采动地表移动变形与建筑物损坏程度评价的再认识

实测数据分析的目的是认识地表移动规律和确定预计参数,而沉陷预计的目的是评价采动损坏程度。无论实测数据分析还是形变预计,地表倾斜、曲率和水平变形等主要指标都是基于下沉和水平位移2个移动分量;不均匀下沉在引起地表倾斜和曲率变形的同时,也会导致采动建筑物水平变形和破坏。通过分析起伏地形和不均匀沉陷在实时位形上对地表变形的作用关系,建立了地表水平和起伏条件下采动地表倾斜变形引起的地表水平变形表达式;以采动地表正曲率变形为例,分析确定了建筑结构长度、高度、最大挠度、挠度比与地表曲率的关系,定性给出了建筑结构顶部伸长量、拉伸变形及其影响规律;进一步分析了建筑结构与地基相互作用的反力分布以及拉伸和剪切作用下建筑物损伤破坏特征。在继承我国现行规范中采动建筑物损坏评价优点的基础上,针对硬性分级存在的不足以及I,IV级损坏再划分的模糊性,借鉴英国沉陷工程师手册中考虑建筑物结构长度影响的思想,建立了综合考虑水平变形、建筑物结构长度和挠度比的采动损坏分等定级指标体系;实验结果分析表明,同等采动地表变形条件下建筑结构越长其损坏越严重,证明该指标体系的损坏程度评价结果比现行规范中单纯考虑地表变形的方法更科学、客观,同时消除了原来I,IV级损坏再划分的模糊性和不确定性。

Further discussion on mining deformation and building damage classification

The aim of surface monitoring and data analysis is to determine the law of surface movement and parameters of prediction.The prediction of surface subsidence is used for the evaluation of mining damage degree.Whether the field monitoring data are used for the analysis or prediction of surface deformation,the surface slope,curvature and strain are derived from the two components,i.e.surface subsidence and horizontal movement.Uneven mining subsidence may cause surface tilt and curvature change,and result in building deformation and damage.The impact regularities to strain are obtained by analyzing the uneven subsidence and topography on the deformed configuration.The expressions of horizontal deformation derived from mining slope are established under the conditions of horizontal surface and terrain undulation,respectively.The relationships between the length,height,maximum deflection,deflection ratio of structure and the positive curvature of surface are analyzed and determined.The elongation and tensile strain for upper structure are calculated qualitatively.The behavior of a structure in a curvature area and its damage features are given further under tensile and shearing conditions.Based on the inheritance of advantages for the classification criterion of mining damage in the current Chinese standard,and reference to the damage degree with the change of building length in Subsidence Engineer’s Handbook,a synthetic classification indices to building damage are established.The structure length,horizontal strain and the building deflection ratio are considered in order to improve the disadvantage of stiff classification and the fuzziness of reclassification for damage category I and IV.The site experiments show that the longer the structures the severe the mining damages under the same surface deformation conditions.This demonstrate that the new indices are reasonable and objective compared with traditional stiff method in current specification.The uncertainty and fuzziness to the further reclassifications for building damage category I and IV are avoided.