A cavity expansion–based solution for interpretation of CPTu data in soils under partially drained conditions     

Pin-Qiang Mo  Xin-Wei Gao  Wenbo Yang  Hai-Sui Yu 《国际地质力学数值与分析法杂志》2020,44(7):1053-1076

A cavity expansion–based solution is proposed in this paper for the interpretation of CPTu data under a partially drained condition. Variations of the normalized cone tip resistance, cone factor, and undrained-drained resistance ratio are examined with different initial specific volume and overconsolidation ratio, based on the exact solutions of both undrained and drained cavity expansion in CASM, which is a unified state parameter model for clay and sand. A drainage index is proposed to represent the partially drained condition, and the critical state after expansion and stress paths of cavity expansion are therefore predicted by estimating a virtual plastic region and assuming a drainage-index–based mapping technique. The stress paths and distributions of stresses and specific volume are investigated for different values of drainage index, which are also related to the penetration velocity with comparisons of experimental data and numerical results. The subsequent consolidation after penetration is thus predicted with the assumption of constant deviatoric stress during dissipation of the excess pore pressure. Both spherical and cylindrical consolidations are compared for dissipation around the cone tip and the probe shaft, respectively. The effects of overconsolidation ratio on the stress paths and the distributions of excess pore pressure and specific volume are then thoroughly investigated. The proposed solution and the findings would contribute to the interpretation of CPTu tests under a random drained condition, as well as the analysis of pile installation and the subsequent consolidation.  相似文献   

基于一阶弹性波方程的能量互相关成像条件          下载免费PDF全文

张晓语  杜启振  张树奎  公绪飞 《地球物理学报》2019,62(1):289-297

基于地震波场能量构建的能量互相关成像条件,具有易实现、物理意义明确及背向散射压制效果明显等优势.但是,目前构建的能量互相关成像条件仅适用于二阶弹性波方程,难以直接应用于一阶弹性波方程.为此,本文针对一阶弹性波方程,基于能量守恒定理及能量密度,构建以速度-应力为参数的能量范数以表征弹性波场能量,将速度-应力能量范数拓展为能量内积以提取弹性波场反射能量.震源端与检波端的基矢量正方向保持一致的基础上,构建得到可有效压制背向散射的弹性波能量成像条件.数值模拟结果表明:该成像条件可以得到背向散射压制、振幅有效保持的能量成像结果.  相似文献   

SH波水平入射穿越垂直断层隧道动力响应分析     

杜修力  苏驰翔  黄景琦  王媛  赵密  欧阳文龙 《震灾防御技术》2019,14(2):269-280

结合黏弹性人工边界的时域波动输入方法和显式有限元法，设计了含垂直断层三维场地的SH波输入方法。基于建立的输入方法，研究了垂直断层对隧道地震响应的影响，并通过自由场算例验证了该方法具有较好精度。数值模拟结果表明:对于断层迎波侧的隧道结构，断层会对其地震动响应产生显著的放大作用，对于断层逆波侧的隧道结构，断层会对其产生隔离地震动的作用；相对周围围岩，断层介质的剪切波速越小，其产生的放大效应和隔震效果也会越显著；断层宽度越小，其对隧道地震动响应的影响范围也就越小，但是断层宽度的变化对于断层两侧隧道的地震动响应的影响并不明显。  相似文献   

黔南坳陷下石炭统打屋坝组页岩气地质条件及勘探前景     

苑坤  方欣欣  王婷  陈榕  林拓  覃英伦  卢树藩  罗香建 《地质论评》2020,66(S1):115-116

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基于二次场的可控源电磁法三维有限元-无限元数值模拟   总被引：2，自引：2，他引：0       下载免费PDF全文

张林成  汤井田  任政勇  肖晓 《地球物理学报》2017,60(9):3655-3666

本文提出了一种新的混合有限元-无限元三维可控源电磁法(CSEM)问题快速高精度正演模拟算法.首先从电场双旋度方程出发,推导了水平电偶极子源的二次场边值问题,采用无限元代替截断边界条件和有限元离散内部计算区域的新策略,达到减小计算区域的目的,基于并行直接求解技术,实现多源CSEM问题的快速精确求解.其次,通过层状解析模型测试,一方面验证了新算法的正确性,另一方面通过与其他三种已知CSEM问题求解策略进行对比,表明了本文提出的基于二次场有限元-无限元算法具有离散区域小、求解速度快和计算精度高等优点.最后,通过3D模型计算,清晰直观地模拟了场源阴影效应,为野外数据的处理与解释提供指导.  相似文献   

Efficient DEM‐based overland flow routing using integrated recursive algorithms          下载免费PDF全文

Pin‐Chun Huang  Kwan Tun Lee 《水文研究》2017,31(5):1007-1017

Two primary concerns in performing watershed overland flow routing are the numerical instability and computational efficiency. The stability of executing an explicit scheme has to be maintained by observing the Courant–Friedrich–Lewy criterion, which is adopted to confirm that the numerical marching speed is larger than the wave celerity. Moreover, there is another criterion of time step devised in previous studies to avoid back‐and‐forth refluxing between adjacent grids. The situation of refluxing usually occurs on flat regions. In light of this, the selection of a small time increment to honor both restrictions simultaneously is believed to decrease the computational efficiency in performing overland flow routing. This study aims at creating a robust algorithm to relax both restrictions. The proposed algorithm was first implemented on a one‐dimensional overland plane to evaluate the accuracy of the numerical result by comparing it with an analytical solution. Then, the algorithm was further applied to a watershed for 2D runoff simulations. The results show that the proposed integrated algorithm can provide an accurate runoff simulation and achieve satisfactory performance in terms of computational speed.  相似文献   

Revised runoff curve number for runoff prediction in the Loess Plateau of China     

Wenhai Shi  Ni Wang  Miaomiao Wang  Donghao Li 《水文研究》2021,35(10):e14390

The soil conservation service (now Natural Resources Conservation Service) Curve Number (SCS-CN), one of the most commonly used methods for surface runoff prediction. The runoff calculated by this method was very sensitive to CN values. In this study, CN values were calculated by both arithmetic mean (CN_C) and least square fit method (CN_F) using observed rainfall-runoff data from 43 sites in the Loess Plateau region, which are considerably different from the CN₂ values obtained from the USDA-SCS handbook table (CN_T). The results showed that using CN_C instead of CN_T for each watershed produce little improvement, while replacing CN_T with CN_F improves the performance of the original SCS-CN method, but still performs poorly in most study sites. This is mainly due to the SCS-CN method using a constant CN value and discounting of the temporal variation in rainfall-runoff process. Therefore, three factors—soil moisture, rainfall depth and intensity—affecting the surface runoff variability are considered to reflect the variation of CN in each watershed, and a new CN value was developed. The reliability of the proposed method was tested with data from 38 watersheds, and then applied to the remaining five typical watersheds using the optimized parameters. The results indicated that the proposed method, which boosted the model efficiencies to 81.83% and 74.23% during calibration and validation cases, respectively, performed better than the original SCS-CN and the Shi and Wang (2020b) method, a modified SCS-CN method based on tabulated CN value. Thus, the proposed method incorporating the influence of the temporal variability of soil moisture, rainfall depth, and intensity factors suggests an accurate runoff prediction for general applications under different hydrological and climatic conditions on the Loess Plateau region.  相似文献   

线性不等式约束平差模型的一种解算方法     

曾磊  左廷英  罗亮 《北京测绘》2010,(4):1-3,17

不等式约束是实际测量中存在的一种约束,本文利用整标集法求解附线性不等式约束平差模型。首先了介绍带有不等式约束平差的最小二乘问题转化成凸二次规划问题,然后在Kuhn-Tucker条件下把二次规划问题转换成线性互补问题的基础上,利用整标集法来求出参数的最佳估值,最后通过一个数值算例来说明了该方法的可行性。  相似文献   

Latitudinal and local variations of the life history characteristics of the thalassinidean decapod, Upogebia yokoyai: A hypothesis based on trophic conditions     

Miho Yamasaki  Takahiro Nanri  Shino Taguchi  Yoshitake Takada  Masayuki Saigusa 《Estuarine, Coastal and Shelf Science》2010

Mean total length of the eldest cohort (MTLe) of the thalassinidean decapod, Upogebia yokoyai sampled at 16 sites showed a latitudinal variation from south-west islands of the Ryukyu Archipelago (24° N) to the Seto-Inland Sea of Japan (34° N). Local variations were however also found from sites in the same latitudes. The level of the organic content in each habitat showed a positive correlation with MTLe. We hypothesized that MTLe is strongly affected by the trophic condition, resulting in the local variations. To test this hypothesis, two estuaries with different organic content were compared; Kodono River (Kochi Prefecture, 33° N) which was relatively oligotrophic and Sakata River (Hiroshima Prefecture, 34° N) which was highly eutrophicated. The Kodono River population showed slow growth after settlement, and growth stopped in May to June. This population survived for only one or two years, resulting in small MTLe. On the other hand, the Sakata River population showed fast growth from August to December. This population survived for three years, resulting in large MTLe. Maturation was estimated to occur two years after settlement in both populations. Low salinities may partially affect MTLe. Habitats in the Seto-Inland Sea (33.5–34.8° N) were eutrophicated, but many habitats in the subtropical islands (24–31° N) were relatively oligotrophic. Latitudinal variation of MTLe was reflected by the geographical difference in trophic condition. A negative relationship between population density and growth was found, which was explained in terms of reduced survival of recruits in the eutrophicated habitats.  相似文献   

Effects of engineering geological condition on response of suspension bridges     

Junjie Wang  Shide Hu  Xiao Wei 《Soil Dynamics and Earthquake Engineering》1999,18(4):345

The geological condition may vary largely from one support to another for a long span bridge. The effect of geological variability and spatial variation produced by propagation and coherence loss of seismic ground motion on the response of long span suspension bridges is investigated in this article. The case of Jiangyin Yangtse River Bridge, a suspension bridge with a main span of 1385 m, is studied in detail. Numerical results show that the geological difference at the supports has a significant effect on the seismic response of long span suspension bridges and, that it is unacceptable to neglect the difference. The effect of the propagation of seismic ground motion on the response of long span suspension bridges is far more important than that of the coherence loss. The response of bridges varies greatly with the horizontal apparent velocity in a very complex way, and there is a critical horizontal velocity for a given response quantity.  相似文献