Abstract:For a long time it was rarely dealt with the effect of site conditions to earthquake damage in the area,where intensity was more than 9 degree.By detailed studies both in the Railway-North and Eastern Mine Districts of Tangshan city,it was discovered that in the high intensity region the intensity anomaly due to the site conditions was still very obvious.The main factors are as follows:
Ground: Soil(1) The buildings located on limestone,well-cohered san-dstone with thick stratum or on thin eluvial overburden on bed rock were damaged in 2-3 degree of intensity lower than that on other con-structions site;the damage of buildings located on shale or shale with thin strata of sandstone is more serious than that on limestone and sandstone,because the rock is looser,lamellation,stratum and crackle are much developed.(2) The damage on ordinary clayey Soil,clayey sand is heavier than that on bed rock.But the intensity of damage pre-fers to be dependent upon the property of bed rock,the thickness of quaternal overburden and type of constructions rather than property of the very quaternal deposite.The up limit of thickness of the over-burden on limestone,being able to effect the damage is ≥20 m for sim-plstory building and ≥35 m for multistory buildings;While asthe up limit of the thickness of the quaternal overburden on sandstone is ≥20 m for simplstory buildings;on shale-is about 15 m for simplstgry buildings.(3) The grotind soils which may be failed during strong ground motion are as follows:1) unstable soil,2) non-uniform soil,3) saturated olayey soil (puddiy soil) and 4) liquefacted sandy soil.
Local Topography: Local topography obviously effects on the earthquake damage.Such topography includes isolated hill,deep quarry,mountain slope and the top or slope of hills,consisted of strong weathered sha-le.Within the identical intensity region and on the identical,ground soil,the constructions on above-mentioned local topography were sub-jected heavier hazard than that far away from them for its amplifying effect
The hazard of building within or near by the calapsed area of the coal mine also appears heavier due to increased deformation of ground surface during earthquakes.
