等容的

To give the definition of the mass concrete and to concrete\'s cracks together with practical meanings of control ,and give a brief review on the research in the field at home and abroad, at last, methods to control temperature crack of the mass concrete from several aspects such as design measures,concrets material, construction schedules.etc are summed up; To explain the physical mechanics of the concrete and computing methods-Difference Method and Finite Element Method, and illustrate the application of their specific methods repectively;Several temperature factors that can influence the temperature stress of mass concrete baseplate are analyzed. The influence degree of temperature factor can be got through the ANSYS simulation computation the control of temperature can control the temperature stress, consequently control the temperature crack of mass concert baseplate; through the influence of the crack resistance ability of mass concrete baseplate which takes the reinforcement as a part is analyzed. By ANSYS simulation, the best suited volume ratio of reinforcement is found out, at same time the layout of reinforcement with the same volume ratio can also affect the resistance ability of mass concrete baseplate. Sum up of above analysis, anti-crack function of steel bar in early mass concrete baseplate is obvious, so it\'s necessary to consider beneficial effect of construction steel bar in research of temperature control on mass concrete baseplate.

本文先容了大体积混凝土及混凝土裂缝的基本概念，对国内外在这个领域里的研究现状作了扼要叙述，并从结构设计、混凝土材质、施工措施等方面总结了大体积混凝土温度裂缝控制的方法及防止措施；阐述了混凝土的基本物理力学性能，总结了大体积混凝土温度计算的方法——差分法和有限元法，并分别举例说明其具体应用的方法；分析了影响大体积混凝土底板温度应力的几种温度因素，利用ANSYS模拟计算，得出了每种因素的影响程度，通过分析提出了在这几种温度影响因素下如何通过控制温度以达到控制温度应力从而来控制裂缝的具体建议；针对大体积混凝土基础底板中配筋的不同对混凝土底板抗裂能力的影响不同，利用ANSYS进行模拟分析，得出底板中最合适的体积配筋率，同时分析了在相同体积配筋率下钢筋的具体布置对大体积混凝土基础底板抗裂能力的影响，分析表明，配置钢筋对混凝土结构的开裂阻止作用明显，在研究大体积混凝土温度裂缝题目时，要考虑钢筋在其中的有利作用。

Based on this idea, the author has chosen two typical loess sections of Luochuan, and Xifeng for this study, collected the successive loess columns; To probe the conditional experiments of BeO sample preparation and measurement, and improve the existing method; On the basis of the technology improvement, the author has finished 402 samples' BeO preparation and AMS measurement; Also at the same time, to separate quartz from samples at 1 cm interval for both Luochuan and Xifeng sections systematically, to carry out measurements of quartz grain-size, SUS, grey scale, carbonate content and bulk sample density; By using the grain size model, the author has set up the chronological framework for both Luochuan, and Xifeng sections and the time sequence of millennial scale abrupt climate events recorded in loess strata, and reconstructed the East Asian monsoon history over 130ka by using multi proxies; Finally, to discuss the possible mechanisms of palaeoclimatic changes tentatively.

详细地球科学的发展离不开高精度和高分辨率的研究。运用长寿命核素如〓Be作为环境过程的示踪，已成为不可替代的有效工具。本论文选择洛川、西峰两个典型的黄土剖面，连续采集柱状样；探索了BeO样品制备、测量的条件实验，改进了原有的方法，完成了402个BeO样品的制备和AMS测量；同时还系统地分离洛川、西峰剖面高分辨率（1cm）黄土、古土壤样品中的碎屑石英，测量了碎屑石英粒度，以及全样的磁化率、灰度、碳酸盐含量和容重等古气候代用指标；采用粒度年代模式建立了洛川剖面和西峰剖面的年代标尺，建立了黄土地层记录的千年尺度的气候突变事件的时间序列，多指标重建了最近130ka东亚季风变迁史；初步讨论了古气候变迁的可能机制。

The split between the two groups can hardly be papered over.

这两个团体间的分歧难以掩饰。

This approach not only encourages a greater number of responses, but minimizes the likelihood of stale groupthink.

这种做法不仅鼓励了更多的反应，而且减少跟风的可能性。