土工合成纤维土补强机理试验研究及工程应用   总被引：5，自引：0，他引：5  

张艳美  张旭东  张鸿儒 《岩土力学》2005,26(8):1323-1326

对土工合成纤维土（TEXSOL）的补强机理进行了理论分析,研究了各种因素对纤维土补强特性的影响规律及已有纤维土强度计算经验公式的缺陷,并在大量试验的基础上确定了一系列经验系数如K,Q,R,P等,得出了各种影响因素与纤维土补强特性的关系。研究结果表明,纤维土粘聚力的增量与纤维的韧度、细度及纤维土的配合比等参数有关;提出了能反映多种影响因素的纤维土补强计算经验公式;最后将直壁高度法推广到纤维土挡墙的设计中,并应用所提公式对纤维土挡墙进行了内部稳定分析。  相似文献   

搅拌桩复合地基平面模拟的简化方法探讨   总被引：12，自引：0，他引：12  

邓永锋  洪振舜  刘松玉  胡银宝  蔺宁君 《岩土力学》2005,26(Z1):209-212

水泥土搅拌桩(DMM)在高速公路工程中得到广泛应用,人们也希望能对该复合地基在路堤荷载下的地基的变形深入了解,其数值分析是一种重要的方法。但是,采用三维有限元进行数值模拟在高速公路工程中容易造成数组过大,计算时间并且收敛性比较差,因此把三维问题简化为二维问题是众望所归。在把三维问题简化二维平面问题简化计算时,最重要的是参数的折减。基于水泥土搅拌桩复合地基的特性,结合理论分析提出了一种参数折减的方法。并依据连盐高速公路实测的数据验证了该参数简化方法的可行性。  相似文献   

有明黏土中搅拌桩施工时的孔隙水压力     

沈水龙  蔡丰锡  顾伟华 《岩土力学》2006,27(4):648-652

深层搅拌桩施工时,固化剂的注入与叶片的搅拌作用不可避免地会扰动周围土体,改变桩周土体中的应力状态,产生超静孔隙水压力。在高灵敏性的日本有明黏土中搅拌桩施工时对周围土体中的孔隙水压力进行了现场监测。监测结果表明周围土体中产生了很高的超静孔隙水压力,其量值较土体的初始上覆压力还要大,使土体中的有效应力为零,处于张拉状态,但是该超静孔隙水压力在初始阶段消散得非常快。为分析施工引起的超静孔隙水压力,将搅拌桩施工时和周围土体的相互作用采用受剪的孔穴扩张过程来模拟,提出一种简单的方法来计算搅拌桩施工时周围土体中的超静孔隙水压力,同时考虑了固化剂注入时的膨胀压力与旋转叶片在搅拌时所产生的剪切力的作用。超静孔隙水压力由土的不排水抗剪强度、剪切力、注浆压力和孔隙压力系数所确定。所提出的计算方法得到实测数据的验证。  相似文献   

混凝土芯水泥土搅拌桩的有限元研究   总被引：12，自引：4，他引：8  

董平  秦然  陈征宙 《岩土力学》2003,24(3):344-348

混凝土芯水泥土搅拌桩是适用于软土地基处理的一种新型复合桩 , 具有施工方便 、造价低廉 、单桩承载力高等优点 。 在静试验的基础上, 采用弹塑性有限元方法研究了该桩在竖向荷载下的力学性状 ,包括桩土和桩内外芯应力比 , 荷载的传递, 桩侧塑性区分布以及沉降特性等 。  相似文献   

水泥土搅拌桩桩身质量的电阻率分析   总被引：2，自引：0，他引：2  

刘志彬  刘松玉  经绯  曹德洪 《岩土力学》2008,29(Z1):625-630

通过对某高速公路软基处理试验段水泥土搅拌桩芯样强度与电阻率指标的分析发现,水泥土搅拌桩的桩身质量与其施工工艺密切相关;在特定的施工工艺条件下,水泥掺入比与搅拌均匀性是影响桩身质量的2个重要因素;在相同深度处,桩身水泥土芯样的竖向电阻率高于其水平向电阻率;桩身水泥土芯样的电阻率与其无侧限抗压强度之间存在着很好的线性相关关系;水泥体芯样水平向电阻率的标准差在一定程度上反映了水泥掺入量和搅拌均匀性。综上所述,利用水泥土的电阻率及其相关指标对大规模施工条件下水泥土搅拌桩的桩身质量进行定量分析是一种经济、无损、简便和科学的方法。  相似文献   

柔性荷载下粉喷桩复合地基承载特性试验研究   总被引：8，自引：1，他引：7  

陈善雄  许锡昌  赵文光 《岩土力学》2007,28(2):274-278

开展了粉喷桩复合地基承载性能试验,实测了柔性荷载下桩、土应力,探讨了复合地基中桩土应力比及其变化规律。研究表明,粉喷桩复合地基载荷-沉降曲线一般表现为缓变型;粉喷桩复合地基承载力宜按相对沉降法取相对沉降比为0.01所对应的压力。由于砂垫层的流动补偿作用,柔性荷载下桩土应力比随荷载的增加变化较为平缓,在复合地基承载力基本值附近桩土应力比变化范围为1.73～6.83,平均值为3.20。  相似文献   

Organic carbon inputs,common ions and degassing: rethinking mixing dissolution in coastal eogenetic carbonate aquifers          下载免费PDF全文

Jason D. Gulley  Jonathan B.Martin  Amy Brown 《地球表面变化过程与地形》2016,41(14):2098-2110

Caves deliver freshwater from coastal carbonate landscapes to estuaries but how these caves form and grow remains poorly understood. Models suggest fresh and salt water mixing drives dissolution in eogenetic limestone, but have rarely been validated through sampling of mixing waters. Here we assess controls on carbonate mineral saturation states using new and legacy geochemical data that were collected in vertical profiles through three cenotes and one borehole in the Yucatan Peninsula. Results suggest saturation states are primarily controlled by carbon fluxes rather than mixing. Undersaturation predicted by mixing models that rely on idealized end members is diminished or eliminated when end members are collected from above and below actual mixing zones. Undersaturation due to mixing is limited by CO₂ degassing from fresh water in karst windows, which results in calcite supersaturation. With respect to saline groundwater, controls on capacity for mixing dissolution were more varied. Oxidation of organic carbon increased pCO₂ of saline groundwater in caves (pCO₂ = 10^–2.06 to 10^–0.96 atm) relative to matrix porosity (10^–2.39 atm) and local seawater (10^–3.12 atm). The impact of increased pCO₂ on saturation state, however, depended on the geochemical composition of the saline water and the magnitude of organic carbon oxidation. Carbonate undersaturation due to mixing was limited where gypsum dissolution (Cenote Angelita) or sulfate reduction (Cenote Calica) increased concentrations of common ions (Ca²⁺ or HCO₃^?, respectively). Maximum undersaturation was found to occur in mixtures including saline water that had ion concentrations and ratios similar to seawater, but with moderately elevated pCO₂ (Cenote Eden). Undersaturation, however, was dominated by the initial undersaturation of the saline end member, mixing was irrelevant. Our results add to a growing body of literature that suggests oxidation of organic carbon, and not mixing dissolution, is the dominant control on cave formation and enlargement in coastal eogenetic karst aquifers. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Determination of residence time and mixing processes of the Ubatuba,Brazil, inner shelf waters using natural Ra isotopes   总被引：1，自引：0，他引：1  

Willard S. Moore  Joselene de Oliveira 《Estuarine, Coastal and Shelf Science》2008

Coastal waters contain elevated dissolved activities of short-lived radium isotopes, ²²³Ra and ²²⁴Ra, having half-lives of 11.4 and 3.66 days, respectively. The input of these isotopes near the coast must be balanced by decay and mixing into the open ocean, where excess activities are zero. Since the decay rate is known, in the ideal case the mixing rate may be determined from the offshore distribution of these isotopes. This study found that samples collected in June 2000 followed the expected exponential decrease with distance offshore. We assign a dispersion coefficient of 28–39 m² s⁻¹ for this study. During January 2002 and November 2003, there was not a consistent decrease of activity with distance offshore. This is likely due to the ruggedness of the coastline, where many bays and small islands interrupt simple mixing patterns. To estimate exchange rates during 2002 and 2003, we used a model based on the decrease in the ²²⁴Ra/²²³Ra activity ratio (AR) with time for samples isolated from fresh inputs of Ra. This model yielded residence times of 1–2 weeks for samples collected within 20 km of the coast. We used this residence time to calculate the flux of ²²⁸Ra (half-life = 5.7 years) to the study area necessary to maintain the enrichment relative to ocean water. This enrichment is a factor of ten greater than the flux of ²²⁸Ra expected from submarine groundwater discharge (SGD) occurring within 50 m of shore.  相似文献   

The effect of the wave-induced mixing on the upper ocean temperature in a climate model   总被引：3，自引：1，他引：2  

HUANG Chuanjiang  QIAO Fangli  SONG Zhenya 《海洋学报(英文版)》2008,27(3):104-111

The significant underestimation of sea surface temperature （SST） and the temperature in the upper ocean is one of common problems in present climate models. The influence of the wave-induced mixing on SST and the temperature in the upper ocean was examined based on a global climate model. The results from the model coupled with wave-induced mixing showed a significant improvement in the simulation of SST and the temperature in the upper ocean compared with those of the original model without wave effects. Although there has still a cold bias, the new simulation is much closer to the climatology, especially in the northern ocean and tropical ocean. This study indicates that some important physical processes in the accurate simulation of the ocean may be ignored in present climate models, and the wave-induced mixing is one of those factors. Thus, the wave-induced mixing （ or the effect of surface waves） should be incorporated properly into climate models in order to simulate or forecast the ocean, then climate system, more accurately.  相似文献   

Impact of wildfire on source water contributions in Devil Creek,CA: evidence from end‐member mixing analysis     

Helen Y. Jung  Terri S. Hogue  Laura K. Rademacher  Tom Meixner 《水文研究》2009,23(2):183-200

A geochemical and end‐member mixing analysis (EMMA) is undertaken in Devil Canyon catchment, located in southern California, to further understanding of watershed behaviour and source water contributions after an acute and extensive wildfire. Physical and chemical transformations in post‐fire watersheds are known to increase overland flow and decrease infiltration, mainly due to formation of a hydrophobic layer at, or near, the soil surface. However, less is known about subsurface flow response in burned watersheds. The current study incorporates EMMA to evaluate and quantify source water contributions before, and after, a catchment affected by wildfires in southern California during the fall of 2003. Pre‐ and post‐fire stream water data were available at several sampling sites within the catchment, allowing the identification of contributing water sources at varying spatial scales. Proposed end‐member observations (groundwater, overland flow, shallow subsurface flow) were also collected to constrain and develop the catchment mixing model. Post‐fire source water changes are more evident in the smaller and faster responding sub‐basin (interior sampling point). Early post‐fire storm events are dominated by overland flow with no significant soil water or groundwater flow contribution. Inter‐storm streamwater in this smaller basin shows an increase in groundwater and a decrease in soil water. In the larger, baseflow‐dominated system, source water components appear less affected by fire. A slight increase in lateral flow is observed with only a slight decrease in baseflow. Changes in the post‐fire flow regimes affect nutrient loading and chemical response of the basin. Relatively rapid recovery of the chaparral ecosystem is evidenced, with active re‐growth and evapotranspiration evidenced by the fourth post‐fire rainy season. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献