【作者】 罗爱忠；

【导师】 邵生俊；

【作者基本信息】 西安理工大学 ， 岩土工程， 2008， 硕士

【摘要】 真三轴仪是一种任意应力路径下测试土力学特性的试验仪器。西安理工大学研制了一种新型压力室真三轴仪,它具有伺服步进电机驱动滚珠丝杆推进活塞产生压力的液压/体变控制器独立施加三向主应力的自动控制系统。本文首先进行了国内外同类仪器的比较分析和新型真三轴仪仪器性能的测试与调试;进而,利用该真三轴仪,进行了重塑黄土的真三轴试验,分析了真三轴应力条件下不同含水率重塑黄土的强度变形特性。通过以上的研究工作,得到了如下的一些认识:(1)西安理工大学真三轴仪采用轴向刚性板加载、侧向双轴液压柔性囊加载的三向加载方式;侧向双轴相邻液压囊之间采用径向弹性伸缩、平面弹性转动的薄壁钢板有效隔离;三向均应用伺服步进电机驱动滚珠丝杆推进活塞的液压/体变控制器加载,实现了三向独立加载、互不干扰。经测试分析,仪器系统性能稳定。(2)经过调试及控制系统的完善,能够完成各类常规试验及特殊试验:①应力、应变控制式等中轴应力比试验;②等球应力试验;③加卸荷循环应力路径试验;④侧向卸荷试验;⑤蠕变试验;⑥应力诱导各向异性试验。(3)通过对不同初始含水率和不同固结围压条件下的重塑黄土的试验分析表明,同一含水率及固结围压条件下,随着中主应力比的增大,应力应变曲线由强硬化型逐渐转化为弱硬化型或理想塑性;同一固结围压及中主应力比值条件下,随着含水率的增大,应力应变曲线由弱硬化型或理想塑性转化为强硬化型;同一含水率及中主应力比值条件下,随着固结应力增大,应力应变曲线也由弱硬化型或理想塑性转化为强硬化型。(4)通过重塑黄土的强度变化规律分析,不同应变条件下π平面上重塑黄土屈服曲线与其破坏曲线基本相似;不同含水率条件下π平面上黄土的破坏曲线相似,且随着含水率的增大逐渐向内收缩。通过π平面上重塑黄土破坏轨迹的拟合分析,邢义川所提出的破坏面的形状函数能很好地描述重塑黄土π平面上的破坏曲线,该破坏曲线位于摩尔库仑破坏面及松岗元SMP破坏面之外、广义米塞斯圆之内。(5)通过不同含水率重塑黄土应力空间破坏面变化规律分析,应用广义米塞斯准则和SMP准则建立了描述不同含水率黄土强度破坏面的准则;引用姚仰平等提出的变换应力空间方法,修正剑桥模型,提出了能够反映重塑黄土含水率变化的三维应力空间弹塑性模型的思路。更多还原

【Abstract】 A true triaxial apparatus is a testing system measuring the mechanics characteristics of soil under three-dimension principle stress condition.A new true triaxial apparatus with a new structural cell was developed by the geotechnical engineering institute in Xi’an University of Technology.By comparison loading ways of different true triaxial apparatuses both at home and abroad,the new true triaxial appratus’s charateristics was summarized as following:A kinds of hydraulic/Variable apparatus with stepper motor servo-driven was developed,which was used to load independently principal stress,and the corresponding automatic control system was developed.Furthermore,the true triaxial testing of remolded loess was executed on the new true triaxial apparatus,the characteristic of the stress-strain curve of the true triaxial testing of remolded loess and the the strength of the Loess remodeling was analyzed under different water content.Through the above research work,some points as following:(1)In this paper,the rigid axial loading,lateral load biaxial are flexible,lateral adjacent biaxial between the use of hydraulic radial capsule flexible scalable,flexible rotation of planar thin-walled steel effective segregation of the three independent axial loading system was used on the Xi’an university of technology true triaxial apparatus;and servo stepper motor driven hydraulic / variable load controller was used,the loading process of the independent three principal stress was realized,Noninterference direction stress and strain can be forecasted.(2)The true triaxial apparatus can to complete various types of conventional and special test pilot,the pilot project are:①The stress path test and the strain path test with the constant middle principal stress ratio b;②constant mean stress test;③and Unloading Stress test on cycle path;④lateral unloading test;⑤creep test;⑥stress-induced anisotropy test.(3)By analysis the experimental datas of remodeling loess under the conditions of adoption of different initial moisture content of consolidation pressure,the same consolidation pressure and moisture conditions,with the increase of the ratio of axial stress,stress-strain curve of the hard-liners gradually hardening into a weak ideal or plastic;the same consolidation pressure and the ratio of axial stress conditions,as the moisture increases,the stress-strain curve from weak sclerosis or idealism into hard plastic;the same moisture content and the ratio of axial stress conditions,as the consolidation stress increases,stress-strain curve from weak or hardened into a tough idea plastic state.(4)through analysis the remolded loess the Strength change rule,under the different strain condition,on theπplane,of the the yield curve of remolded loess and damage curve was basic similar;Under the different moisture content condition in theπplane,the loess damage curve is similar,and along with moisture content enlargement,the curve contracts inward,through to destroy path’s fitting analysis,on theπplane,the failure curve was well described by function which Yi-chuan Xing proposed,this failure curve located at mole of coulomb line and outside loose hillock Yuan SMP criterion curve,under same condition Mises circle.(5)on theπplane,through analysis the stress space failure change rule analysis of the remolded loess with the different water content,the application generally Mises criterion and the SMP criterion has established the description different water content loess intensity failure plane criterion;the transformation stress space method proposed by Yang-ping Yao etal was quoted to revises the Cambridge model and to establish the elastoplasticity model,which can reflect the deformation properties of remolded loess with water content change on the three dimensional stress space.更多还原