加固膨胀土路堑边坡中框架梁的内力计算   总被引：1，自引：0，他引：1  

吴礼舟  黄润秋 《岩土力学》2005,26(7):1113-1117

锚杆框架梁是一种较好的加固膨胀土路堑边坡方式,但其设计理论依据仍不统一,未形成成熟的规范,多依靠工程经验。Winkler地基梁和半无限弹性体理论被用来计算框架梁的内力,在Winkler假设的前提下,着重分析了现浇梁和预制梁在不同长度条件下的内力分布。结果表明：框架梁的设计完全依据膨胀力是欠合理的,建议采用Winkler地基梁和半无限弹性体理论计算框架梁的内力,并结合工程实例,提出了相关的建议。  相似文献   

膨胀土的强度特性研究   总被引：9，自引：3，他引：6  

谭罗荣  孔令伟 《岩土力学》2005,26(7):1009-1013

研究了膨胀土的强度指标c,?与含水量?、干密度 及饱和度sr的关系,以及强度与膨胀压力p之间的关系,结果表明：c,tan?和 ,sr,?的关系与膨胀压力p和 ,sr,?的关系相似;任何状态的膨胀土的强度,皆可表示为饱和状态的强度和吸力引起的,并可用不同状态土的膨胀压力表示的附加强度两部份。  相似文献   

弱膨胀土浸水变形特性及其预测   总被引：1，自引：0，他引：1  

高游  孙德安  吕海波 《岩土力学》2015,36(3):755-761

对取自江苏省淮安市的膨胀土进行了浸水后的膨胀变形和压缩变形试验。在竖向压力25~800 k Pa范围下,研究了不同初始含水率和初始干密度对浸水膨胀变形特性的影响。结果表明:浸水饱和膨胀变形量主要取决于初始干密度,且初始含水率也有一些影响;在相同的含水率下,膨胀变形量随着干密度的增加而增大;在相同干密度条件下,含水率越大,浸水膨胀变形量略微减小。根据各组的固结状态线和浸水饱和膨胀后状态线的交点,得出了介于浸水膨胀和浸水压缩的分界状态线,此线基本上不受初始含水率的影响,进而可以判定不同孔隙比、不同竖向压力下土样处于浸水膨胀还是压缩。最后,基于浸水变形试验结果,提出了一种简便的预测弱膨胀土在不同竖向压力下膨胀变形量的方法。  相似文献   

膨胀性充填裂隙峰前本构关系实验研究     

陈金刚  徐平  张龚  李亚帮 《岩土力学》2011,32(10):2998-3003

以钠基膨润土为充填介质,水泥砂浆为裂隙壁制作充填裂隙,采用法向压缩、侧向约束的方式,对不同宽度和不同含水率条件下膨胀性充填裂隙的本构关系进行了探讨,获得了大量应力、应变实验数据.研究表明,膨胀性充填裂隙峰前本构关系可划分为3个阶段:流变阶段、压密阶段和弹性阶段.实验开始时,充填裂隙即进入流变状态,也就是说应力基本保持不...  相似文献   

Exploring aberrant bivalve shell ultrastructure and geochemistry as proxies for past sea water acidification     

Sabine Hahn  Erika Griesshaber  Wolfgang W. Schmahl  Rolf D. Neuser  Ann‐Christine Ritter  Rene Hoffmann  Dieter Buhl  Andrea Niedermayr  Anna Geske  Adrian Immenhauser 《Sedimentology》2014,61(6):1625-1658

Throughout much of Earth's history, marine carbonates have represented one of the most important geological archives of environmental change. Several pivotal events during the Phanerozoic, such as mass extinctions or hyperthermal events have recently been associated with ocean acidification. Nevertheless, well‐defined geological proxies for past ocean acidification events are, at best, scarce. Here, experimental work explores the response of bivalve shell ultrastructure and isotope geochemistry (δ¹³C, δ¹⁸O and δ²⁶Mg) to stressful environments, in particular to sea water acidification. In this study, the common blue mussel, Mytilus edulis, was cultured (from early juvenile stages to one year of age) at four pH regimes (pH_NBS 7·2 to pH 8·0). Shell growth rate and ultrastructure of mainly the calcitic portion of the shells were compared between experimental treatments. Specimens exposed to low‐pH environments show patches of disordered calcitic fibre orientation in otherwise well‐structured shells. Furthermore, the electron backscattered diffraction analyses reveal that, under acidified conditions, the c‐axis of the calcite prisms exhibits a bimodal or multi‐modal distribution pattern. Similar shell disorder patterns have been reported from mytilids kept under naturally acidified sea water conditions. In contrast, this study found no evidence that different pH regimes affect shell carbon, oxygen or magnesium isotope ratios. Based on these observations, it is proposed that: (i) stressful environments, in this case low sea water pH, predictably affect bivalve biomineralization patterns; and (ii) these findings bear potential as a novel (petrographic) proxy for ancient sea water acidification. An assessment of the applicability of these data to well‐preserved fossil shell material from selected time intervals requires additional work.  相似文献   

陕西宝鸡市新近系硬粘土工程地质特性 与斜坡失稳效应     

石菊松  曲永新  李滨  吴树仁 《地质通报》2013,32(12):1911-1917

陕西宝鸡市新近系硬粘土包括风成三趾马红土和“古三门湖河湖相堆积”的硬粘土,是西北地区典型的硬粘土地层之一,也是控制宝鸡市北坡黄土塬边大型滑坡分布的关键地层。为了深入认识该类特殊岩土,尤其是膨胀性粘土矿物（蒙脱石和其混层矿物）,根据该类地层的空间分布特征采集了30多个岩土样品,在宏观与细观结构特征分析基础上,利用移液管法、精细X-射线衍射（XRD）技术、乙二醇与乙醚极性有机分子吸附法,完成了样品粒度成分的定量分析和粘土矿物的精细测定,分析其膨胀势,并结合区域滑坡分布与工程边坡病害,揭示其边坡灾害效应。  相似文献   

Mechanical behaviour of expansive soils after several drying and wetting cycles     

《Geomechanics and Geoengineering》2013,8(4):213-221

This paper presents results from an experimental study performed on natural and compacted expansive soils in different loose and dense states using principally osmotic oedometers. The loose soils showed significant shrinkage, while the dense soils produced a swelling accumulation during the suction cycles. These cycles induced an equilibrium stage, which indicates an elastic behaviour of the samples under suction cycles. At the end of suction cycles, a loading/unloading test was performed on all samples at different constant suctions to define LC (loading collapse) yield curve as well as the newly defined SC (saturation curve) yield curve. Generally, the suction cycles for the looser soils approached the LC and SC yield curves while they became the same at the equilibrium state. For the denser soils producing the swelling strain accumulation, the unique LC and SC curves were activated together. Additionally, we found that at the equilibrium stage, both initially loose and dense samples presented the same mechanical parameters. In other words, the LC or SC yield curves superimposed for different initial states of the samples at the equilibrium stage. Moreover, these compression curves provided sufficient data to propose a simplified model for the mechanical behaviour of the swelling soils at the equilibrium stage.  相似文献   

南水北调潞王坟段弱膨胀土膨胀性研究   总被引：1，自引：0，他引：1  

项伟  董晓娟 《岩土力学》2012,33(4):986-992

河南新乡潞王坟段膨胀土系第三系泥灰岩风化而成,以高岭石黏土矿物为主,具有弱膨胀性,其膨胀变形特性受孔隙结构影响比较大。为了清楚地研究试验段弱膨胀土的膨胀特性,从有荷膨胀变形、膨胀应力、循环胀缩变形3个方面进行研究,得出不同于以往其他膨胀土的膨胀变形特性：（1）当初始干密度比较小时,上覆压力超过膨胀应力,此时试样遇水不发生膨胀变形,反而出现明显的湿陷现象;当压实度大于96%后,即使上覆压力超过膨胀应力,试样遇水后也不发生湿陷现象,膨胀变形随上覆压力增大而趋于稳定值;（2）试验段弱膨胀土的膨胀应力随初始含水率的增加先增大后减小,出现膨胀应力峰值;（3）随着循环胀缩级数的增加,弱膨胀土的胀缩特性迅速降低,在循环级数达到4时,其胀缩特性就趋于稳定。上述3方面的膨胀特性充分表明,该弱膨胀土的膨胀特性与孔隙结构有着密切的关系  相似文献   

南宁膨胀土非线性流变模型研究   总被引：1，自引：0，他引：1  

李珍玉  肖宏彬  金文婷  易文 《岩土力学》2012,33(8):2297-2302

对南宁非饱和膨胀土进行一系列的加载-卸载固结蠕变试验,得到了不同含水率的膨胀土在不同应力水平下应变-时间曲线和不同时刻的应力-应变等时曲线簇。通过对膨胀土各阶段蠕变变形的分析,得到了膨胀土的固结蠕变是包含有黏弹性变形和黏塑性变形成分的非线性蠕变。采用模型流变与经验流变理论相结合的方法,将膨胀土的蠕变变形分成线性和非线性两部分进行分析,蠕变柔量和线性黏弹性模量随时间减小,而线性黏塑性模量随时间增大。结合膨胀土的线性黏塑性模型和非线性黏塑性经验模型,建立能够描述膨胀土非线性流变的黏塑性本构方程。根据试验所得数据,通过非线性拟合方法得到各模型参数,用该模型进行数值分析得到的理论与蠕变试验结果对比非常吻合。研究成果为实际工程提供了流变变形计算分析的可靠依据。  相似文献   

输电线路节理化岩体注浆锚杆基础抗拔力模型试验研究     

孙益振  郑卫锋  范志强 《岩土力学》2012,33(1):78-82

针对输电线路注浆锚杆基础特点,根据相似理论设计了节理化岩体注浆锚杆基础抗拔模型试验,模型设计中考虑了岩石弹性模量、浆体弹性模量、节理迹长、节理倾角、锚杆埋深5个因素的变化,选择5因素4水平的正交试验方法进行了模型试验研究。结果表明,岩石弹性模量对注浆锚杆基础抗拔力的影响最大,其次为锚杆埋深、节理倾角、浆体弹性模量、节理迹长。试验过程中以剪切破坏和开裂破坏为主,并以此分析了注浆锚杆的传力机制,得出浆体与锚杆和岩体之间的黏结强度是控制试验结果的主要因素,影响着锚杆的极限抗拔力和破坏状态,在施工过程中应注意质量控制。  相似文献