塑料套管管侧前注浆桩承载特性的现场试验研究

为提高塑料套管混凝土桩（简称TC桩）的承载性能,结合桩侧注浆技术,发展和形成了塑料套管管侧前注浆桩（简称TCSG桩）。通过现场试验,对TCSG桩、TC桩和扩径塑料套管混凝土桩（简称TCLD桩）3种桩型在不同时期进行了静载试验,并引入了3种易于应用的单桩沉降计算模型对各桩体的沉降进行了计算。试验结果和沉降模型计算分析表明：与TC桩相比,TCSG桩增加了8.3%～20.0%的承载力,并减小了19.8%～33.5%的沉降,而TCLD桩降低了10.0%～16.7%的承载力,且增加了13.2%～43.8%桩体的沉降;TCSG桩的轴力衰减速率大于TC和扩径的TCLD桩的,TCSG桩的前、后期的平均轴力衰减速率相差不大,TC桩后期的平均轴力衰减速率相比前期提高了1.1%～14.2%,而TCLD桩却降低了5.9%～21.9%;在前、后期静载时,TCSG桩在各级荷载下的平均单位侧摩阻力相比TC桩分别提高了14.5%～39.6%和9.2%～28.6%,扩径后的TCLD桩则分别降低了4.9%～11.8%和11.5%～30.7%;管侧前注浆后的TCSG桩的时效特性不显著,扩径后的TCLD桩的侧摩阻力随时间减小而端阻力则增大;基于桩土荷载传递的单桩沉降计算模型能够较好地预测塑料套管桩的沉降。     

水土压力统一计算理论的提出和发展

地下结构上水土压力的合算与分算既关系到基坑围护的设计,又关系到地下结构的抗拔桩设置。现场数据表明,砂性土采用水土压力分算是合理的,但黏性土采用水土压力合算是否合理一直是学术界与工程界争论的焦点问题。为解决争议,笔者提出了可以统一水土压力合算与分算的方法,作为一个逻辑上自洽的理论,实现了水土分算与合算之间的过渡,为水土合算提供了理论基础。回顾该理论的提出过程,对其合理性做了进一步说明,分析了该理论的学术价值和发展前景。     

Dynamic motion and tension of marine cables being laid during velocity change of mother vessels

Flexible segment model （FSM） is adopted for the dynamics calculation of marine cable being laid. In FSM, the cable is divided into a number of flexible segments, and nonlinear governing equations are listed according to the moment equilibriums of the segments. Linearization iteration scheme is employed to obtain the numerical solution for the governing equations. For the cable being laid, the payout rate is calculated from the velocities of all segments. The numerical results are shown of the dynamic motion and tension of marine cables being laid during velocity change of the mother vessels.     

Prediction of risk in submarine tunnel construction by multi-factor analysis: A collapse prediction model

Abstract

Collapse is a major threat in tunnel construction. How to predict collapse risk accurately and timely is a complicated problem. In this paper, a non-linear mathematical model is applied to obtain the potential risk indices for a submarine tunnel using statistical analysis based on previous submarine tunnels, such as the Seikan tunnel and Xiang’an tunnel. Rough set theory is used to screen risk indices, determine each indicator value, and classify risk factors. Traditional weight calculation methods that are overly dependent on expert experience and other subjective factors are optimized and improved. Based on the frequency of each risk factor, the objective weight value of each risk index is determined according to weight back analysis theory. The ideal point method is used to calculate the collapse risk level. Predictions made by this new method are consistent with the actual tunnel collapse risk levels. This new method provides theoretical and technical basis for effectively predicting tunnel collapse.     

基于OpenGL的规则格网地形法线计算优化研究

本文探讨了OpenGL的光照计算原理以及法线在光照计算中的作用,针对规则格网地形的几何结构特征提出了直接计算、方程法以及迭代法计算地形平均法线的3种方法,并分析了各自的优缺点。实验证明,迭代法由于用加法代替乘法计算,同时又避免了不必要的重复法线计算,计算效率具有明显优势。     

辅助角法在坐标方位角反算中的应用

坐标方位角反算是测量中最基本的计算之一,但传统的方位角计算方法涉及到象限问题,判断容易出错,尤其让一些初学者感到迷惘。为了使坐标方位角反算变得直观简单,提出了利用辅助角来计算坐标方位角的方法,并对其特点及应用进行了分析。     

高斯投影复变换的数值计算方法

高斯投影复变换的数值计算简单快捷,具有重要的工程应用价值.从数值计算角度出发,使用计算机代数系统Mathcad,Matlab以及Mathematica对高斯投影复变换进行了改进:只需建立正算变换计算式而不再需要建立反算变换计算式.对于复方程,利用系统的求根函数直接求解.对于复积分,研究了积分级数分析法、椭圆积分函数法及...     

人工神经网络在感热通量计算中的应用

感热通量计算方法的研究是边界层研究中最重要的内容之一。基于中日JICA计划项目中青藏高原东缘四川盆地温江站的边界层铁塔观测资料初步研究了使用人工神经网络(ANN)计算边界层感热通量的方法,并将ANN和经验公式法计算得到的感热通量分别和真值作相关和误差分析。对2009年4月和5月的两个个例研究的结果表明:ANN计算结果和真值的相关性都高于经验公式法且趋势变化和真值更加吻合,ANN计算的2009年4月的感热通量与真值的均方根误差(RMSE)稍大于经验公式法,但2009年5月的RMSE明显小于经验公式法。     

GPS-RTK技术在高等级公路横断面测量中的应用

推出了在线路坐标系下任意中桩点的切线方位角和中桩点的坐标计算公式,求出了该中桩处横断面上任意点的坐标,提出了将GPS-RTK技术应用于路线横断面测量的基本思路和数据处理方法.     

Adsorption of H<Subscript>2</Subscript>O,NH<Subscript>3</Subscript> and C<Subscript>6</Subscript>H<Subscript>6</Subscript> on alkali metal cations in internal surface of mordenite and in external surface of smectite: a DFT study

Adsorption of H₂O, NH₃ and C₆H₆ on H- and alkali metal-exchanged structures of mordenite and on corresponding cations on the smectite layer is investigated by ab initio density-functional calculations. Proton or an alkali metal cation compensates one Al/Si framework substitution and resides in the extra-framework position of zeolite or above flat smectite layer close to the Al/Si substitution. Pronounced similarities between zeolite and smectite are observed in changes of the adsorption energies and location of the external cation with changing character of the external cation. Calculated adsorption energies exhibit the following trend: E(NH₃) > E(H₂O) > E(C₆H₆). Because of looser contact with the framework, zeolitic cations are stronger adsorption centers and calculated adsorption energies of zeolites are by ~20–30% larger than cations of smectites. The highest adsorption energy is calculated for H-exchanged structures and down the group of alkali metal cations a decrease of the adsorption energy is observed. Deviations from the smooth variation of the adsorption energy are caused by: (1) formation of strong hydrogen bonds in H-exchanged structures, (2) adsorption induced migration of the external Li⁺ cation, and (3) steric hindrances of the flat C₆H₆ molecule adsorbed on the cation in the cage of zeolite.