Numerical analysis of a double layer rubber dam

A new rubber dam with two layers of dam bodies anchored closely into a rigid base is proposed to improve the water-retaining ability of the conventional rubber dam. Numerical studies using FLAC^2D software are conducted to analyze the behavior of the proposed double layer rubber dam. Laboratory model tests are also carried out to verify the accuracy of the numerical model. It is found that the optimal internal water head in the upstream dam normalized by its cross-sectional perimeter ranges from 0.35 to 0.45, and that in the downstream dam ranges from 0.32 to 0.40. The double layer rubber dam has optimal perimeter ratio of 0.8 and optimal anchoring distance normalized by cross-sectional perimeter of upstream dam of 0.08. For same ultimate external water head, the cross-sectional perimeter of the double layer rubber dam increased by 25.7%–49.6% than that of conventional rubber dam in different design parameters. However, the requirements of the maximum circumferential tensile strength of the upstream and downstream dams decreased by 40.8%–62.9% and 51.9%–69.6%, respectively. Assuming the material cost is determined by length and maximum circumferential tensile strength of membrane materials, the total material costs of the proposed double layer rubber dam reduce at most 82.2% than those of the conventional rubber dam in different design parameters.     

JSP遇水膨胀橡胶的研制

介绍一种新型的遇水膨胀防水橡胶。通过分子设计，制得了一种以功能性丙烯酸酯为基的专用膨胀树脂，它与橡胶混炼、硫化后，材料在淡水、碱水和盐水中的膨胀倍率可分别达到６．２倍、４．２倍和４．０倍，且在水中的溶出物仅占自身的０．５％以下。     

关于橡胶密封件密封失效的探讨

本从橡胶密封密封失效的原因着手，系统地论述了密封件设计，选型，装配等要素，详细介绍了密封件的类型，材质和使用常识等。     

橡胶缓冲减振装置的系列试验

为掌握新开发的，用于大型履带式推土机行走系橡胶缓冲减振装置的综合性能，对该装置进行了系列试验，同时为了比较不同防振橡胶配方的性能差别，特选择三种配方的橡胶减振装置做了对比试验。解决了具体实施试验的基干难题，成功地进行了系列试验，获得了第一数据。     

新型橡胶减振驱动链轮性能研究

章针对应用于大型履式推土机驱动链轮橡胶减振新结构，建立了其减振模型并推导出相应的传递率函数，章同时分析了橡胶减振器参数的取值对减振性能产生的影响。     

压延成型与挤出成型橡胶防水卷材生产方法比较

介绍了压延出片成型和L型机头挤出成型这两种生产橡胶防水卷材的工艺设备,并作了比较;提出了规范橡胶防水卷材生产工艺和设备的建议。     

Influence of nanofibers prepared from rice husk on the properties of natural rubber

Different concentrations of rice husk fibres have been mixed with natural rubber to study the effect on the properties of rubber mixtures and vulcanisates. Cellulose nanofibers were added in different concentrations up to 100 phr. The aim was to improve the mechanical properties of the composite, swelling resistance, and rheological properties. The research studied microstructure of prepared composites and properties of rubber mixes and vulcanisates, using transmission electron microscopy (TEM) and X-ray diffraction. Rice husk fibres derived from treating the husk with sodium hydroxide followed by careful drying and grinding in ball mill were used as filler in natural rubber formulations. These treated fibres improved the tensile strength up to an optimum concentration (20 phr) and then started to decrease in effect. A marked improvement in the modulus of elasticity and hardness of rubber mixtures also occurs.     

橡胶支座隔震技术在灾区重建工程中的应用

隔震结构体系是区别于传统抗震结构体系的一种被动控制体系,通过设置隔震层来吸收并消耗地震能量,减小结构的地震反应,确保结构的安全。本文通过采用橡胶支座隔震技术的四川某灾后重建工程实例,运用时程分析法对隔震结构的地震反应进行了计算分析。分析结果表明,隔震结构在罕遇地震作用下仍处于弹性工作状态,结构具有较好的抗震性能。本文同时介绍了橡胶隔震支座的施工工艺及注意事项,希望对今后类似工程有一定借鉴作用。     

预处理对橡胶水泥混凝土的强度及抗渗性能的影响

将经过Cacl2溶液及NaoH溶液预处理的40目、60目橡胶粉以不同的掺量等体积代替河砂作为细集料制备橡胶水泥混凝土．以研究橡胶粉经过预处理后对橡胶水泥混凝土力学强度及抗渗性能的影响。试验证明：当橡胶粉掺量达到20％时．Cacl2溶液预处理的方式能使橡胶混凝土强度较未经预处理的橡胶水泥混凝土强度提高15．2％．改性效果明显。Cacl2溶液预处理的方式对提高橡胶水泥混凝土的力学性能明显优于NaoH溶液的预处理方式。     

Theoretical investigation of the strength and stability of special pseudospherical shells under external pressure

The paper is devoted to a new shape of a shell of revolution with negative Gaussian curvature. The main part of the meridian of the shell is a plane curve of the Huygens tractrix. Geometrical properties of the middle surface of the shell of revolution are presented. The membrane state of stress for a family of shells with constant capacity and constant mass under uniform external pressure is analysed. The critical pressure, buckling modes and equilibrium paths for the family of shells are calculated with the use of the FEM (the ANSYS system). Results of the analytical and numerical investigations are presented in tables and figures. A stable post-critical behaviour of presented shells is pointed out which is not typical for most shell structures.     

Numerical analysis of surface subsidence in asymmetric parallel highway tunnels

Tunnelling related hazards are very common in the Himalayan terrain and a number of such instances have been reported. Several twin tunnels are being planned for transportation purposes which will require good understanding for prediction of tunnel deformation and surface settlement during the engineering life of the structure. The deformational behaviour, design of sequential excavation and support of any jointed rock mass are challenging during underground construction. We have raised several commonly assumed issues while performing stability analysis of underground opening at shallow depth. For this purpose, Kainchi-mod Nerchowck twin tunnels (Himachal Pradesh, India) are taken for in-depth analysis of the stability of two asymmetric tunnels to address the influence of topography, twin tunnel dimension and geometry. The host rock encountered during excavation is composed mainly of moderately to highly jointed grey sandstone, maroon sandstone and siltstones. In contrast to equidimensional tunnels where the maximum subsidence is observed vertically above the centreline of the tunnel, the result from the present study shows shifting of the maximum subsidence away from the tunnel centreline. The maximum subsidence of 0.99 mm is observed at 4.54 m left to the escape tunnel centreline whereas the maximum subsidence of 3.14 mm is observed at 8.89 m right to the main tunnel centreline. This shifting clearly indicates the influence of undulating topography and in-equidimensional noncircular tunnel.     

橡胶粉改性沥青混凝土配合比设计方法研究

针对采用普通SMA级配设计橡胶粉改性沥青混合料不能满足对SMA沥青混凝土空隙率要求的问题，通过大量室内试验，比较了采用普通SMA级配和间断级配的橡胶粉改性沥青混凝土的物理性能，提出了橡胶粉改性沥青混合料的设计方法。     

Ionic strength effect on copper biosorption by Sphaerotilus natans: equilibrium study and dynamic modelling in membrane reactor

Biosorption of copper by Sphaerotilus natans in different conditions of ionic strength and pH was studied by performing sorption tests in batch and membrane reactors. Equilibrium batch tests evidenced the negative effect of ionic strength and the positive effect of pH on biosorption performances: the highest determined value for copper specific uptake, q, was about 60 mg/g at pH 6 and about 15 mg/g at pH 4. A competitive equilibrium model was successfully fitted to experimental data at different ionic strength levels to account for copper-sodium competition. In membrane reactor tests, experimental profiles of copper concentration in the permeate vs. time did not evidence a significant effect of ionic strength at low pH values (4 and 5). On the other hand a more remarkable effect of ionic strength on copper concentration in the permeate was observed at pH 6. Experimental profiles of continuous biosorption in the membrane reactors were successfully simulated by developing a dynamic model accounting for Cu-Na competition and for binding ability of cells fragments.     

北京黄村立交桥橡胶支座更换施工

北京黄村立交桥地处京开高速躇段，交通负荷繁重，使用2年后，桥台位置处的圆形板式橡胶有不同程度的偏位：在不阻断交通的前提下，采用YBD250-18扁形专用千斤顶成功完成了24块橡胶支座的复位或更换。     

Postbuckling behaviour of stainless steel (SUS304) columns under loading-unloading cycles

Based on the equilibrium configuration paths, this study investigates the postbuckling behaviour, including the shape recovery capability, of stainless steel (SUS304) columns after a complete loading-unloading cycle. Experiments were conducted and later numerical simulation was carried out in order to analyze the observed buckling and postbuckling behaviour. Large deflection analysis is necessary for slender columns. Moreover, comparison of the experimental critical load with analytical predictions verifies the fact that physical nonlinearity should be taken into account to analyze the column’s buckling behaviour comprehensively. Thus, based on large deflection theory as well as the nonlinear stress-strain relations, the load-deformation curves of the columns during a complete loading-unloading cycle have been predicted by using the finite element modelling (FEM) code ANSYS.Precise and quantitative analyses of the results verify the fact that the material’s stress-strain properties, both in tension and compression, attribute to the column’s buckling behaviour.     

里东村滑坡稳定性分析及防治

运用极限平衡法和传递系数法对里东滑坡的稳定性问题进行了分析和评价,并根据滑坡_T程地质特征和稳定性分析结果,结合该地区已有滑坡的防治T程经验,提出了“斜坡前缘抗滑桩＋削坡＋格构护处理＋封填裂缝＋截、排水工程”的滑坡体综合治理方案。     

橡胶混凝土整体道床减振性能分析

城市轨道交通的减振设计中,除常用的降低刚度外,还可以通过增加阻尼耗散能量的方法进行吸振处理,但相关研究较少。本文提出一种新型的低成本减振措施--橡胶混凝土基础隔振轨道,通过耗散振动能量达到减振目的。采用三维动力有限元模型,施加模拟振动荷载,分析了马蹄形隧道及盾构隧道中,橡胶混凝土整体道床的动力特性及减振效果。研究结果表明：对于同一种隧道结构,两种道床型式下各拾振点的1/3倍频程频谱变化规律基本一致|橡胶混凝土整体道床系统的加速度级均小于普通整体道床系统的加速度级,20Hz以下频段的减振效果更加明显,这对于轨道交通低频振动控制具有十分重要的意义。     

Metals contained and leached from rubber granulates used in synthetic turf areas

The aim of this study was to quantify metals contained in and leached from different types of rubber granulates used in synthetic turf areas. To investigate the total content of metals, ca 0.5 g of material was added with HNO₃, HF and HClO₄ and microwave digested with power increasing from 250 W to 600 W. Leachates were prepared by extraction of about 5.0 g of material at room temperature for 24 h in an acidic environment (pH 5). Leaching with deionized water was also performed for comparison. Aluminium, As, Ba, Be, Cd, Co, Cr, Cu, Hg, Fe, Li, Mg, Mn, Mo, Ni, Pb, Rb, Sb, Se, Sn, Sr, Tl, V, W and Zn were quantified by high-resolution inductively coupled plasma mass spectrometry (HR-ICP-MS) and ICP optical emission spectrometry (ICP-OES).Results indicated that the developed method was accurate and precise for the multi-element characterization of rubber granulates and leachates. The total amount and the amount leached during the acidic test varied from metal to metal and from granulate to granulate. The highest median values were found for Zn (10,229 mg/kg), Al (755 mg/kg), Mg (456 mg/kg), Fe (305 mg/kg), followed by Pb, Ba, Co, Cu and Sr. The other elements were present at few units of mg/kg. The highest leaching was observed for Zn (2300 μg/l) and Mg (2500 μg/l), followed by Fe, Sr, Al, Mn and Ba. Little As, Cd, Co, Cr, Cu, Li, Mo, Ni, Pb, Rb, Sb and V leached, and Be, Hg, Se, Sn, Tl and W were below quantification limits. Data obtained were compared with the maximum tolerable amounts reported for similar materials, and only the concentration of Zn (total and leached) exceeded the expected values.     

有限元边坡稳定安全系数的影响研究

在边坡稳定性有限元分析中,常将安全系数定义为沿某一特定滑面的抗滑力与下滑力之比。针对该定义下分析结果表现出来的不合理现象,将纯粘土圆弧滑面边坡解析解与该定义下的数值解进行对比分析,结果表明泊松比对边坡稳定安全系数影响较大,当泊松比接近0.5时,边坡安全系数与解析解完全一致。典型算例分析也验证了这个规律,表明在一般情况下泊松比对该定义下的边坡安全系数也有相同的影响规律。     

Effect of the particle size ratio on macro- and mesoscopic shear characteristics of the geogrid-reinforced rubber and sand mixture interface

As a new type of material for civil engineering projects, the rubber and sand mixture is widely used in roadbed fillers, offering environmental benefits over traditional tyre disposal methods. This study uses a large-scale direct shear apparatus to examine the interface shear properties of the geogrid-reinforced rubber and sand mixture, considering different particle size ratios (r), rubber contents, and normal stresses. Based on indoor tests, direct shear models of the mixture with different values of r are established in PFC^3D, revealing the meso-mechanical mechanism of the mixture in the direct shear process. The results show that when r is greater than 1, incorporating a certain amount of rubber particles can increase the shear strength of the mixture. The r values of 15.78, 7.63, and 3.98 correspond to an optimal rubber content of 30%, 10%, and 20%, respectively. When r is less than 1, mixing rubber particles can only reduce the shear strength of the mixture. When the rubber content is low, the smaller the value of r, the greater is the thickness of the shear band. Furthermore, the normal and tangential contact forces are greater. The fabric anisotropy evolution law of the mixture is consistent with the change in the contact force distribution.