拉剪应力状态下岩体裂隙扩展的断裂力学机制及物理模型试验   总被引：3，自引：1，他引：2  

黄达  金华辉  黄润秋 《岩土力学》2011,32(4):997-1002

开挖卸荷岩体裂隙面通常处于拉剪应力状态。在裂隙应力和变形状态分析的基础上,采用线弹性断裂力学理论和物理模型试验研究了拉剪应力状态下裂隙扩展的力学机制。岩体裂隙在拉剪应力状态下沿裂隙面间的滑动抗剪摩擦力消失,裂隙起裂沿Ⅰ型张拉裂隙断裂韧度KⅠ最小的方向起裂,并最终发展与卸荷拉应力方向垂直;拉剪应力状态下岩体的总位移方向平行于拉应力方向,通过合理的位移假设,基于能量及线弹性断裂力学理论,求解了拉剪应力状态下分支裂隙扩展过程中尖端的动态应力强度因子和扩展长度判据;通过拉剪应力状态下单裂隙扩展物理模型试验验证了理论推导的正确性。  相似文献   

护坡工程中保温板防冰冻设计   总被引：1，自引：0，他引：1  

孙晓明  杜少敏  孔达 《岩土力学》2008,29(Z1):399-402

寒冷地区的护坡工程经常会由于土基冻胀而产生隆起、或是在冰弯矩作用下产生推坡的现象,从而使护坡工程在风浪淘刷下产生破坏。利用聚苯乙烯保温板阻隔大气负温对土基的侵袭,提高土基地温,从而减小冻深,削弱冻胀,避免护坡遭受破坏。经过对聚苯乙烯保温板的物理力学性质及冻融特性的试验分析,指出重度、含水率、导热系数、抗压强度、冻融循环次数对聚苯乙烯保温板保温效果的影响。提出护坡工程的抗冰冻设计方法,对有关问题的进一步研究和护坡抗冰冻设计具有参考意义。  相似文献   

基于振动台试验的抗滑桩加固斜坡桥基研究     

雷达  蒋关鲁  孙圣杰  戚志慧  李安洪 《岩土力学》2019,40(1):127-134

基于工程实践中研究斜坡桥基抗震加固的需要,设计并完成前后排抗滑桩加固滑坡桥基的振动台模型试验。通过加载不同频率、加速度峰值的正弦波,分析振动时桥墩基桩、抗滑桩的受力变形规律,探讨滑坡破坏发展过程和动力响应特性。试验结果显示,前后排抗滑桩均应与桥基保持合理距离,有利于桥墩基础的受力变形;受桥梁上部结构的动力影响,桥墩基桩应变沿桩深衰减,衰减速度与土体抗力相关;当后排抗滑桩开裂后,桩身应变骤降,桩后土压力出现卸荷效应,但抗滑桩仍有潜在的承载能力,同时滑坡从稳定性最差的区域开始破坏,逐渐产生频段耦合效应,在后排抗滑桩达到承载极限前,频段耦合效应显著,达到承载极限后,卸荷效应显著。  相似文献   

四川盆地火成岩发育区地震波传播规律及成像方法     

陈康  冉崎  韩嵩  龙隆  何青林  陈骁  彭达 《物探化探计算技术》2019,(3):285-292

多口钻井证实四川盆地西南部地区发育火成岩,火成岩主要分布在龙潭组内部,火成岩发育区地震资料存在岩下地震同相轴连续性较差、反射能量弱等现象,火成岩下屏蔽效应机理不清、岩下地震反射井震标定能量相位差异大,明确火成岩区地震波传播规律是地震资料采集、处理解释的基础。这里从地震波反射透射基本原理出发,阐述了火成岩地层的反射透射能量及对下伏地层的屏蔽机理,利用波动方程地震模拟及偏移,分析了不同火成岩分布模型对下伏地层地震信号的屏蔽作用,采用低频补偿、逆时偏移等方法改善岩下成像质量。结果表明:火成岩发育会不同程度导致下伏地层地震透射能量的衰减,纵向多套火层岩发育时,下伏地层屏蔽效应明显,发育区地震表现为类似生物礁的外形隆起、内部杂乱反射特征,下部多次反射较多且能量较强。通过低频优势频带保护处理、利用全波场波动方程偏移成像等方式可以改善岩下地震成像质量。  相似文献   

High‐Precision Measurement of Stable Cr Isotopes in Geological Reference Materials by a Double‐Spike TIMS Method     

Chun‐Yang Liu  Li‐Juan Xu  Chun‐Tao Liu  Jia Liu  Li‐Ping Qin  Zi‐Da Zhang  Sheng‐Ao Liu  Shu‐Guang Li 《Geostandards and Geoanalytical Research》2019,43(4):647-661

Chromium (Cr) isotopes have been widely used in various fields of Earth and planetary sciences. However, high‐precision measurements of Cr stable isotope ratios are still challenged by difficulties in purifying Cr and organic matter interference from resin using double‐spike thermal ionisation mass spectrometry. In this study, an improved and easily operated two‐column chemical separation procedure using AG50W‐X12 (200–400 mesh) resin is introduced. This resin has a higher cross‐linking density than AG50W‐X8, and this higher density generates better separation efficiency and higher saturation. Organic matter from the resin is a common cause of inhibition of the emission of Cr during analysis by TIMS. Here, perchloric and nitric acids were utilised to eliminate organic matter interference. The Cr isotope ratios of samples with lower Cr contents could be measured precisely by TIMS. The long‐term intermediate measurement precision of δ^53/52Cr_{NIST SRM 979} for BHVO‐2 is better than ± 0.031‰ (2s) over one year. Replicated digestions and measurements of geological reference materials (OKUM, MUH‐1, JP‐1, BHVO‐1, BHVO‐2, AGV‐2 and GSP‐2) yield δ^53/52Cr_{NIST SRM 979} results ranging from ?0.129‰ to ?0.032‰. The Cr isotope ratios of geological reference materials are consistent with the δ^53/52Cr_{NIST SRM 979} values reported by previous studies, and the measurement uncertainty (± 0.031‰, 2s) is significantly improved.  相似文献   

The Early Jurassic magmatism in northern Guangdong Province,southeastern China: Constraints from SHRIMP zircon U-Pb dating of Xialan complex     

XinQi Yu  YongJun Di  GanGuo Wu  Da Zhang  Yong Zheng  YanPei Dai 《中国科学D辑(英文版)》2009,52(4):471-483

This paper reports SHRIMP zircon U-Pb ages of 196±2 Ma for granite, and 195±1 Ma for gabbro from the Xialan complex in the Meizhou area, northern Guangdong Province. These results shed new light on the calm stage of magmatic activity in southeastern China during 200-180 Ma, and revealed that the back-arc extension induced by the subduction of the western Pacific plate may have begun at 195 Ma at least. Field observation on the fresh outcrops allows us to recognize some features formed by magma mixing. A par...  相似文献   

强干扰地区CSAMT数据信息熵与有理函数滤波的处理方法   总被引：1，自引：1，他引：0  

雷达  赵国泽  张忠杰  赵福刚  王书民  王刚 《地球物理学进展》2010,25(6)

CSAMT在强干扰地区采集的数据,尽管在测量时采取了多种多样压制干扰的措施,但强干扰余音仍是影响CSAMT数据质量的主要因素.如何在数据处理时进一步削减干扰,是提高CSAMT反演数据质量与反演解释效果的重要一环.本文主要针对矿山强电磁干扰的特点,从美国Zonge公司的GDP仪器为选频测量数据出发,提出了一种基于信息熵去噪与有理函数滤波相结合的数据处理方法.首先采用CSAMT数据误差熵处理,逐次剔除大的干扰数据,直到得到满意的信息熵,从而提取实际的有用信号数据.然后对经过信息熵处理后的测深曲线,进行有理函数滤波处理.再次剔除干扰大的跳点,得到较圆滑的测线纯异常数据.通过数字模型验证,其方法正确,精度较平均处理结果高.经在强干扰矿山实测数据处理表明,该处理方法压制干扰效果明显,可以达到提高信噪比,改善实测数据质量的目的.  相似文献   

Possible correlation between miocene global climatic changes and magnetic proxies,using neuro fuzzy logic analysis in a stratigraphic well at the Llanos foreland basin,Colombia     

Ana Da Silva  Vincenzo Costanzo-Álvarez  Nuri Hurtado  Milagrosa Aldana  Germán Bayona  Oswaldo Guzmán  Diego López-Rodríguez 《Studia Geophysica et Geodaetica》2010,54(4):607-631

In this work we have assessed the hybrid algorithm of NeuroFuzzy logic (NFL), to establish a correlation between global climatic changes (benthic foraminiferal δ¹⁸O data), experimental S-ratio (factor characterizing stability of remanent magnetization) and magnetic susceptibility (κ). Magnetic proxies have been measured in 44 samples of the Colombian stratigraphic well Saltarín 1A (distal Llanos foreland basin). κ and Sratios were linked to global δ¹⁸O data assuming a constant accumulation rate for a 305 meters thick stratigraphic interval flanked by the two palynological age constrains available. This interval encompasses, from top to base, the bottom of the Guayabo formation, the León, and the upper unit of the Carbonera formations (lower to middle Miocene). The best inference is accomplished applying a Takagi-Sugeno-Kan (TSK) fuzzy model with four fuzzy rules and the δ¹⁸O, S-ratios and κ data used in a linear form to train the system. These results are interpreted as the outcome of a significant influence of global climatic changes upon magnetic proxies. A stronger correlation is perhaps prevented by the likely influence of local and regional tectonic events and climatic changes that could have affected the distal segment of the Colombian Llanos foreland basin during Miocene times. We argue that late diagenesis of primary magnetic minerals and the assumption of a constant accumulation rate might have a minor influence on these results.  相似文献   

Temporal and spatial distribution of virioplankton in large shallow freshwater lakes     

程凯  裴达  赵以军  邓凤霞  刘伟  赵进 《中国海洋湖沼学报》2010,28(4):868-873

Virioplankton dynamics at seven sample sites (from two freshwater lakes) with different trophic states were monitored over the period of a year. Water was sampled monthly from August 2004 to July 2005, and the abundances of viruses and bacteria were measured using direct epifluorescence microscopy counting. Results indicated that both natural and anthropogenic factors could influence the distribution of virioplankton. Temporally, viral abundance was significantly correlated to bacterial density and water temperature. Spatially, viral abundance was significantly correlated to trophic state. This in turn indicated that viral abundance was directly dependant on host abundance in eutrophic lakes, while trophic state and temperature could drive the distribution of virioplankton. The virus-bacteria ratio was significantly lower in less productive water-bodies. The result implied that the control of virioplankton on their hosts may change according to the host density.  相似文献   

土石比对碎石土强夯地基加固效果影响规律瑞利波检测分析     

黄达  金华辉 《岩土力学》2012,33(10):3067-3072

为了探讨土石比及大粒径块石对碎块石土强夯加固效果的影响规律,对3组不同土石比条件下碎块石土强夯地基的瑞利波检测数据进行了对比分析。夯后波速曲线具有明显的突变性,并随着土石比的减小其突变程度增强,突变段与大粒径块石有较好的对应性。波速增加比例曲线具有垂直分区特征,土石比对强夯加固区厚度影响较大。大块石对周边土体存在较强的扰动作用,夯后波速曲线往往表现为突然锐减,特别是当其位于夯后场地表层或较多大块石距离较近时表现更加明显。当大块石位于强加密区内时,加固深度随着大块石埋深增加而减小,且其埋深越靠近波速增加峰值点时加固深度越浅。研究成果对碎块石填土强夯地基的设计和施工具有参考价值。  相似文献