上海花木雨水泵站沉井丸脚垫层施工经验

随着施工技术发展，沉井制作由原来的分支制作分节下沉，发展成分制作一次下沉，沉井刃脚由原来用垫木满足地基承载力的施工方法，改成用混凝土垫层做临时基础，通过总结工程实践，介绍沉井混凝土垫层施工设计实例和结构计算。     

雨水泵房沉井施工技术

北仑发电厂雨水泵房沉井施工过程中,通过应用加筋地基垫层、超高井体分节制作、沉井下沉形式自由转化、涌土治理、加强观测实时纠偏等项技术,提高了施工效率,节约了成本。     

某泵房沉井施工技术

结合某沉井工程实例 ,对砂垫层的设计、素混凝土垫层的制作、沉井下沉及封底等相关的技术问题作了必要的总结 ,为今后同类工程的施工提供参考     

谈晋城市凤台街改造工程沉井施工技术

从场地处理,沉井分节,铺垫、支撑、立模、绑扎钢筋,沉井混凝土浇筑、养生、拆模,沉井制作和下沉过程中的质量控制几个方面,介绍了晋城市凤台街改造工程沉井施工技术,同时积累了一些施工经验,为类似工程提供参考。     

可分离式悬挑脚手架在沉井施工中的应用

在软土地基上进行的沉井工程施工,一般都采用分节制作、分节下沉、再次接高的施工方法。在此过程中,往往涉及到一个常见的反复工作量,那就是施工脚手架的重复搭、拆。由于沉井工程一般都为封闭结构,沉井内部施工材料均要从顶部贯入和撤出,不仅增加成本,而且占用工期。而在沉井内部采用可分离式悬挑施工脚手架,随沉井分节制作和接高分次搭设到位,在沉井下沉时脚手架随沉井一起下沉,可有效解决脚手架的反复搭拆问题。1工程概况南通天生港电厂取排水工程,水泵房采用钢筋混凝土多格矩形沉井结构,平面尺寸为40m×20·8m,沉井总高19·8m。本工程位…     

大口径沉井不排水下沉法施工技术

根据工程实例，确定了制作下沉的方法，详细阐述了分节制作一次下沉的施工工艺，就施工中常见的疑难问题提出了预防处理措施，以使沉井的施工结果满足设计要求。     

沉井结构砂垫层计算实例及质量控制

1沉井概述 （1）沉井结构是个上无顶盖、下无底板的地下构筑物,由于是通过自重下沉的,故名为“沉井”。砂垫层是沉井制作和开挖下沉时的稳定措施。沉井结构分为钢筋混凝土结构、钢壳填芯混凝土结构、预置钢混凝土结构、房屋纠偏的砖石结构等类型。     

江滩涂泥上的沉井施工技术

结合池州市供排水有限责任公司江口水厂一期工程施工实践,介绍了沉井分节制作排水下沉的施工方法,分别阐述了基坑开挖,刃脚垫层,立井筒内模和支架,钢筋绑扎,沉井下沉等关键工序施工步骤,并提出了施工质量要求,对今后同类工程有指导意义。     

沉井施工在炼钢厂旋流池工程中的应用

上海宝钢漩流池外圆筒高26.1m,采用沉井施工,是迄今宝钢最深的沉井。针对地下承压水头高、地质条件复杂、同时间又有邻近大基坑施工影响等不利施工条件,介绍了沉井分节制作、降承压水、纠偏、抗浮、封底等技术措施,保证了沉井顺利下沉到位。     

电梯基坑挖有地下水施工技术

以具体工程为例,对电梯基坑挖有地下水施工技术进行了研究,介绍了钢护筒沉井设计方法,着重从施工流程、沉井下沉、混凝土垫层施工方面探讨论述了具体的施工技术,以解决电梯基坑挖施工中的难题。     

Experimental investigations of anchoring of open caissons by means of horizontal piles (for purposes of discussion)

Conclusions Investigations established a high bearing capacity from a vertical load of piles horizontally jacked in at a considerable depth. Thus, the possibility of using horizontal piles for anchoring open caisson against buoyancy is confirmed. Editor's Note. For the wide use of progressive designs of thin-walled open caissons sunk in a thixotropic jacket it is important to solve the problem of anchoring the latter. The present article, which considers one of the possible methods of anchoring open caissons, is published (for purposes of discussion) in connection with this.Kharkov Institute for General Construction and Sanitary Engineering Planning of Industrial Establishments. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 5, pp. 13–14, September–October, 1975.     

沉井施工在实际工程中的应用与问题分析

结合某金属板带厂熔铸车间3个外形尺寸相同的沉井施工实例,从沉井制作、下沉、封底3个方面研究了沉井施工过程中的控制措施.同时,对沉井下沉系数进行计算,分析了沉井对周围土的扰动原因.针对沉井施工中常见的突沉现象,下沉纠偏问题提出了相应的解决方法,使工程顺利完成.     

非均质软土地基上吸力式沉箱抗拔承载力数值分析

针对非均质软土地基上吸力式沉箱的抗拔极限承载力,运用大型有限元分析软件ABAQUS进行了三维非线性数值分析。通过一定数量的数值计算与分析,较系统地考察了沉箱承受拉拔荷载过程中主动侧土体与结构接触状态对沉箱极限承载力的影响。由此表明:软土地基的不排水抗剪强度、吸力式沉箱结构的长径比、荷载作用点位置等因素对于主动侧土体与结构的接触状态具有一定影响。通过与有关模型试验结果及极限分析上限解的对比分析,在一定程度上验证了有限元计算模型与数值分析结果的合理性。     

Failure envelope considering the ultimate tensile capacity of suction caissons in sand

Little analytical work has been done to elucidate the ultimate capacity of suction caissons under vertical tensile (V), lateral (H), and moment (M) loads in soils. In this paper, in order to reveal the effect of vertical tensile, lateral, and moment loads on the ultimate capacity of suction caissons in sand, an analytical investigation was made using a traditional bearing capacity theory. Taking account of the vertical equilibrium of an annular element of a skirt, through the vertical tractions inside and outside the skirt of a suction caisson when a vertical tensile load is applied, the vertical displacement of the soils adjacent to the skirt of the suction caisson was presented. The most appropriate bearing capacity equation for predicting the experimental results was shown for suction caissons having an embedment larger than a diameter in sand. For the deformation-load responses of suction caissons with various embedment ratios in sand, subjected to inclined tensile loads, there was a good agreement between the results obtained from laboratory tests and those predicted by the present method. The failure surfaces, considering the ultimate tensile capacity in the H-M, H-V, and M−V planes, and in the H-M−V space, for suction caissons in sand, were presented.     

水平荷载长期作用下沉井变位特性的模型试验研究

为研究在水平荷载长期作用下软土中沉井基础的变形特征,设计并实施了3组模型试验。首先进行了预试验以确定模型沉井的水平承载力,然后分别研究了模型沉井在不同大小的水平荷载作用下荷载–变形曲线、被动区土压力分布特征、沉井顶部水平位移、被动区土体水平位移的短期、长期变形特征。基于本次试验数据,对理想弹塑性的p–y曲线按照加载时间和荷载大小予以修正。修正后的理论计算结果与实测值基本一致,并对依托工程进行了试算,修正后的p–y曲线可为软土地区的沉井水平变形计算提供理论依据和设计指导。     

Vertical dynamic impedance of suction caissons

Nowadays, suction caissons are being increasingly deployed as foundations to support offshore wind turbines (OWTs). Due to the overturning moment induced by waves and wind, vertical forces are the dominating ones acting on these foundations. In this study the dynamic stiffness and damping coefficients of suction caissons embedded in a viscoelastic soil layer over bedrock, subjected to vertical dynamic load were investigated. Numerical analyses of representative 3D finite element models were performed, while the numerical modelling was validated against existing analytical solutions for end bearing piles. The vertical dynamic response of suction caissons was evaluated by considering the effects of the foundation’s geometry, i.e. the slenderness ratio, and the stiffness of the soil layer on the vertical dynamic impedance of suction caissons. Results showed that the overall dynamic response is profoundly affected by the skirt length and by the variation of soil stiffness with depth.Mathematical expressions of the dynamic stiffness and damping coefficients were derived pertaining to foundations with various slenderness ratios and embedded in different soil profiles. The proposed expressions can be implemented in structural models used for the dynamic analysis of the support structure of a wind turbine, taking thus into consideration the effects of soil-structure-interaction.     

控制软土地基中沉井不均匀沉降的措施

以扬州第二发电厂2号雨水泵房工程为例,介绍了控制软土地基中沉井不均匀沉降的措施,具体阐述了沉井的设计计算和施工方案及阻沉措施,为软土地基上施作沉井提供了新的思路。     

采矿塌陷区综合治理——以唐山市南部塌陷区为例

中国是矿产资源大国和矿业大国,矿产资源开发带来的塌陷给矿业城市的生态环境造成了严重的破坏。概括地介绍了我国采矿塌陷区的基本状况,分析了唐山市南部采矿塌陷区对生态环境的影响,并针对采矿塌陷区环境的污染问题,说明了利用采矿塌陷地进行生态修复是保护土地资源,恢复和治理生态环境的有效手段之一,研究性、探索性地提出了采矿塌陷示范区建设的技术措施,为采矿塌陷区的生态修复以及环境的综合治理做出了示范。     

Numerical simulation of caisson installation and dissipation in kaolin clay and calcareous silt

Caissons are widely used to support fixed platforms in shallow water or moor floating platforms in deep water. Although the installation and pullout behaviours of caissons have been explored extensively, few studies are on the dissipation of excess pore pressures induced by installation of the caisson. The pull-out capacity or bearing capacity of the caisson under undrained conditions is enhanced by dissipation of excess pore pressure, given the caisson is installed in normally consolidated cohesive soil. This paper reports numerical simulations of caisson installation and the subsequent dissipation. The analyses were carried out using a coupled effective stress-pore pressure large deformation finite element (LDFE) approach incorporating the modified Cam-Clay model. The robustness of the LDFE model was validated by comparing the penetration resistance with centrifuge testing data and the guidelines. Caissons in two fine grained soils, kaolin clay and calcareous silt, were explored. The geometry of the caisson was varied to encompass the typical sizes of caissons. The dissipation responses at four locations near the caisson tip were interpreted. A normalised dissipation time around caissons is proposed, by modifying the conventional expression for a cone.     

Risk assessment in the maintenance of offshore caisson operations

Undertaking maintenance of offshore caissons is a pervasive challenge that involves an array of risks and uncertainties. Despite the adoption of standardised and routine maintenance procedures that are subject to on-going improvements, the rate of failure in offshore caissons remains relatively high. To manage the effect of risk and uncertainties associated with the maintenance of offshore caissons, expert judgment can be drawn upon to better understand and capture the issues that contribute to their failure. Using a case study of an offshore hydrocarbon discharge caisson in the North Sea of the United Kingdom, expert judgements from industry practitioners are obtained using the Delphi Interview and Analytic Hierarchy Process (AHP) technique to rank 14 possible recovery options. Sensitivity analysis is used to ascertain the suitability of each of the options. Results reveal that the Delphi technique employed provided a robust means to garner invaluable insights from experts about the issues associated with caisson failure. The corollary is the development of a framework that serves as a point of reference to identify and assess the risks in offshore caisson maintenance operations. This framework can also be used in conjunction with existing probabilistic methods to improve the effectiveness of decision-making during operations and maintenance.