Engineering Geological Map of Lower Saxony 1: 50 000 — Building land

The Engineering Geological Map 1: 50 000 (IGK50) is from geological map 1: 50,000 derived and shows the spatial distribution of the different building ground types at 2 m depth. Underlying layers cannot always be derived from the IGK50. For this purpose, the drilling database or the geoarchive of the LBEG can provide further data. With the help of criteria and rules, relationships are established between the nature, composition and formation of the geological units and the load-bearing capacity as well as the risks of the subsurface as a building ground. Different geological units with similar geotechnical properties were combined into a building ground type. For the removal of the structural loads into the subsurface, near-surface layers are of minor importance because a frost-free foundation requires a depth of the foundations of at least 0.8 m. Peat is a particularly risky building ground that reacts to loads from structures or groundwater sinks with heavy sacks. Low-power overlays from 0 to 2 m are therefore taken into account only if they are peat, which is represented in these cases. General information for foundation measures and, if necessary, other safety measures can be derived from the building ground types and targeted project-related investigations can be planned. The soil groups according to DIN 18196 are specified for the respective building ground types. The IGK50 cannot replace construction ground tests according to DIN EN 1997-2 (DIN 4020). In the area of organic/biogenic (building ground type 3, e.g. peat), the low-consolidated (building ground type 5, e.g. Klei, Auelehm) as well as the non-binding (building ground types 10, 11, 12, e.g. sand, gravel) loose rocks must generally be counted with groundwater levels at the foundation level (rejection to basement or formation of the basement with pressure-resistant insulation). In the case of binded floors (construction basic types 4, 5, 6, 7, 8, e.g. clay, sludge) it is necessary to count on moisture from precipitation in the area of the usually filled with water-conducting working space of the excavation pit. There, the water must be drained through suitable drainage systems. On the issue of flood hazards, the "Geological Map of Lower Saxony 1: 50 000 — Evaluation of flood hazards" (GHG50) of the LBEG or information is sought from the lower water authority. A particular geotechnical risk is due to water-soluble rocks in the underground (deposits of the Zechstein, Upper Buntsandstein, Middle mussel limestone and Upper Jurassic (Münder Mergel)). There can be reductions and earth falls. Information on earthquakes and land-prone areas is kept at the LBEG and is shown in the "Map of Geohazards in Lower Saxony 1: 25 000 — Earthfall and Lowering Areas" (IGG25).