天坑的等级评价方法

Methodology of grade evaluation for Tiankeng

为了减少天坑等级评价中的主观性,通过分析天坑规模参数特征,选取天坑容积作为评价指标。运用皮尔逊Ⅲ型曲线作为计算模型,结果表明皮尔逊Ⅲ型曲线对天坑规模参数拟合程度较好,具有一定的适用性。根据模型计算样本上、下限频率值,结合等比数列排频划分法将其分为4级,并计算各级分界值对应下的容积值V作为评价天坑等级的标准,即:小型V≤5.43 Mm3;中型5.43 Mm3<V≤18.11 Mm3;大型18.11 Mm3<V≤45.26 Mm3;特大型V>45.26 Mm3。通过与现有方法比较,认为该方法既能反映天坑样本总体情况,又能减少人的主观性因素,具有一定的科学价值和现实意义。

In order to reduce the subjectivity in the Tiankeng grade evaluation,the Tiankeng volume is selected as an evaluation index by analyzing the characteristics of Tiankeng scale parameters such as depth,diameter and volume .Pearson-Ⅲis used as a calculation model.The results show that the curve is feasible in a better fitting degree to the Tiankeng scale parameters to some extent.Therefore the upper and lower limits of frequency values for the model calculating samples are divided into four parts based on the frequency arrangement of geometric progression.The cubage values corresponding to the division values are regarded as a criterion of Tiankeng grade evaluation.The small Tiankeng's volume (V)is≤5.43 Mm3,the medium one is 18.11 Mm3≥V>5.43 Mm3,the large one is 45.26 Mm3≥V>18.11Mm3,and the extra-large one is V>45.26 Mm3.This method can not only reflect the total situation of Tiankeng samples,but also reduce subjectivity,with a scientific value and practical significance.