山区急倾斜煤层开采上覆岩层弯曲挠度预计

为了研究山区急倾斜煤层开采上覆岩层的弯曲变形规律,建立了上覆岩层弯曲变形的力学模型,运用弹性力学中的薄板弯曲理论,推导了上覆岩层弯曲挠度的预计公式,利用此公式对上覆岩层的弯曲挠度进行了计算。研究结果表明:(1)由于山区急倾斜煤层覆岩的线性荷载的作用,岩板的弯曲挠度曲线不再具有对称性,岩板弯曲挠度的最大值偏向于岩板倾斜的下山方向;(2)岩板弯曲挠度随着采深的增大而增大,岩板弯曲挠度最大值出现的位置逐渐由下山方向向采空区中点移动,但是最大挠度出现的位置不会越过采空区中点而位于倾斜岩板的上山方向;(3)岩板弯曲挠度随着山地倾角的增大而增大,岩板挠度最大值出现的位置距离采空区中点越来越远;(4)岩板弯曲挠度随着煤层倾角的增大而减小,岩板弯曲挠度最大值出现的位置距离采空区中点越来越远。     

Numerical studies of anchored sheet pile wall behavior constructed in cut and fill conditions

The construction of sheet pile walls may involve either excavation of soils in front or backfilling of soils behind the wall. These construction procedures generate different loading conditions in the soil and therefore different wall behavior should also be expected. The conventional methods, which are based on limit equilibrium approach, commonly used in the design of anchored sheet pile walls do not consider the method of construction. However, continuum mechanics numerical methods, such as finite element method, make it possible to incorporate the construction method during the analyses and design of sheet pile walls. The effect of wall construction type for varying soil conditions and wall heights were investigated using finite element modeling and analysis. The influence of construction method on soil behavior, wall deformations, wall bending moments, and anchor forces were investigated. The study results indicate that walls constructed by backfill method yield significantly higher bending moments and wall deformations. This paper presents the results of the numerical parametric study performed and comparative analyses of the anchored sheet pile walls constructed by different construction methods.     

Dynamic Scaling of the Generalized Complementary Relationship Improves Long-term Tendency Estimates in Land Evaporation

Most large-scale evapotranspiration(ET) estimation methods require detailed information of land use, land cover,and/or soil type on top of various atmospheric measurements. The complementary relationship of evaporation(CR) takes advantage of the inherent dynamic feedback mechanisms found in the soil-vegetation-atmosphere interface for its estimation of ET rates without the need of such biogeophysical data. ET estimates over the conterminous United States by a new, globally calibrated, static scaling(GCR-stat) of the generalized complementary relationship(GCR) of evaporation were compared to similar estimates of an existing, calibration-free version(GCR-dyn) of the GCR that employs a temporally varying dynamic scaling. Simplified annual water balances of 327 medium and 18 large watersheds served as ground-truth ET values. With long-term monthly mean forcing, GCR-stat(also utilizing precipitation measurements)outperforms GCR-dyn as the latter cannot fully take advantage of its dynamic scaling with such data of reduced temporal variability. However, in a continuous monthly simulation, GCR-dyn is on a par with GCR-stat, and especially excels in reproducing long-term tendencies in annual catchment ET rates even though it does not require precipitation information.The same GCR-dyn estimates were also compared to similar estimates of eight other popular ET products and they generally outperform all of them. For this reason, a dynamic scaling of the GCR is recommended over a static one for modeling long-term behavior of terrestrial ET.     

Prediction of bridge temperature field and its effect on behavior of bridge deflection based on ANN method

In recent years, the bridge safety monitoring has been paid more attention in engineering field. However, the financial and material resources as well as human resources were costly for the traditional...     

Priestley-Taylor公式的改进及其在互补蒸散模型中的应用

Priestley-Taylor公式是无平流的假设条件下提出的,而实际情况很难满足。为了消除基本假设所带来的计算误差,原公式中引入修正系数α。但大量研究表明,修正系数α具有很大的时空变异性,取值具有很大的不确定性。本文尝试直接引入平流项的方法来反映平流的影响作用。通过在乌江鸭池河流域进行实例验证分析,结果表明该方法具有一定的合理性,能够为冬季蒸散发的计算提供最小能量保证。相比原有的修正系数法,蒸散发的计算精度得到有效提高。特别是原有公式计算出现的冬季偏小、夏季偏大的情况得到了有效的改善。     

藤田公式改进及其在台风预报中的应用

在考虑环境气压的影响下,引进环境半径参量对藤田公式改进并将其应用到9711号台风研究预报中.结果表明:①改进的藤田公式能够基本解决藤田公式计算的外围气压和气压梯度偏小这一问题,合理地给出整个台风域内气压和气压梯度力的分布.②改进的藤田公式由于引入了环境半径的影响,使得计算的风向内偏角减小而风速增大;特别是它能使台风外围...     

Probability of serviceability failure in a braced excavation in a spatially random field: Fuzzy finite element approach

A simplified framework is proposed for evaluating the probability of “serviceability failure” in a braced excavation in a spatially random field. Here, the “serviceability failure” is said to occur when the excavation-induced wall or ground movement exceeds specified limiting values. Knowledge of this probability can aid in engineering decision-making to prevent damage to adjacent infrastructures. The proposed framework consists of five elements: (1) finite element method (FEM) for analyzing wall and ground responses in a braced excavation, (2) fuzzy set modeling of parameter uncertainty, (3) spatial averaging technique for handling spatial variability, (4) vertex method for processing fuzzy input through FEM model, and (5) interpretation of fuzzy output. The proposed framework is demonstrated through a well-documented case history. The results show the proposed framework is simple and effective for assessing the probability of serviceability failure in a braced excavation in a spatially random field. To focus on the proposed fuzzy FEM approach, the scope of this paper is limited to one-dimensional modeling of spatial variability with an assumed exponential autocorrelation function.     

基于CEEMD和改进小波阈值法的钢架结构沉降数据去噪方法

在钢架结构安全监测过程中,针对沉降数据易受外界环境噪声干扰的问题,在互补集合经验模态分解(CEEMD)的基础上提出改进小波阈值函数的去噪方法。首先对含噪信号作CEEMD分解,得到各种本征模函数(IMF);之后选取IMF分量使用改进小波阈值去噪;最后重构IMF信息,取得降噪后的信号。仿真结果表明,基于CEEMD和改进小波阈值法的混合方法能够有效滤除信号中的噪声分量,提高沉降数据监测精度。     

LZ-73型连续造斜器在兰陵铁矿勘查中的应用

LZ系列连续造斜器作为一种定向造斜的工具,广泛应用于石油领域。而在小口径固体矿产钻探,则缺乏相应的成熟技术,一直未能较大范围的推广。针对兰陵铁矿矿区的地层情况与其造成钻孔普遍偏斜的原因,结合矿区连续造斜器的应用,介绍了LZ-75型连续造斜器的工作原理和2种定向方法,以及一些使用心得。