55mm

With the re-analysis on the tests data presented in reference ( 1 ), it is discovered that the variation coefficients of core specimens of three different diameters have no obvious difference , so the reliability of φ 55mm core specimen is not worse than those of larger core specimens .

通过对文献[1]的试验数据的重新整理发现三种不同直径芯样强度的离散程度很接近，因此φ55mm芯样可靠性并不比大直径芯样差。

The study results indicated that the thickness of the scroll case of Longtan hydropower station can reduce from 50 ~ 63mm to 42 ~ 55mm . After that , their intensities can exert satisfactorily , meet require of the structure security , and bring remarkable economic and social benefit .

研究结果表明，龙滩电站蜗壳钢衬厚度可以从50～63mm减薄到42～55mm，钢衬厚度减薄后，其强度得到了充分发挥，满足结构安全要求，并可带来显著的经济效益和社会效益。