道路勘测设计实践环节批量量化考核方法

目前各高校在道路勘测设计实践环节多采用基于团队作业的考核方法,即小组打分法.受限于教学资源,教师利用该方法难以根据学生的个人能力给出公正客观的成绩.为避免片面、主观的考评现状,发挥团队作业的教学优势,提出了批量量化的考核方法,并详细介绍了其设计思路,以期在师生比偏小的现状下提高实践教学的质量、增加学生的积极性和参与度、...     

福建台风灾害特征及其防御对策研究

根据历史台风路径、强度和灾害实况等资料,对影响福建的台风灾害划分为较大、重大和特大3个等级,同时提出按照3个等级进行科学设防,从而提高防灾抗灾的主动性,减少盲目性。研究表明,(1)在1949~2005年的57 a里,福建共出现特大台风灾害40次,平均约3年出现2次;在所有台风移动路径中,直接登陆型台风的致灾风险最大,闽南-粤东地区是历史上我国大陆遭受特大台风灾害最频繁的地区,平均每年有1个西太平洋台风穿过巴士海峡后在闽南-粤东沿海登陆。(2)地形作用极易在迎风坡形成台风暴雨中心,戴云山脉东南侧的德化、安溪、南安和永春的台风暴雨平均雨量分别是崇武(沿海站)的3.1,2.8,2.7和2.7倍。(3)防台减灾是一个涉及全社会方方面面的科学-社会系统工程,只有政府组织领导,依靠行政手段,动员全社会防灾抗灾,才能把灾害减轻到最小程度。     

DEFORMATION OF THE BRITTLE-PLASTIC TRANSITION ZONE AT THE POST-SEISMIC RELAXATION PERIOD: A CASE STUDY OF THE RED RIVER FAULT

The transition from microscopic brittle deformation to microscopic plastic deformation is called brittle-plastic transition, which is considered as a key layer for determining the limit of lower continental crust seismicity. The depth and deformation mechanism of the brittle-plastic transition zone is controlled mainly by temperature. Besides, the strain rate and fluid pore pressure also affect the transition during the different deformation stages at the seismic cycle. In this paper, microstructure observation of catalcastic samples collected from the Red River Fault was carried out using optical polarized microscopy and scanning electron microscopy. The morphology, microstructures of deformation characteristics, mineral composition, water-rock reaction, pressure solution, exsolution, crack healing in the samples were systematically observed. The mineral components quantitative analyses were examined using the EDS. Water-rock reaction and pressure solution were systematically observed under SEM. The fabric of the main minerals in the samples was measured using electron backscattered diffraction(EBSD). Based on these analyses, the deformation mode was setup for the brittle-plastic transition zone of the fault during the post-seismic relaxation period. Both brittle deformation and plastic deformation were developed in the cataclastic samples. EBSD data shows that the c axial fabrics of quartz present low-temperature plastic deformation characteristics. The feldspar deformed as cataclastic rock, and the micro-fracture in feldspar was healed by static recrystallized quartz and calcite veins. The calcite vein underwent plastic deformation, which represents the post-seismic relaxation deformation. Based on the analysis of deformation mechanism of cataclastic samples in brittle-plastic transition zone of the Red River Fault, and combined with previous studies, we concluded that the brittle fracture and fracture healing is the main deformation mode at brittle-plastic transition zone in the post-seismic relaxation. High stress and high strain rate at post-seismic relaxation lead to brittle fracture of high-strength minerals such as feldspar in rocks. Plastic deformation occurs in low-strength minerals such as quartz and mica. Under the fluid condition, micro-fractures were healed by quartz and calcite. The minerals such as quartz and calcite in the fracture transformed from static recrystallization to dynamic recrystallization with stress gradually accumulating. With fracture healing and stress accumulation, the fault strength gradually increases which could accumulate energy for the next earthquake.     

青藏高原东北缘海原构造带马东山阶区深部电性结构特征及其构造意义

海原一六盘山构造带是青藏高原东北缘地区的一条重要边界,在海原断裂带和六盘山断裂带接触区形成了特殊的马东山挤压阶区,本文对跨过该挤压阶区一条密集测点大地电磁剖面数据进行了处理和二维反演,获得的深部电性结构图像揭示在马东山挤压阶区深部电性结构表现为在高阻背景下镶嵌多个向西南倾斜的低阻条带电阻率结构样式,并在深度约25 km汇聚到中下地壳低阻层内,共同组成"正花状"结构;海原一六盘山构造带西南侧到陇中盆地区间呈现高、低阻相互"楔合"的深部结构特征,而其东北侧的鄂尔多斯西缘带自地表到中下地壳为较完整的高阻块体.另外结合跨过海原断裂带中段和西秦岭造山带的大地电磁探测结果,对海原一六盘山构造带分段性及其两侧的陇中盆地和鄂尔多斯地块的接触关系进行了研究分析.大地电磁探测成果佐证了在海原断裂带中段为具有走滑特点的断裂,而其尾端与六盘山断裂带斜交区域的马东山地区发生了强烈的逆冲推覆与褶皱变形;活动构造研究发现沿海原断裂带所产生的左旋走滑位移被其尾端的马东山、六盘山以东西向的地壳缩短调节吸收,GPS观测表明青藏高原东北缘地区现今构造变形分布在海原一六盘山构造带以西上百公里的范围内,陇中盆地一海原一六盘山构造带和鄂尔多斯地块一线的深部电性结构图像也很好地解释了该区变形状态:海原一六盘山构造带带及西南盘的陇中盆地的中下地壳非常破碎,在青藏高原向北东方向的推挤下容易发生变形,而北东盘鄂尔多斯地块地壳结构完整,很难发生构造变形.对海原一六盘山构造带马东山阶区和龙门山构造带的深部电性结构及变形特征等进行了比较分析,发现该区有与2008年汶川地震相似的深部构造背景,应重视该区强震孕育环境的探测研究.     

精确测定地震计传递函数

提出联合阶跃标定与带精确电流测量的正弦波标定来确定地震计传递函数的方法。首先,使用阶跃标定确定地震计等效机械摆的自振周期和阻尼,得到地震计低频特性。随后,使用正弦波标定并引入电流测试技术,测定地震计全频段频率响应,幅频响应更加准确,同时可获得相频响应。最后,构建与地震计传递函数特征一致的结构来描述传递函数,采用最优化方法拟合求取地震计传递函数。该方法具有原理清楚、操作简单、易于实现、结果精确等优点,特别适用于地震计用户测试、地震计传递特性与厂方参数及各地震计间一致性和长期稳定性的验证,结果符合反馈型地震计传递函数特点。     

波浪作用下刚性框架浮体及其锚绳运动数值模拟精度分析

由小尺度刚性杆件构成的复杂结构近年来多用于海洋平台建设和海洋监测浮标制作以及海洋增养殖人工浮鱼礁的设计。采用有限单元法和集中质量点法建立波浪作用下刚性框架浮体及其锚绳运动数值模型,探讨空间单元划分、时间离散步长、数据保存格式对刚性框架浮体和柔性锚绳运动模拟精度的影响,分别给出此三者之间的匹配关系。研究结果表明:框架浮体的单元划分可依据是否出水给定,单元的划分比建议取0.05;锚绳的单元划分与其上端连接的浮体浮力有关,当锚绳的拉力主要由上端浮体浮力产生时锚绳单元的划分影响较小,当锚绳的拉力主要由波浪力产生时锚绳单元的划分比建议取0.02;空间单元划分与时间离散步长存在匹配关系,通过减小时间步长来追求数值模拟精度时必须同时考虑保存运动物理量截断误差的影响。     

台阶式变深水槽造波的解析研究

利用特征函数展开法对台阶式变深水槽中推板式造波机造波问题进行了研究,建立了相应速度势和波面的解析表达式。与高阶边界元方法(HOBEM)数值结果进行了对比,验证了本解析解的正确性。通过数值试验,研究了台阶对入射波的影响,同时分析了造波板所在位置(上部台阶)水深、水槽工作区(下部台阶)水深、造波板运动周期和造波板水平位置等因素对生成波浪高度的影响。由此选择合适的造波板所在位置及水深来得到所需要的波浪高度,进而根据需要生成波浪的周期和波幅来反演造波板的运动。     

The reflection of regular and irregular waves by a partially perforated caisson breakwater on a step bed

This study examines the reflection of regular and irregular waves from a partially perforated caisson breakwater located on a step bed. The step bed is treated as an idealized rubble mound foundation. Based on the linear potential theory, an analytical solution is developed to calculate the reflection coefficient of the structure subjected to regular waves. The matched eigenfunction expansion method is used for the solution. The regular wave method is also extended to irregular waves using a linear transfer function. The calculated results obtained for limiting cases are exactly the same as corresponding results given by the previous researchers. The present predictions also agree well with experimental data in the published literatures. Numerical experiments are conducted to examine the variations of the reflection coefficient versus its main effect factors, and some interesting results are presented.     

三维波动方程基准面校正方法的应用研究

波动方程基准面校正处理被认为是当地表高程变化剧烈、地表一致性假设又不成立的情况下对于常规高程基准面校正的必要替代. 在二维波动方程基准面校正方面,前人已经作了大量工作,并且在实际应用中获得了良好的效果,应该将其进一步推广到三维. 本文采用三维频率空间域有限差分波场延拓算子以“逐步－累加”的方式实现了三维波动方程基准面校正,并对实际数据进行了处理. 对于西部某三维数据的实际计算结果表明,相对于传统的模型法高程静校正,波动方程基准面校正更合理地实现了基准面校正,有助于提高后续的速度分析精度和成像质量.     

配置法在卫星轨道积分中的应用

介绍了配置法的基本原理和计算方法,探讨了其在卫星轨道积分中的应用。分析了不同的积分步长与方法阶数对积分精度的影响,并确定了适宜的积分步长与方法阶数(与Bernese软件的缺省值一致)。此外,通过与用传统数值积分方法设计的联合积分器计算结果进行比较,得出了配置法的一些优点:可以取较大的积分步长;配置法直接给出的是各个积分区间的多项式系数,用户无需进行内插和拟合即可方便地得到任意时刻的卫星位置和速度。