The soil hydrologic response to forest regrowth: a case study from southwestern Amazonia     

Sarah Godsey  Helmut Elsenbeer 《水文研究》2002,16(7):1519-1522

As a large and dynamic land‐use category, tropical secondary forests may affect climate, soils, and hydrology in a manner different from primary forests or agricultural areas. We investigated the saturated hydraulic conductivity K_sat of a Kandiudult under different land uses in Rondonia, Brazil. We measured K_sat at four depths (12·5, 20, 30 and 50 cm) under (a) primary forest, (b) a former banana–cacao plantation (SF1), and (c) an abandoned pasture (SF2). At 12·5 cm, all three land uses differ significantly (α = 0·1), but not at the 20 and 30 cm depths. At 50 cm, K_sat was significantly greater in the former pasture than in other land uses. Lateral subsurface flow is expected during intense rainfall (about 30 times per year) at 30 cm depth in SF1 and at 50 cm depth in the forest, whereas the relatively low permeability at shallow 12·5 cm in the SF2 may result not only in lateral subsurface flow, but also saturation overland flow. For modelling purposes, recovering systems seem to have K_sat values distinct from primary forest at shallow depths, whereas at deeper layers (>20 cm) they may be considered similar to forests. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Extension of the Griffith's fracture criteria to saturated clays     

K.M. Dgu  M. Souli  B. Ladanyi 《国际地质力学数值与分析法杂志》2003,27(4):275-288

Inglis [1] has solved the problem of distribution of stress in an elastic plate around an elliptical hole. His works clarify the role of cracks in the failure of an elastic material. However, his solution cannot be applied to saturated clay because he considers only total stresses, while, in saturated clay, the criterion of rupture should be expressed in terms of effective and not total stresses. The solution of Atkinson and Craster [2] using Biot's poroelasticity theory, shows that there is no high pore pressure in the vicinity of the crack tips for saturated clay. The major difference between this approach and the Biot's theory of is that, in saturated clay, strain is a function of the variation of the effective stress [3], while, in poroelastic media, strain is only a function of the variation of the total stress [4, Equation 2.2]. Also in their solution there is continuity between the pore fluid and the inner fluid in the crack. Their solution is valid for poroelastic media involving a movement of the pore fluid. In our solution there is no movement of the pore fluid (Undrained condition). In this paper we have solved the same problem as Inglis [1], but for the particular case of saturated clay obeying elastic law. By solving this problem we obtained the expressions for pore pressure, effective stress, total stress and displacements. The results show that not only the total stress but also the pore pressure and the effective stress are also high in the vicinity of the crack tips. A new failure criterion, based on Griffith's strain energy principle [5] and maximum tensile stress [6], valid for saturated clay is developed in this paper. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

利用黄河泥沙围出“渤海湖”的初步设想   总被引：1，自引：0，他引：1  

郝戬 《地球信息科学学报》2001,3(3):76-79

本文是一个关于将渤海变成淡水湖的水利工程的构想。让黄河的大量泥沙通过人工导流的方式沿莱州湾南岸与渤海海峡沉积延伸,产生的陆地将渤海封闭并逐渐形成淡水湖。这一工程将陆地连接山东半岛与辽东半岛,并为华北提供巨大淡水库,具有显著的经济、生态效益。具体实施上,可通过两道渔网式围栏促使黄河泥沙定点沉积并阻挡浪潮侵蚀,通过加强汛期水量增加黄河口泥沙。  相似文献   

饱和油藏CO2非混相吞吐增油规律研究——以印尼南苏门答腊盆地典型油藏为例     

程子芸  丁伟  张晓玲  曲良超  代芳文 《地质论评》2023,69(Z1):249-251

  相似文献   

基于OpenSees的砂土本构模型对比研究          下载免费PDF全文

周林禄  苏雷  邱志坚  凌贤长  张安琪 《地震工程学报》2022,44(1):128-135

饱和砂土液化是由地震引起的一种最常见的工程地质现象,也是造成重大地震灾害的主要原因之一。由于成因的复杂性和所造成灾害的严重性,饱和砂土液化一直是土动力学和岩土地震工程研究领域的重要课题。针对饱和砂土液化问题,基于开源地震工程数值计算平台OpenSees,对材料库中的4种砂土本构模型进行数值计算。采用二维u-p单元模拟土颗粒位移和孔隙水压力,分析和对比4种模型在循环动力荷载作用下的加速度、超孔隙水压力、位移、剪应力-剪应变和平均有效应力路径方面的响应结果。研究结果表明:(1)砂土对输入加速度表现出一定的放大效应,对于不同的模型,该放大效应存在一些差异;(2) Stress Density模型在循环动力荷载作用下易产生永久变形;(3)在循环动力荷载作用下,PDMY模型和CycLiqCPSP模型的强度逐渐降低,直到完全消失;(4) Stress Density模型和Manzari Dafalias模型在循环动力荷载下表现出明显的剪胀效应。研究成果对砂土液化的数值模拟问题具有重要的理论价值,可为饱和砂土的液化模拟和砂土本构模型的选取提供参考。  相似文献   

基于原位双环、试坑浸水试验和数值模拟反演的Q3黄土饱和渗透系数对比研究     

蒋小虎  黄跃廷  胡海军  陈铄  陈锐  王崇华  汪慧  康顺祥 《岩土力学》2022,43(11):2941-2951

为准确获取原状Q3黄土的竖向和水平饱和渗透系数,进行了原位、室内试验测试以及数值模拟反演,并应用大型试坑浸水试验检验了所获饱和渗透系数的可靠性。进行了不同内径尺寸的原位双环入渗试验,获取了竖向饱和渗透系数,并应用室内试验测试了竖向和水平饱和渗透系数以及持水曲线;应用COMSOL软件对双环入渗试验进行数值模拟,检验了所测饱和渗透系数的可靠性,利用正交试验获得了最优的竖向和水平饱和渗透系数取值,并利用反演结果对试坑进行数值模拟,将其水分入渗情况与实测值对比。研究结果表明：在现场进行双环入渗试验时选取较大内径的双环获得的竖向饱和渗透系数更为合理。针对双环入渗试验,数值模拟反演所得最优饱和渗透系数在竖向上接近于原位试验所得竖向饱和渗透系数、水平向上接近室内所测水平向饱和渗透系数,竖向饱和渗透系数比水平向饱和渗透系数更加显著地影响水分入渗过程。通过对大型试坑水分入渗情况的验证,检验了反演所得最优饱和渗透系数的可靠性。  相似文献   

粉细砂地层防渗帷幕综合施工方法          下载免费PDF全文

丁跃军 《探矿工程》2015,42(4):76-78

四川省武都水库右岸EL574 m灌浆平洞揭露出厚度2.3～9.8 m的粉细砂层,普通水泥高压灌浆无法形成可靠的防渗帷幕。采用高压旋喷、湿磨细水泥、化学灌浆的组合处理方式,取得了较好的施工效果。通过钻孔压水、大功率声波CT、单孔声波、钻孔全景数字成像等方法检测,表明达到了设计防渗要求。  相似文献   

太行山东麓北拒马河冲积扇结构探测及地震砂土液化判别     

刘莎莎  丰成君  谭成轩  邓亚虹  戚帮申  孟静  张鹏  宋焱勋  慕焕东  周永恒 《地球学报》2022,43(1):82-92

北拒马河冲积扇及邻近地区位于太行山东麓,地表覆盖全新世(Qh)松散砂土与粉土,该区域地下水埋深较浅,潜在地震最大震级达6.5级,在地震作用下存在发生砂土液化危险性.通过野外地质调查、工程地质钻探和高密度电阻率法勘探揭示北拒马河冲积扇地层结构特征.在此基础上,采用原位标准贯入试验和室内动三轴试验评价北拒马河冲积扇饱和砂土...  相似文献   

粉土中筒型基础贯入阻力的研究     

马文冠  刘润  练继建  郭绍曾 《岩土力学》2019,40(4):1307-1312

筒型基础在海洋工程中应用广泛,贯入阻力的准确计算是筒型基础成功应用的关键。在海洋工程中,粉土是介于砂土与黏土间的特殊土,现有计算方法中将粉土等同于砂土,忽略了黏聚力c对贯入阻力的影响。开展了粉土中筒型基础的现场贯入试验,观测了自重下沉阶段与负压贯入阶段筒型基础贯入阻力与贯入深度的关系,提出了粉土中计算沉贯阻力的方法,并对不同筒端形式的减阻效果进行了深入分析。研究结果表明,采用现有规范方法计算粉土中筒型基础的贯入阻力值较实测值偏小20%,提出的两种方法不仅适用于计算粉土中筒型基础的贯入阻力,而且能够反映负压贯入阶段的减阻效果;尖筒端可使筒端阻力减少50%,减阻环可使筒侧摩阻力减少50%,但减阻环会破坏筒壁周围土体,形成渗流通道,导致负压失效。  相似文献   

饱和土地下源u-P形式解答动力响应计算     

丁伯阳  宋宥整 《岩土力学》2019,40(2):474-480

一直以来,由Biot孔隙弹性动力方程得到的饱和土地下源Green函数都是u-w形式（u为固相介质位移,w为流相相对于固相的平均位移）。应用两相介质纵波解耦理论,得到了饱和土半空间地下点源荷载的u-P形式（P为孔压）Green函数频域解答;克服了u-w形式Green函数在边界元（BEM）积分时的增根影响。再由Hankel反演,结合Somigliana表象积分,完成BEM计算。并以计算结果分析了地下集中力作用时,饱和土位移、孔压、排水量等动力特性,这对地铁等交通工程、地震工程、土-结构动力相互作用（SSI）的响应计算都具有较重要应用价值。  相似文献