Hydraulic properties analysis of the unsaturated cracked soil

Morphological parameters of cracks significantly affect the hydraulic conductivity of cracked soil. A laboratory test was conducted to study the hydraulic properties of cracks. The dynamic development of cracks in soil during drying and wetting was measured in the test. Based on the test results, the relationships between the morphological parameters and the soil water content were quantified. According to the fractal model, the soil-water characteristic curve (SWCC) and permeability functions for the cracked soil were predicted based on the dynamical development process of the cracks. A crack-pore dual media model was established to simulate the ponding infiltration in the unsaturated cracked soil. The variations of the pore water pressure in different part of the fractal model are quite different due to the impact of the cracks. This result illustrates that the prediction of the hydraulic properties for the cracked soil is reasonable.     

Numerical Simulation on Freezing Process of Saturated Granlar Soil

The relation between ice pressure and load as a criterion of segregated ice initiation is introduced into the rigid ice model to simulate frost heave in saturated and granular soil. The calculated results show that unfrozen water content, thermal conductivity and hydraulic conductivity change greatly in frozen fringe. In numerical simulations, the influence of load, hydraulic conductivity and property of soil containing water on the process of soil freezing are analyzed, and the simulation curves such as cumulative heave,the change of depth of frozen and the distributions of water content are similar to the observations reported elsewhere.     

Numerical Simulation on Freezing Process of Saturated Granular Soil

Introduction Soil freezing and thawing have a harmful impacton roads and buildings in cold regions. For example,frost heave and thawing settlement lead to cracks, set-tlement and structure breaking. A number ofreports[1-3]indicated that the frost heave induced bywater transfer could exceed the volume of water chan-ges because of water freezing in the cells. The mainmodels for coupled heat and moisture transfer infreezing soil are hydrodynamic models and rigid icemodels[1,2]. Though the hydrod…     

生物炭对生物滞留池水文效果的影响

为了研究生物炭的添加对生物滞留池雨水下渗、持水能力及水力停留时间的影响,在一野外中试生物滞留池中加入了4%（w/w）的生物炭,对该生物滞留池进行了导水率测试和3次溴示踪模拟降雨实验.研究结果表明:与无生物炭的对照组相比,生物炭的施用将填料土的饱和导水率增大了1.5倍;生物滞留池的水力停留时间延长了近1 h;渗流区的体积含水量增加了11%~23%;施用生物炭可全面提高生物滞留池的水力表现,避免溢流,削减洪峰,增加保水,减少雨水径流的排放.      

心墙水力劈裂与孔压关系的探讨

基于Biot固结理论的有效应力二维数值模拟方法,研究了堆石坝的粘土心墙水力劈裂过程中孔隙水压力的变化．分析了坝体竣工期粘土心墙中的拱效应,探讨了从竣工固结到蓄水过程和稳定渗流期粘土心墙中孔隙水压力的变化分布特点,并对心墙发生水力劈裂的可能性进行判断．研究结果表明：堆石坝粘土心墙内部孔隙水压力梯度的模拟分析能更加合理地解释水力劈裂发生与蓄水速度和心墙低渗透性的关系,因此,分析考虑水位上升过程中粘土心墙内孔隙水压力分布情况是研究心墙水力劈裂发生机理的重点．     

中俄原油管道地基土冻融及热学性质试验研究

中俄原油管道是我国能源战略通道之一，管道穿越大兴安岭多年冻土区，工程地质条件十分复杂，尤其是在伊勒呼里山附近，冻胀和融沉严重影响了管道的正常运营. 为了研究伊勒呼里山附近多年冻土的冻融性质与热学性质，对该区段内的冻土进行冻胀、融沉及导热系数试验，并对试验数据进行回归分析与影响因素分析. 研究结果表明:细粒土塑性指数小于10时，冻胀率不一定随初始含水量的增加而增加，在研究区域内进行管道垫层施工或挖填材料选择时应选用砂砾或碎石，并做好防排水措施；融沉系数随含水量的增加而增大，随干密度的增加而减小，其中粉土对融沉作用十分敏感，不适合作为管道地基，而细砾才是最佳的冻土地基；导热系数分别随总含水量和干密度的增大而增大，其中粗粒土的导热系数大于细粒土，而冻土的导热系数则比融土的高；当含水量小于10%时，融土的导热系数则高于冻土. 不同试验方法所得的结果也具有显著的差异，粗粒土扰动样的导热系数宜采用热流计法测量，细粒土扰动样的导热系数宜采用热线法测量，而原状样的导热系数宜采用比较法测量.      

波浪荷载作用下各向异性海床瞬态液化研究

为探究各向异性海床在波浪作用下的瞬态液化问题,采用有限元法求解RANS （reynolds averaged navier-stokes）方程及k-ε湍流模型进行数值造波,通过求解Biot多孔弹性方程获得海床瞬态响应,进而建立了波浪-各向异性海床耦合作用的二维数值仿真模型. 在完成对新建模型的验证后,基于此模型系统地研究了波浪及海床特性对各向异性海床瞬态液化的影响. 研究结果表明:海床瞬态液化深度随波高、周期增大而增大,随海床饱和度增大而减小;当海床垂向渗透系数在一定范围内时,海床最大液化深度随垂向渗透系数增大而减小,超出该范围时,海床垂向渗透系数对海床最大液化深度的影响不明显;海床瞬态液化深度对水平方向渗透系数的改变不敏感.      

Numerical simulation of drawdown and land deformation in pumping-recovery tests performed on a circular excavation

A mathematical model, which not only fully couples fluid flow and solid skeleton deformation in unsaturated porous elastic media but also considers deformable diaphragm walls, is formulated in axially symmetric cylindrical coordinates for drawdown and land deformation. Based on this model, pumping-recovery tests in various conditions are numerically simulated to reveal the effects of elastic modulus of soil E and initial saturated hydraulic conductivity K_(sat0) on hydraulic head and land deformation. The heterogeneity with respect to E and K_(sat0) is separately taken into account. Large elastic modulus of soil contributes to both dewatering process and deformation control. Either large or small initial saturated hydraulic conductivity may cause relatively high groundwater table, while the larger one leads to smaller displacements.     

Simulation of excess pore water pressure during deep soil mixing columns installing

Most of current studies of deep soil mixing (DSM) methods are focused on the soil strength improvement and soil treatment effectiveness. But the DSM installation leads to excess pore water pressure and soil disturbance, which will bring great harm to adjacent structures, such as shell tunnels and historic buildings. The procedure of excess pore water pressure buildup while large number DSM columns are installed is complicated. In order to find methods to predict and simulate the excess pore water pressure during DSM column installation, the complicated dissipation and buildup of excess pore water pressure through in-situ test are studied in this paper. In-situ test was conducted in soft clay near the Huangpu River in Shanghai. The pore water pressure was investigated by an automatic monitoring system. Test results indicate that the excess pore water pressure induced by one DSM column installation is composed of the compaction pressure and the reversing pressure. The empirical equations of excess pore water pressure dissipation and buildup were built by mathematical fitting methods. A compound method is proposed to simulate the excess pore water pressure due to DSM installation. Using this method to predict the excess pore water pressure in the situ test, results show a well agreement between the prediction and the measurements.     

降雨作用下基覆型边坡失稳特征及承载力试验研究

为了研究降雨诱导基覆型边坡失稳特性，采用室内模型试验方法对基覆型边坡在暴雨作用下的失稳过程及机制进行了系统研究. 通过探讨降雨前后边坡内土体含水率和孔隙水压力在时间、空间上的变化特性，揭示降雨诱导的边坡失稳机制. 同时通过坡顶加载方法研究了雨后边坡承载力变化规律. 研究结果表明:随着降雨的发展，在坡脚处首先出现土体液化流动现象，随后出现土体局部脱落；随着降雨的持续进行，土体脱落破坏的范围逐渐增大，进而导致上方土体临空面加大，土体破坏后随即被雨水饱和软化而向下滑动，后方土体进一步被侵蚀，最终造成了一定深度和宽度的边坡破坏现象；边坡内土体含水率升高与孔隙水压力的增大是导致边坡失稳破坏的主要因素；降雨停止后，边坡可以承受的极限荷载先增大后减小，最后趋于稳定，而基覆型边坡在顶部静荷载作用下破坏模式呈现出整体和局部滑移模式.      

考虑边界土体性质悬浮隧道地震响应分析

悬浮隧道地震响应研究是确保该新型交通结构物安全的重要内容,现有的研究往往忽视了驳岸结构的影响,将其简化为铰支、固支等简单约束形式。考虑了悬浮隧道驳岸结构周围岩土性质对其边界条件的影响,研究在横向地震作用下悬浮隧道的地震响应特性;采用大质量法,以Messina海峡悬浮隧道方案为基本模型,结合我国东部海域海床岩土性质,计算得到了地震作用下悬浮隧道管体位移、弯矩、扭矩和锚索索力,并对驳岸段长度Lsh和粘性土剪切模量G进行了参数分析。研究表明,悬浮隧道管体最大位移和弯矩出现于跨中、最大扭矩出现于两端、索力增量最大值出现于短索;弹性支撑有利于管体受力,但不利于锚索索力控制;驳岸段计算长度和粘土剪切模量的变化会对悬浮隧道地震响应特性带来显著影响,且影响规律较为复杂,可能与悬浮隧道结构动力特性、地震波的特性等相关参数具有耦合关系,需要进一步的研究探索。     

高速公路软土路基沉降变形的研究

由于软土具有压缩性高、含水量大、强度低和透水性差等特点,在软土地基上修建高速公路时,面临的首要问题是路基的稳定和变形,特别是对路面变形要求非常严格的高速公路工程,控制软土地基的过量沉降变形成为关键性的技术问题。     

Groundwater Waves in a Coastal Fractured Aquifer of the Third Phase Qinshan Nuclear Power Engineering Field

IntroductionEarlier work on tidal fluctuating groundwaterlevels emphasized the use of the observed water-level fluctuations to calculate aquifer parameters.Many researchers studied the relations betweengroundwater wave and tidal fluctuation[1~4].Michael[5]studied the tidal filtering methods tradi-tionally applied to surface water measurements todetermine mean levels. It also can be applied totidally fluctuating groundwater to determine themean hydraulic gradient. Erskine[6]studied thetidal os…     

高速公路软土路基沉降变形研究

软土具有压缩性高、含水量大、强度低和透水性差等特点,在软土地基上修建高速公路时,首要面临的是路基的稳定和变形问题,特别是对路面变形要求非常严格的高速公路工程,控制软土地基的过量沉降变形将成为公路工程建设的关键技术问题所在。     

基于非饱和非稳定渗流场的滑坡稳定性分析

以鹰厦铁路K290滑坡为原型,基于降雨入渗情况下滑坡体呈饱和-非饱和渗流状态下,通过计算得到坡体孔隙水压力和体积含水量随降雨及地下水位变化的基本规律,进一步导入SIGMA/W程序并依据坡体孔隙水压力和体积含水量及地下水位变化特征分析了滑坡应力场,探讨了降雨强度、降雨持时和水位变化对滑坡体稳定性的影响.     

离心模型试验中土的渗透相似特性

土的渗流和渗流控制是土力学和土木工程建设中的一项极其重要的课题。土工离心模拟技术在研究渗流方面具有明显的优势,通过对模型施加N倍的离心加速度,保证模型的应力水平与原型一致,就可以用模型反映、表示原型。通过介绍离心模拟技术在研究土的渗透系数方面的一些研究成果,同时结合自身研究成果,可得出离心机中土的渗透系数的公式。     

隧道断层开挖引起的地下水系统变化分析

在岩层中开挖隧道时以及开挖后,地下水会倒灌进隧道中.利用SEEP/W程序,对倒灌进隧道的地下水的水量及水位变化进行了二维有限元分析.研究对象是位于韩国Gyeongnam市Cheonseong山区的Wonhyo隧道,隧道模型范围内既有湿地,也有断裂带,选取了隧道沿途的4个典型区域进行研究.通过DFN模型计算了岩层中的导水...     

膨胀土土水特征曲线的研究

对不同地区膨胀土的原状样和重塑样进行了脱湿土水特征曲线试验,并采用VG模型对试验数据进行拟合。结合VG模型拟合的参数,着重分析了矿物成分和孔隙结构对膨胀土土水特征曲线的影响。结果表明:在同一初始干密度下,膨胀土含蒙脱石亲水性矿物越多,脱水速率越慢,持水性能越强;同一土质的重塑样,初始干密度越大,则其进气值越大,脱水速率越慢;在初始干密度相同的条件下,原状样的土水特征曲线与重塑样的不同,其脱水速率较缓慢,残余含水量较高,表现出较强的持水性能。     

液压式检漏方法和装置的研究

在实际的工作中经常能遇到机械设备液压系统和管路系统发生漏水、漏油、漏气的问题。这种液压系统泄漏不仅能产生严重的安全问题,而且还会影响设备的技术性能和经济性能,甚至还会损坏设备、停工,停产,乃至产生环境污染。本文分析了液压系统泄漏的原因和对常用检漏方法进行比较并介绍了一种新型液压式自动检漏装置。     

降雨作用下土质边坡水分迁移特征研究

针对降雨诱发边坡失稳的特点,从水分迁移的角度出发,结合非饱和土力学,采用有限元法分析了不同降雨强度作用下边坡内部水分迁移的特征;通过数值模拟得到:降雨作用下,边坡内部孔隙水压力呈层状分布,坡脚处孔隙水压力最大,坡顶次之,坡中最小;边坡中的水分主要沿垂直和倾斜方向迁移,迁移速度由表层向深部逐渐减小,迁移方向也随深度和时间而改变;体积含水率呈非线性分布,且非饱和区非线性化程度较饱和区的高;土体渗透系数随降雨强度的增大而增大,当土体饱和时其渗透系数为饱和渗透系数。