Finite Element Analysis on Interaction of Neighboring Highway Tunnels under Construction

Recently, the construction of neighboring highway tunnels with small interval gets more and more in China. The construction of such tunnels proceeds usually by excavating one after another. The second tunnel is constructed with the surrounding rock disturbed by the first one. And the construction of second tunnel also has effect on the first excavated one. For revealing the interaction laws of such tunnel construction in combination with the engineering practice of Lanfeng tunnel at Jinshan Road in Chongqing, The FE numerical simulation analysis was used to study the characters of surrounding rock deformation, stress field, and plastic zone of the tunnel. From this analysis, it clearly shows that the excavation of second tunnel has significant influence on the first one. This study provides a scientific basis for design and excavation of neighboring highway tunnels.     

Analysis of the Static Stability of Tailings Dam under Coupled Deformation and Seepage Fields

The static stability of a tailings dam is analyzed with a finite element approach, which takes into account the effect of plastic deformation, temperature, saturation and void ratio on the properties of soil materials, the effect of water and soil interaction and the extended Mohr-Coulomb failure criterion. The concept of yield approaching degree is introduced, which is defined as the ratio of the existing equivalent stress to the yield stress taking into account the effects of different influencing factors. The response of the tailing dam subjected to the coupled saturated/unsaturated seepage and deformation is simulated, considering that the dry beach is 100-meter long and the starter dam is jammed, respectively. The important indexes such as the deformation and the phreatic surface of the dam are obtained. The distribution of the yield approaching degree in the whole dam under the given condition is obtained, which can provide not only a general stability assessment of the dam, but also important information to the decision-making for the reinforcement and maintenance of the dam.     

Analysis on Foundation Pit Deformation of a Commercial Building in Hangzhou

The foundation pit deformation of a commercial building in Hangzhou is calculated by using calculation method related to foundation pit deformation. The calculation results by m method show that the maximum deformation is 29.2mm and the real maximum deformation is 174.6mm. The deformation character obtained by foundation coefficient method is different from the real deformation. There are lots of factors influencing foundation deformation. According to practical engineering condition, in this study, the influencing factors for soil parameters, bracing condition, condition for insertion of retaining wall into soil and construction speed are determined. The calculation method used is analyzed and modified. Finally, a useful and valid method for calculating foundation deformation is presented, by which the foundation pit deformation in practical project can be forecasted and analyzed.     

ANALYTICAL SOLUTION OF RING SHELL LINING WITH ANNULARLY VERTICAL WALLS MADE CONTACT WITH SURROUNDING ROCK

In this paper,the ring shell lining with annularly verticalwalls made contact with the surrounding rock is considered as a combinationstructure formed of ring shell,inner and outer annular barrels on elastic fo-undation.The complex equation and its solutions of ring shell under deadload of lining and vertical and horizontal surrounding rock pressures are de-rived by the method of complex function.The governing equation and itssolution of the barrels on elastic foundation are also derived by theory ofcylindrical shell.And then,the ring shell lining is assembled by the subst-ructures by means of compatibility conditions of internal forces and defor-mations between them.In the paper,all formulas for the practical computa-tion in engineering are derived,the numerical examples are given and theeffects of the parameters of the lining on the work behaviours of lining alsoare discussed preliminarily     

Study on Mismatched Engagement of Hourglass Worm Gearing with The Worm Generated by A Cone and The Wheel Generdted by A Straight Profile Hob

A method to make the hourglass worm gearing with the property of mismatchedpoint contact has been proposed.The worm and the hob of the worm gearing is generated by a coneand a straight line located on the cone respectively. The basic principle of the worm gearing has beenanalysed. The formulas for calcultating the machining parameters has been obtained. And the toothcontact of the worm gearing has been investigated.The result shows that this worm gearing could getopint contact well.     

Determination of Load Share between Gear Teeth with Contact Finite Element Method

The determination of load share between teeth is a complex problem in gear strength calculation. On the basis of contact finite element method this paper considers the production-assembly error as initial gap to get the finite element model which meets load share between teeth in gear meshing. Through calculating and comparing the result with that from ISO formula to get the load share between teeth which meets the requirements in actual usage.     

聚合物基/稻壳粉复合材料的表面改性研究

使用JC2000A型接触角测量仪测试并研究了蒸馏水和甘油两种液体在稻壳粉填充聚乙烯(PE)、聚丙烯(PP)、聚氯乙烯(PVC)复合材料表面的接触角.研究表明:通过酸碱处理可明显改变接触角及其随时间变化的规律;其中效果最好的是以水作为探测液时,经酸处理后的PE/稻壳粉复合材料.通过方差分析得知表面改性处理方式对接触角有相当显著的影响.     

Quantitative aspects of solid-state C-NMR spectra of humic substances from soils of volcanic systems

Cross-Polarisation Magic Angle Spinning Carbon-13 Nuclear Magnetic Resonance spectroscopy (CPMAS ¹³C-NMR) represents one of the most powerful tools to investigate soil organic matter (SOM) mainly because of its inherent capacity to provide a semi-quantitative evaluation of carbon distribution. A critical parameter during acquisition of CPMAS ¹³C-NMR spectra is the contact time required to obtain the cross-polarisation between proton and carbon nuclei. The procedure to evaluate the best contact time for the acquisition of a quantitative CPMAS ¹³C-NMR spectrum is to perform Variable Contact Time (VCT) experiments. In this work the structural features of a number of purified humic substances from Italian and Costarican volcanic soils were investigated by CPMAS ¹³C-NMR spectroscopy after having performed preliminary VCT experiments. The VCT experiments showed that the average contact times vary according to the origin and chemical structure of the humic material. The optimal contact times (OCT) for nine humic samples were between 250 and 800 μs These values were different from the time of 1000 μs that is commonly applied as the best average contact time for humic materials. Moreover, by comparing the NMR data to those obtained by elemental analysis (C/H ratio), it appeared that the efficiency of the cross-polarisation between protons and carbons, and hence the contact time, is affected not only by the number of protons, but also by their distribution over the molecules. The evaluation of errors in quantitative estimation of the different carbons revealed that the use of OCT generally reduced by half the loss of signals occurring when the average contact time of 1000 μs is used in CPMAS ¹³C-NMR spectra of humic substances.     

Effect of subcritical hydrophobicity in a sandy soil on water infiltration and mobile water content

Recent research shows that most soils are more or less water repellent. Already subcritical water repellency may cause incomplete soil wetting and preferential flow. Both processes potentially reduce the residence time of water and solutes in the vadose zone, resulting in an enhanced risk of groundwater contamination. The objective of the present paper is, therefore, to evaluate the impact of reduced soil wettability on the soil water infiltration rate and to investigate the tendency towards preferential flow with the analysis of the immobile water content in the infiltration zone. In november 2002, a field experiment was done in a coniferous forest, 30 km N of Hannover, Germany. Soil hydrophobicity was quantified by measuring the contact angles. The hydraulic conductivity of the podsolic sandy soil was measured depth‐dependent with a double‐ring tension infiltrometer in three soil horizons. To quantify possible preferential‐flow effects, a LiBr‐Tracer was added to the infiltrating water to evaluate the mobile water‐content fraction after infiltration. Additionally, infiltration rates of water were compared with infiltration rates of ethanol which were determined after water infiltration at the same locations. Results show that the actual water repellency of field‐moist soil was mainly subcritical (contact angle <90°). Water infiltration rates were reduced due to subcritical repellency by a factor of 3–170 compared with ethanol infiltration rates (exclusion of wetting effects). This spatially variable infiltration behavior was not clearly reflected neither by the small‐scale contact‐angle measurements nor by the analysis of the average immobile soil water content in the infiltration zone. We conclude that this specific infiltration behavior of water caused by small‐scale wettability effects may temporarily reduce the local connectivity of water‐flow pathways.