埋置简谐扭转荷载作用下广义Gibson饱和地基动力响应

考虑地基为饱和半空间,研究了广义Gibson饱和地基内作用简谐扭转动荷载时地基的动力响应问题。从Biot饱和地基固结理论出发,结合扭转振动的特点,建立了剪切模量随深度线性变化的饱和地基扭转振动的动力微分方程,通过Hankel变换求解此微分方程,给出了Hankel变换域内的切向位移和剪应力关于待定系数的表达式。根据饱和地基表面为自由表面,荷载作用面位移连续、剪应力差等于动荷载大小,波的辐射条件等边界条件求解出待定系数,借助Hankel逆变换给出地基内的位移和应力的表达式。通过数值算例研究发现:在同一水平面内,地基内的切向位移和剪应力曲线的实部和虚部都呈现出非常明显的波动变化规律;在竖向平面内,动荷载作用面上部区域内随深度逐渐增大时,地基内切向位移和剪应力曲线的实部逐渐增大,而在动荷载作用面下部区域则正好相反;扭转动荷载的影响范围主要是荷载作用面上下2倍半径区域。     

Vertical dynamic response of a rigid foundation embedded in a poroelastic soil layer

A simplified analytical method is presented for the vertical dynamic analysis of a rigid, massive, cylindrical foundation embedded in a poroelastic soil layer. The foundation is subjected to a time‐harmonic vertical loading and is perfectly bonded to the surrounding soil in the vertical direction. The soil underlying the foundation base is represented by a single‐layered poroelastic soil based on rigid bedrock while the soil at the side of the foundation is modeled as an independent poroelastic layer composed of a series of infinitesimally thin layers. The behavior of the soil is governed by Biot's poroelastodynamic theory and its governing equations are solved by the use of Hankel integral transform. The contact surface between the foundation base and the soil is smooth and fully permeable. The dynamic interaction problem is solved following standard numerical procedures. The accuracy of the present solution is verified by comparisons with the well‐known solutions obtained from other approaches for both the elastodynamic interaction problem and poroelastodynamic interaction problem. Numerical results for the vertical dynamic impedance and response factor of the foundation are presented to demonstrate the influence of nondimensional frequency of excitation, soil layer thickness, poroelastic material parameters, depth ratio and mass ratio on the dynamic response of a rigid foundation embedded in a poroelastic soil layer. Copyright © 2008 John Wiley & Sons, Ltd.     

应用遥感技术连续监测地表土壤含水量

根据地表湿度与地表温度之间的关系,以及气温变化对这种关系的影响分析,经过气象卫星热红外波段信息与地表温度的有效转换,建立起一个连续监测地表土壤含水量的遥感模型。该模型只需无云条件下的白天气象卫星资料,综合考虑了各种植被覆盖条件,所以模型操作简单、易于推广,具有大范围监测土壤含水量的实用性。     

耦合冻土方案的大气模式对祁连山区春季土壤状况的模拟

对黑河流域上游山区水源涵养林区2003年春季土壤温度、湿度变化进行分析,运用耦合冻土参数化和没有耦合冻土参数化的大气模式MM5对该区春季过程进行了模拟,并与观测值进行对比,对模拟的产流量做了初步分析.结果显示:考虑冻土参数化方案对土壤温度模拟的改进主要体现在表层土壤,对深层土壤温度的模拟没有大的改进;考虑冻土参数化方案改进了对100 cm深度以内的土壤含水量的模拟,很大程度上缩小了模拟值与观测值之间的绝对误差.总体来讲,考虑了冻土参数化的模拟结果在一定程度上改进了模式对黑河流域上游季节冻土区土壤温、湿状况的模拟,在一定程度上逼近祁连山区的春季土壤状况.考虑冻土参数化和没有考虑冻土参数化对产流量的模拟表明,冻土参数化对产流量模拟有很大影响,冻土形成的不透水层可以产生更多的地表径流.尽管考虑冻土参数化过程对模拟结果有一定程度的改进,但模拟结果与实测结果还是有一定差距的.因此,进行寒区冻土过程模拟时,还需要进一步对土壤信息、模式物理过程,大气背景场驱动数据以及局地因素进行详细而精确的考虑,以期进一步提高模式在寒区的模拟性能,特别是为高寒山区无观测地带陆气相互作用研究提供依据.     

季节冻土区黑土耕层土壤冻融过程及水分变化

利用黑龙江省水利科学研究院水利试验研究中心综合实验观测场2011年11月-2012年4月整个冻结融化期的实测野外黑土耕层土壤温度和水分数据, 对中-深季节冻土区黑土耕层土壤冻融过程中冻结和融化特征分阴、阳坡进行了分析, 研究了冻融过程中不同深度土壤水分的变化情况, 并探讨了降水对不同深度耕层土壤含水量变化的影响. 结果表明:黑土耕层土壤冻结融化过程分为5个阶段, 历时164 d, 约5.5个月. 阶段I, 秋末冬初黑土耕层土壤开始步入冻结期; 阶段II, 黑土耕层土壤整日处于冻结状态, 阴坡比同样深度的阳坡土壤温度低; 阶段III为黑土耕层土壤稳定冻结期; 阶段IV, 黑土耕层土壤步入昼融夜冻的日循环交替状态, 冻融循环的土层逐渐向深部发展, 阳坡比阴坡融化得更深、更早, 阴坡比阳坡经历冻融循环次数更多; 阶段V为稳定融化期, 在融化过程不存在冻融交替的现象, 直到整个冻层内的土壤全部消融. 各深度位置阴坡土壤温度的最高值出现时间比阳坡晚约0.5 h. 经过整个冻结融化期后, 阴、阳坡各层土壤含水量均大于冻结前, 阴坡土壤含水量比阳坡整体偏低. 在整个冻结融化期, 阳坡地下1 cm、5 cm、10 cm 及15 cm处含水量最大值出现在地下5 cm; 阴坡的含水量整体趋于平稳且在融化期受降水影响明显.     

非饱和土层一维固结特性分析

在Fredlund非饱和土的一维固结理论的基础上进行假设,由得出的液相及气相的控制方程、Darcy定律及Fick定律,采用Laplace 变换、逆变换等数学方法得到了大面积均布瞬时加载下表面为透水透气面、底面为不透水和不透气面的非饱和土层一维固结时间域内的超孔隙水压力、超孔隙气压力及土层沉降的解析解;应用典型算例,分析了不同气、水渗透系数比情况下土体超孔隙水压力、超孔隙气压力消散及土层沉降随时间的变化规律以及不同时间超孔隙水压力、超孔隙气压力消散随深度的变化规律。将得出的结果退化成相应的饱和土的解与太沙基饱和土固结理论结果比较,验证了其正确性。     

基于变分法的均质土坡稳定性分析

在平面应变条件下,从考虑强度折减的滑动土体极限平衡方程出发,推导出一般情况下均质土坡稳定分析的泛函极值等周模型。依据泛函取极值时必须满足的欧拉方程,通过坐标变换对变分问题求解,得到滑裂面函数及其上分布的法向应力函数。对于给定的边界条件及横截条件,土坡稳定问题转化为求解以两个拉格朗日乘子、安全系数和滑裂面一个端点的x坐标为4个未知量的函数极值问题,可以通过数值计算得到最小安全系数及所对应的最危险滑裂面。考虑坡顶拉裂缝,通过算例分析了不同的滑裂面位置及对应的安全系数。通过对ACADS边坡考题算例分析,在不考虑坡顶开裂的条件下,采用该方法的分析结果与依据极限平衡法得到的各裁判答案非常接近,在考虑坡顶开裂时,安全系数略有减小。     

成层土中倾斜荷载作用下桩承载力有限元分析

利用有限元方法对现场单桩水平载荷试验进行模拟,在此基础上,分析了成层土中桩在倾斜荷载作用下其竖向分量的有利作用和横向土抗力分布特点。计算结果表明,在地面下一定范围内,倾斜荷载作用下的桩侧摩阻力比水平荷载作用下的桩侧摩阻力大。在土层分界处土抗力分布有明显的跳跃。达到一定深度后,横向土抗力主要是静止土压力,而由荷载引起的横向土抗力很小。承台能有效减小土体及桩的水平位移。模拟的灌注桩和钢管桩桩顶在地面以上的自由长度较小,竖向分量由于桩身挠曲变形而产生的P-Δ效应较小,所以就算例中的灌注桩和钢管桩而言,荷载倾斜度不大时,荷载竖向分量提高了桩的侧阻并由此增大桩侧土竖向应力,对桩水平承载力总体上起到了有利的作用。     

Analytical solution for one‐dimensional consolidation of unsaturated soils using eigenfunction expansion method

This paper introduces an exact analytical solution for governing flow equations for one‐dimensional consolidation in unsaturated soil stratum using the techniques of eigenfunction expansion and Laplace transformation. The homogeneous boundary conditions adopted in this study are as follows: (i) a one‐way drainage system of homogenous soils, in which the top surface is considered as permeable to air and water, whereas the base is an impervious bedrock; and (ii) a two‐way drainage system where both soil ends allow free dissipation of pore‐air and pore‐water pressures. In addition, the analytical development adopts initial conditions capturing both uniform and linear distributions of the initial excess pore pressures within the soil stratum. Eigenfunctions and eigenvalues are parts of the general solution and can be obtained based on the proposed boundary conditions. Besides, the Laplace transform method is adopted to solve the first‐order differential equations. Once equations with transformed domain are all obtained, the final solutions, which are proposed to be functions of time and depth, can be achieved by taking an inverse Laplace transform. To verify the proposed solution, two worked examples are provided to present the consolidation characteristics of unsaturated soils based on the proposed method. The validation of the recent results against other existing analytical solutions is graphically demonstrated. Copyright © 2013 John Wiley & Sons, Ltd.     

Dynamic characteristics of a large‐diameter pile in saturated soil and its application

This study theoretically investigates the dynamic response of an end‐bearing pile embedded in saturated soil considering the transverse inertial effect of the pile. The saturated soil surrounding the pile is described by Biot poroelastic theory, and the pile is represented by a Rayleigh‐Love rod because both the vertical and radial displacements at the soil‐pile interface are considered. The potential function decomposition method and variable separation method are introduced to solve the governing equations of the soil, in which the vertical and radial displacement components are coupled. The governing equation of the pile is solved using the continuity conditions at the pile‐soil interface. Next, the velocity admittance in the frequency domain and the velocity response in the time domain at the pile top are presented based on the Laplace transform and inverse Fourier transform, respectively. Subsequently, the reduced solution is compared with a 1‐dimensional model solution to verify the validity, and the influences of the slenderness ratio of the pile on the transverse inertial effect of the pile are analyzed. Moreover, Poisson ratio, the slenderness ratio of the pile, and the pile‐soil modulus ratio are studied. Finally, the theoretical and measured curves in the engineering project are compared, and the results demonstrate the good application prospects of the solution presented in this article.     

冻融期东北农田土壤温度和水分变化规律及影响因素分析

为了更好地认识季节性冻融区冻融过程对农田土壤温度和水分的影响, 以吉林省长春市黑顶子河流域为研究对象, 监测了冻融期流域内玉米田和水稻田土壤温度和水分的变化过程。结果表明： 冻融期表层土壤温度主要受积雪厚度影响, 深层土壤温度主要受土壤初始含水率影响。冻结期, 冻结层含水率几乎都呈增加趋势, 其中浅层土壤增幅最大; 冻结速度慢、 初始含水量低、 相邻土层含水量高的土层冻结过程水分增加量更大, 反之则小。融化期, 各下垫面、 土层土壤含水率基本呈下降趋势, 且主要集中在表层0 ~ 30 cm, 水分损失以蒸发为主, 冻结层对土壤蒸发有抑制作用; 冻结层的融化是造成各下垫面不同土层土壤含水率差异, 以及各土层在不同融化阶段土壤含水率差异的主要原因。     

基于集合卡尔曼平滑算法的土壤水分同化

为研究观测资料稀少情况下土壤质地及有机质对土壤水分同化的影响,发展了集合卡尔曼平滑(Ensemble Kalman Smooth, EnKS)的土壤水分同化方案。利用黑河上游阿柔冻融观测站2008年6月1日至10月29日的观测数据,使用EnKS算法将表层土壤水分观测数据同化到简单生物圈模型(Simple Biosphere Model 2, SiB2)中,分析不同方案对土壤水分估计的影响,并与集合卡尔曼滤波算法(EnKF)的结果进行比较。研究结果表明,土壤质地和有机质对表层土壤水分模拟结果影响最大而对深层的影响相对较小;利用EnKF和EnKS算法同化表层土壤水分观测数据,均能够显著提高表层和根区土壤水分估计的精度,EnKS算法的精度略高于EnKF且所受土壤质地和有机质的影响小于EnKF;当观测数据稀少时,EnKS算法仍然可以得到较高精度的土壤水分估计。     

Effects of Soil Composition on Zn Speciation in Drainage Waters from Agricultural Soils

The influence of Zn speciation on Zn transport by drainage from different soils to surface water is examined in a stream catchment in an agricultural area. Drainage waters were collected from two types of soils, a mineral soil (MS) and a soil rich in organic matter (OS) by means of artificial drainage pipes. The speciation of dissolved Zn in the stream and the drainage waters was determined using ligand-exchange and voltammetry. About 50–95% of dissolved Zn is bound in strong complexes, and the free Zn²⁺ ion concentration is in the range of 1–16% of dissolved Zn. A substantial part of Zn is present in weaker organic or inorganic complexes. The simulated Zn speciation using the WHAM VI model is compared to the determined speciation. Free Zn²⁺ concentrations predicted by the WHAM VI model are generally higher than the analytically determined free Zn²⁺, but are mostly within the same order of magnitude. Effects of different soil organic matter content on Zn speciation and transport are discussed. Zn speciation in the drainage at the OS site is influenced by the distribution of organic matter between the solid and solution phase. The abundant organic Zn complexes in solution contribute to facilitate Zn transport from soil into surface waters, through the drainage at the OS site. Drainage from the OS site contributes about twice as much Zn input to the receiving water as the MS soil, as related to specific area. The mineral soil contains much lower organic matter, and a part of Zn bound with inorganic phases can hardly be released by dissolved organic ligands, leading to much higher Zn retention at the MS site.     

上海软土动力参数变异性对土层地震反应的影响

应用模态摄动法求解水平分层均匀土层的地震反应，通过大量的数值计算，讨论上海软土土性变化对土层基本周期和表面地震加速度反应的影响。数值结果表明：准确获取土层的动力参数对土层地震反应计算有重要影响，在现场实测获得较为翔实的土样动力特性参数的基础上，土层土性动力参数变异性所产生的计算误差是有限的。     

表面渗流对生态边坡中客土稳定性影响研究

讨论表面渗流对生态边坡中客土稳定性的影响,设计并进行了同一种客土的无渗流和表面渗流情况下的稳定性试验。表面渗流情况下客土的破坏模式与无渗流情况下相同,即一条沿平面网上表面的平行于原边坡坡面的直线滑动面。利用表面渗流情况下的客土稳定性试验结果,验证了杨俊杰等提出的客土稳定设计图表的适用性。试验结果和理论分析均表明,渗流使客土的稳定性显著降低。     

岩溶石山区坡地土壤剖面水分与蒸发特征——以桂林丫吉试验场为例

选取桂林丫吉试验场岩溶石山坡面上典型覆盖土壤的两个单元体为对象,对其土壤剖面层含水量的分布变化、土壤蒸发速率大小及其相关影响因素进行分析研究,结果表明:(1)土壤剖面最大含水率层位于土壤底部与基岩的交界处,中间过渡层土壤含水量最少,表层土壤水分受外界因素影响而变化显著;(2)在夏季岩溶石山区地表蒸发强烈,直径10cm的土壤柱日蒸发量为5~12mL之间,夜蒸发量在0~3mL之间;(3)几天内决定地表土壤日蒸发量(y)大小的因素主要是太阳辐射(x2)和土壤温度(x4),其关系式可表示为:y=18.018+0.001x2-0.691x4。      

基于RS和GIS的松辽平原黑土流失研究

基于RS和GIS技术,利用1986年TM数据和2001年ETM数据,对松辽平原黑土分布现状与动态变化进行监测研究,分析了黑土流失特点及其时空分布规律,并引入冲沟线密度概念量化黑土流失趋势。结果表明：松辽平原典型黑土面积54 989.92 km^2,沿京哈铁路线呈弧形条带状展布;1986-2001年间,黑土区水土流失面积达3 765.21 km^2,减少速度为251.01 km^2/a,集中在河流两岸、较大建筑用地附近和与盐碱土接壤的地区;仅考虑冲沟的有效作用域,预计到2016年黑土面积平均会有1411.0 km^2/a转变为冲沟,黑土流失状况不容乐观。     

青藏高原唐古拉地区暖季土壤水分对地表反照率及其土壤热参数的影响

为了研究青藏高原暖季土壤水分对冻土区地表热状况的影响,选取2010-2012年5-9月在青藏高原唐古拉气象场获取的气象及其活动层数据,分析了表层土壤水分对地表反照率以及土壤热参数的影响.结果表明：唐古拉站暖季表层土壤含水量集中在0.15～0.27之间,地表反照率值集中在0.14～0.24之间,日平均土壤热导率的波动范围在0.9～2.0 W·m^-1·K^-1之间,土壤热容的波动范围主要集中在0.8×10⁶～1.8×10⁶ J·m^-3·K^-1之间,而土壤热扩散率则主要集中在0.6×10^-6～2.2×10^-6 m2·s^-1之间.土壤水分对地表反照率影响较大,随着土壤水分的增长,地表反照率呈现出明显的减小趋势.土壤水分对地表反照率的影响还受到植被生长周期的影响,土壤水分和地表反照率之间的关系在植被枯萎期和生长期有明显的差异性.唐古拉地区土壤热参数也明显受到土壤水分变化的影响,随着土壤水分的增加,土壤热导率、热容和热扩散率都为增大趋势,但是土壤水分对土壤热导率的影响较为显著,而对土壤热扩散率的影响则不显著.     

辽宁西部沿海地区土壤碳库构成及变化规律研究

基于辽宁西部沿海地区多目标地球化学调查获得的表层和深层土壤碳含量数据,计算了研究区表层（0~20 cm）、中层（0~100 cm）和深层（0~180 cm）的土壤碳密度及储量,探讨了不同分类单元的土壤碳库构成特征及固碳潜力,并对近40年来土壤有机碳变化规律进行研究.结果显示：1）研究区土壤碳库构成以有机碳为主,无机碳储量随深度增加有所增大.表层、中层和深层土壤有机碳密度分别为2.14、7.59和11.27 kg/m²,低于全国多目标调查区平均值和环渤海地区.2）不同分类单元土壤碳库构成具有一定差异：表层土壤元古宇和中生界单元的碳密度较大,而中层和深层表现为古生界土壤碳密度较大;山地土壤碳密度大于丘陵和平原;褐土土壤碳密度最高,潮土最低;林草地土壤碳密度最高,耕地和园地较低.3）研究区表层、中层和深层固碳潜力分别为33.91、103.32和129.37 Mt,其中有机碳的固碳潜力大于无机碳.4）近40年间,土壤有机碳总体呈增加态势,其中,耕地和园地的表层土壤总体表现为碳源效应,释放有机碳量0.29 Mt.棕壤分布区和林地分布区对土壤有机碳的输入贡献最大.     

枫丹白露砂土的环境箱蒸发试验

为研究土壤水分的蒸发机理,自主开发了大型环境箱试验装置,并以枫丹白露砂土为研究对象,室内模拟土壤水分的蒸发过程。该试验在控制大气参数和保持土壤底部水位稳定的条件下,对蒸发过程中大气参数（空气温度、相对湿度和流量）和土壤参数（土壤温度、基质吸力和体积含水量）的变化,特别是土壤表面基质吸力的变化进行了研究。同时根据试验结果对蒸发速率及累积蒸发量进行了计算分析。研究结果表明:蒸发主要限制在土壤浅层区域,浅层土壤的体积含水量和温度的变化均较大;空气温度和土壤蒸发过程对土壤温度的变化具有较大的影响;土壤表面空气相对湿度与蒸发过程具有相关性;土壤基质吸力随着蒸发的进行逐渐增大; 实际蒸发速率呈现3个阶段。