasticity, the Poisson ratio, cohesion and tension strength as test factors and different values of reduction enhancement factors as test levels, an orthogonal test was designed to obtain an optimum simulation scheme. From the analysis of different values of reduction enhancement factors which affect the test indices, an optimum factor combination for modification of parameters could be inferred. By using modified parameters in our numerical simulation, the maximum heights oftbe caving zone and the water-conducting fractured zone in the extensive Xiyi area were determined as 15.06 m and 36.92 m. These values were almost the same as those obtained by similar material simulation (8.5 m and 37.0 m) and empirical prediction (8.4 m and 34.4 m). These results indicate that the modification of parameters is a rational method.     

基于截尾数据对女性寿命的估计

根据英国十七、十八世纪堂区登记册上的数据,提出估计当时英国女性寿命的模型,并用极大似然方法估计出了模型中的未知参数。     

天波传播预测及辅助决策分析

通过对短波经电离层的E层、F2层传播后的场强仿真计算及最高可用频率(MUF)预测，提出了合理选择车载机动短波发射机的部署位置、工作时机和发射频率等要素，使短波通过E层或F2层反射后，到达预定接收点的场强最大。通过软件仿真预测和试验数据的对比，验证了仿真模型的合理性，为短波发射机的部署方案提供了较为合理的辅助决策建议。     

钢管混凝土组合柱受剪承载力分析模型

目前,有关钢管混凝土组合柱构件受剪承载力的试验研究、理论模型及计算方法尚少。为此,基于组合柱受剪试验研究,探讨桁架-斜压场理论用于计算受剪承载力的适用性,并与中国规范T/CECS 188、美国规范AISC、欧洲规范EC4进行对比分析。其中修正桁架-斜压场模型是基于管内外混凝土不同约束条件,以钢管为界划分构件截面区域,提出能够考虑轴压力作用下,钢管约束对管内混凝土强度影响的受剪承载力计算方法。研究表明：桁架-斜压场理论分析方法的计算结果与36组试验数据吻合度高,不仅能够较好反映组合柱构件的受剪机理,且模型计算敏感性受剪跨比、体积配箍率、混凝土强度、轴压比、套箍指标和钢管径厚比等变化参数的影响不大,绝大部分试件的计算值与试验值比值介于0.85~1.15;采用中国规范T/CECS 188计算值普遍低于试验值,未能准确预估构件的实际承载力;采用美国规范AISC、欧洲规范EC4的计算值的离散性较大。     

Lifetime prediction for tantalum capacitors with multiple degradation measures and particle swarm optimization based grey model

A lifetime prediction method for high-reliability tantalum (Ta) capacitors was proposed, based on multiple degradation measures and grey model (GM). For analyzing performance degradation data, a two-parameter model based on GM was developed. In order to improve the prediction accuracy of the two-parameter model, parameter selection based on particle swarm optimization (PSO) was used. Then, the new PSO-GM(1, 2, ω) optimization model was constructed, which was validated experimentally by conducting an accelerated testing on the Ta capacitors. The experiments were conducted at three different stress levels of 85, 120, and 145 °C. The results of two experiments were used in estimating the parameters. And the reliability of the Ta capacitors was estimated at the same stress conditions of the third experiment. The results indicate that the proposed method is valid and accurate.     

基于分段线性模型的专变用户电能配给估计

针对专变用户数量激增引起的用电配给管理问题,提出一种分段线性模型来预测专变用户月平均用电占比数据,实现节能配给的目标.采用N点长数据分段更新生成分段线性模型,从而估计得到下一个月的平均用电占比数值.讨论分析了分段点长N分别取4~8时,分段线性模型预测精度的差异.针对某专变用户2015年以来的实际用电数据进行预测分析,比较验证了预测数值和实际数据之间的误差.结果表明,当最优建模点长N=6时,模型的平均预测误差最小.     

太阳电池工程简化模型参数确定及模型应用

针对现有文献中太阳电池工程简化模型的模型系数值不适用于当今光伏组件的问题,提出简单的仅需利用光伏组件出厂数据的模型系数确定方法.系数b通过拟合25℃下不同辐照度对应的开路电压数据得到,系数a和c分别取短路电流和开路电压的温度系数.不同厂家生产的光伏组件系数b不同,同一厂家生产的不同型号的光伏组件系数b可以取相同值.综合改进后的太阳电池工程简化模型、分段函数形式的太阳电池温度模型和考虑安装条件的入射光强度模型,开展光伏组件电气输出特性的动态仿真.当组件倾角小于最佳倾角时,角度变化对最大输出功率的影响很小;当倾角大于最佳倾角时,角度变化对最大输出功率的影响较大,影响程度随着角度的增大而增大.     

三应力不变量模型预测变形带角

RR二应力不变量模型研究岩石局部化变形带角,得到的预测值与实验中测得的变形带角随平均应力增加而增加的趋势以及随着最小压应力增加而减小的趋势都一致,但是得到的预测值比实测数据略小。在RR二应力不变量模型基础上,通过增加洛德角作为第三应力不变量,选用更加复杂的屈服条件,得到的三应力不变量模型,结合岩石真三轴实验,得到的预测值和实验数据关联度更高。     

基于线性多尺度模型的计算机网络数据流量预测

为了解决网络安全监控问题,提出了一种用于预测网络流量的算法.通过多个不同尺度的线性模型进行网络数据的组合预测,每个尺度的线性模型由经过滤波器滤波后的部分原始数据估计得到,最终的预测流量数据由多个尺度线性模型的平均预测值得到.选择的线性模型为自回归滑动平均模型,且尺度较小的线性模型对应自回归滑动平均模型的阶数较高.结果表明,本算法的预测精度高,整体预测误差的均值在10-3量级.     

时序分析在开采沉陷动态参数预计中的应用

应用时间序列分析法,对开采沉陷动态过程的概率积分法预计参数进行分析,建立动态预计模型。用该模型可对参数的未来值进行预计,然后利用预计结果进一步预计地表的移动变形,解决了开采沉陷的动态预计问题。应用此法,地表下沉的相对预计误差一般为４％左右,与传统方法相比,预计精度可提高５％～１５％。