APPLICATION OF MONTE CARLO MODEL TO SIMULATION OF COMPACTION RATES OF SHALLOW SEDIMENTS IN THE MODERN YELLOW RIVER DELTA

The traditional methods used in the study of shallow sediment compaction, which is one of the important contributors to land subsidence, are usually based on drillings and profile measurement with local computation in the Yellow River Deltaic area. In order to overcome the methodological limitation and restriction in past studies, the Monte Carlo approach and the stratified summation method are adopted. With the borehole data obtained from the Project on Comprehensive Engineering Geological and Hydrogeological Survey in 1987, we numerically modeled the shallow sediments of the whole delta, calculated the compaction rates and analyzed the influence factors of compaction simulation. The results show that the present compaction rates vary in a range from 0.18mm/a to 9.07mm/a. The influence factors of compaction rates are mainly the geotechnical parameters, such as initial porosity and compressibility and the average net accumulation rates, both of which are significantly and positively correlated with the present compaction rates, and the soft layer is the major contributor to the sediment compaction and land subsidence. The results are fit to the history of the Yellow River delta if simulations are made for lobes with time. Combined with the ground subsidence level monitoring data, it is found that the contribution of consolidation and compaction of shallow sediments accounts for about 13% of the total settlement.