مدل نيمه تحليلي براي پيش بيني تغييرمكان لرزه يي شيب ها بر مبناي زلزله هاي ايران

A SEMI-EMPIRICAL MODEL FOR PREDICTING SEISMIC PERMANENT DISPLACEMENT OF SLOPES BASED ON IRAN EARTHQUAKE RECORDS

فلات ايران، يكي از مناطق لرزه خيز جهان است كه به دليل شرايط توپوگرافي ويژه، همواره در معرض زمين لغزش هاي ناشي از زلزله بوده است. در نوشتار حاضر، با استفاده از جمع آوري 3954 ركورد لرزه يي رخداده در ايران و تحليل بلوك صلب اصلاح شده بر مبناي اثر دوران و با به كارگيري ضرايب گسيختگي و طول هاي لغزش مختلف، يك مدل نيمه تحليلي براي پيش بيني تغييرمكان ماندگار لرزه يي شيب هاي خاكي در فلات ايران پيشنهاد شده است. انحراف معيار خطاي مدل در حد قابل قبول و در حدود 0٫6 بوده است. مقايسه ي مدل پيشنهادي با ساير مدل ها نشان مي دهد كه انحراف معيار خطاي مدل در حدود 1٫25 و 3٫33 برابر كمتر از مدل مشابه ارايه شده براي ايران و جهان است. به كارگيري مدل نيمه تحليلي پيشنهادي مي تواند كمك شاياني به شناسايي عملكرد لرزه يي شيب هاي موجود در كشور انجام دهد.

The Iranian plateau is one of the seismic active zones of shallow crustal earthquakes in the world so that annually thousands earthquake occurs in the Iranian plateau. Meanwhile, due to the effect of topographic and geological characteristics of its relief, the Iranian plateau is subjected to diffuse phenomena of landslide, especially in Alborz and Zagros mountains, which are exacerbated by the high seismic activity. The earthquake-induced landslides have reportedly caused major human fatalities and economic losses in Iran. The prediction of sliding displacement can decrease landslide hazards to the civil engineering strcutures. The semi-empirical models have recently received more attention from the geotechnical earthquake engineering practitioners because of their applicability, simplicity, and reasonable performance in large displacements. The rigid block-rotation approach was developed based on the increase of critical acceleration caused by the downward movement of sliding soil mass. This paper represents a semi-empirical model for the earthquake-induced displacement of Iran's slopes using the rigid block-rotation approach. A collection of 3954 strong motion records was used to generate the model based on the results of slidinganalyses. The semi-empirical model is presented based on more than 138,000 rigid block-rotation analyses using several input parameters. The model predicts sliding displacement in terms of yield coefficient (ky), slip length of sliding mass (L), and Arias Intensity (Ia). It is shown that slip length of sliding mass has an important role in the prediction of seismic permanent displacement, which is generally ignored in the semi-empirical models. The proposed model can be simply used to estimate the seismic displacement of slopes and earthquake-landslide hazards in seismic prone regions of the Iranian plateau.