超大型沉井降排水下沉施工

泰州大桥北锚碇沉井基础长67.9 m、宽52 m、高57 m,在沉井下沉的初期,采用降排水下沉。降排水下沉施工成本相比不排水下沉低,且下沉效率高,易控制,可形成良好的下沉导向,并确保沉井的下沉速度和精度,适宜在粉细砂、软塑性亚黏土等地质条件下采用。文章以泰州大桥北锚碇沉井基础为例,介绍了超大型沉井降排水施工的降排水下沉施工工艺。     

A Study of the system control model of caisson dewatering of the north anchorage of Taizhou Bridge

A caisson foundation is applied to the north anchorage of Taizhou Yangtze River Highway Bridge of which the initial caisson sinking requires dewatering. Since the caisson foundation is quite close to nearby buildings, a system control model is established with source (sink) distribution and intensity being the object function, minimum requirements of settlement and deformation of surroundings caused by dewatering and dynamic water levels during different working procedures being constraints, and the design parameter of pumping wells being the variable,so as to lower the jeopardizing of surrounding buildings, which provides a new method for active control over settlement during dewatering. Such a method of dewatering based on system control model should be of significance for similar projects involving dewatering.     

锚碇沉井基础施工期安全监控技术

针对泰州大桥南锚沉井基础的结构特点和施工方法,设计了施工安全监控方案。施工期监测成果分析表明：沉井下沉初期沉井底部刃脚附近水平方向的拉应力较大,将此项物理量作为下沉的控制指标,有效指导了沉井施工;侧壁土压力分布随入土深度呈先增加后减小规律。     

陆上特大型沉井施工技术

泰州大桥主桥采用主跨2×1 080 m三塔两跨两锚碇悬索桥,其中南、北锚碇基础为特大型沉井,矩形平面尺寸为67.9 m×52.0 m,高度分别为41 m,57 m。针对锚碇基础覆盖层深厚、基础尺寸巨大、沉井下沉深度深等特点,通过施工技术的攻关,顺利完成了砂桩复合地基处理、沉井制作和拼装、钢壳沉井混凝土填充、混凝土沉井接高施工、水力机械冲吸式排水下沉和空气吸泥机吸泥下沉等多项施工工序,为今后陆上特大型沉井施工提供了借鉴。文章简要介绍了南、北锚碇陆上特大型沉井的施工技术。     

On-site tests to estimate aquifer permeability of drainage area of south caisson anchorage construction of Taizhou Bridge

During the construction of the south caisson anchorage of Taizhou Bridge, the drainage area is located in the lower reaches of the Yangtze River and the permeability of stratums there is considerable. In order to maintain progress and guarantee safety during the sinking of the caisson, water should be drained in the initial period. Subsequently, detailed information about the aquifer permeability is required to make sure that the drainage will proceed successfully, which consequently necessitates the on-sit...     

泰州大桥南锚沉井基础侧壁土压力监测研究

以泰州长江大桥南锚沉井基础为研究对象,对南锚沉井基础侧壁土压力进行了实时监测。根据大量现场实测资料,结合沉井下沉曲线和下沉施工工艺,系统分析沉井侧壁土压力的大小和变化规律,得出了侧壁土压力分布是非线性的;并会随着下沉深度呈现先增加后减小的趋势,以及对这种分布规律的原因进行了探讨。     

锚碇沉井基础下沉稳定性分析

基于可靠度理论,通过对基桩极限状态方程的分析,得到了基桩极限承载力影响因素。将这一理论运用到大型锚碇沉井下沉施工的稳定性之中,得到了衡量沉井下沉稳定性的三个指标,抗滑动稳定系数,抗倾覆稳定安全系数和下沉稳定系数。以鹦鹉洲长江大桥北锚碇沉井施工为例,通过对鹦鹉洲长江大桥北锚碇沉井不同工况,不同接高阶段、不同下沉阶段中下沉稳定系数的分析可知：同一工况、同一下沉周期内,随着接高次数的增加,稳定系数逐渐增大;同一工况下,稳定系数随着下沉次数的增多而逐渐减小;不同工况中,全截面稳定系数最低。在今后类似锚碇沉井的下沉施工中可采用下沉稳定系数对沉井下沉稳定性加以分析控制。     

Vibration mechanism research of large scale and deep water caisson

According to the construction method of Taizhou Bridge, numerical simulation is conducted to analyze the vibration of caisson under wind and water flows to determine the main factors of the caisson vibration. Meanwhile, the localization system of caissons and anchors of Taizhou Bridge is modeled in order to summarize the vibration mechanism of caissons under deep-water and jet-flow condition, and further pertinent vibration-control measures are proposed. The obtained results are well verified in engineering practice, and consequently the safety risk of positioning the caisson is reduced.     

On site tests to estimate aquifer permeability of drainage area of south caisson anchorage construction of Taizhou Bridge

During the construction of the south caisson anchorage of Taizhou Bridge, the drainage area is located in the lower reaches of the Yangtze River and the permeability of stratums there is considerable. In order to maintain progress and guarantee safety during the sinking of the caisson, water should be drained in the initial period. Subsequently, detailed information about the aquifer permeability is required to make sure that the drainage will proceed successfully, which consequently necessitates the on-site estimation of the aquifer permeability in the drainage area. Therefore, the traditional pumping test and slug test are implemented respectively on site. The comparison of computational results of these two tests indicates that they are consistent overall. Notwithstanding, as slug test can be conducted with portable facilities in a short time and the manipulation is easy and few people need to be involved, the advantages of slug test is conspicuous compared with the traditional pumping test. It could be speculated that slug test will gain a prevalent application in the measurement of aquifer permeability in the future.     

Technical Research on Control of Caisson Construction for the Middle Tower Foundation of Taizhou Bridge

The real-time informational monitoring system is adopted in the construction of middle tower foundation of Taizhou Bridge for the first time. The geometric state of the caisson, the stress of upstream and downstream anchorage cables, underwater topography, the drag forces of the caisson cutting edge and frictional resistances of the sidewall and etc. are monitored in real time. According to the synthesized data analysis and decision-making system, the spatial states of the caisson are adjusted in time to locate and embed the deep water caisson precisely. The offset error of the caisson is less than 30 cm and the vertical error is 1/363 at the final stage. The control technology for construction of large caisson under deep water is concluded and would be helpful for the construction of bridge foundation in the future.     

Taizhou Yangtze River Bridge—the first kilometer level three-pylon two-span suspension bridge in the world

Taizhou Bridge, located at the middle of Jiangsu Province, connecting Taizhou City and Zhenjiang City, started in Dec. 2007. The bridge is the first kilometer level three-pylon suspension bridge in the world, and it adopts longitudinal herringbone shape steel middle pylon for the first time in the world. The foundation of the middle tower is the deepest underwater caisson in soil on earth. A great many of technical innovations such as the design techniques of three-pylon suspension bridge,precisely locating and bottom-sealing techniques of the large scale caisson foundation, manufacturing, combination techniques of steel and concrete in the middle tower, welding of extra thick steel plate, manufacture and control techniques of abnormal sections of the middle tower and so on were introduced.     

软土地基上大型沉井基础安全监控模型

为了提高软土地基上大型沉井基础稳定性评价和安全监控的有效性,以江阴长江公路大桥北锚碇沉井基础为对象,在研究影响其稳定和安全运营主要因素的基础上,探讨了监控系统的主要结构,并从基础位移监控、基础抗滑稳定监控和地基土稳定监控3个方面建立了散索鞍水平位移监控模型、沉井前侧地基土水平向反力监控模型和基底反力监控模型.在综合现场观测数据和数值模拟结果的基础上,探讨了监控模型中原因量的主要构成及其与监控效应量之间函数关系的确定方法,并给出了江阴长江公路大桥北锚碇沉井基础主要控稳模型——散索鞍水平位移监控模型在通车运营期的具体函数表达式.研究结果表明,基础变位是软土地基上大型沉井基础的主要控稳因素,通过安全监控模型对其进行控制能为建筑物的安全运营提供保障.     

Introduction to steel pylon hoisting of Taizhou Yangtze Bridge

Taizhou Yangtze River Bridge is the first three-pylon two-span suspension bridge in the world. The middle pylon adopts deep water caisson foundation. The superstructure of the middle pylon employs herringbone shape along the bridge, and portal shape in the transverse direction for the first time in China. In this paper, the basic construction procedure, equipment, construction steps, the key construction technologies and methods of steel pylon are introduced.     

Comparison of seismic capacity/demand ratios of two kinds of foundation schemes of Taizhou Bridge

Pile group foundation and caisson foundation are two common foundation schemes of long-span bridges, and the seismic performances of the two kinds of foundations are different. Taking Taizhou Bridge as an example, which is the first kilometer level three-pylon two-span suspension bridge in the world, two foundation schemes are designed for the middle pylon, and two whole bridge models with two different foundation schemes of the middle pylon are established respectively in this paper. The effects of foundation-soil interaction are simulated by equivalent linear soil springs whose stiffnesses are calculated according to m method. Seismic capacity/demand ratios of the two models are calculated. The following conclusions can be drawn: the weak positions of the two schemes are not the same; if caisson foundation is adopted for the middle pylon, the weak position is the bearing capacity of the middle pylon foundation, while if pile group foundation is adopted for the middle pylon, the weak position is the bearing capacity of the side pylon foundation.     

干湿交替作业沉井施工技术

结合宜兴市丁蜀污水处理厂较大沉井结构施工实践,介绍了沉井施工技术工作流程和方法,采用管井降水技术确保施工,提出了分段下沉和边下沉边进行上部沉井结构制作的工艺,沉井下沉作业时,基于信息化施工,采用人工挖土和水冲法(干湿交替作业法)相结合的施工方法,可以节约工期、有效控制下沉速度,保证下沉垂直度,工程质量良好,对沉井施工是一个极其有效的施工方法。     

斜井沉箱设计及有限单元法

本文阐明了莱芜铁矿斜井沉箱尺寸及位置确定的方法。对沉箱在流砂侧压力作用下的变形和应力用有限元法作了全面分析。     

泰州大桥悬索桥南锚碇基础的变形及超载安全度分析

 锚碇作为悬索桥的主要承力结构物,其变形是影响悬索桥安全的重要因素。针对泰州大桥悬索桥的南锚碇基础,建立了三维的地层-结构模型,应用大型数值软件Flac3D和超载分析法,假定锚碇的超载为大缆拉力按比例增加,研究了锚碇基础的变形随大缆拉力超载系数的变化规律。结果表明,在大缆拉力为设计载荷,即大缆拉力超载系数λ=1时,数值模拟计算结果与现场实测结果接近;在超载情况下,当λ<3.5时,锚碇基础最大变形随大缆拉力超载系数基本呈线性增加;当λ>3.5时,锚碇基础变形随大缆超载系数呈非线性增加;而当λ=3.81时,锚碇基础的水平位移达到极限值。因此,综合考虑锚碇基础的土体塑性区分布和变形控制要求,得到了泰州大桥悬索桥南锚碇基础的超载安全度为3.81的结论,可为泰州大桥工程的稳定性评价提供参考依据。     

太原北郊污水处理厂改扩建工程提升泵房沉井施工

介绍了太原市北郊污水处理厂改扩建工程提升泵房沉井施工方案,包括沉井的制作、沉井的下沉、沉井下沉的观测、沉井的纠偏等。     

现代气压沉箱施工过程的三维有限元分析

从开挖卸荷、刃脚挤土、沉箱-土体侧摩擦作用三方面对气压沉箱施工引起的土体扰动进行分析,并结合工程实例,对气压沉箱施工全过程进行三维有限元数值模拟.通过与现场监测数据的比较,验证了三维计算模型及数值模拟方法的合理性和有效性.结果表明:沉箱侧壁边缘处地表沉降最大;随着沉箱下沉,地表沉降逐渐增大,沉降影响范围随之扩大;沉箱周边土体的水平位移较小,浅层土体偏向沉箱移动,深层土体偏离沉箱移动;考虑刃脚挤压扰动可以有效减小沉箱边缘处最大地表沉降.     

沉井在不同真空预压处理程度的软土地基中下沉阻力特征研究

目前国内外暂无沉井基础与真空预压处理技术结合的研究。试验通过模型来模拟沉井在不同真空预压处理程度的软土地基中的下沉,对沉井侧摩阻力、刃脚底部阻力进行分析,并通过数值模拟进行对比分析,这对实际工程与理论研究都有参考意义。试验结果表明:随着真空预压处理时间的增加,沉井在软土地基中下沉时的侧摩阻力逐渐增加,靠近刃脚附近侧摩阻力减小的趋势消失;刃脚底部的土压力随着沉井下沉缓慢减小,其中刃脚斜面的土压力占比较工程实际偏大;在软土基础中沉井自重荷载在真空预压处理后提高了250%,且当含水率降低到45%左右时,沉井自重荷载有明显的提升;现有理论计算方式对于刃脚踏面的竖向受力计算偏大,对于刃脚斜面的竖向受力计算偏小。