Manifestation and measurement of the fractal characteristics of karst hydrogeological formations

A new method of estimating the fractal dimension of the percolation backbone of karst systems, which are discharged through karst springs, is presented. This method is based on the simulation of the spring by the MODKARST deterministic mathematical model. Application has been made to the Psiloritis karst formation in Crete, which feeds the periodically brackish karst spring “Almiros” in Crete. Furthermore, the estimated dimension justifies an independently determined power law that quantifies the sea intrusion into the karst system.     

河南商城汤泉池温泉电阻率成像

电阻率成像法在地热勘查中,可以客观较真实地反映断层、热储地质体的基本特征.本文阐述了地电成像的原理、方法以及汤泉池温泉地热地质条件,对4条电阻率成像剖面进行了解释及综合分析,为定井提供了依据.     

双流县春季气候变化特征分析

利用四川省双流县1965~2008年春季降水、温度资料,分析双流县44年的春季气候变化特征。结果表明:①双流县3~5月降水的变化有1.52年、6.96年、18.36年的主要时间尺度;双流县3~5月温度的变化有10.56年时间尺度。②双流县春季降水的突变发生在20世纪80年代中期,自此以后降水逐渐由多变少;温度的突变发生在20世纪90年代中期,自此以后温度逐渐由偏低变为偏高;降水的突变早于温度的突变。③根据春季降水量和温度的主要时间尺度,估计近期春季降水量可能偏少;近期春季温度总体趋势可能偏高。     

Design,simulation, and large‐scale testing of an innovative vibration mitigation device employing essentially nonlinear elastomeric springs

This study proposes an innovative passive vibration mitigation device employing essentially nonlinear elastomeric springs as its most critical component. Essential nonlinearity denotes the absence (or near absence) of a linear component in the stiffness characteristics of these elastomeric springs. These devices were implemented and tested on a large‐scale nine‐story model building structure. The main focus of these devices is to mitigate structural response under impulse‐like and seismic loading when the structure remains elastic. During the design process of the device, numerical simulations, optimizations, and parametric studies of the structure‐device system were performed to obtain stiffness parameters for the devices so that they can maximize the apparent damping of the fundamental mode of the structure. Pyramidal elastomeric springs were employed to physically realize the optimized essentially nonlinear spring components. Component‐level finite element analyses and experiments were conducted to design the nonlinear springs. Finally, shake table tests using impulse‐like and seismic excitation with different loading levels were performed to experimentally evaluate the performance of the device. Experimental results demonstrate that the properly designed devices can mitigate structural vibration responses, including floor acceleration, displacement, and column strain in an effective, rapid, and robust fashion. Comparison between numerical and experimental results verified the computational model of the nonlinear system and provided a comprehensive verification for the proposed device. Copyright © 2014 John Wiley & Sons, Ltd.     

应用水文地球化学方法分析郑家泉域水文地质条件

本文利用钻孔水化学数据和地球化学模拟方法,分析了郑家泉泉域基岩裂隙含水层各钻孔之间的水力联系和地下水补迳排特征.研究表明泉域北部的基岩裂隙含水层为条带状分布,到南部逐渐混合,郑家泉水的补给源主要来自西部和北部.     

Orthotropic frost heaving force distribution characteristics for tunnel structures under hydro-thermo-mechanical coupling;

In cold regions,the frost heave of surrounding rock could lead to additional force on lining struc⁃ tures,which impairs the durability and safety of tunnels. This paper analyzed the distribution characteristics of tunnels’frost heave force in seasonally frozen regions. Firstly,energy conservation and mass conservation prin⁃ ciples were introduced,and a hydro-thermal-mechanical coupling model of frozen surrounding rock considering orthotropic frost heaving deformation was constructed. The reliability of the model was verified with the monitor⁃ ing result of the Qingshashan tunnel. Furthermore,the numerical model of the Dongtianshan tunnel was con⁃ structed,and distribution characteristics of temperature fields,water fields,and frost heave force were studied. In addition,various influencing factors on the tunnel’s frost heave force were analyzed,including the minimum temperature,the initial formation water content,the modulus ratio of the frozen and unfrozen surrounding rock,and the orthotropic frost heave coefficient. The simulation results show that the frozen depth of the tunnel is not uniform,the smallest at the arch foot and the largest at the center of the inverted arch. The maximum frozen depth difference was 48 cm. The frozen depth difference was due to the largest geometric curvature at the arch foot. At the same time,due to the minimum freezing depth and largest geometric curvature at the arch foot,the bending and folding of the arch foot of the lining are the most significant,and the von Mises stress at the arch foot is the largest. During one freezing-thawing period,the water content change includes four stages：freezing,thawing,stagnating and dissipating. After 20 freeing-thawing periods,in the water stagnating stage,the volu⁃ metric water contents at the lining top and sides increased by 10. 46% and 4. 21%,respectively,and the volumet⁃ ric water contents at the arch foot and lining bottom decreased slightly. The frozen surrounding rock produced both normal and tangential stress on the lining. Among them,the top arch and inverted arch are mainly manifest⁃ ed as compressive stress,while the compressive stress of the arch foot is minor and partially represented as ten⁃ sile stress. The frost heave force distribution patterns under different minimum air temperatures,initial water contents,modulus ratios between frozen and unfrozen surrounding rock,and orthotropic coefficients of frost heave deformation are the same. Normal stress distributions outside the lining are“mushroom-shaped”as a whole. The decrease in temperature could extend the freezing area,and the increase of orthotropic frost heave deformation coefficient could concentrate frost heave strain’s direction,which could significantly promote the frost heave force. The modulus ratio between frozen and unfrozen surrounding rock was negatively related to frost heave force,and the initial water content was positively related to frost heave. The orthotropic coefficient of frost heave deformation has the most significant influence on the value and distribution of frost heave force. After 20 years of freeze-thaw cycles,the difference of water field under different initial formation water content reduced,which leads to the little difference in frost heaving force of the tunnel under different initial formation water contents. The frost heave force distribution is mainly the result of the competition between the temperature field and the lining geometry. The minimum freezing depth leads to the smallest frost heave force at the arch foot. However,the deformation of the lining causes the arch foot to press against the surrounding rock,which could increase the compressive stress on the arch foot. For the tunnel with a small lining thickness,the extrusion effect of the arch foot to the outer surrounding rock is more prominent,which leads to a more considerable frost pressure at the arch foot. Overall,the frost heave force distribution of tunnels in cold regions should consider the influence of temperature conditions,water conditions,anisotropy of surrounding rock frost heave deformation,and lining geometry. Copyright © 2023 Institute of Microbiology, CAS. All rights reserved.     

温泉钙华沉积的影响因素

钙华是在泉水、河水、湖水、洞穴周围沉积的非海相碳酸钙沉积物。钙华是陆地水循环过程中物质迁移的一种表现形式,研究钙华的形成有助于了解局部水文循环中的物质迁移规律并间接了解古气候与古水文地质条件。部分温泉的泉口附近沉积有形态多样的钙华。本文综述温泉钙华的形成过程、钙华沉积的主要影响因素和它们之间的相互影响关系。水化学条件是钙华沉积的物质基础和必要条件,水动力条件是钙华沉积的充分条件,生物效应对钙华沉积起到加强的作用,沉积环境通过影响水化学条件或水动力条件间接控制钙华的沉积。     

Mechanical behavior of porous solid considering mesoscopic elastic buckling

In this work, the elastic buckling of porous solids was investigated using a lattice spring model (LSM). The capability of the LSM to solve elastic buckling problems was comprehensively verified by comparing well-established numerical and analytical solutions. Following this, the buckling of a porous solid was studied, in which two porous structures were considered, ie, the random porous model and the Voronoi porous model. The results reveal that both the porosity and the shape of the pores influence the elastic buckling bearing capacity of the porous solid. Finally, the mechanical responses of a porous solid with an extra high porosity (0.85) were numerically investigated. Our numerical results demonstrated that the nonlinear elastic response of the porous solid might come from its mesoscale elastic buckling. This work shows the ability and promise of using the LSM as a fundamental numerical tool for the deep investigation of the buckling mechanical behavior of porous solids.     

华南晚三叠世前陆盆地的成因地层格架及演化历史

在详细研究盆地中各类沉积体系的沉积构成和演化过程的基础上,通过成因地层对比,建立了残留海湾—前陆盆地的成因地层格架。根据沉积体系的时空组合及其与相关等时性地层面的配置关系,划分出了3个构造沉积幕,每个构造沉积幕都是盆地基底荷载挠曲变形至弹性回跳过程的沉积响应。海平面升降变化和盆内软沉积物压实沉降虽然不能触发和主控盆地基底的构造挠曲旋回,但对各构造沉积幕的地层构型和持续时间有重要影响。盆地基底荷载挠曲变形与海平面升降或压实沉降过程以不同方式叠加,产生各种类型的构造沉积幕,与前陆盆地共生的还有后陆盆地和残留的弧后盆地。     

低温环境下含表面裂隙硬岩温度场及冻胀演化过程分析

寒区含表面裂隙硬岩与大气连通,易受外界低温环境引起裂隙内部水分凝结,造成裂隙带附近形成温度场突变,进而随水冰相变产生冻胀力,二者随着冻结活动处于动态演化之中,涉及到温度场、渗流场及应力场等多场问题。目前的研究大多依据数值模拟结果,描述裂隙岩体温度场、应力场分布特征及规律,考虑从基础理论解析计算角度,探究低温环境下裂隙岩体温度场、冻胀力演化规律鲜有报道。针对含表面裂隙硬岩在低温环境下发生的冻结现象,从传热学理论、相变理论、弹塑性力学及断裂力学理论等多角度出发,探讨随着冻结深入含表面裂隙硬岩内部温度场及冻胀荷载演化过程,提出对应解析表达式,引入多场耦合数值程序Comsol-Multiphysics进行数值模拟验证,结果表明,文中提出的温度场及冻胀荷载演化解析表达式与数值模拟结果具有较好吻合度,可满足对含表面裂隙半无限板模型温度场、应力场演化过程分析,对于裂隙岩体在低温环境下温度场、应力场演化及热-力耦合分析具有较好借鉴价值。