裂纹深度和形状对构件断裂韧度的影响

在弯曲疲劳试验机上对几组包含有不同ａ／ｗ值的贯穿裂纹和不同ａ、ｃ值半椭圆裂纹的构件进行弯曲疲劳实验。结果表明,对于６０Ｓｉ２ＭｎＡ钢来说,无论是表面裂纹还是贯穿裂纹,在线裂纹情况下,其断裂韧度值比深裂纹高出２５％左右。当ａ／ｗ值大于０．１时,无论ａ／ｗ如何变化,ＫＩＣ值基本保持不变。裂纹形状对断裂韧度的影响也不明显。     

滇西重力场动态趋势变化与断层运动

以绝对重力做控制,对滇西网1985—2010年流动重力资料进行统一平差处理,平均点值精度为12×10 ^-8 ms^-2 /a;单点重力时变曲线主要呈现出季节性的上下波动和长期性的上升或下降趋势运动,部分点重力动态变化与丽江7.0级地震孕育过程相吻合;基于长期观测的重力场年变化率反映了重力场在一段时期内的趋势性变化：1985—1995年和1996—2003年年变化率图像可能反映丽江7.0级地震前后能量的累积、释放和调整,2003年以后剑川断裂、鹤庆 洱源断裂和红河断裂北段附近重力值上升速度均超过10×10 ^-8 ms^-2/a;基于初始断裂运动模型正演模拟的滇西重力场年变化率图像与实测图像非常相似,说明断裂运动对重力场趋势性变化有重要贡献;基于长期观测的重力场年变化率反演的滇西主要活动断裂年错动量与地质上给出的结果相仿,基本上反映了各断裂的活动性质。     

基于能量判据的剪切破坏型危岩主控结构面断裂扩展研究

将剪切型危岩主控结构面按受力机理归纳为压剪和拉剪两种形式,其本质是Ⅰ-Ⅱ复合型裂纹的断裂扩展问题。应用最大应变能释放准则,建立危岩主控结构面开裂角θ0和断裂韧度GIC的计算方法。选取重庆万州首立山典型危岩进行计算,结果表明,其断裂角与基于最大周向应力准则的断裂角计算结果一致,主控结构面的开裂方向均是指向临空面方向,初步验证了方法的可行性。     

陕西中南部现今地壳垂直形变研究

收集陕西中南部1970年以来的多期精密水准测量数据,用基于GPS垂直运动速率约束的动态平差方法获得区域垂直运动速度场。分析表明,地壳垂直运动总体表现为山地、高原相对隆升,盆地相对下沉。相对于关中盆地,西部秦岭、陇山上升速率为4~5 mm/a,北秦岭造山带为2~3 mm/a,盆地北部的鄂尔多斯南缘为3~4 mm/a;相对于北秦岭,汉中盆地下沉速率为1.0 mm/a左右,安康等北大巴山裂谷下沉速率接近20 mm/a;秦岭北缘断裂垂直滑动速率为1.3~1.8 mm/a,华山山前断裂为2.0~2.8 mm/a,渭河断裂小于1.0 mm/a,渭河盆地北缘断裂为1.0~2.5 mm/a,南部断裂为0.7~1.1 mm/a。     

海原断裂东段至六盘山断裂西段GPS剖面地壳变形与应变积累分析

利用2004~2013年3期GPS速度场数据,从断裂两侧的水平挤压、拉张与走滑等3方面,对海原断裂东段至六盘山断裂西段GPS剖面变形与应变积累进行研究。结果表明：1)海原断裂东段与六盘山断裂西段在运动方式上具有较强的一致性;2)在近10 a时间尺度上,该活动断裂整体表现为以左旋走滑为主,兼顾压性变化的运动特征,在上、下盘的相对运动差异速率上,走滑方向上达到2.0~5.5 mm/a,断裂垂直方向上约为0.5~3.0 mm/a。     

渭河盆地现今三维地壳运动及断裂活动性研究

渭河盆地GPS(1990~2015年)水平运动速率为4.3~11.6 mm/a,方向在107.8°E和110.5°E依次由西部的SEE转为中部的SE及东部的近E向。1980~2014年水准资料揭示,该地区垂向以继承性运动为主,速率-4.6~6.2 mm/a。鄂尔多斯地块以3 mm/a抬升,内部差异运动小于1 mm/a;盆地相对其以5 mm/a下沉,相对秦岭以4 mm/a下沉。垂向运动在凹陷和凸起区表现为四象限特征,断块/断裂交接处差异运动大、地震多发,西、南部断裂活动大于东、北部。岐山-马召等断裂以差异运动为主,渭河断裂中段达5 mm/a,其他断裂在3 mm/a以内。     

利用长期GPS观测资料分析昆仑断裂现今滑动速率与地壳活动特性

利用昆仑断裂区域的GPS观测资料,通过高精度数据处理获取区域地壳运动速度场,进而通过速度剖面线估算昆仑断裂现今形变速率。结果表明,昆仑断裂在94°E、101°E、103°E附近的现今滑动速率分别为12.8±1.9 mm/a、6.1±0.9 mm/a、0.7±2.1 mm/a。进一步分析得到如下结论：1）本文估算的昆仑断裂10 a尺度的现今滑动速率和万年尺度的地质学结果基本一致,说明现今滑动速率可以作为断裂地震风险性评估的有效输入数据;2）昆仑断裂东段具有向东逐渐减小的滑动速率,减少的速率可能主要被阿尼玛卿山的地壳增厚和断裂东段的顺时针旋转所吸收;3）昆仑断裂的西大滩-东大滩地震空区位于高应变区。     

240B型柴油机机破原因分析

针对某机务段２４０Ｂ型柴油机机破事故中的破损件连杆及连杆螺栓进行解剖,通过断口电镜分析、金相分析、化学成分及机械性能试验得出,机破是由于曲轴连杆颈碾瓦后,连杆大头端颈面出现裂纹导致疲劳断裂造成的。     

2022年门源6.9级地震的GPS形变特征

利用1999～2021年的GPS观测资料研究2022年门源6.9级地震震中附近区域的地壳形变特征。速度场在祁连山-海原地震带两侧呈现出明显的“南大北小”特性。发震断层速度剖面结果显示,断层两侧挤压速率为3.1 mm/a,走滑速率为3.9 mm/a,这与走滑为主的震源机制解一致。门源地震位于主应变率场和面膨胀率场高值区向低值区过渡的梯度带上,发生在最大剪应变率场和应变率第二张量不变量高值区边缘地区。同震库仑应力触发了大部分的余震,对冷龙岭断裂到海原断裂的地区有一定的应力加载作用。综合地壳形变特征和库仑应力等分析结果认为,冷龙岭断裂到海原断裂地区的地震危险性有所提高。     

恩施断裂中段第四纪活动特征与位移速率

对恩施断裂中段构造地貌、断裂剖面与洪积扇变形的分析表明,断裂在第四纪活动明显,以正倾滑兼右旋走滑为特征.根据洪积扇位错的水平距离、垂直高差以及形成时代,估算出断裂在中更新世晚期至晚更新世早、中期的右旋运动速率为0.43～0.5 mm/a,垂直运动速率0.07～0.17 mm/a.     

Surface morphology of soil cracks in Yuanmou Dry-hot Valley Region, Southwest China

Surface morphology of soil cracks is one of the important factors influencing the water evaporation rate in cracked soil in Yuanmou Dry-hot Valley Region, Southwest China. Quantitative study of the complicated surface morphology of soil cracks is a prerequisite for further studies of soil-cracking mechanisms. The present paper establishes a quantitative indicator system by application of concepts and methods originating from Fractal Geometry and Network Analysis. These indicators can effectively express the complicated features of soilcrack network structure. Furthermore, a series of values related to soil-crack morphology was obtained by image processing on field photos of soil-crack quads, and gradation criteria for the degree of development of soil cracks were determined. Finally, the changes in values of the morphological indicators under different degrees of development were analyzed in detail. Our results indicate that （1） the degree of development of soil cracks can be divided into five grades, i.e., feeble development, slight development, medium development, intensive development and extremely intensive development; （2） the values of the indicators change predictably with increasing degree of development of soil cracks. The area density （Dc） increases, and both the area-weighted mean ratio of crack area to perimeter （AWMARP）, which reflects the intensity of cracking, and the index r, which is related to the connectivity of a soil crack, grow uniformly （albeit with different forms）. AWMRAP increases at a geometric rate while r shows logarithmmic growth, indicating a gradual increase in the connectivity of a soil crack. Nevertheless, the areaweighted mean of soil-crack fractal dimension （AWMFRAC） shows a decreasing trend, indicating a gradual decline in the complexity of cracks as area density increases.     

Finite water depth effect on wave-body problems solved by Rankine source method

Finite water depth effect for wave-body problems are studied by continuous Rankine source method and non- desingularized technique. Free surface and seabed surface profiles are represented by continuous panels rather than a discretization by isolated points. These panels are positioned exactly on the fluid boundary surfaces and therefore no desingularization technique is required. Space increment method is applied for both free surface source and seabed source arrangements to reduce computational cost and improve numerical efficiency. Fourth order Runge-Kutta iteration scheme is adopted on the free surface updating at every time step. The finite water depth effect is studied quantitatively for a series of cylinders with different B/T ratios. The accuracy and efficiency of the proposed model are validated by comparison with published numerical results and experimental data. Numerical results show that hydrodynamic coefficients vary for cylinder bodies with different ratios of B/T. For certain set of B/T ratios the effect of finite water depth increases quickly with the increase of motion frequency and becomes stable when frequency is relatively large. It also shows that water depths have larger hydrodynamic effects on cylinder with larger breadth to draft ratios. Both the heave added mass and damping coefficients increase across the frequency range with the water depths decrease for forced heave motion. The water depths have smaller effects on sway motion response than on heave motion response.     

Failure mechanisms of post-earthquake bedrock landslides in response to rainfall infiltration

Among the triggering factors of post-earthquake bedrock landslides,rainfall plays an important role.However,with slope variation,the mechanism of its effects on the failure of rock landslides is not clear.Here,from the viewpoint of fracture mechanics,and based on post-earthquake conditions,the mechanisms of crack propagation,water infiltration and development of the sliding surface were investigated.Then,according to the upper boundary theorem,the effects of water infiltrated into fractures on the stability of rock slopes were analyzed quantitatively.Finally,an example is presented to verify the theory.The results show that the propagation and coalescence of cracks and the lubrication of incipient sliding surfaces are the main causes of the failure of post-earthquake rock landslides in response to rainfall.     

油气田裂缝密度定量研究方法

本文首先简要评述了目前研究裂缝方法的优缺点。用实例介绍了裂缝密度的定量估计方法,这种方法能将岩芯资料和地震资料有机地结合起来。应用这种方法不但能预测区域性裂缝及油气分布规律,而且能回答所获得成果的正确程度。     

Influence of excavation schemes on slope stability: A DEM

Slope failure due to improper excavation is one of common engineering disasters in China. To explore the failure mechanism of soil slope induced by toe excavation, especially to investigate the influence of excavation unloading path and rate on slope stability, a numerical slope model was built via particle flow code PFC2 D. The development of crack and strain during excavation were obtained and used to evaluate the deformation characteristics.Furthermore, excavation types representing different unloading paths and rates were compared in terms of crack number and strain level. Results indicate that crack number and strain level induced by horizontal column excavation are much greater than those of vertical column excavation and oblique excavation.The crack number and strain level increase with excavation unloading rate. Besides, the feasibility of taking the average strain of slope surface and the average value of maximum strain along monitoring lines to represent the global deformation characteristics were discussed. This study can provide a theoretical guidance for slope monitoring and preliminary optimal selection of excavation scheme in the design and construction of slope engineering.     

青海德尔尼铜(钴)矿床矿石矿物特征及其地质意义

青海德尔尼铜(钴)矿床赋存于东昆仑阿尼玛卿蛇绿岩套中部,岩石类型主要有蛇纹石化的方辉橄榄岩、纯橄榄岩和二辉橄榄岩,矿石类型主要为块状、条带状含铜黄铁矿矿石,矿床成因存在多种认识。通过野外详细观察、室内显微镜下矿石矿物特征鉴定以及电子探针分析,确定德尔尼铜(钴)矿床的矿石矿物主要为黄铁矿,其次为磁铁矿、磁黄铁矿、黄铜矿、闪锌矿和方铅矿等,矿石结构以半自形粒状结构为主;钴元素在早期黄铁矿中比较富集,晚期黄铁矿中较贫,w(Co)/w(Ni)值指示黄铁矿与巴西Sossego铁氧化物-铜-金矿一致;早期黄铁矿、黄铜矿、闪锌矿的微量元素质量比值指示矿床成矿温度为200℃~300℃,属于中温环境,进一步证明了该矿床不是岩浆型矿床,属于海底喷流-沉积成因。矿床成矿过程可划分为4个阶段:海底喷流-沉积阶段、构造变形阶段、热液阶段和表生氧化阶段,其中前两个阶段为铜、钴、锌的主要成矿期。     

A method for surface roughness parameter estimation in passive microwave remote sensing

Surface roughness parameter is an important factor and obstacle for retrieving soil moisture in passive microwave remote sensing.Two statistical parameters,root mean square (RMS) height (s) and correlation length (l),are designed for describing the roughness of a randomly rough surface.The roughness parameter measured by traditional way is independence of frequency,soil moisture and soil heterogeneity and just the ″geometric″ roughness of random surface.This ″geometric″ roughness can not fully explain the scattered thermal radiation by the earth's surface.The relationship between ″geometric″ roughness and integrated roughness (contain both ″geometric″ roughness and ″dielectric″ roughness) is linked by empirical coefficient.In view of this problem,this paper presents a method for estimating integrated surface roughness from radiometer sampling data at different frequencies,which mainly based on the flourier relationship between power spectral density distribution and spatial autocorrelation function.We can obtain integrated surface roughness at different frequencies by this method.Besides "geometric" roughness,this integrated surface roughness not only contains "dielectric" roughness but also includes frequency dependence.Combined with Q/H model the polarization coupling coefficient can also be obtained for both H and V polarization.Meanwhile,the simulated numerical results show that radiometer with a sensitivity of 0.1 K can distinguish the different surface roughness and the change of roughness with frequency for the same rough surface.This confirms the feasibility of radiometer sampling method for estimating the surface roughness theoretically.This method overcomes the problem of ″dielectric″ roughness measurement to some extent and can achieve the integrated surface roughness within a microwave pixel which can serve soil moisture inversion better than the ″geometric″ roughness.     

Influence of non-dimensional strength parameters on the seismic stability of cracked slopes

Cracks in rock or soil slopes influence the stability and durability of the slopes. Seismic forces can trigger slope disasters, particularly in the cracked slopes. Considering the nonlinear characteristics of materials, the more generalized nonlinear failure criterion proposed by Baker is adopted. The influence of non-dimensional strength parameters on the stability of cracked slopes under earthquakes is performed using the upper bound limit analysis. The seismic displacement is calculated by adopting the logarithmic spiral failure surface according to the sliding rigid block model. Based on the existing studies, two methods for the stability analysis of cracked slopes under earthquakes are introduced: the pseudo-static method(with the factor of safety(Fs) as an evaluation index), and the displacement-based method(with the seismic displacement as an evaluation index). The pseudo-static method can only determine the instantaneous stability state of the cracked slope, yet the displacement-based methodreflects the stability variation of cracked slopes during earthquakes. The results indicate that the nondimensional strength parameters affect the factor of safety and seismic displacement of slopes significantly. The non-dimensional strength parameter(n) controlling the curvature of strength function shapes on the slope stability is affected by other parameters. Owing to cracks, the effect of non-dimensional strength parameters on seismic displacement becomes more significant.     

基于GPT2w模型计算中国地区对流层加权平均温度的精度分析

以2015年GGOS Atmosphere格网产品和探空站资料为参考值,评价GPT2w模型在中国地区计算对流层加权平均温度Tm的精度和适用性。结果表明：1）在中国地区,1°分辨率的GPT2w模型精度和稳定性优于5°分辨率,且GPT2w模型表现出显著的系统性误差;2）Tm的bias和RMS误差均具有明显的时空变化特性,季节变化表现为春冬季较大、夏季较小,空间变化上RMS误差表现为随纬度增加而变大;3）受地形起伏和Tm日周期变化影响,Tm在中国西部和东北地区误差较大。
     

Fluid Flow Past a Circular Cylinder with Tandem Rod and Staggered Rod at Low Reynolds Number

The flow past a primary cylinder with one tandem control rod and one staggered control rod is simulated in this paper through solving the Navier-Stokes equations.Two examples are simulated to validate the model,and the results matched well with those of previous researches.The Reynolds number based on the diameter of the primary cylinder is 500.The diameter ratio between the control rod and the primary cylinder(d/D) is 0.25.It was found that the effect of the combination of one upstream tandem control rod and one staggered control rod on the hydrodynamics of the primary cylinder is a linear superposition of the effect of a corresponding single control rod,and the effect of the upstream tandem control rod is dominant at larger spacing ratios such as G/D = 2.For the combination of a downstream tandem control rod and a staggered control rod,the effect of the control rods is different from that of the corresponding single control rod in the region of 0.2G/D0.5 30?α120? and 0.9G/D1.4 30?α50?,where the additional effect is obvious.In this case,the effect of the downstream tandem control rod is dominant at small spacing ratios(such as G/D = 0.1).At moderate spacing ratios such as G/D = 0.4,the effects of the tandem control rod and the staggered control rod are comparable in both cases.