计算水平桩的修正双参数法

指出了双参数法微分方程在公式推导与参数取值方面存在的不足,对微分方程中深度的幂数进行了修正并推导出计算公式。修正参数后的推导公式克服了原公式取值只能为正整数1和有限个小数的缺陷,使取值可取任意整数和小数,从而拓宽了参数的取值范围。当桩在弯矩和水平力共同作用时,利用桩的边值问题可求得桩身各截面的弯矩、剪力、位移、转角。实例计算证明,用修正后的幂数作为参数,推导正确,取值灵活且与实测值很接近。     

Perspectives of the Expert and Experienced on Challenges to Regional Adaptation for Sea Level Rise: Implications for Multisectoral Readiness and Boundary Spanning

This study focuses on adaptation to sea level rise (SLR) in the specific context of the Hampton Roads region of southeastern coastal Virginia. It analyzes the perspectives of stakeholders who are experts in and have experience with SLR to develop an informed understanding of the region’s ability to address SLR and its readiness to pursue adaptation using a whole-of-community approach. A survey of the expert and experienced reveals (1) what they prioritized as the top three most challenging phases of regional adaptation and (2) what issues within those priority areas were the most pressing. Our findings point to the importance of meso- and micro-level boundary spanning across organizations and the whole of the community to ensure that multiple organizations and individuals in a region can be engaged in adaptation. Finally, this work briefly discusses how boundary-spanning approaches can provide a region a pathway toward overcoming barriers to effective climate-related adaptation.     

考虑入射角和局部地形影响的地面地震动效应分析

本文通过建立考虑局部地形条件的场地模型,采用粘弹性理论设置人工边界,考虑入射角进行等效地震荷载输入,对五种不同地形和坡度的场地进行地面地震动效应分析。结果表明,凹状河谷地形和凸状山脊地形相比于平地地形来说对地震动具有放大效应,坡顶的地震响应要高于坡底的地震响应,地面地震动响应大致呈现与地形类似的形状,迎波面地震响应要高于背波面地震响应。     

探地雷达的时域有限差分模型

正弦和余弦变换把三维问题转化为二维问题。透射边界条件消除从区域边界的反射，采用超吸收技术改善透射边界条件的后期不稳定性。把这一理论应用于探地雷达模型，得到了很满意的结果。     

水槽侧壁对任意三维结构波浪力的影响

基于势流理论,采用高阶边界元法在线性频域内研究水槽中波浪对任意结构的作用。探讨水槽侧壁对垂直圆柱和方箱所受到的波浪力的影响,研究水槽宽度与入射波长以及结构特征长度之间的关系,重点研究横向立波的产生及其共振对结构受到的水平力和垂向力的影响。     

抗拔桩在地下车站主体结构计算模型中的边界条件研究

抗拔桩在地下车站主体结构计算中作为一个边界条件常被设置为3种型式,以广州地铁2、8号线换乘站南洲站的2号线部分作为计算实例,将这3种常见的边界条件进行计算对比分析,提出一个合理的边界条件,可为今后带抗拔桩的地下车站主体结构计算提供参考。     

饱和土与结构动力相互作用影响函数

依据外力作用下两相饱和土介质动力响应的基本解，构造了柱面荷载作用下，饱和土与结构动力相互作用影响函数，解决了用边界元法分析饱和土与结构动力相互作用的关键问题。     

Simple Lagrangian formulation of bubbly flow in a turbulent boundary layer (bubbly boundary layer flow)

For the theoretical consideration of a system for reducing skin friction, a mathematical model was derived to represent, in a two-phase field, the effect on skin friction of the injection of micro air bubbles into the turbulent boundary layer of a liquid stream. Based on the Lagrangian method, the equation of motion governing a single bubble was derived. The random motion of bubbles in a field initially devoid of bubbles was then traced in three dimensions to estimate void fraction distributions across sections of the flow channel, and to determine local bubble behavior. The liquid phase was modeled on the principle of mixing length. Assuming that the force exerted on the liquid phase was equal to the fluid drag generated by bubble slip, an equation was derived to express the reduction in turbulent shear stress. Corroborating experimental data were obtained from tests using a cavitation tunnel equipped with a slit in the ceiling from which bubbly water was injected. The measurement data provided qualitative substantiation of the trend shown by the calculated results with regard to the skin friction ratio between cases with and without bubble injection as function of the distance downstream from the point of bubble injection.List of symbols B law of wall constant - C _f local coefficient of skin friction - C _f0 local coefficient of skin friction in the absence of bubbles - d _b bubble diameter [m] - g acceleration of gravity [m/s²] - k ₁ k₄ proportional coefficient - k _L turbulent energy of the liquid phase [m²/s²] - L representative length [m] - l _b mean free path of a bubble [m] - m _A added mass of a single bubble [kg] - m _b mass of a single bubble [kg] - N _x ,N _y ,N _z force perpendicular to the wall or ceiling exerted on a bubble adhering to that wall or ceiling [N] - P absolute pressure [Pa] - Q _G rate of air supply [/min] - q _L ⁽ⁱ⁾ turbulent velocity at the ith time increment [m/s] - R> _ex Reynolds number defined by Eq. 32 - T _*L integral time scale of the liquid phase [s] - U velocity of the main stream [m/s] - ,¯v,¯w time-averaged velocity components [m/s] - u,v,w turbulent velocity components [m/s] - û _L ,v_L root mean square values of liquid phase turbulence components in thex- and y-directions [m/s] - V volume of a single bubble [m³] - X,Y,Z components of bubble displacement [m] - x _s ,y _s ,z _s coordinate of a random point on a sphere of unit diameter centered at the coordinate origin - root mean square of bubble displacement in they-direction in reference to the turbulent liquid phase velocity [m] - local void fraction - _m mean void fraction in a turbulent region - regular random number - R _v increment of the horizontal component of the force acting on a single bubble, defined by Eq. 22 [N] - t time increment [s] - ₁ reduction of turbulent stress [N/m²] - _L rate of liquid energy dissipation [m²/s³] - _m coefficient defined by Eq. 30 - law of wall constant in the turbulent region in absence of bubbles - ₁ law of wall constant in the turbulent region in presence of bubbles     

水下砂卵石地层盾构隧道越江段注浆压力研究

近年来,江(海)底盾构隧道建设日益增多,对于水下段而言,由于地层渗透性强、埋深浅等因素影响,盾尾同步注浆压力的合理控制显得尤其重要,而探明盾构隧道在施工过程中孔隙水压力的分布对工程实践意义重大。本文依托常德沅江过江隧道工程,结合工程现场地形、地质、气候以及水文条件,采用FLAC^3D有限元分析软件对盾构施工扰动下的地层孔隙水压力分布进行系统分析。研究结果表明:(1)综合考虑各种因素确定渗流场中削减边界为20 m,即模型构建时沿开挖方向前后多取20 m长度,可使模拟结果更能真实反映越江隧道围岩各处孔隙水压力的变化规律;(2)盾构隧道掘进过程中,拱顶、拱底和左右拱腰处的动水压随掘进距离的变化趋势大致相同,拱底动水压量值最大,左右拱腰次之,拱顶最小,并根据区间动水压力变化规律给出满足岸边段和水下段要求的注浆压力。     

金山铁路既有线提速路基动力响应分析

基于无限元人工边界和基床—路堤—场地子结构系统,建立上海金山铁路既有线有限元模型,根据实测路基响应特征构造基床顶面动荷载,模拟列车以现行速度通过路基产生的动荷载,分析列车在现行速度43km· h-1和目标速度160 km· h-1范围内变化时,普通路基在动荷载作用下的动力响应规律.研究发现:如果既有线路基床不改造,列车速度从43km· h-1提高至160km· h-1时,基床顶面动应力峰值将增大17％左右;路基面动应力沿基面以下深度方向呈指数形态衰减;与现行速度条件下基床顶面以下6.2m的影响深度相比,提速后影响深度增加了1.2m.