Response of Building Adjacent to Stiff Excavation Support System in Soft Clay

A three-story school supported by shallow foundations was affected by an adjacent 12.2-m-deep excavation in soft clay in which the excavation support system was a 0.9-m-wide secant pile wall braced by both cross-lot struts and tiebacks. The school is a reinforced concrete frame structure with exterior reinforced concrete foundation walls. This paper summarizes the conditions at the site and presents correlations among construction activities, measured deformations and distortions, and attendant damage in the school. The lateral ground movements associated with the excavation were monitored with four inclinometers placed around the school. The building movements were monitored with optical survey points established on interior columns, exterior walls and on the roof, and with tiltmeters installed on the exterior foundation walls. The damage to the school mainly consisted of 300 to 500-mm-long hairline cracks in nonload bearing walls. Only a few cracks had widths greater than 6 mm. The school deformed such that the portion closest to the excavation sagged and the remainder hogged. Damage was first observed in the area of sagging when angular distortions reached 1/940 and the excavation was approximately 5.5-m deep. Angular distortions as large as 1/300 were observed at the end of the project. The data suggest that angular distortions had to be less than 1/1000 to preclude any damage to the school.     

Strengthening of a Damaged Multistory Building Constructed on a Slope Composed of Soil Prone to Slump-Type Settlement

The case of the deformation of a multistory tenement building on the slope of a ravine composed of soils prone to slump-type settlement is discussed. Measures taken to strengthen the foundations and slope, and results of observations on the effectiveness of their use are cited.     

小变形下考虑摩擦效应的桩基水平承载分析方法

当前我国各类大型工程建设对桩基设计提出了更高的要求,桩基水平承载计算是一个突出问题。从传统水平受荷桩分析方法入手,推导考虑侧壁摩擦力的桩基水平承载挠曲微分方程,提出小变形下考虑摩擦效应的桩基水平承载计算方法(fm法)。编制相应的分析程序,通过算例验证方法的正确性和有效性。进一步比较传统m法与本文fm法的异同,并深入探讨尺寸效应对桩基水平承载的影响,可供工程参考。     

Probabilistic analysis of ultimate seismic bearing capacity of strip foundations

This paper presents a reliability analysis of the pseudo-static seismic bearing capacity of a strip foundation using the limit equilibrium theory. The first-order reliability method (FORM) is employed to calculate the reliability index. The response surface methodology (RSM) is used to assess the Hasofer–Lind reliability index and then it is optimized using a genetic algorithm (GA). The random variables used are the soil shear strength parameters and the seismic coefficients (k_h and k_v). Two assumptions (normal and non-normal distribution) are used for the random variables. The assumption of uncorrelated variables was found to be conservative in comparison to that of negatively correlated soil shear strength parameters. The assumption of non-normal distribution for the random variables can induce a negative effect on the reliability index of the practical range of the seismic bearing capacity.     

层状基础的动力响应分析

基于剪切梁理论,利用振型叠加法及振型函数正交性,求得体系的参与系数及稳态动力响应的封闭型解析式;最后针对算例,利用龙格—库塔法得出土层的最大响应图（位移、剪应力、加速度）。     

重庆某长江大桥南城隧道洞室地基三维数值模拟分析

本文针对重庆"骑龙经典"工程下卧重庆某长江大桥南城隧道洞室地基进行定性分析以及二维、三维数值模拟分析。在进行数值分析时采用加载系数法分别对隧道毛洞、隧道衬砌施加岩石自重和各倍数建筑荷栽标准值,并对分析结果进行比较。经综合分析表明,高层建筑的施工不会影响隧道洞室的稳定性,高层建筑可以按照常规方法进行设计。文章对建筑施工和监测提出了限定条件和建议。     

深水海上风电三筒导管架基础受力及浮运分析

以中国福建某较深海域风电场为背景,提出一种海上风电宽浅型三筒导管架基础结构,继而通过建立考虑分层土体的基础整体有限元模型,对分层土中宽浅型三筒导管架基础静动力特性及浮运稳性展开研究。研究结果表明,正常荷载作用下此基础结构法兰倾斜率为3.98‰,满足规范要求：极限荷载作用下,基础结构各部位应力满足要求;基础-塔筒-机组整体共振校核满足要求：基础可在4级风浪以内的海况下进行自浮远距离拖航浮运;等效疲劳荷载作用下,基础结构疲劳损伤满足要求。     

Uplift Performance of Transmission Tower Foundations Embedded in Clay

The contribution to the uplift stiffness and capacity provided by the clay beneath the base of shallow footings typical in configuration to those employed to support high voltage electricity transmission towers is examined. Pore pressures developed at the base of appropriately scaled footings founded on clay were measured over a wide range of uplift rates in a geotechnical centrifuge. These measurements, coupled with data from tests on identical footings founded on sand, are used to provide insights into the influence of uplift rate on the failure mechanism and footing capacity. Data from a series of undrained triaxial extension tests, conducted over a range of strain rates, are presented and these data combined with finite element back-analyses of the centrifuge uplift tests are used to provide designers with a means of assessing the capacity and load–displacement response of footings on clay subjected to high rates of uplift in service.     

不均匀地基上不埋板基的计算方法

文章介绍不均匀地基上不埋板基的计算方法。     

Bridge Resting on an Ice Body at High Altitude

In some of the snow‐bound, glaciated regions of the high mountains, roads may have to pass over ice. In most cases, the road alinement is selected to avoid large stretches of ice; smaller ice bodies are either not permanent (forming only in winter), or can be easily destroyed, as well as the road formation constructed over them. The bridge described in this paper is of a semi‐permanent nature and is founded upon a perennial ice body in a very cold and glaciated mountainous region of Northern India, at an altitude of 5,580 m (18,307 ft) above sea level. This is a unique motorable bridge which has the triple distinction of being the world's highest, of being semi‐permanent, and of being founded upon a permanent ice body. Described here are the sequence of events which led to the construction of this bridge and details of the construction.