| In the past decade,most of the deltas in the world have suffered severe floods,invasions and wetland degradation.The number of people affected has reached 300million,and the area affected is as high as 260000 km~2.A large number of studies have proved that the ground subsidence caused by consolidation and compaction of the lower overlying strata of the delta is the main factor causing the fragility of the delta.Thanks to the advanced technology and complete observation network,such as the phenomenon and influence mechanism of subsidence of the Mississippi Delta ground has been studied and results,restricted by technology and observation equipment,China's Delta subsidence research started late,less data,the method is backward,the low level of research.But,like the the Yellow River Delta this unique River Delta Basin by the shallow sediment,the river changed many times,multi lobe interlacing superposition,the sediment consolidation shows unique characteristics of temporal and spatial variations.This paper studies the consolidation and compaction characteristics of the delta,which is based on the drilling and section of the past.Based on the extensive collection of drilling information and shallow engineering geological parameters of the Yellow River Delta,this paper starts from the reality of the Yellow River Delta.Based on the Monte Carlo method in mathematical geology and the one-dimensional consolidation theory of the sand foundation,the consolidation compaction rate of the whole delta plain is simulated according to the deposition thickness and the starting and ending time of the different lobes in the Yellow River Delta.Then,by using the Geographic Information System(GIS)tool,the crustal distribution map of the delta plain is obtained by the Kriging method,which has a whole understanding of the temporal and spatial characteristics of compaction settlement in the Yellow River Delta.Finally,the results of compaction compaction calculation are compared with the actual results.The simulation results show that the simulated results agreed well with the actual results.In addition,several different pseudo-random number generators in the Monte Carlo model are discussed.Finally,the most suitable three pseudo-random number generators are selected by comparison experiments.The influence of different model input parameters on the output of the model is discussed through the experimental analysis.Through the simulation of homogeneous(single attribute)strata,the main factors influencing the compaction settlement rate of the simulated strata and the main types of compaction subsidence are found.On the basis of the accuracy and simulation time of the trade-off model,the best simulation times are obtained through a series of simulation experiments.Considering the soft soils with high water content,high compressibility,low shear strength and low bearing capacity in the Yellow River Delta,it is considered that the secondary consolidation and compaction(Creep)in the Yellow River Delta is calculated.The results show that the creep of the sedimentary strata occupies a certain proportion in the total consolidation settlements which are expected to exceed 200mm locally.Finally,based on the above calculation and simulation,through comparison with those of the InSAR observations and geodetic measurements,quantitative analysis of shallow sediment consolidation of the natural factors in the share of total settlement in the delta ground,provides a new understanding for the further understanding of the the Yellow River Delta land surface subsidence pattern,and also provide technical support for the response to the relative sea-level rise,wetlands,seawater intrusion and ecological resources protection. |
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