基坑降水回灌技术在济南东客站新建工程中的应用

以济南东客站基坑工程为研究对象,针对室内外渗透系数差异比较大的问题进行了实地单井、群井抽水试验,并采用Aquifer Test软件对水位量测曲线、水位标准变化曲线等数据进行拟合分析。采用Visual Mod Flow软件对基坑进行了三维渗流数值计算、基坑涌水量计算及基坑降水井设计。对基坑回灌井、回灌加压系统及回灌水处理系统等施工工艺进行设计,研究成果为基坑降水设计与施工提供理论依据,对今后类似工程具有很好的借鉴意义。     

深基坑降水方案的确定

结合具体工程实例,介绍了基坑降水方案的选择,进行了基坑降水设计计算,阐述了防渗帷幕的设置和回灌系统的布置,提出了基坑降水施工的建议,积累了深基坑降水经验。     

深井和回灌井联合系统的设计和应用

介绍了深井和回灌井联合系统的基本原理,阐述了该系统的设计步骤,并结合工程实例分析了其优点和应用前景,认为用深井和回灌井联合系统降水法能有效降低基坑地下水位,控制邻近建筑物的沉降。     

深井和回灌井联合系统在复杂深基坑中的设计和应用

深井和回灌井联合系统降水法能有效降低基坑地下水位，控制邻近建筑物的沉降。本文总结了该系统的设计步骤，并结合工程实例分析了其优点和应用前景。     

二元结构含水层悬挂式帷幕深基坑降水计算方法研究

帷幕结合基坑内降水的方案是深基坑工程中地下水控制的主要趋势,而至今业内对悬挂式帷幕降水条件下的设计尚无统一的计算方法。本文以汉口长江I级阶地某基坑工程为实例,基于二元结构含水层特点,提出了承压—无压条件下的修正大井法,并分别运用修正大井法、半封闭承压含水层非稳定流半解析法和数值模拟等方法,对不同帷幕深度条件下基坑涌水量和降深进行了计算,并开展对比分析。研究结果表明:承压—无压修正大井法较其它大井法更能刻画二元结构基坑降水帷幕的实际作用;半封闭承压含水层非稳定流半解析法在小程序辅助下,可实现水位降深的计算,且与数值解吻合度较高,可满足此类基坑降水设计的便捷计算需求。     

深基坑降水与回灌数值试验研究

以某深基坑降水工程为研究目标,利用有限元方法对其进行了没有回灌条件下的不同井深的降水数值试验,也设定了基坑内有无疏干井两种试验工况,检验了疏干井对降水效果的影响程度.在数值试验分析的基础上,确定了该基坑的最优降水方案,在最优方案的基础上,考虑了回灌井对降水的影响,检验了回灌井对降水影响范围的控制作用,最终确定了在满足工程降深要求的前提下对周边环境影响程度最小的降水与回灌方案,这为同类地质条件下的相似基坑工程的降水方案优化设计提供了参考.     

基于渗流原理求解工程降水降落曲线的有限单元法

在渗流基本原理的基础上提出利用三角形相似求解稳定潜水井的基坑降水降落曲线的有限单元法。采用该方法计算了实际工程案例的降落曲线,并与解析解和实测值作了对比,结果表明该计算方法更接近实测值。该方法可为基坑工程等降水工程的地下水控制设计提供依据。     

城市核心区深大基坑的降水及回灌

结合上海静安区大中里项目,针对城市核心区的深大基坑降水所涉及的基坑安全、降水和回灌对周围保护建筑的沉降影响等问题,通过系统性的抽水试验,并结合降水及回灌数值模拟,对基坑开挖过程中的降水方案进行了设计,并对降水造成的周边建筑物的沉降量进行了预测。从后续施工过程的监测数据发现,本工程前期所进行的数值模拟及现场试验,对深基坑开挖过程中的基坑安全控制及周边建筑物的沉降控制起到了有效的指导作用。基坑开挖过程中实现了按需降水,通过控制回灌量有效减小了周边建筑物的沉降,为今后类似的深基坑降水提供了一定的借鉴。     

回灌法在基坑降水中的设计与应用

井点回灌法在基坑降水中的应用仍属于探索阶段,目前尚无成熟的设计方法作为参考。本文根据群井理论推导出了一种简便、可行的回灌设计方法,该设计方法提出了一种新的回灌量和回灌井间距的计算公式,并就施工中易产生问题的环节提出了控制措施。该研究成果成功用于武汉市二郎庙污水处理厂二期工程中,从该工程的实践中得到一些结论可用于类似工程作为实践参考。     

富水卵石层抽灌一体化设计与实践

在富水卵石层敞开式基坑降水施工过程中,对于周边环境保护至关重要.通过资料调查、现场抽水试验,并借助Visual ModFlow建立水文地质概念模型,进行三维渗流数值法计算,分析坑外回灌保护周边环境的可行性.抽灌一体化技术在实际工程中取得了显著的成效,对于类似基坑降水工程和抽灌一体化绿色施工具有一定的推广作用.     

Comparison and evaluation of analytical models for the design of geosynthetic-reinforced and pile-supported embankments

Geosynthetic-reinforced and pile-supported (GRPS) embankments are becoming more and more popular as this technique showed good performances in practice. Various design methods were introduced to analyze GRPS embankments. However, the applicability of these design methods was not always fully validated. This paper focuses on the review of projects containing field observations of GRPS embankments. The comparison results showed that the assumptions related to the subsoil support, geosynthetic, arching shape, and its evolution are not consistent in the analytical methods. Comparison results with twenty-five full-scale cases and six series of experiments emphasize that these available design methods produce significantly different results in predicting loads transfer mechanism. The analytical models predict arching for cohesionless fill better that for cohesive fill soils. Besides, the analytical methods which consider subsoil support such as the CUR226 and EBGEO methods give results that are in a better agreement with experimental data as compared to other methods which do not consider the subsoil support. The CUR226 (2016) analytical model seems to be able to give the best performance with measured data when compared to other design methods. Finally, the results pointed out that the limit equilibrium model is adequate and has good performance.     

A new analytical solution for the displacement of fully grouted rock bolt in rock joints and experimental and numerical verifications

This study proposes a new analytical solution to predict displacement of a fully grouted rock bolt intersected by single rock joint. The main characteristics of the analytical model, consider the bolt profile and joint movement under pull test condition. The anchorage capacity of fully grouted bolts has been studied for many years; however, the bolt profile and its effect on bolt shear resistance are poorly understood. Investigations of load transfer between the bolt and grout indicate that the bolt profile shape and spacing play an important role in improving the shear strength between the bolt and the surrounding strata. Rock displacement is a sum of elastic part and a jump part due to the presence of joints planes. The performance of the proposed analytical model is validated by experimental method and comparison with numerical modeling. The results showed that there is a promising agreement between analytical and numerical methods. Studies indicate that the displacement rate between the bolt and the rock declines exponentially. Which is dependent on the bolt characteristics such as: rib height, rib spacing, rib width and thickness grout, material and joint properties.     

建筑设计的城市设计逻辑及其应用

本文阐述了建筑设计中的城市设计逻辑,介绍了与之相关的城市设计分析方法。最后结合作者的实践案例介绍了现代城市设计分析方法在建筑创作中的应用。案例表明以城市设计分析方法处理现实中的建筑设计问题,可使建筑设计与城市环境既协调又富有创意,也使城市建筑生成和评价更加理性,更加科学。     

强震区隧道衬砌作用力计算方法探讨

应用常规的数值法和解析法进行了强震区隧道衬砌作用力计算分析,通过对比分析发现常规方法存在一些问题,需要进行修正和改进。具体表现为:解析方法在具体使用中加力存在困难、解析和数值计算结果相差较大、对围岩类别的影响考虑不够、对隧道深浅埋的影响考虑不够。针对常规方法在强震区隧道衬砌作用力计算方面存在的问题,提出使用‘传力单元’来施加解析计算中荷载和通过对比修正来形成数值计算中初始应力场的方法,对常规计算方法进行了一些改进,采用改进后的方法进行强震区隧道衬砌作用力的计算得到比较满意的结果。     

双圆盾构隧道衬砌不同内力计算模型对比分析

盾构隧道衬砌结构的内力大小及分布规律对衬砌管片的设计和施工控制具有重要的意义,尽管单圆盾构的内力计算模型已经比较成熟,但对于双圆盾构的内力计算仍有待进一步研究.文章拟对目前国内所采用的双圆盾构内力计算模型进行综合分析,并与所建议的双圆盾构梁-弹簧法比较分析表明:在相同边界条件下,双圆盾构衬砌结构的内力解析解获得的轴力和弯矩值一般偏大,数值解最小,而实测值介于二者之间,但不同方法计算结果所表现的分布规律基本一致,证明作者所提出的双圆盾构梁-弹簧模型可为双圆盾构衬砌结构的设计和施工提供参考依据.     

混凝土悬臂深梁设计方法的试验研究及其在上海博物馆工程中的应用

本文绘出14片悬臂深梁在一次加载和反复加载下的试验结果。讨论破坏形态，分析受力性能，提出承载力计算公式，计算值与试验值符合良好。在试验基础上提出悬臂深梁设计方法，并应用于上海博物馆工程16片悬臂深梁设计。根据模拟关系近似估计实际的悬臂深梁的承载能力及大体的安全储备，对设计提出改进意见，供工程应用及修订规范参考。     

Simplified procedures for seismic design verification and evaluation of lead rubber bearing base‐isolated buildings based on free‐vibration response

Base isolation has seen widespread application to buildings and infrastructures over the past four decades. However, there is a lack of methods for assessing the performance of a base‐isolated structure at the end of construction and during its service life. To this end, simplified methods are developed for verifying isolation design and evaluating seismic demands of rubber‐bearing‐supported base‐isolated buildings based on their free‐vibration response, which could be obtained using field (on‐site) testing. The base isolation layer consists of lead rubber bearings (LRBs) and linear natural rubber (LNR) bearings. For design verification purposes, analytical solutions are provided to benchmark the free‐vibration response of base‐isolated buildings, considering the general case of a multilinear hysteretic isolation response representing multiple LRBs with distinct mechanical specifications. In seismic demand evaluation, seismic capacity of an isolation system is estimated using free‐vibration response of various amplitudes that cover a range of expected seismic intensity of interest. Seismic demands are obtained when capacity coincides with an earthquake response spectrum at a compatible damping level. Procedures are developed for the potential use of snap‐back tests and verified using experimental and numerical data.     

Nonlinear numerical simulation of punching shear behavior of reinforced concrete flat slabs with shear-heads

This paper examines the structural response of reinforced concrete flat slabs, provided with fully-embedded shear-heads, through detailed three-dimensional nonlinear numerical simulations and parametric assessments using concrete damage plasticity models. Validations of the adopted nonlinear finite element procedures are carried out against experimental results from three test series. After gaining confidence in the ability of the numerical models to predict closely the full inelastic response and failure modes, numerical investigations are carried out in order to examine the influence of key material and geometric parameters. The results of these numerical assessments enable the identification of three modes of failure as a function of the interaction between the shear-head and surrounding concrete. Based on the findings, coupled with results from previous studies, analytical models are proposed for predicting the rotational response as well as the ultimate strength of such slab systems. Practical recommendations are also provided for the design of shear-heads in RC slabs, including the embedment length and section size. The analytical expressions proposed in this paper, based on a wide-ranging parametric assessment, are shown to offer a more reliable design approach in comparison with existing methods for all types of shear-heads, and are suitable for direct practical application.     

Methods of calculating thawing and freezing in beds of structures on nonflowing types of permafrost

The causes of and conditions for the manifestation of distortions in calculations conducted by the method of auxiliary temperatures are exposed. It is indicated that the distortions are maximum beneath the edges of structures, where the design frost depth may be on the low side by a factor of two and more. A computational method, which is free of exposed drawbacks and which indicates agreement with the results of numerical modeling is developed, proceeding from analytical solution of the problem of the motion of the phase interface in quasi-stationary approximation. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 2, pp. 18–22, March–April, 1995.     

建筑设计方法与思路探究

跟随市场潮流,现代建筑设计师也要结合时代的特征学会先进的设计方法,进而形成自己独有的设计思想和风格。本文主要对建筑设计方法和思路进行了分析,介绍了建设设计的主要方法,并探讨了现代建筑设计的思路发展方向。