冻融循环对土体强度变形参数的影响          下载免费PDF全文

张渭军 《探矿工程》2020,47(6):86-91

在寒区工程建设中，冻融循环会引起土强度和变形特性发生改变。为了研究多次冻融循环后土的强度和变形参数的变化量，本文以冻融和非冻融的粉质粘土饱和试样为研究对象，通过固结排水三轴剪切试验、三轴等向压缩试验和弹性模量试验，比较了冻融循环对土样强度参数和变形参数的影响。试验结果显示：冻融和非冻融试样的应力—应变关系曲线均呈应变硬化型，对于原状试样冻融作用破坏了其结构性；冻融作用导致土体强度的降低，主要体现在粘聚力的降低，约降低了55.6%；冻融循环对变形参数有明显的影响，其中最明显的是弹性模量的降低，降低了31.2%。该研究结论可为工程冻害处理提供参考，也可为相关研究的数值计算提供试验参数。  相似文献   

沁水盆地南部长治区块煤层气田的地应力特征     

戴朝霞  孙蓓蕾  曾凡桂 《现代地质》2020,34(2):266-272

煤层气的生成、运移及富集等都与地应力的特征有直接的关系,掌握煤储层的应力特征对煤层气田的勘探和开发具有重要意义。基于沁水盆地南部长治区块煤层气开发区18口煤层气井的测井数据,利用带有残余构造应力的Anderson模型,分析垂向应力、最小及最大水平地应力的分布规律。结果表明:垂向应力基本上呈东西走向对称分布,东西部的应力大,中部应力小,数值在15.2~16.5 MPa之间;最小水平主应力自西向东呈现高→低→高→低的分布特点,数值在10.2~19.3 MPa之间;最大水平主应力也是自西向东呈现高→低→高→低的分布,数值在13.0~34.2 MPa之间。研究区东部所受埋深影响大于所受构造影响,而西部受到的构造影响大于其所受的埋深影响。研究区地应力分布规律与煤层气井的产气量存在高度相关性,研究成果可以为煤层气的勘探、开发和安全生产等方面提供参考。  相似文献   

Enhancement of backtracking search algorithm for identifying soil parameters     

Yin-Fu Jin  Zhen-Yu Yin 《国际地质力学数值与分析法杂志》2020,44(9):1239-1261

In this paper, an enhanced backtracking search algorithm (so-called MBSA-LS) for parameter identification is proposed with two modifications: (a) modifying the mutation of original backtracking search algorithm (BSA) considering the contribution of current best individual for accelerating convergence speed and (b) novelly incorporating an efficient differential evolution (DE) as local search for improving the quality of population. The proposed MBSA-LS is first validated with better performance than the original BSA and some other typical state-of-the-art optimization algorithms on a benchmark of soil parameter identification in terms of effectiveness, efficiency, and robustness. Then, the efficiency of the MBSA-LS is further illustrated by two representative cases: identifying soil parameters from both laboratory tests and field measurements. All comparisons demonstrate that the proposed MBSA-LS algorithm can give accurate results in a short time. Finally, to conveniently solve the problems of parameter identification, a practical tool ErosOpt for parameter identification is developed by integrating the proposed MBSA-LS and some other efficient algorithms for readers to conduct the parameter identification using optimisation algorithms.  相似文献   

安徽庐枞盆地泥河玢岩型铁矿床地质-原生晕地球化学找矿模型   总被引：1，自引：1，他引：0  

张赞赞  张舒  吴明安  写熹  吕博  魏国辉 《矿床地质》2020,39(2):305-325

开展长江中下游地区玢岩型铁矿床轴向原生晕地球化学分析及建模,可弥补地球物理勘探结果的多解性及探测精度的局限性,对定位和评价深部盲矿体具有至关重要的作用。文章在以往研究的基础上,开展庐枞盆地泥河玢岩型铁矿床钻孔原生晕的研究工作,采用多元统计分析方法,查明了主要成矿指示元素在不同地质体中的富集和亏损,确定了磁铁矿、硫铁矿和硬石膏矿体的矿中、近矿及远矿指示元素组合,结合矿床成因模型,建立了泥河玢岩型铁矿床地质-原生晕地球化学找矿模型,通过罗河和小包庄玢岩型铁矿床的佐证,认为该模型可以应用于长江中下游成矿带玢岩型铁矿床的勘探工作中。  相似文献   

断层附近地应力扰动带宽度及其影响因素   总被引：3，自引：3，他引：0  

翁剑桥  曾联波  吕文雅  刘奇  祖克威 《地质力学学报》2020,26(1):39-47

在建立正断层模型的基础上，利用三维有限元数值模拟方法研究了断层附近地层中的地应力变化规律。其结果表明，由于断层活动，在断层附近普遍发育应力扰动带；在应力扰动带范围内，地应力方向和大小发生明显的变化，断层中部附近应力值普遍较低，而断层端部的应力值通常异常增大。应力扰动带的分布范围主要受断层规模的控制，与断裂带的岩石力学性质、断层走向、断层面形态和边界应力条件等因素也密切相关。随断层长度和断距逐步增大，应力扰动带的宽度相应增加。断裂带的岩石越破碎，其岩石弹性模量越低，断层对地应力的影响宽度越大。断层走向与区域最大水平主应力方向越接近垂直、断距与断层长度的比值越大，区域内的差应力越大，则扰动带宽度与断层规模的比值也越大。选择渤海湾盆地BZ-X油田进行验证，在建立油田实际三维地质模型基础上，根据边界应力条件，利用三维有限元方法对沙河街组二段的地应力分布进行了数值模拟计算。根据断层周围的地应力变化，确定了应力扰动带的分布范围，断层附近应力扰动带宽度的分布规律与正断层模型分析结果相一致。   相似文献   

水岩作用下泥质板岩软化非线性机制研究     

黄智刚  左清军  吴立  陈福榜  胡圣松  朱盛 《岩土力学》2020,41(9):2931-2942

水岩作用下泥质板岩表现出明显的软化特征。通过单轴压缩试验分析了泥质板岩软化过程中单轴压缩强度、弹性模量和泊松比与吸水时间之间的关系；借助核磁共振试验研究了水岩作用下泥质板岩软化过程中孔隙的产生、扩展和贯通规律，分析了泥质板岩软化过程中孔隙度与吸水时间之间的关系；采用电镜扫描试验分析了水岩作用下泥质板岩软化过程中微观结构的演变规律，基于分形理论研究了不同浸泡时间下泥质板岩分形维数的变化规律；运用非线性动力学理论，选取微观结构孔隙形状分维值、孔隙度、单轴抗压强度、弹性模量作为描述泥质板岩与水溶液相互作用系统的变量，建立了水岩作用下泥质板岩的软化模型，结合试验数据验证了模型的适用性。结果表明：泥质板岩单轴抗压强度、弹性模量随吸水时间增大而减小，呈负线性相关，而泊松比与吸水时间之间的关系不明显；在浸泡初期，水岩作用强烈，泥质板岩内部微孔隙会发生扩展贯通进而形成更大尺寸的孔隙，孔隙度在浸泡初期增长较快；随着浸泡时间的延长，水岩作用减弱，孔隙度增长速率趋缓；随着吸水时间的推移，泥质板岩内部孔隙相互连通，进而形成复杂网状结构的大孔，泥质板岩分形维数呈对数增长，最终趋于稳定；采用非线性模型计算的结果与试验数据较接近，说明泥质板岩的软化过程具有明显的非线性动力学特征，利用非线性动力学模型可以较好地表征水岩作用下泥质板岩的软化规律。研究成果可为软岩?水相互作用理论研究提供参考。  相似文献   

保国寺大雄宝殿抗震性能分析及加固对策探讨     

陆函  张蓓蕾  彭骁  符映红 《防灾减灾学报》2020,(1):6-12

通过对保国寺大殿结构振动特性现场测试,得到大殿时程分析和频谱分析,结合建筑结构、材料以及使用现状,建立有限元分析模型,并用模态分析验证该建模的真实性。结合宁波地区场地条件,通过该有限元模型在不同烈度地震作用下的反应,评定地震破坏程度。根据现场调查及模型分析结果给出保国寺大殿维护与加固建议。  相似文献   

采坑型滑坡地质力学模式研究--以贵州省福泉滑坡为例     

王小明  史文兵  梁风  马文鹏 《防灾减灾学报》2020,(1):13-19

福泉滑坡具有顺倾上硬下软的结构特征,采用颗粒流离散元模拟采动滑坡的变形破坏全过程,研究福泉滑坡在露天开采条件下变形破坏的地质力学模式。基于颗粒流离散元程序,引入平行粘结模型,通过参数标定确定细观参数与宏观力学性质的关系,据此建立斜坡模型,模拟斜坡采动过程中的变形破坏全过程,确定该类采动滑坡形成的地质力学模式;研究滑坡滑动过程中的速度和能量变化以及堆积特征。研究表明:斜坡采动过程中,潜在滑面顺层滑移,后缘拉裂,裂纹从下往上向软弱面拓展,前缘坡脚处岩体形成锁固段,斜坡出现由前缘至后缘缘递减的蠕滑变形,随着斜坡进一步采动,锁固段发生剪切破坏,前缘坡体启动,中后部裂缝贯通—滑移,斜坡整体失稳破坏,形成牵引式采动滑坡,该类滑坡形成的地质力学模式可分为:滑移—拉裂—剪断3个阶段;对滑坡运动过程的模拟可知,采坑积水是小坝组受灾的关键转化因子。  相似文献   

New formulae for capacity energy-based assessment of liquefaction triggering     

Yasaman Jafariavval 《Marine Georesources & Geotechnology》2020,38(2):214-222

Abstract

Liquefaction of loose saturated soil deposits is a hazardous type of ground failure occurring under earthquake excitations. Therefore, an accurate estimation of liquefaction potential is extremely important in geotechnical engineering. In the current study, a new model is proposed which estimates the level of strain energy needed for liquefaction initiation. A compiled database containing cyclic tests gathered from previously published works was used to develop new models to predict liquefaction potential. M5′ algorithm was used to find the best correlation between parameters. It was shown that not only the derived formulas are acceptably accurate but also they feature a very simple structure in comparison with available formulas in the literature. The proposed equations are accurate, physically sound and uncomplicated. Furthermore, safety factors were given for different levels of risk, which can be useful for engineering practice. In addition, the influence of different predictors on the liquefaction potential was evaluated and also the significance of input variables was assessed via sensitivity analysis. Finally, a new model was introduced for preliminary estimation of liquefaction potential.  相似文献   

Unified numerical study of shallow foundation on structured soft clay under unconsolidated and consolidated-undrained loadings     

Santosh Kumar Yadav  Guan-lin Ye  Usama Khalid 《Marine Georesources & Geotechnology》2020,38(4):400-416

Abstract

Based on a new elasto-plastic constitutive model, this paper presents a soil–water coupled numerical prediction of the bearing capacity for shallow foundation constructed on Ballina soft clay for unconsolidated undrained (UU) and consolidated undrained (CU) conditions. This elasto-plastic constitutive Shanghai model has an advantage of describing the mechanical behaviour of over-consolidated and structured soil under different loading and drainage conditions, by using one set of material parameter. In this paper, the Shanghai model used for both UU and CU conditions has the same initial parameters obtained from laboratory test results. The loading conditions and consolidation stages vary based on construction details. The predicted bearing pressure-settlement responses for UU and CU, approves the field observation. The phenomenon of gaining the bearing capacity due to consolidation is captured and explained by the use of soil–water coupled numerical analysis with a new elasto-plastic model. The stress strain behaviour, stress paths and the decay of the structure of elements at different depths presented in this study, reveal the mechanism for the difference between UU and CU conditions to understand the foundation behaviour. Effect of the initial degree of soil structure on the bearing capacity is also addressed. Overall, this approach provides the integrated solution for the shallow foundation design problems under short and long-term loadings.  相似文献