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一、引言众所周知,混凝土坝内裂缝至为普遍,数十年来消灭裂缝一直是筑坝技术中的重大课题,混凝土坝内裂缝由荷重所引起者极少,绝大部分是由体积变化所引起,据实测资料在大体积混凝土内水分的变化仅限于表面0.50公尺以内,故混凝土体积变化主要是由于温度变化,消灭裂缝必须从控制温度着手。温度变化引起的裂缝大致可以分为以下两类:(1)表面裂缝,混凝土凝结期间,内部温度不断上升,因此在中央形成压应力,在表面形成拉应力,如图1乙所示。由于初期混凝土具有较大塑性,这些应力是
I. INTRODUCTION As we all know, cracks in concrete dams are common. For decades, eliminating cracks has been a major issue in damming technology. Cracks in concrete dams are very few caused by load, and most of them are caused by volume changes. According to the measured data, the change of water content in mass concrete is limited to the surface of 0.50 meters. Therefore, the change of concrete volume is mainly due to the temperature change, and the elimination of cracks must be controlled from the control temperature. Cracks caused by temperature changes can be divided into the following two categories: (1) surface cracks, the concrete temperature during the condensation, the internal temperature is rising, so the formation of compressive stress in the center, the formation of tensile stress on the surface, as shown in Figure 1 B. These stresses are due to the greater plasticity of the initial concrete