N_ZONE_ALEA_PPRN_20140351_S_032

The mapping of the hay removal of clays in the commune of Préchac 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）普雷沙克公社（Préchac）境内黏土胀缩现象（shrink-inflating）绘图，提取自法国地质与采矿研究局（BRGM）编制的省级地质绘图成果。该绘图为黏土土壤胀缩现象（shrink-inflating）发生概率的分区图。法国地质与采矿研究局（BRGM）最初以纯物理准则为依据，依托该省地质图编制敏感性图（susceptibility map），解译地质图时针对每个地质构造综合考量了以下因素： —— 地质构造内黏土物质占比（岩性分析 (lithic analysis)）； —— 黏土相中膨胀性矿物占比（矿物组成 (mineralogical composition)）； —— 该物质的岩土工程特性 (geotechnical behavior)。 针对已识别的每一处黏土构造，最终的灾害等级由上述敏感性等级结合灾害性胀缩（sinister swelling）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。