N_ZONE_ALEA_PPRN_20140308_S_032

The mapping of the hay removal of clays in the commune of Saint-Jean-le-Comtal 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.热尔省圣让勒孔塔尔市镇内黏土胀缩现象的分区图源自法国地质矿产调查局（Bureau de Recherches Géologiques et Minières，BRGM）编制的该省全域分区图。该图为黏土胀缩现象发生概率的分级区划。法国地质矿产调查局（BRGM）最初基于纯物理准则，依托该省地质图编制了易发性分区图（susceptibility map），编制过程中针对每个地质单元，综合考量了以下因素： — 地层内黏土物质占比（岩性分析）； — 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。 针对每一个已识别的黏土地层，最终的灾害等级由上述易发性等级结合灾害性胀缩密度确定，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。