N_ZONE_ALEA_PPRN_20140315_S_032

The mapping of the hay removal of clays in the commune of Saint-Mézard 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.热尔省（Gers）圣梅扎尔（Saint-Mézard）公社范围内黏土胀缩（shrink-inflating）现象的专题制图数据，提取自法国地质与矿业研究局（BRGM）编制的全省系列制图成果。该制图为黏土土壤胀缩现象发生概率的分区图件。法国地质与矿业研究局（BRGM）首先基于纯物理准则，依托该省地质图件编制了易感性分区图，编制过程中针对每个地质单元，综合考量以下因素：— 地层内黏土物质占比（岩相分析）；— 黏土相中膨胀矿物占比（矿物组成分析）；— 岩土材料的工程特性。针对每一个已识别的黏土地层，最终的灾害等级由上述易感性等级结合灾害性胀缩密度确定，该密度以每100平方千米实际出露的城市化地表为统计基准。