非饱和直剪仪改造及砂土-结构剪切试验

土与结构相互作用问题涉及实际工程的多个方面,研究土-结构接触面力学特性是解决该问题的基础。通过对常规非饱和直剪仪进行改造,并利用改造的非饱和直剪仪进行非饱和砂土-结构接触面剪切试验,研究了基质吸力、结构面类型和净法向应力对接触面抗剪强度的影响。结果表明：基质吸力对非饱和砂土-结构接触面的界面黏聚力影响较大,对界面摩擦角影响较小;随着基质吸力的增加,非饱和砂土-混凝土接触面的抗剪强度先增大后减小,存在峰值效应;基质吸力对非饱和砂土-钢接触面的抗剪强度影响较小,基质吸力不变的条件下,随着净法向应力的增加,砂土-钢接触面的抗剪强度呈非线性增长;净法向应力对非饱和砂土-结构接触面对应基质吸力的界面摩擦角（δb）的影响较小。最后,建立了基于峰值效应的非饱和砂土-混凝土接触面抗剪强度公式。     

一种测试不同温度下非饱和土土-水特征曲线的试验装置

研究目的：研制一种试验装置,以实现对非饱和土土-水特征曲线温度效应的有效测试。创新要点：1．研制了一种温控非饱和土三轴试验装置,包括加载系统、吸力控制系统和温度控制系统;2．利用研制的温控非饱和土三轴试验装置,对不同温度（25,40和60℃）以及不同应力（40100和200kPa）条件下的非饱和土土-水特征曲线进行了试验测定。研究方法：1．总结分析已有的温控三轴仪所采用的加热方式的优缺点,提出环向加热压力室内水体的方法;2．基于GDS非饱和土三轴仪,研制可实现温度控制功能的温控非饱和土三轴仪（图1、2）;3．开展不同温度及不同应力条件下非饱和土土水特征曲线的试验研究。重要结论：1．所研制的温控非饱和土三轴仪的实用效果得到验证;2．温度的升高将引起非饱和土持水性能的降低。     

一种测试不同温度下非饱和土土-水特征曲线的试验装置（英文）

研究目的:研制一种试验装置,以实现对非饱和土土-水特征曲线温度效应的有效测试。创新要点:1.研制了一种温控非饱和土三轴试验装置,包括加载系统、吸力控制系统和温度控制系统;2.利用研制的温控非饱和土三轴试验装置,对不同温度(25,40和60°C)以及不同应力(40,100和200 kPa)条件下的非饱和土土-水特征曲线进行了试验测定。研究方法:1.总结分析已有的温控三轴仪所采用的加热方式的优缺点,提出环向加热压力室内水体的方法;2.基于GDS非饱和土三轴仪,研制可实现温度控制功能的温控非饱和土三轴仪(图1、2);3.开展不同温度及不同应力条件下非饱和土土-水特征曲线的试验研究。重要结论:1.所研制的温控非饱和土三轴仪的实用效果得到验证;2.温度的升高将引起非饱和土持水性能的降低。     

毛细水作用下低路基强度和变形特性研究

低路基中,地下水因土壤基质对水分的吸力作用,导致路基土干湿状态发生变化,进而影响路基的强度及变形特性.路基土是非饱和土,其强度变化和变形特性需采用非饱和土理论解释.本文介绍毛细水作用下低路基强度和变形特性的主要研究成果.     

压实非饱和土的模量与含水率关系分析(英文)

为了客观可靠地评价实际工程中路基压实土的工程性能,在路基填筑设计时考虑了道路实际服务期内气候变化对路基压实土性能的影响. 鉴于含水率测试方法简单且应用广泛,直接采用含水率代替吸力寻求压实非饱和土模量和含水率之间的联系. 采用非饱和土三轴仪对不同初始压实含水率和经历干湿过程后不同含水率土样进行常含水率三轴试验,分析了含水率和围压等对土体模量的影响规律. 研究结果表明: 土体含水率的增加会引起非饱和压实土体模量的降低,且在试验含水率范围内非饱和压实土体模量随含水率呈指数规律变化; 土体模量随围压的增大而增加,但含水率对模量的影响较围压对模量的影响更为显著. 该研究可为服务期内非饱和压实路基土的性能变化评价提供参考.     

考虑滞回效应的非饱和土弹性剪切模量简化模型（英文）

目的:非饱和土的弹性剪切模量是预测土体变形和土工建筑物正常使用服役性能的重要参数之一。本文旨在提出一个描述非饱和土弹性剪切模量的简化模型,减少标定模型参数所需要的耗时非饱和土试验,并考虑吸力、应力、干湿循环及孔隙比对弹性剪切模量特性的影响。创新点:1.提出考虑滞回效应的非饱和土弹性剪切模量简化模型;2.减少标定模型参数所需要的试验。方法:1.基于前人非饱和土弹性剪切模量试验结果,考虑非饱和土中土颗粒间的平均骨架应力及毛细水提供的法向应力作用,通过理论推导建立非饱和土弹性剪切模量的半经验简化模型;2.通过文献中不同非饱和粉土及砂土的弹性剪切模量试验结果验证简化模型的适用性。结论:1.得到一个描述非饱和土弹性剪切模量的简化模型,该模型仅需两个模型参数,减少了标定模型参数所需要的耗时非饱和土试验;2.通过四组不同非饱和土弹性剪切模量试验数据验证了简化模型的适用性,表明该模型能考虑吸力、应力、干湿循环以及孔隙比对弹性剪切模量特性的影响;3.由于进行了简化,该模型可能存在少量预测误差,在宽应力和吸力范围内运用该模型时需要谨慎。     

土工织物加筋非饱和土强度试验研究

在室内拉拔、摩擦试验基础上选取土工合成材料,对选取的土工合成材料进行加筋效果试验,分析了土工合成材料与非饱和土体相互作用特性及加筋效果,得出一些有益的结论,同时对存在的问题提出了建议,为以后土工合成材料在不同地区的工程应用及科研提供了理论参考依据.     

考虑盐溶液渗入影响的膨胀土边坡稳定性分析

为分析盐溶液渗入对膨胀土抗剪强度及边坡工程的影响,引入渗透吸力修正了Fredlund抗剪强度公式中的有效应力,得到了盐溶液渗入条件下的非饱和膨胀土抗剪强度公式,并应用于微分Morgenstern-Price法的推导,得到了安全系数的递推求解式.进行KCl溶液和NaCl溶液改性膨胀土的室内直剪试验,发现2种盐溶液均降低了...     

正交各向异性土石坝非饱和稳定渗流分析

基于固定网格有限元法和土体基质吸力与饱和度之间的相互关系,推导了基质吸力的渗流控制方程,对渗透系数各向同性与各向异性的均质土石坝进行了稳定渗流场的数值模拟,研究水—土特性模型参数对渗流的影响,分析了基质吸力、流速矢量、孔隙压力、渗流量、渗流速度的变化规律.结果表明,坝体内的渗流量和渗透速度与土体渗透系数各向异性关系密切,Van Genuchten模型中α对吸湿曲线的影响较大.提出了在实践工程中考虑土体的非饱和及各向异性更合理,且慎重确定土体吸湿曲线的各参数.     

蓄水池及排水管对边坡稳定性影响分析

本文模拟的是某边坡上的废弃蓄水池及排水管对边坡的稳定性影响。废弃的蓄水池在高降雨强度的情况下容易形成汇源积水,积水在边坡体内渗流,致使边坡的安全系数降低。运用有限元软件SEEP对某蓄水池的非饱和土边坡进行渗流模拟,分析了蓄水池积水渗流的渗流场及对边坡安全系数的影响,同时模拟了排水管堵塞与畅通的情况对边坡安全系数的影响。     

Coupled Numerical Analysis of the Stability Behaviour of Unsaturated Soil Slopes Under Rainfall Conditions

Thebasicstressvariablesintheconstitutivemodelde velopedbyAlonsoetal[5] aresoilnetstressandsoilmatricsuctions ,whicharedefinedby　　　σ″ =σ -ua (1)　　　s=ua-uw (2 )whereσisthetotalstress,uwistheporewaterpressureanduaistheporeairpressure .　　Thenetmeanstresspanddeviatoricstressqarede finedas　　　p =σ1+2σ33-ua (3)　　　q =σ1-σ3(4 )　　Asgenerallyregarded ,thesoilsuctioniscomposedoftwoparts ,matricsuctionandosmosissuction .TheosmosissuctionisneglectedoriginallyinAlonsoetal′smodelandhe…     

Effect of suction change on water content and total volume of an expansive clay

A laboratory study was carried out on both natural and compacted specimens to investigate the complex soil-water interaction in an unsaturated expansive clay. The laboratory study includes the measurement of soil-water characteristic curves, 1D free swelling tests, measurement of swelling pressure and shrinkage tests. The test results revealed that the air-entry value of the natural specimen was quite low due to cracks and fissures present. The hydraulic hysteresis of the natural specimen was relatively insignificant as compared with the compacted specimen. Within a suction range 0 to 500 kPa, a bilinear relationship between free swelling strain (or swelling pressure) and initial soil suction was observed for both the natural and compacted specimens. As a result of over-consolidation and secondary structures such as cementation and cracks, the natural specimens exhibited significant lower swelling (or swelling pressure) than the compacted specimen. The change of matric suction exerts a more significant effect on the water phase than on the soil skeleton for this expansive clay.     

Numerical Analysis of Soil Plug Inside Suction Foundations During Suction Penetration by Discrete Element Method

The phenomenon of the soil plug usually rising inside the suction foundations during suction penetration was quantitatively described and predicted. The formation process of the soil plug was simulated and calculated by DEM （discrete element method） model. The seepage flow, the self-weight of soil, the friction on the chamber wall as well as the suction inside the chamber are considered as the main external forces in the process. The results are compared with a set of laboratory model tests performed by using three soil types （sand, silty clay and clay） in the Bohai Sea area. The heights of soil plug from numerical estimations are lower than those from model test results, mainly because the suction pressure and friction resistance are applied in an ideal way under the numerical simulation.     

Estimation of Heights of Soil Plug Inside Bucket Foundations During Suction Penetration by Deformable Discrete Element Modeling

Bucket foundations[1 ,2]are a relatively newtype offoundation usedto support offshore structures .Each bucketfoundation consists of a thin cylindrical steel shell ,cappedwithalid of steel or concrete .Thefoundationcan penetrateinto sea floor when pumping …     

Influences affecting the soil-water characteristic curve

INTRODUCTION The soil-water characteristic curve (SWCC) gives the relationship between the amount of water in the soil (i.e. gravimetric or volumetric water content) and soil suction (i.e. matric suction at low suction and total suction at high suction). Many properties of a partially saturated soil such as the coefficient of permeability, shear strength and volume strain, pore size distribution, the amount of water contained in the pores at any suction, can be obtained from the SWCC. …     

Investigation of the hydro-mechanical behaviour of fouled ballast

In this study, a fouled ballast taken from the site of Sénissiat, France, was investigated. For the hydraulic behaviour, a large-scale cell was developed allowing drainage and evaporation tests to be carried out with monitoring of both suction and volumetric water content at various positions of the sample. It was observed that the hydraulic conductivity of fouled ballast is decreasing with suction increase, as for common unsaturated soils. The effect of fines content was found to be negligible. For the mechanical behaviour, both monotonic and cyclic triaxial tests were carried out using a large-scale triaxial cell. Various water contents were considered. The results were interpreted in terms of shear strength and permanent axial strain. It appeared that the water content is an important factor to be accounted for since any increase of water content or degree of saturation significantly decreases the shear strength and increases the permanent strain. Constitutive modelling has been attempted based on the experimental results. The model in its current state is capable of describing the effects of stress level, cycle number and water content.     

不饱和聚酯树脂气干性研究

多元醇和多元酸发生缩和反应生成聚酯,聚酯溶解于苯乙烯制成不饱和聚酯树脂。缩聚反应进行的程度对不饱和聚酯树脂的气干性能有很大影响。生产过程中,通过优化控制反应终点酸值,优化设计醇、酸比例,可制得气干性能优良的不饱和聚酯树脂。