采动影响下逆断层特征参数对断层活化的作用规律

笔者分析了采动影响下断层滑移的主要影响因素,以数值模拟为研究手段,利用FLAC 3D建立了逆断层简化模型,分析了不同断层倾角、不同落差及采掘工作面与断层不同距离的断层带附近煤岩体弹性能、断层面正应力与剪应力、断层滑移量的变化规律,从而揭示了采动影响下逆断层特征参数对断层活化的基本作用规律。研究结果表明：上盘或下盘开采,断层带附近煤岩体弹性能集中程度随工作面与断层距离的增大而降低,随断层倾角及落差的增加而增大,但下盘开采对断层带的能量集中程度较上盘高。下盘开采时剪应力较上盘显著增加,但正应力变化较小,易于断层活化。上盘或下盘开采,随工作面与断层距离的增加,断层滑移量减小。上盘开采,随断层倾角增大,断层滑移量增加;随断层落差增大,断层滑移量减小。下盘开采,随断层倾角增大,断层滑移量减小;随断层落差的增大,断层滑移量增加。     

施工阶段大跨径预应力混凝土刚构桥腹板开裂机理

进行了大跨径预应力混凝土刚构桥腹板开裂机理研究,基于弹性力学平面问题分析方法,推导了集中荷载作用下的板件应力函数表达式,绘制了不同受压边长与集中荷载长度比（d/a）下的横向应力曲线,拟合了集中荷载作用下构件的横向应力求解函数,构造了混凝土刚构桥腹板在预应力集中荷载作用下等效压力矩形的选取方法,并基于平面应力的表达式提出了在三维情况下沿预应力轴线的横向应力计算方法。通过建立某预应力混凝土刚构桥0~3#段实体有限元模型,分析施工过程中刚构桥混凝土腹板在不同等级预应力作用下的开裂情况。结果显示：有限元裂缝模拟与实桥腹板开裂范围一致,有限元应力分析结果下限值与推导的横向应力求解函数计算结果接近,变化趋势一致,印证了横向应力函数求解方法的正确性。     

重组竹的单轴与纯剪应力应变关系

重组竹是将竹丝束平行组坯、经高压胶合而成的一种生物质复合材料,是一种极具潜势的建筑结构材料。研究重组竹的基本力学性能和应力应变关系,是建立此类材料本构关系和进行重组竹结构非线性分析的基础。将重组竹理想化为横向各向同性复合材料,通过试验,给出了重组竹各主轴方向的单轴与各主平面的纯剪力学参数,建立了各种应力状态下的应力应变关系。结果表明,重组竹力学性能优于常用的结构用木材,且变异性较小。重组竹顺纹受拉强度约是顺纹受压强度的2倍;横纹受拉强度远远低于横纹受压强度;横切面内的剪切模量及强度远远低于另外两个方向,且横纹剪切强度是顺纹剪切强度的3倍。重组竹的应力应变关系和破坏模式与纤维参与受力程度密切相关。顺纹受拉时,拉应力完全由纤维承担,破坏表现为纤维的脆性拉断,强度最高,应力应变为完全线性关系;其他应力状态下,破坏均发生在基体或纤维-基体界面,若裂纹的扩展受到纤维限制,破坏呈渐进性,强度较低,应力应变曲线由早期的线性关系转入后期的非线性关系;当裂纹的扩展未受到纤维限制,破坏强度最低,应力应变呈线性关系。     

直剪法用于糙米内摩擦角的测定与研究

利用土工合成材料综合测定仪（直剪仪）,以水分含量14.57%的糙米为样品,测定了在不同的法向压应力、不同的剪切速率下糙米的剪切应力并计算出内摩擦角。实验结果表明：糙米的剪切应力随着法向压应力（25kPa～100kPa）的增大而增大;剪切速率（1.33mm/min～2.67mm/min）较低时糙米的内摩擦角随着法向压应力的增大而减小;随着剪切速率（1.33mm/min～5.20mm/min）的增大,糙米的内摩擦角减小。     

含水率对糙米内摩擦角影响的实验研究

利用土工合成材料综合测定仪,以江苏盐城产糙米为样品,测定了在不同法向压应力和不同含水率的条件下,糙米的剪切应力并计算出内摩擦角。实验结果表明:在剪切速率不变时,糙米的内摩擦角通常会随着法向压应力的增大而逐渐减小;当法向压应力较小(25kPa)时,糙米的内摩擦角会随着含水率的增加而逐渐增大。当法向压应力较高(75kPa～100kPa)时,随着含水率的增加,糙米的内摩擦角逐渐增大,达到某一峰值后,随着含水率的继续增加而逐渐降低。     

稻谷仓壁材料摩擦系数的实验研究

利用土工合成材料综合测定仪测定了不同法向压应力（25 kPa、50 kPa、100kPa、150 kPa、200 kPa）下稻谷（水分含量为13.55%、15.14%、17.00%、19.19%w.b）与不同仓壁材料（不锈钢板、混凝土板、木板）的摩擦系数。结果表明：稻谷与不锈钢板摩擦系数较小,与混凝土板和木板的摩擦系数较大;随着法向压应力的增大,稻谷与各仓壁材料的摩擦系数均呈不同幅度的减小;随着水分的增大,稻谷与各仓壁材料的摩擦系数增大。根据实验结果,可拟合出摩擦系数与法向压应力、水分含量的关系方程。     

门架式抗滑桩结构模型试验研究

为了对门架式抗滑桩的结构特性有进一步的认识和提升,进行了门架式抗滑桩三维地质力学模型试验与门架式抗滑桩结构模型试验。通过在桩身内部贴置应变片以及桩身的关键位置处放置千分表,来测量在推力荷载施加过程中,门架式抗滑桩的桩身应力变化特点及关键位置点的位移变化特征。试验结果表明：门架式抗滑桩桩前、后排桩桩顶位移大于滑动面处位移,后排桩桩身位移大于前排桩桩身位移;前、后排桩桩身内力均呈现明显的“s”型分布,桩顶应力不为零,其数值随着推力荷载的增大的而增大。     

濮阳粮食典型减产年与主要气象灾害分析

用调和权重线性滑动平均处理方法,分析历年粮食产量,将减产幅度≥5%的年份定为典型减产年,通过气象灾害分析,找出造成粮食减产的主要气象灾害。结果表明：干旱和雨涝灾害是造成当地粮食减产的主要气象灾害。随着粮食产量水平的提升,气象灾害造成的经济损失呈加大趋势。在加强抗旱、防涝工程建设的同时,应加强对空中水资源的开发利用,同时还要大力推广节水灌溉技术,充分发挥有限水资源的最大经济效益,是农业可持续发展的保障。     

波浪循环荷载作用下滨海软土水平向动力特性试验研究

为研究海上风电桩基在波浪荷载作用下,产生水平向循环荷载对桩基周围土体动力特性的影响,以唐山地区滨海软土为研究对象,通过室内动三轴试验,研究不同围压、动应力幅值和振动次数条件下对软土水平向动力特性的影响。结果表明：软土水平向动强度随围压增加而增加,随振动次数增加而减小;动应力幅值增大,破坏振次减小;水平向动应变εd随振动次数增加变大,且动应力幅值越大,增速越明显,变化规律遵循Monismith模型;动应力幅值改变时,软土水平向动模量变化明显,当围压减小,动弹性模量减小;曹妃甸软土水平向间具有明显的结构性,不同围压条件下,随动应力幅值增加动阻尼比均表现增大趋势。     

小麦堆压缩特性的实验研究

利用回弹模量仪对小麦堆（河南产）（水分为11.7%,13.33%,15.18%,16.55%,18.18%w.b）的密度和无侧向膨胀压缩体变模量进行了实验测定,实验选定加在样品顶部的压应力为：50 kPa、100 kPa、150 kPa、200 kPa、250 kPa、300 kPa,通过计算得出对应的样品平均竖直压应力为：36.8 kPa、74.8 kPa、110.9 kPa、153.4 kPa、184.7 kPa、221.0 kPa。进而得到样品所受的平均压应力为：18.3 kPa、41.9 kPa、66.7kPa、91.0 kPa、110.9 kPa、133.248 kPa。实验结果表明：在同一水分下,随着平均压应力的增大,小麦堆的密度也增大。在同一水分下,随着平均压应力的增大,小麦堆的体变模量也增大。拟合方程为y=axb,其中参数a、b随水分的不同而变化。     

Effective Unloading Area between Cantilever Piles

The formation mechanism of the arching effect between cantilever piles is studied according to their stress characteristics. The soil arch is classified into three types based on its position in a space coordinate system, namely, a horizontal arch, a vertical arch and a free face arch. The master factor for distribution of unloading area between piles is the horizontal arch effect. The range of effective unloading area is defined. Based on the failure pattern of soil arches and the relationship between soil strength theory and the static equilibrium principle of soil arches, a calculation model is established by considering the presence of geostatic stress and sliding thrust force. The relation between soil strength and critical height is studied by variation of cohesion and friction angle. In addition, the impact of canonical distributions of the earth pressure to the vector height of unloading area is also discussed. Finally, the calculation model is verified by an example from real engineering work.     

Novel method for fault line selection in arc suppression coils system using transient energy

In order to overcome low sensitivity of the protection based on transient components when the faulty voltage passes zero, regarding arc suppression coill branch as a healthy feeder line, using the relation of its transient energy and all feeders of transient energy amounting to zero, this paper presents an improved fault line selection method in arc suppression coils system using transient energy. This method has no requirements of detection fault close angle and pre setting, has a good anti interference ability and adaptability to various faults occurred in the systems with arc suppression coils. Large amount of digital simulation results show that the proposed method is effective and reliable.     

小型水稻收割机纵轴流脱粒分离装置结构设计与试验

为解决中国南方丘陵山区大型收割机具通过性差,横轴流式收割机脱粒损失率大的难题,设计一种小型轴流式水稻联合收割机脱粒装置,将其装配在收割机整机上进行了田间脱粒损失率试验。结果表明：弹性脱粒杆齿齿距、导条螺旋升角、凹板筛直条倾角3 个影响因素对水稻脱粒损失率影响显著;对各因素最优组合的取值为弹性脱粒杆齿齿距a=90 mm,导条螺旋升角α =23°,凹板筛直条倾角θ =14°,此时的水稻脱粒损失率为1.51%,达到国家标准小于3%的要求,试验数据为小型轴流式水稻联合收割机的产业化提供了技术保障。     

Mechanical Performance of a Vertical Seismic Isolation System Employing a Dish Spring

The base isolation technique has been widely used in different countries to reduce seismic disasters during earthquakes. But most of these devices are effective only in horizontal earthquake responses and do not work well in vertical earthquake responses. We propose a vertical seismic isolation system composed of a dish spring and a visco-elastic damper. To study the stiffness and damping performance of this isolation system, a series of tests under static and dynamic loads were performed. The results show that this system is effective in solving problems related to strong vertical bearing capacity and vertical damping of vertical isolation. The system has not only appropriate vertical stiffness and damper performance, but also excellent mechanical performance. In addition, it is compact, easy to manufacture, and can serve as an ideal vertical damping device.     

3D Dynamic Coupled Mechanical and Hydraulic Analysis of Geogrid-reinforced Pile-supported Embankments

In order to investigate the dynamic behaviors of geogrid-reinforced pile-supported embankments under traffic loading, three-dimensional coupled mechanical and hydraulic numerical simulations are conducted using FLAC 3D. Four cases are studied including unreinforced and no-pile embankments, reinforced embankments, pile-supported embankments, and geogrid-reinforced pile-supported embankments. The behaviors of vertical displacement, horizontal displacement, pile-soil stress ratio, excess pore water pressure and acceleration under four cases are analyzed. It is found that the vertical displacement, nonuniform settlement and horizontal displacement of geogrid-reinforced pile-supported embankments are smaller than those of other cases due to soil arching effect and reinforcement effect. Pile-soil stress ratio decreases with the increase of loading number. The crest value of acceleration and the time for acceleration to be steady are also smaller than those of other cases. The dissipation velocity of excess pore is quicker than that of unreinforced embankments.     

直墙拱形巷道围岩应力场分析

为得出直墙拱形巷道围岩应力分布规律,应用复变函数弹性理论推导了直墙拱形巷道围岩应力分布的解析表达式。对直墙拱形巷道边界的围岩应力和巷道水平线方向的围岩应力分布规律进行分析,并考虑直墙拱形巷道断面高宽比和侧压系数对其影响规律。研究表明：在不同巷道断面高宽比、侧压系数下,直墙拱形巷道围岩应力集中区域主要集中在直墙底部底角处、拱形顶板中点附近和底板中部3个位置。不同巷道断面高宽比下,直墙拱形巷道沿水平线的应力分布规律基本相同。侧压系数大于1时,采用巷道断面高宽比小于1较有利于巷道稳定;侧压系数小于等于1时,采用巷道断面高宽比大于1较有利于巷道稳定。     

A Difficulty of Symmetrical Stress Model

There is mased differences between experimental and analytical results in the frame of symmetric stress model,when the notable stress gradient exist,or outstanding microstructure is to be considerated,or wavelength is too shorter in dynamic problems. Other difficulty is introduced in linear elastic statics of homogeneous isotropic solid that.The problem is that,neighbor boundaries of a angle domain are subjected to two shear forces not equal each other. The problem is not solved in the frame of symmetric stress model. In the frame of the asymmetric stress and couple stress model in present paper this difficulty is sovlved. It is show that,as the distance from the boundaries increase the solving in the frame of asymmetric stress model tent to that in the frame of symmetric stress model.     

Mechanical and Deformation Characteristicson Shield Tunnel Segment with Cracks

The 3D Goodman element is used to simulate segments' cracks in one section of shield tunnel in Guangzhou. Mechanical and deformation characteristics of segment structure responded to varied depth of cracks is analyzed in this paper. Meanwhile, research on coefficient of lateral earth pressure, soil coefficient and ground water level on mechanical and deformation characteristics is carried out. The research result shows that along with the increase of cracks' depth, the tensile stress, pressure stress reach the maximum value while the increment is not too much. However, when the depth equals to the thickness of segment, the reinforcements' tensile stress has increase sharply, even exceeded the allowable value. Moreover, the maximum number of tensile stress, horizontal and vertical convergent value of shield tunnel segment with cracks increase with the reduction of the coefficient of lateral earth pressure and soil coefficient, and increase with the increase of ground water level as well. Specific repair measure has been taken to segments' cracks in this section of shield tunnel based on the conclusions. In general, this section of shield tunnel is stable and safe now, and there is no longer new cracks appeared.     

Time Effect Experimental Analysis of the Soil Arch Effect of Anti sliding Pile

Soil arching effect is important for stabilizing the soil behind anti sliding pile. The creep of soil mass will inevitably lead to the formation of soil arching, which has time effect. In this analysis, an indoor thrust pile model test is proposed. The characteristics of stress distribution in the soil and the time effect of soil arching behind anti sliding pile are analyzed. The experimental data acquired by the soil pressure cells arranged along the normal direction of the thrust show that soil arching effect is enhanced with the increase of thrust.The thickness of soil arch increases with time.And the data obtained by soil pressure cells arranged along the direction of the thrust show that the horizontal soil arching effect increases and then gradually extends.The scope of stress dispersion has very large growth along the normal direction as time goes on.