Abstract:

The problem how to apply a finite element method of elastic plane to simulate the stress field of Hebei-Shandong brush structure is discussed here. The structure,formed in Late Mesozoic,is a gigantic tectonic system seated in the second subsidence belt of Neocathaysian system,with its pillar of stress being western Shandong uplift,and the rock slice between two rotation surfaces being Hebei-Shandong subsiding area. The tectonic system is resulted from the relative shear movement of the pillar and the rock slice said above,both pushed by famous Tancheng-Lujiang fault belt in the east.Ever since its formation,the system has controlled the geological structure as well as oil distribution in the region where it stretched to Have studied the history of structural evolution in this region,the authors consider that the system was formed under the effects of driving stress inside rotation layer. Two simulation programs related to the system were discribed,one is simplified regular boundary program,the other is actual boundary program. 17 simulations were carried out by methods of adjusting boundary conditions and elastic parameters The results of the stress field simulation show that loci of the driving stress was a brush-shape,the neighbourhood of the pillar (i. e. the inside rotation layer and the converging part) is the place where stress concentrated. It is also shown clearly that the simulating value of the driving stress decreases rapidly and exponentially along radial direction and from the convering part to the diverging part. The reduction amplidude of tensile stress is larger than that of compressive stress,and the stress value on uplift is higher than that of adjacent depression. The properties of the simulated stress field are basically agreed with the strain pattern of Tancheng-Lujiang brush structure,thus some of geological phenomena can be explained,whereas their disagreements show from the opposite side that Hebei-Shandong brush structure is really resulted from multistage tectonic stress fields of different modes.