Dataset Direct Download Service (WFS): N_ZONE_ALEA_PPRN_20140300_S_032

The mapping of the hay removal of clays in the commune of Saint-Christaud in the Gers department is extracted from the departmental mapping from the BRGM. This mapping is a zoning of the probability of occurrence of the phenomenon of shrink-inflating of clay soils. A susceptibility map was first drawn up on the basis of purely physical criteria by the BRGM from the geological maps of the department, which were interpreted taking into account the following factors for each geological formation: — the proportion of clay material within the formation (lithic analysis); — the proportion of blowing minerals in the clay phase (mineralogical composition); — the geotechnical behavior of the material. For each of the clay formations identified, the hazard level is ultimately the result of the level of susceptibility thus obtained with the density of sinister swelling, reported to 100 km² of actual urbanised outcropping surface.本数据集所用的热尔省（Gers department）圣克里斯托公社（commune of Saint-Christaud）内黏土土壤胀缩现象绘图数据，提取自法国地质与矿产研究局（BRGM）的省级绘图成果。该绘图为黏土土壤胀缩现象发生概率的分区制图成果。BRGM首先基于纯物理准则，利用该省地质图编制了易感性图（susceptibility map），在编图过程中针对每个地质单元综合考量了以下因素： — 地质单元内黏土物质占比（岩相分析）； — 黏土相中膨胀性矿物占比（矿物组成分析）； — 该物质的岩土工程特性。 针对所识别的全部黏土地质单元，最终的灾害等级由上述所得易感性等级与灾害性胀缩密度共同确定，该密度以每100平方公里实际出露的城市化地表为统计基准。