点荷载法测试易风化泥质岩强度的可靠性分析   总被引：1，自引：0，他引：1  

张国锋  刘志双  陈显坤  王永望  解毅 《岩土力学》2014,35(Z1):292-298

在川南地区在近年的煤炭开发过程中,多数基建矿井在巷道开拓期间大量出现围岩软弱、易风化、节理裂隙发育、变形大、支护难、多次返修等严重困扰矿井正常投产的支护难题,为合理选取支护技术,必须对软岩类型及等级进行划分。首先进行地质工程调查,选择巷道主要分布的厚层黑灰色泥岩为研究对象,在井下采用点荷载测试仪对新鲜不规则岩块进行强度测试。在对可疑数据采用Grubbs准则进行取舍后,采用传统法、ISRM法、工程分级法分别进行点荷载强度计算,所得结果采用F检验法和t检验法对各公式计算结果进行随机误差和系统误差检验,研究各方法的适宜性。研究发现,在对泥岩进行点荷载测试时,传统法和ISRM法较工程分级法所得单轴抗压强度平均值的随机误差和系统误差小,更适宜作为该类岩性进行工程软岩分级评价时的重要指标;点荷载所获泥岩强度值的偏差系数在11%～30%范围内,与一般岩石单轴抗压强度测定值偏差系数接近,具有可靠、快速、方便、费用低的优点,适宜作为围岩取样困难的巷道进行软岩类型评价的测试方法。  相似文献   

Multiple‐support response spectrum analysis using load‐dependent Ritz vectors          下载免费PDF全文

Ziqi Wang  Armen Der Kiureghian 《地震工程与结构动力学》2014,43(15):2283-2297

Load‐dependent Ritz (LDR) vectors are used in conjunction with the multiple‐support response spectrum (MSRS) combination rule for analysis of structures subjected to spatially varying earthquake ground motions. The LDR vector approach for MSRS analysis is motivated by the fact that LDR vectors in general are more accurate and computationally simpler than eigenvectors in mode superposition analysis, and because many researchers and engineers are using LDR vectors in linear structural dynamic analysis. Mode truncation rules for the original MSRS method are modified to apply to LDR vectors. Two methods for selecting LDR vectors for multicomponent MSRS analysis are introduced. Idealized models of two real bridges with differing structural characteristics are used to investigate the accuracy and efficiency of the two LDR‐MSRS methods in comparison with results obtained by the original MSRS method as well as an extended version that accounts for the static contribution of truncated modes. The results show that the LDR‐MSRS method is generally more accurate than the original MSRS method and at least as accurate as the extended MSRS method. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

基于BP神经网络的北京夏季日最大电力负荷预测方法     

李琛  郭文利  吴进  金晨曦 《气候与环境研究》2019,24(1):135-142

利用2006~2017年北京夏季（6~8月）逐日最大电力负荷和同期气象资料,分析最大电力负荷与各种气象因子的相关性,基于BP（Back Propagation）神经网络算法,建立了两种夏季日最大电力负荷预测模型并对比。结果表明:北京夏季周末基础负荷远小于工作日,剔除时应加以区分;气象因子对气象负荷的影响具有累积效应,累积2 d时两者的相关性最强;结合实际,根据自变量的不同分别建立了两种日最大电力负荷预测模型;经实际预测检验,两种预测模型均取得了较好的预测效果,能够满足电力部门的实际需求,其中自变量中加入前一日气象负荷的模型效果更优。  相似文献   

新疆农业区电力负荷与天气的关系   总被引：2，自引：0，他引：2  

杨静  郝毅  陈冬梅  江波 《气象》2009,35(1):114-118

用2005--2006年新疆农业区电力负荷与气象资料,统计得出电力负荷的年、季变化与农事活动周期相符,电力负荷日变化的次高峰与日最高气温、最小相对湿度出现时间较一致.将逐月的日平均电力负荷及变化量分别与气压、气温、空气湿度、风速和降水量做相关分析,并将有无降雨日分段统计.结果表明,电力负荷与降水量、湿度和气温的变化关系较为密切.利用逐步回归方程将4种不同模式模拟的电力负荷进行了误差分析,发现要素差值模式的模拟效果较好,并对2007年5月的电力负荷进行了预测检验及误差分析,得出:在降雨日,用上一日负荷计划当日负荷的误差高达63.2%,而用要素差值模式预测电力负荷的误差为18.7%,月平均预测误差由前者的26.0%下降到13.4%.  相似文献   

Transient response of a beam on viscoelastic foundation under an impact load during nondestructive testing   总被引：1，自引：1，他引：0  

孙璐罗飞全  陈东晖 《地震工程与工程振动(英文版)》2005,4(2):325-333

Beam responses under an impact NDT load are studied using the Fourier and Laplace transforms. Numerical computation is performed for a parametric study of beam and load parameters. It is shown that under an impact load, the time duration for displacement to vanish is ten times longer than that for velocity and acceleration. The maximum response is achieved first in acceleration, followed by velocity, and finally displacement, all of which occur before the impact load is removed. At the moment that the impact load is removed from the beam, there is a discontinuity in the velocity and acceleration responses, but not in displacement response. The effect of K and ph on beam response is much less significant than that of El and C, which have similar effect on beam response. As El increases, peak values of displacement, velocity and acceleration response decrease. The effect of K on beam response only becomes appreciable after the impact load is removed. While the peak of displacement remain almost unchanged as K increases, the displacement response decays to zero faster for large K values than for small K values.  相似文献   

周期反复荷载作用下高轴压比框架柱抗震性能的试验研究   总被引：6，自引：1，他引：5  

张国军  吕西林  白国良 《地震工程与工程振动》2005,25(6):70-75

本文是关于框架柱在低周反复荷载作用下抗震性能的试验研究。根据16个“上”形试件在固定轴向荷载和水平周期反复荷载作用下的试验结果,首先讨论了影响框架柱开裂荷载的因素,接着深入分析了混凝土强度等级、轴压比、长细比、纵筋配筋率、箍筋形式及配箍特征值等因素对框架柱的延性和位移转角的影响。最后,根据本次试验结果,分析和讨论了框架柱轴压比超限问题和轴压比超限时配箍特征值的取值问题。  相似文献   

Asymptotically Matched Layer (AML) for transient wave propagation in a moving frame of reference     

《Computers and Geotechnics》2017

The paper presents an Asymptotically Matched Layer (AML) formulation in a moving frame of reference for transient dynamic response of a multi-layer 2D half-space. A displacement based finite element formulation of the convected domain problem is presented together with the AML formulation in which the original convolution integrals are represented via two auxiliary displacement-like state-space variables. A parametric study of the AML parameters is conducted for optimizing the absorbing properties. The performance is demonstrated on a single- and a two-layered half-space for various velocities of an impulse Ricker load. Excellent absorbing properties are demonstrated in both half spaces.  相似文献   

Experimental Study on the Cyclic Behavior of Monopiles in Fine Sandy Beds Under Regular Waves     

HUANG Ting  ZHENG Jin-hai  ZHANG Ji-sheng  YUAN Yu  WU Bin 《海洋工程》2017,31(5):607-617

This paper presents an experimental study on the wave-induced behavior of monopiles. Laboratory experiments were conducted at the constant initial state of the sandy beds in a wave flume with a soil trench. The responses of the pile-head displacement, the pile strain and the pore water pressure on regular waves were investigated. The experimental results show that the monopiles lean along the direction of the wave progression and the inclination increases with the duration of wave actions. The pile-head displacement (consisting of the permanent displacement and cyclic displacement) increases as the wave height increases, especially more significantly for the permanent displacement. The head-fixed pile suffers from larger wave load than that on the head-free pile under the same wave condition. Increasing pile diameter or fixing fins on the monopile is effective in reducing the pore water pressure in the upper part of the bed and the permanent displacement.  相似文献   

Small- and large-scale model tests on the buckling property of slender pile     

Long Chen  Jiangwei Shi  Geng Chen 《Marine Georesources & Geotechnology》2017,35(8):1058-1067

Slender piles embedded in soft ground or liquefied soil may buckle under vertical load. In this paper, both small- and large-scale model tests are conducted to investigate the buckling mechanisms of a slender pile and the lateral earth pressure acting on the pile. To observe the buckling of a slender pile, the strain-controlled loading method is adopted to apply a vertical load. When the two ends of a slender pile are hinged, the buckling mechanisms of small- and large-scale model tests are same. It should be noted that this applies only to a system with a small ratio of pile bending stiffness to soil bending stiffness. An applied vertical load increases with an increasing pile head settlement until it reaches the critical buckling load. By further increasing the pile head settlement, the measured load approaches the critical buckling load. In the large-scale model test, the measured lateral earth pressure (i.e., active and passive) acting on the slender pile varies linearly with the lateral pile displacement when the measured range is 3–5?m beneath the ground. A critical buckling calculation method has been adopted to compare with the conventional “m” method. The two-sided earth pressure calculation method can achieve more approximate results with the model test.  相似文献   

地震荷载作用下兰州地铁隧道结构动力响应          下载免费PDF全文

苏永奇  马巍  李明永  王谦 《地震工程学报》2015,37(4):938-943

根据《兰州轨道交通1号线一期工程地震安全性评价报告》所给出的100年超越概率63%、10%和2%的场地基岩地震加速度时程,利用有限差分软件进行地下隧道硐室的地震反应分析。在模型底部施加基岩地震动,设置监测点监测衬砌结构的弯矩、轴力及剪力随时间的变化过程,得到100年超越概率63%、10%及2%工况下的隧道结构地震响应。结果表明:隧道衬砌结构最大弯矩位于拱顶处,最大轴力位于拱顶和拱底处,最大剪力位于上侧壁或下侧壁处;隧道结构内力随着超越概率的降低而增大;以超越概率63%的结构最大内力为基准值,在超越概率10%和2%时,弯矩分别增大1.2和1.7倍,轴力分别增大1.3和1.5倍,剪力分别增大1.5和2.9倍,增幅最大。这可能预示着隧道结构在强地震动作用下会发生剪切破坏。  相似文献