Study on mechanical behaviors of interface with cemented soil slurry between gravel and concrete by simple shear tests

The mechanical behaviors of the interface between coarse-grained soil and concrete are investigated by simple shear tests under conditions of cemented soil slurry (clay mixed with cement grout). The results show that the relation curve between shear stress and shear strain appears stress-strain softening and shear dilatation is significant. The point of peak strength and the position when the shear dilatation occurs are related to normal stress. In addition, shear dilatation occurs before the shear stress reaches peak value. In shear failure state, with the same height, the shear displacement increases as the normal stress increases. While with the same normal stress and at the same height, the shear displacement increases as the concrete content increases. A particle flow model of simple shear test between interface between coarse-grained soil and concrete is constructed by PFC (particle flow code). The disturbed height of the sample and the main influence factors are determined by analyzing the laws of particle motion at different heights inside the sample. The PFC results show disturbed height of the sample is related to maximum particle diameter of the soil, normal stress and roughness of the interface (with or without slurry) etc. In terms of the coarse-grained soil, the shear displacement is significant in the area which is close to the interface and about 3-4 times of the maximum particle diameter, and informed the obvious shear band. Further, the thickness of the interface can be regarded as the value.     

Simple Shear Test of Interface between Sand and Structure under High Stress

By using a simple shear apparatus that is developed from RMT-150B,a series of simple shear tests of interface between saturated sand and structure under high normal stress were carried out to study constitutive law and shearing stiffness of interface to provide some theoretical evidences for design and calculation of projects concerned with mechanical problem of interface.In test,sand was consolidated in upper shearing box firstly,then,shear was started and testing data was recorded under high and constant normal stress.During the process,sand can deform relatively freely.It is shown that the relation curve between shear stress and shear displacement under high normal stress in simple shear tests is different from that in direct shear tests,and the complete shearing deformation process of interface under high stress can be described as a nonlinear elastic-perfect plastic form;Weibull distribution with three parameters can overcome the mathematical deficiencies of hyperbola in NEPP.The new model which is established by substituting Weibull distribution for the hyperbola of NEPP better agrees with the testing data.The regressive results of the initial shearing stiffness demonstrate that the linear function is slightly better than power function to express the relation between the initial shearing stiffness and normal stress.Based on the new interface model,the formula of tangential shearing stiffness is proposed,meantime,the change trend of tangential shearing stiffness of the new model is compared with that of NEPP.     

红层泥岩桩岩接触面本构模型试验及数值模拟

桩-岩（土）接触面力学特性的研究是桩基承载机理研究的基础。通过红层泥岩桩岩接触面大型直剪试验,研究了红层泥岩桩岩接触面的力学特性,结果表明：接触面剪应力先随剪切位移增大而增大,在达到峰值后,剪应力随着剪切位移增大而降低,并最终趋于稳定值,应力应变曲线呈现出应变软化的特征。根据剪切试验结果,推导出桩岩接触面应变软化本构方程。利用fish语言对FLAC^3D中自带的理想弹塑性接触单元进行二次开发,并应用开发的模型对桩岩接触面直剪试验进行了数值模拟,分析剪应力与剪切位移之间的关系,证明了该本构能够较好地模拟接触面间的应变软化特性。     

钢筋混凝土无腹筋细长梁剪切破坏机理模型研究综述

根据现有关于钢筋混凝土无腹筋细长梁剪切破坏机理问题的研究成果,介绍了基于修正压力场理论的抗剪模型、临界剪切裂缝理论、塑性理论、压力路径理论、劈裂破坏理论和基于截面应变分析的抗剪模型的基本假设、核心观点及受剪承载力计算方法,并给出总结、归纳及评析;另一方面,利用相关试验数据和ACI-DAfStb无腹筋细长梁剪切破坏数据库,分别对不同理论模型的受剪承载力计算公式进行了设计参数的影响评估和统计评估;并展望了无腹筋细长梁剪切破坏机理研究的发展方向。研究结果表明：不同理论模型的部分假设缺少直接的试验依据支持,梁腹混凝土的受拉（劈裂）或受剪（骨料咬合）以及受压区混凝土对抵抗剪力的贡献成为抗剪机制的主要分歧;不同受剪承载力计算公式对不同影响因素的考虑方式的合理性和计算结果的准确度均有待进一步提高。后续深入研究应综合考虑剪切破坏问题的随机性和物理属性,利用先进测试技术、应力演化分析方法,进一步揭示剪切破坏机理。     

Experiments on influence of slurry kinds on mechanicalbehavior of interface between gravel and concrete

The mechanical behavior and mechanism of the interface between structure and coarse grained soil are investigated through simple shear tests on the conditions of bentonite slurry, clay slurry and without slurry, respectively. The results indicate that different kinds of slurry have important influence on shear strength. Compared with the interface without slurry, the shear strength with bentonite slurry reduces by 45% approximately, significantly more than clay slurry which reduces by 10%. The value of the friction angle with bentonite slurry is about 60% of that with clay slurry. Shear displacement increases as upright stress increases when reaches its failure states at the same height, and shear displacement with bentonite slurry is smaller than that with clay slurry when with the same upright stress and height. The upright displacement with bentonite slurry is greater than that with clay slurry under the same upright stress. In addition, shear dilatation is apparent under the low normal stress when without slurry. Otherwise, it appears as shear contraction.     

栽培因素对甘蓝型优质杂交油菜品质性状的影响

为了研究播期、密度、施氮量、施磷量、施钾量5个主要栽培因素对甘蓝型优质杂交油菜品质性状的影响,以‘油研599’和‘三北98’为材料,运用五元二次正交旋转组合设计进行试验研究。结果表明,芥酸含量与播期、施氮量间均呈负相关,与密度呈正相关;硫苷含量与播期呈负相关、与施钾量呈正相关;含油率与播期、施氮量间均呈负相关,与密度、施钾量呈正相关;种子蛋白质含量与播期、施氮量间均呈正相关,与密度、施钾量呈负相关;油酸含量与施磷量呈负相关,与施氮量呈正相关;棕榈酸含量与施钾量呈负相关,与‘油研599’的播期、密度、施氮量、施磷量均呈正相关,与‘三北98’的播期、密度、施氮量、施磷量均呈负相关;硬脂酸含量与播期、密度、施磷量、施钾量间均呈正相关;亚油酸含量与密度、施氮量呈正相关,与施钾量呈负相关;亚麻酸含量与施氮量、施钾量呈正相关;廿碳烯酸含量与播期呈负相关。栽培因素对品质性状的影响有的呈相关,有的呈负相关,正负相关会发生部份相互抵消,每一个处理品质性状的表现都是5个因素综合作用的结果。在5个因素与10个品质性状的50对简单相关中,有26对在2个品种中表现一致,有24对在2个品种中表现不一致。播期、密度、施氮量、施磷量4因素对2个品种芥酸含量的影响较大、播期、密度、施氮量、施钾量4个因素对2个品种棕榈酸含量的影响较小。多个栽培因素的综合作用不能根本性的改善杂交油菜的品质性状。     

A Static Liquefaction Constitutive Model for Granular Materials Based on the Micromechanical Analysis

Based on the static liquefaction of granular materials, an elastoplastic static liquefaction constitutive model was proposed in the framework of critical state soil mechanics. The yielding surface and hardening rules were obtained by integrating the contact force of the model proposed by Chang and a non-associate flow rule was adopted as well. The model has taken the state dependent dialatency law and the effect of initial density to the stress-strain relationship into consideration. The parameters of the model are simple and have certain physical meanings. The predicted results obtained by the model have a good agreement with the undrained triaxial test of Toyoura sand and sand-silt mixture.     

Micromechanis Analysis of Load-transfer Mechanism is Single-fibre Fregmentation Test

The paper presented a new micomechanics load-transfer model for single-fibre fragmentation test. The interfacial shear streength and the crack will develop along the interface. The fibre stochastic strength distribution was modelled by a two-parameter Wibull distribution. The influence of the interfacial bonding strength and fibre axial-tensile strength on stress states in components of composites was discussed. The interfacial state during the fragmentation process may be one of following three states: 1) fully bonding; 2) partial bonding; 3) fully debonding; according to the fibre axialtensile strength and interfacial properties (including interfacial bounding shear strength, interfacial friction coefficient and matrix radial pressure) after elastic constants and geometrical parameters of composites phases are given. The necessary conditions for these three states were discussed- Finally, a suitable definition of the critical fibre length was given and the critical length was constrouted by two parts :debonding fibre length and bonding fibre length.     

固结煤矸石抗剪强度特征试验

依据现场大型剪切试验和室内直剪试验,研究了固结煤矸石的抗剪强度特性。试验剪应力-剪位移过程曲线表明,一定含水率条件下的固结煤矸石呈现明显的粘塑性体力学特性。以现场大型剪切试验煤矸石作为试样配料进行了室内直剪试验,分析了含水率和密实度对良好固结煤矸石试样剪应力-剪位移试验曲线以及抗剪强度参数的影响,在此基础上探讨了试样内煤及其它细颗粒的状态变化对固结煤矸石抗剪强度的弱化作用机理,最后对比分析了现场大型剪切试验抗剪强度参数值和室内直剪试验抗剪强度参数值的差异及其产生的主要原因。     

考虑滑移和剪切变形的单箱双室组合箱梁剪力滞效应

为准确分析单箱双室组合箱梁的剪力滞效应,考虑钢混凝土的界面滑移效应和钢腹板的剪切变形,针对顶底板和翼板定义不同的剪力滞翘曲位移函数,基于能量变分法推导出单箱双室组合箱梁剪滞效应的控制微分方程及其闭合解。以单箱双室组合箱梁算例为基础,利用该方法分析其剪力滞效应的规律,结果表明：在同时考虑滑移和剪切变形时,组合箱梁的挠度比初等梁理论解大,且其挠度随界面滑移刚度的增大而减小;组合箱梁在均布荷载作用下,滑移量与荷载值近似成正比关系;在相同条件下,钢箱梁底板的剪力滞效应较混凝土顶板显著。     

页岩烧结保温砌块砌体基本力学性能试验研究

通过对页岩烧结保温砌块砌体轴心抗压、沿通缝抗剪、剪压复合抗剪性能试验研究,分析其破坏特征和破坏机理。试验结果表明:页岩烧结保温砌块砌体受压破坏时,在竖向灰缝附近形成主裂缝,接近极限荷载时砌体出现表皮剥落现象;沿通缝抗剪破坏模式主要为单剪破坏,脆性明显;剪压破坏有剪磨、剪压和斜压3种类型;实测轴心抗压强度平均值高于规范值,沿通缝抗剪强度、复合抗剪强度平均值低于计算值,并分别给出砌体轴心抗压强度平均值、抗剪、剪压复合受力抗剪强度平均值建议公式;剪压复合抗剪强度随着压应力的增大而增大;建立了页岩烧结保温砌块砌体受压应力应变关系表达式;给出该类砌块的弹性模量和泊松比的建议值。     

GFRP肋式剪力连接件受力性能对比试验研究

剪力连接件是保证GFRP混凝土组合梁/板中两种不同材料共同工作的重要构造,设计了矩形肋和T形肋两类GFRP肋式剪力连接件,进行了3组共8个GFRP肋式剪力连接件的推出试验,包括：矩形肋开孔、T形肋开孔、T形肋不开孔3组GFRP肋式剪力连接件,得到了其破坏形态、极限承载力、荷载滑移曲线及荷载应变变化规律,重点研究肋内开孔及肋的截面形式对GFRP肋式剪力连接件受力性能的影响。试验结果表明：GFRP肋式剪力连接件的破坏形态均为混凝土劈裂破坏;对比矩形肋开孔试件,T形肋开孔试件强度高、延性好;对比T形肋不开孔试件,T形肋开孔试件强度与延性均能提高。基于试验结果,建立了考虑肋内开孔及肋截面形式影响的GFRP肋式剪力连接件极限承载力计算公式,拟合得到了GFRP肋式剪力连接件的荷载滑移曲线上升段的理论模型,建立了其抗剪刚度计算公式。     

Behavior of Loose Sand-structure Interface Undergoing High Frequency Cycle Shearing

The behavior of loose sand-structure interface under the high frequency cycle shearing is analyzed by using Particle Discrete Element Method (DEM).The changes of sand box porosities of DEM model and sand volume strains are examined in detail.The results show that sand volumetric shrinkage due to shearing is not obvious in spite of the larger loose sand particle friction coefficients and particle stiffness.The particle stiffness ratio has a little effect on the mechanical properties of sands.In addition,the decrease in volume of sand under shearing is more obvious with the increase of the confining pressures.Moreover,the decrease in volume of loose sand under shearing is greater with the increase of the high frequency cycle shear amplitude and the shear frequency.     

Experimental Research on Municipal Solid Waste Landfill''s Strength Character in a Refuse Dump of Chongqing

With the development of economic and society,more and more waste landfill gradually threaten to the development of the city.Some special tests are done to study the relationship of the Municipal solid waste(MSW) strength and the stability of MSW landfill structure.A geo-technical test with the soil samples collected at the scene is done in the laboratory through direct sheared device and the thri-axial sheared device,the disciplinarian and factors are analyzed.The results are referenced to the design and construction of new-built MSW and finished rubbish field.It is shown that some parameters such as composition,particle magnitude,water content,compressing method,intensity and time,will greatly affect the strength character of MSW.     

Stress Distribution in Fixed Anchor Length of Compression Type Anchor in Soft Rock Mass

To study stress distribution in fixed anchor length of compression type rock anchor cable, field test was carried out. Strain sensors were placed in the grout paste in fixed anchor length with certain interval. Axial and radial strains of the grout were noted by test. Shear stress distribution curve along the fixed anchor length was obtained by stress-strain relationship and static equilibrium analysis. Analysis results prove that maximal shear stress on the interface can achieve upper level and move forward when the load increases; the transmission length is short; shear stress transfers forward; and three dimensional state is obvious around capacity plates in soft rock mass.     

On the Type of Stress-strain Relation Curves and the Critical State for Soils

In order to discuss the influence of stress history on the constitutive relations for soils,a series of drained conventional triaxial compression tests for normally consolidated and overconsolidated clays have been carried out.It is found through comparing the stress-strain relation curves under the different stress histories that the overconsolidated ratio is the determining factor for volumetric strain.The volumetric strain is less sensitive to consolidation pressure,however.For the shear capacity,the consolidation pressure is the determining factor,but the influence of the overconsolidated ratio can not be neglected since it determines whether there will be strain hardening or strain softening as well as the grade of strain softening.Despite that,the soil specimens will finally reach a unified critical state and approximately the same residual strength.According to the principle of interaction between plastic volumetric and shear strains,the mechanism of generating two types of stress-strain relation curves for clays is explained.It is shown that the critical state is a pure process of shearing deformation in which the interaction between plastic volumetric and shear strains completely disappears.The critical state is independent of the previous stress history.     

THE EVALUATION OF SHEAR STRENGTH TAKING ACCOUNT OF SPAN-TO-HEIGHT RATIO OF SIMPLE BEAMS UNDER UNIFORM LOADS

By introducing the span-to-height ratio,this paper deduces wo evaluating equations of shear strength of simple reinforced concrete beamwith stirrups and under uniform loads.This makes the shear stressing concept consistent with the evaluating equations,thus improves the evaluating equationsof shear strength of the New Code.Two equations are provided with auto-regulating function on shear strength for a cross section of beam.They aresimple and convenient in evaluation.The working time used for design is not increased and 10% of stirrups is economized in frequent conditions of span-to-height ratio.     

河道淤泥气泡混合轻质土剪切流变特性及模型

利用剪切流变试验对以水泥为固化剂的河道淤泥气泡混合轻质土的流变特性进行了试验研究。试验结果表明,经固化处理的河道淤泥气泡混合轻质土在荷载作用下具有类似于硬粘性土的流变特征。剪切流变可以分为3个阶段：在剪应力水平较低时,剪切流变曲线呈衰减稳定型;随着剪应力水平的提高,剪切流变曲线呈非稳定的等速型;当剪应力水平增大到一定程度时,剪切流变曲线呈加速型。河道淤泥气泡混合轻质土的流变性随着混合轻质土强度的提高而降低。根据试验所呈现的剪切流变规律,可以发现河道淤泥气泡混合轻质土的剪切流变符合七元件黏弹塑性剪切流变模型,模型能够比较好地描述河道淤泥混合轻质土在各种剪应力水平下的衰减、等速以及加速流变过程。     

Shear Lag Effect of Concrete Box Girders Considered Varying Flange-depths

According to concrete box beam which flanges depth varying along the orientation of cross section, using variational principle of potential energy, new analysis method of shear lag is proposed for single cell concrete box beam. For simply supported girders and cantilever girders, general analysis of varying flange-depths influence on positive and negative shear-lag effect and deflection have be done. It's shown that varying flange-depths have influence both on sectional stress and deflection. Considering the varying flange-depths have effect on the calculation results of up to 15%.     

Trial heterogeneity and variance models in the genetic evaluation of potato tuber yield

Genetic evaluation aims to identify genotypes with high empirical breeding values (EBVs) for selection as parents. In this study, 2157 potato genotypes were evaluated for tuber yield using 8 years of early‐stage trial data collected from a potato breeding programme. Using linear mixed models, spatial parameters to target greater control of localised spatial heterogeneity within trials were estimated and variance models to account for across‐trial genetic heterogeneity were tested. When spatial components improved model fit, correlations of errors were mostly small and negative for marketable tuber yield (MTY) and total tuber yield (TTY), suggesting the presence of interplot competition in some years. For the analysis of multi‐environment trials, a variance model with a simple correlation structure (with heterogeneous variances) was the most favourable variance structure fitted for TTY and PTY (per cent marketable yield). There was very little difference in model fit when comparing a factor analytic structure of order 2 (FA2) with either FA1 or simple correlation structures for MTY, indicating that simple variance models may be preferable for early‐stage genetic evaluation of potato yield.