韶钢炉卷主轧机设备基础大体积混凝土温度和裂缝的控制实践

以韶钢炉卷主轧机设备基础大体积混凝土施工为例，从大体积混凝土配合比的确定、温度应力分析、混凝土保温材料厚度计算、混凝土的泵送和浇筑、后期养护以及大体积混凝土内部温度的监测等方面进行了理论应用研究，为同类型设备基础的施工提供切实可行的实践经验。     

基础大体积混凝土施工的裂缝控制

介绍了某125t转炉基础大体积（9127m^3）混凝土施工中,为降低结构混凝土中心温度和内外温差,采取减少水泥用量和内掺法增加粉煤灰掺合料用量,投入大石（Dmax=150mm）,以稳定结构混凝土体积,同时掺入缓凝型减水剂,结构混凝土内部通入冷却水等综合技措。获得了既避免大体积混凝土温度裂缝,又降低大体积混凝土成本的技术经济效果。可供大体积混凝土设计、施工参考。     

解决大体积混凝土温度应力措施的探讨

通过工程实践，介绍了为避免温度应力造成大体积混凝土基础裂缝的措施．其中突出说明在基础内预置水管用水冷却措施的使用和建议。     

筏板基础大体积混凝土施工防裂措施

通过炼钢转炉基础筏板大体积混凝土施工,介绍了大型设备的基础大体积混凝土的施工技术,分析了大体积混凝土产生裂缝的主要原因,提出了防止混凝土温度裂缝的主要技术措施和控制方法.     

朝阳大桥主墩承台大体积混凝土温控过程

大体积混凝土有害裂缝产生的主因是混凝土中胶凝材料水化热快速升高引起的温差应力与混凝土本身强度增长慢之间矛盾发展的直接结果。提前采取措施控制大体积混凝土的内、外温度及内外温差能有效预控大体积混凝土裂缝的产生,是混凝土质量控制的重点。     

大体积混凝土基础施工与温度控制技术

安徽省新广电中心项目一期工程中的主楼简体承台基础CT-1等厚度达3.5m,属大体积混凝土结构.为克服大体积混凝土因水化热过高产生裂缝,施工采取优化混凝土配合比、设置后浇带、斜面分层浇筑和实施混凝土浇筑后温度监测等一系列措施,成功地控制了温度和混凝土裂缝的产生,确保了该大体积混凝土基础承台的施工质量.     

大体积混凝土施工实践

通过二炼钢转炉基础底扳大体积混凝土施工，介绍了大体积混凝土的施工技术及防止混凝土温度裂缝的控制方法。     

大体积混凝土施工技术分析

以武汉钢铁集团鄂城钢铁有限责任公司矿渣微粉工程磨机基础为例.分析了大体积混凝土技术.混凝土浇筑的施工方法等进行了分析。通过采用严密的施工组织措施、合理的配合比设计、先进的温度控制和监测手段、科学的浇灌和养护方法,实现了大体积混凝土施工,基础施工完成后未产生有害裂缝,混凝土浇筑质量良好。     

济钢120t转炉基础裂缝防治措施

混凝土施工出现裂缝的主要原因,一是混凝土受力;二是混凝土体积变形,即混凝土在硬化过程中由于温度变化而引起体积变化。济钢120t转炉基础属于大体积混凝土施工,为防止出现温度裂缝,重点采取了控制混凝土所用材料、配合比、内部降温等措施,取得了较好效果。     

3 200 m3高炉工程大体积混凝土施工技术

在大体积混凝土施工中,为了防止混凝土出现裂缝,合理选用混凝土原材料,降低水泥水化热;并利用水冷管控制混凝土内外温差,成功地解决了大体积混凝土易出现裂缝技术难题.     

Structural Stability of Concrete Gravity Dams Strengthened by Rockfill Buttressing: Hydrostatic Load

Rockfill buttressing is often considered to strengthen existing gravity dams that have inadequate stability to resist the estimated hydrostatic and seismic loads. Various simplified methods for static stability analyses of composite concrete–rockfill dams, which represent the rockfill as equivalent forces, are discussed. Numerical analyses of composite dams using nonlinear rockfill and interface constitutive models are then considered. Hydrostatic stability analyses of a 35?m composite dam are carried out to compare the results obtained from simplified methods and numerical analyses. Parametric analyses are performed to investigate the effects of various modeling parameters such as the friction angle of the concrete–fill interface, the friction angle of the concrete–foundation interface, and the reservoir elevation during the fill placement. Numerical analyses results show that lowering the reservoir prior to construction of the rockfill does not have a significant effect on the stress response of the strengthened dam in the case analyzed. For design purpose, it is shown that the simplified minimum/maximum earth pressure method is always on the safe side irrespective of the concrete–rockfill friction angle.     

浅谈现浇混凝土楼板裂缝在施工过程中的控制

现浇混凝土楼板经常出现裂缝，造成裂缝原因很多，裂缝形成多种多样，本文介绍了裂缝的存在的形式，产生原因，以及在设计施工，原材料控制中采取减少或避免楼板产生裂缝的措施。     

Simulation of Temperature and Stress Fields during RCC Dam Construction

The worldwide experience in the construction of roller-compacted concrete (RCC) dams together with the use of numerical solutions, allows the simulation of different scenarios in a computer. It is well documented that thermal control is one of the most important problems for RCC dam construction. The dam temperature changes due to the heat produced by the internal hydration of concrete and the environmental boundary conditions influencing the elastic modulus and creep properties of concrete. The construction process was simulated to study how the temperature and stress change during dam construction. The numerical methodology considers the effect of temperature on the elastic modulus and the creep behavior of concrete. A 3D finite-element program was developed to simulate the construction process. An engineering application of this methodology is presented by simulating the construction of an RCC gravity dam in southern China. The results show how the temperature and stress change with the construction process. The results also show that it is feasible to build RCC dams in low temperature seasons without additional temperature control measures.     

广重集团三机车间改造加固实例

通过查明混凝土结构和基础的危害程度,将栈桥结构和基础缺陷分为一般缺陷、较严重缺陷和严重缺陷,并采取相应的处理对策和多种技术措施,使结构整体功能达到设计要求和延长使用寿命的目的,经过施工方案优化后,采用树根桩加固旧基础;用混凝土套子法加固旧柱。并指出施工中应注意事项。     

高炉大体积混凝土基础水化热温差的控制

高炉大体积混凝土基础的施工是土建部分最关键的工序,施工中很容易产生水化热温差裂缝,严重影响工程质量,造成经济损失.控制好水化热内外温差是大体积混凝土施工中的关健问题.     

大体积混凝土施工实践

通过热风炉基础施工,介绍了大体积混凝土的施工技术防止混凝土温度裂缝的控制方法。     

Heat Conduction Waves in Bilayer Cement Concrete Structures

The temperature propagation in a layered structure is of great importance in determining the thermal induced strain in the structure, and in particular the thermal induced stress along the interfaces of the structure due to the different thermal expansion coefficients of the layer media. In this paper, an exact analytical solution is obtained based on the Fourier-Biot heat conduction equation for a two-layer structure with or without a base boundary. Characteristic frequencies or the temperature fluctuation response of two-layer structures are identified. Once the temperature distribution is known, one can compute the stress distribution in the structure. The application of the model to understanding measured temperature data for two-layer structures such as concrete pavements is addressed.     

“跳仓”施工法施工技术应用

文章简要论述在大体积混凝土工程施工中,将超长的混凝土块体分为若干小块体间隔施工,经过短期的应力释放,再将若干小块体连成整体,依靠混凝土抗拉强度抵抗下一段的温度收缩应力的施工方法———跳仓施工法。     

深部开采环境问题

文中对深部开采的环境问题，诸如地应力、岩爆与地震、地热及降温、火灾预测等问题作初步探讨。