为研究压实黄土地基湿陷变形规律和已有湿陷变形计算方法的可靠性,开展室内杨凌压实黄土地基载荷浸水模型试验,应用一维湿陷系数法、弦线模量法和切线模量法三种方法计算其湿陷变形量,并与实测结果进行对比.实验结果表明压实黄土地基浸水后,湿陷变形很快发生,随后湿陷变形量随时间几乎不再增加,湿陷变形集中在附加应力作用的地基上部土层.三种方法计算的湿陷变形结果表明:荷载板受荷较小时,不考虑侧向挤出和考虑侧向挤出修正系数的一维湿陷系数法所得湿陷变形量分别接近和大于实际变形量;受荷较大时,不考虑侧向挤出和考虑侧向挤出修正系数的一维湿陷系数法所得湿陷变形量均远小于实际变形量.基于原位载荷试验获得的弦线模量不适用于重塑压实黄土地基湿陷变形量计算.切线模量法由于未能较好考虑初始屈服面的弹性变形,计算所得湿陷变形量大于实际变形量.

针对干湿循环作用下盐渍化黄土侧限变形问题,系统开展了侧限压缩试验及溶陷试验,研究了氯盐盐渍化黄土在不同干湿循环路径、不同干湿循环次数及不同初始干密度下的一维固结压缩特性和溶陷变形特性.结果表明:压实盐渍化黄土的压缩变形随初始干密度的降低而增大,随干湿循环次数和增湿饱和度的增加而增大;土样e-lgp(e为孔隙比,p垂直压力)曲线变化幅度及压缩系数随初始干密度的减小和干湿循环次数的增多而增大;不同干湿循环路径下土样的e-lgp曲线在干湿循环次数低于5次时差异较大,在干湿循环次数达到10次时趋于一致;盐渍化黄土溶陷特性对各类条件的敏感程度依次为增湿饱和度、干湿循环次数、初始干密度.针对不同条件下盐渍化黄土溶陷系数曲线的不同表现形式,建立简易3参数模型,并与试验数据对比,表明该模型能够表征初始干密度及干湿循环次数对溶陷系数的影响规律.研究成果可为盐渍化黄土的干湿循环效应认知提供参考.

水利工程中库水位的周期性波动以及库岸边坡的复杂地质条件,使得库岸滑坡地质灾害频发.为研究库水位升降速率以及岩土体力学参数对岸坡稳定性的影响,本文以山美水库为研究对象,在采用包辛涅斯克(Boussinesq)非稳定渗流浸润线解析解计算的基础上,使用三维斜坡稳定性计算模型Scoops 3D进行库岸边坡稳定性计算.通过多工况计算比较得到:库岸边坡稳定性随着库水位下降速率增大而降低,而较大的库水位上升速率对库岸边坡稳定性有利;岩土体力学参数对库岸边坡稳定性的影响程度由大到小依次是:内摩擦角,土体重度,黏聚力.

闽北山区分布大量的残积土边坡,在夏季台风暴雨的侵害下,极易发生大型滑坡,研究该区域在降雨作用下边坡的稳定性具有重要的现实意义.为此,通过无人机倾斜摄影技术建立边坡表面地形图,运用ABAQUS软件进行降雨条件下三维边坡应力场和渗流场的耦合分析,研究了边坡土体渗流场变化规律并对边坡稳定性进行评价.结果表明,降雨对边坡表层土体产生的影响最大,边坡深部降雨入渗响应时间迟于边坡表层.在降雨初期,降雨入渗以垂直坡面入渗为主,降雨后期以竖直入渗为主.滑坡区域在空间上为椭球形,滑移面为从坡顶到坡脚贯通的圆弧形滑面,边坡产生了滑动,模拟结果与现场破坏及监测结果相吻合.

为研究拉裂—滑移式黄土崩塌的稳定性问题,分别采用极限平衡法和突变级数法得到崩塌体的最小安全系数计算公式和稳定性评价模型,以正交试验法得到的25个试验边坡为算例进行对比分析,得到拉裂—滑移式黄土崩塌稳定性评判准则,并进行实例验证.结果 表明,各控制变量中,对崩塌体稳定性影响最大的为边坡坡角,最小的为黄土的天然重度;利用突变级数法得到的稳定性评价结果与极限平衡法得到的结果基本一致.这说明突变级数法在分析拉裂—滑移式黄土崩塌稳定性时,可综合考虑多种因素的影响,弥补了极限平衡法带来的不确定性,具有实际应用价值.

乡村振兴战略需要综合型创新人才作保障,这既是农业院校工科专业人才培养的历史使命,也是农业院校新工科建设应该瞄准的方向.力学系列课程作为水利土木类专业创新人才培养的学科核心,由于诸多原因力学系列课程难以支撑新工科人才培养的总目标.以提升学生的核心素质与创新能力为目标,通过打破力学系列课程界限、重整课程内容来构建农业院校水利土木类合理知识结构,强化"三基"教学,注重创新性综合应用能力培养;通过典型科研成果反哺教学,激发学生的好奇心和兴趣、训练学生的力学思维、提升学业挑战度,实现合理增负与创新能力培养的目标;最终构建出农业院校水利土木类专业力学系列课程教学新模式.

通过饱和原状黄土常规三轴试验和非饱和原状黄土等吸力三轴试验研究吸力和净围压对非饱和黄土强度变形的影响,并用HUANG等、胡冉等和方祥位等提出的土水特征曲线模型分析剪切过程中排水规律.研究结果表明:等吸力下原状土样固结剪切体积变形随净围压增大而增大;等净围压下原状土样固结剪切体积变形量随吸力的增大基本呈减小趋势.p-q平面内饱和土CSL线逐渐超过低吸力下非饱和土CSL线,原因在于随着p值增大,相对于非饱和土,饱和土孔隙比越来越小,较小孔隙比对抗剪强度的贡献逐渐大于非饱和土吸力对抗剪强度的贡献.应用固结稳定的数据拟合出HUANG等和胡冉等提出的模型参数,并预测剪切过程中的排水量,发现剪切速率对排水量有影响,这两种模型适用于剪切速率慢,排水充分的情况,而方祥位等提出的模型对不同剪切速率会拟合出不同的参数.

Take typical widened levee for example, taking clay and arenosol serve as materials of old levee body and widing body, the paper uses numerical analysis software to calculate the seepage and deformation characteristics of widened levee under water level.The results show that the water content contour line is discontinuous at the intersection of the old and new levee body, the total water head contour line is rejected by the interface, and the water content and the total head appear sharply lower.Seepage slope significantly changed at the interface and widened subgrade toe.The maximum settlement of the widened levee appears at the shoulder of the new levee, and the settlement is related to the height of the water level.The vertical deformation of the levee foundation is saddle shaped.The lateral deformation of the widened levee shows the trend of the old and the new levee moving outwards.The change of the seepage field is caused by the difference of the new and old filling properties of the subgrade under the seepage action of river water.Deformation is caused by the influence of seepage field on the stress field under the effect of new levee self weight.

随着短肢剪力墙结构体系在高层建筑当中的应用,对于短肢剪力墙的承载力研究已经成为一项重要内容,尤其是抗震研究,本文通过对一字形短肢剪力墙的模拟抗震研究,分析了一字形短肢剪力墙在地震荷载作用下的应力云图.

Soil-water characteristic curve (SWCC) is an important characteristic of unsaturated soil. This paper investigates the total suction of the MX-80 bentonite, under different saturation and different concentrations of sodium chloride solutions. To create the soil-water characteristic curves for different amounts of NaCl, but same dry densities, the study used chilled-mirror dew-point WP4 potentiometer. The experimental results show that the concentration of salt in pore water has significant influence on the bentonite. With the increase of the NaCl concentration, the samples total suction increased gradually and the matric suction decreased. When the soil saturation was greater than 50%, the pore solution’s addition led to the rapid increase of the soil’s total suction. The low concentration of salt has relatively little effect on the matric suction of the MX-80 bentonite; while when the ion concentration is high, the solutions’ matric suction has a very significant impact on the soil matric suction.

为研究粉煤灰改良Q3黄土填料变形特性的效果,进行了不同粉煤灰掺量和养护龄期条件下改良Q3黄土填料的室内压缩与湿陷变形试验.试验结果表明:适量添加粉煤灰能够很好的改良Q3黄土填料的变形特性;粉煤灰改良Q3黄土填料的压缩系数随着粉煤灰掺量和养护龄期的增加而逐渐减小;粉煤灰掺量小于15％时,湿陷系数随着粉煤灰掺量的增加而减小;粉煤灰掺量大于15％时,湿陷系数随着粉煤灰掺量的增加而增加;15％粉煤灰掺量改良Q3黄土填料的湿陷系数随着养护龄期的延长而逐渐减小.试验条件下,粉煤灰改良Q3黄土填料的最优掺量为15％.

The bearing capacity,deformation law and strength of loess are influenced by its structural characteristic. We con-centrate on the structural evolution of undisturbed loess by performing unconsolidated - undrained shear tests to investigate the structural evolution under regular triaxial test characterized as compact - shear stress condition. The results show that increase of the initial water content turns the stress - strain curves from softening type to hardening type,while the confining pressure incre-ment changes the stress - strain curves from weak hardening into relatively strong hardening,demonstrating that the two factors in-fluence the structural evolution significantly. When the loess is not disturbed by consolidation process,both the initial water con-tent and confining pressure have impacted on the structural evolution routine,the structure damps faster under lower confining pressure than it does under higher confining pressure. In a lower water content environment,the damping of the structure is more sensitive to confining pressure than it is under higher water content.

为规避有限元极限分析法应用于边坡计算中的奇异点问题,并进一步提高该算法的精度和效率,基于有限元极限分析理论,通过二次圆锥优化Mohr-Coulomb屈服准则,利用优化后的屈服准则衡量离散单元,依据预定应力、应变的阈值搜索出边坡塑性区离散单元,对塑性区网格单元标记并局部自适应,通过该过程的多次循环迭代,实现网格有目的局部自动加密,多次优化并最终找出合理的剪切带.实例计算结果表明,模型3次自适应后均能达到理想的精度和误差控制,验证了网格自适应方法的有效性.

以泾阳黄土滑坡滑带土为研究对象,采用HJ-1型环剪仪对不同有效法向应力下重塑黄土进行了环剪试验,研究在单级剪和多级剪下的大位移高速滑带土的峰值强度、残余强度及其变形规律.试验结果表明:重塑黄土的峰值黏聚力及残余黏聚力均随着有效法向应力的增加而增大,但对内摩擦角的影响不明显.在较大有效法向应力作用下,剪切面土粒越容易沿剪切方向形成定向排列,试样的沉降变形随有效法向应力的增加而增大,多级剪所得残余强度较单级剪大.脆性指数随法向应力的增大而减小,但不同状态下试样的脆性指数均相差较小.

With the loess in Jingyang landslide zone as the research object ,HJ‐1 type of ring shear apparatus is adopted to carry out the single grade ring shear tests of the remolded loess in Jingy‐ang county to study the strength varying laws of remolded loess with different moisture contents , dry density and shear speed under the larger shear displacement . T he research results indicate that the stress‐strain curves of soil body appear to be weakened ;the cohesion force and internal friction angles decrease with an increase in moisture contents .The larger the shear speed reaching the peak value is ,the smaller the required shear displacement is and the larger the internal cohe‐sion force is ,but its effect upon the internal friction angle is not obvious .The dry density and peak value strength are found to be in positive correlative relation without obvious effect upon re‐sidual strength .The brittle index decreases with an increase moisture content and shear speed .

[目的]研究膨胀潜势、含水率对膨胀土抗剪强度的影响,为膨胀土强度理论研究及其工程应用提供参考.[方法]采用固结不排水试验方法,通过TFB-1型非饱和土应力应变控制式三轴仪,分别测定取自陕西汉中、安康的2种膨胀土样及2种土样1∶1(质量比)混合土(简称汉中土、安康土、混合土)3种不同膨胀潜势的膨胀土在不同含水率下的抗剪强度指标,应用Microsoft Excel软件,绘制3种膨胀土的抗剪强度指标与含水率、自由膨胀率的关系曲线,探讨膨胀土抗剪强度与含水率、膨胀潜势的关系及变化趋势.[结果]3种膨胀土的含水率与非饱和膨胀土的抗剪强度指标呈负相关关系,当含水率由12％增大到24％时,汉中土、混合土、安康土3种膨胀土的黏聚力分别降低56.83,53.74和61.61 kPa,三者的内摩擦角分别降低7.87°,9.12°和9.58°;3种膨胀土的膨胀潜势与非饱和膨胀土的抗剪强度指标呈正相关关系,汉中土、混合土、安康土的膨胀潜势依次减弱,当三者分别处于同一含水率(12％,15％,18％,21％和24％)时,汉中土、混合土、安康土的抗剪强度指标依次减小.[结论]非饱和膨胀土的抗剪强度与含水率、膨胀潜势密切相关.

文章从岩土工程名人感召式教学的内涵与构成出发，以Terzaghi名人事迹为例，阐述了岩土工程名人感召式教学的目的，并提出了岩土工程名人感召式教学的实践策略。

【Objective】This study analyzed the error sources of free swelling ratio test to provide basis for improving its accuracy.【Method】The study took expansive soil samples from Ankang and Yangxian in Shaanxi and Handan in Hebei.The Ankang expansive soil samples were sieved to particle diameters(d≤0.1mm,0.1mmd≤0.25 mm,and 0.25mmd≤0.5mm),and the free swelling ratios were tested.The Ankang expansive soils were also modified with sodium metasilicate and cationic-type polyacrylamide to 16 different soil samples to study the influences of gradation composition.The mass ratios of sodium metasilicate were 0.5%,1.0%,2.5%,and 5.0%,and the mass ratios of cationic-type polyacrylamide were 0.1%,0.5%,1.0%,and 2.5%,respectively.Then the expansive swelling ratios of three kinds of expansive soils under 10,15 and 25 ℃ were tested and the quality of soil samples in the soil cup with and without being cooled in drying oven were investigated.【Result】The free swelling ratio of Ankang expansive soil with size of≤0.1mm was 20%.When the size was between 0.25 and 0.5mm,the result was 53% with differenceof 33%.For the modified soils,when mass ratio of sodium metasilicate was 1.0%and mass ratio of cationic-type polyacrylamide was 0.1%,the free swelling ratio of modified soilⅠ and the soilⅡ were 23% and40%.The next error source was the environment temperature.The result decreased by 43% when the temperature decreased from 25℃to 15℃.Cooling had minor effects on mass of soil samples.【Conclusion】In order to increase the accuracy of the free swelling ratio,it is suggested to divide the soil samples to three size groups,0to 0.1mm,0.1mm to 0.25 mm,and 0.25 mm to 0.5mm,and the corresponding mass fractions should be 0-20%,20%-50% and 20%-50%,respectively.It is also helpful to cool the samples to 25 ℃.

为了研究结构性黄土在固结、剪切全过程中的结构演变,进行了三轴试验,定义了固结结构强度和结构强度固结比,研究了一直被忽略的固结对结构的影响问题,以及围压和含水率对不同初始结构黄土的影响,基于损伤理论建立了剪切过程中不同初始结构的黄土的损伤演化数学模型.结果表明,固结结构强度随含水率的增大而降低,低含水率下的降幅大于高含水率下的降幅,结构强度固结比在高围压下变化幅度较大.初始切线模量随含水率的升高迅速减小,低含水率下随围压升高其先减小后增大,高含水率下随围压升高其一直增大但增幅较小.黄土在低围压下的损伤速度要快于高围压下的.围压和初始结构共同决定了结构的演化规律,固结对初始结构的破坏程度将决定剪切过程的结构演化,偏应力起到破坏作用,围压具有压损和压硬两种作用,黄土结构演化过程并非是单纯的损伤过程,其程度和方向内部取决于初始结构条件,外部取决于荷载大小和荷载性质.

膨胀土因其高胀缩性带来很多工程问题,膨胀土的收缩及开裂对工程危害更大.通过对安康膨胀土进行收缩试验与开裂试验,研究膨胀土的收缩变形特性与开裂规律.结果表明:膨胀土的收缩变形受初始含水率的影响显著,受干密度影响较小,给出了计算收缩应变的公式;非饱和膨胀土的收缩变形存在各向异性,以侧向变形为主,并随着含水率增加向各向同性过渡;裂缝的长度、宽度服从对数正态分布,面积服从负指数分布,交点服从均匀分布,裂缝的交角以90°左右为主;厚度越大、温度越高开裂含水率越高.