Simulation Study Of Evolution Characteristics Of Dynamic Response In The Site Of Blowing Sand Reclamation

The site of blowing sand reclamation has a distinct causing properties and engineering properties with the Onatural sedimentary site. The original of deep marine soft soil has become the large area of soft substratum soil of the new land. The soil layer is unconsolidated and continuous disturbance by the outside factors, going through "forming, consolidation, carrying" characteristics. Seismic waves imported from the bedrock can be directly into the marine soft soil covering at the bottom of the sea bedrock directly, combining with this kind of site in seismically active areas, being "High risk area" of producing long-period seismic damage from the strong earthquake of the far field. Therefore, to study the dynamic characteristics of reclaimed land have instructions and prevention effect to the earthquake prevention and disaster reduction in the construction.In this thesis, the degree of consolidation of soft soil and compactness of the reclaimed sand in the beibu gulf as the breakthrough point, the reclaimed sand and marine soft soil collected from reclamation area of Fangchenggang of Guangxi as the research object. To prepare the soil samples in the different levels of compacted using the laboratory simulation technique, to obtain basic performance indexes of the reclamation soil by consolidation and other conventional mechanical test. Using the ANSYS software, under different degree of compactness, to analysis the evolution characteristics of the predominant period and the dynamic response under the horizontal shear wave by vertical incidence from the bedrock. And in a framework of given the compaction degree of the medium of various reclaimed soil, to study the influence mechanism of the various soil layer thickness to the dynamic characteristics and the dynamic response, in order to provide the basis for engineering construction.The main research contents and results are as follows.1. Findings through the modal analysis under different compaction degree of the reclamation area are as follows. Natural frequency of the reclamation area in each order is a linear growth, and growth of curvature has an exponential positive correlation with the compactness degree. High order vibration mode has a severe influence on the dynamic action of the field, but its modal participation factor is small. The proportion of the horizontal vibration increase gradually, as the increase of soil compaction degree, the vertical vibration is on the contrary. While the compaction degree reaches a certain value, the proportion of torsional vibration increases suddenly and has a very high score.2. Findings through the spectrum analysis under applying response spectrum of the horizontal seismic acceleration are as follows. With the increase of ground soil stiffness, node displacement is more and more significant especially in the middle area of soft soil, and development gradually in the direction of the bedrock, but the vibration displacement of the reclaimed sand shows a slow and steady trend gradually. Predominant frequency of the site develops in the direction of high frequency components gradually, having an exponentially tend with the increase of soil compactness.3. Findings through the transient dynamic analysis under horizontal shear wave which is vertical incidence from the bedrock are as follows. Amplification effect of the reclamation area to the horizontal seismic action is very significant, along with the change of soil depth, and reaching the maximum in the surface of the reclaimed sand, but the relationship with soil depth is not positively correlated. It has an obvious filtering function for the composition of the long period in the vertical ground motion. With the increase of compactness degree, filtering effect is significant, but the impact on the V/H spectrum is on the contrary. So the aseismic design for the high-rise building, it should be given full consideration that the influence of the soil compaction degree to the vertical ground motion.4. Findings through the transient dynamic analysis in the site under different thickness of the marine soft soil are as follows. Magnified effect of the ground peak acceleration is linear negatively related to the soil thickness. This is because the thicker of the marine soft soil layer has larger vibration isolation and filtering function. Response spectrum curve has two bimodal in the saddle, and dominant frequency is gradually evolution from the one peak to peak value of more than with the increase of soil thickness. The seismic energy in the remarkable cycle component gradually decreases, and the predominant period of the site increased gradually, absorption effect to the high frequency part of seismic wave increases, amplification effect to the Vertical seismic decreases.5. Findings through the transient dynamic analysis in the site under different thickness of the reclaimed sand are as follows. Seismic amplification effect decreases with the increase of reclaimed sand layer thickness, predominant period of the site gradually developing in the direction of short period. When the thickness of the reclaimed sand has increased to a certain value, increasing thickness of sand layer continually, magnification of the seismic response increases, and there will be more predominant period in the site at this time, which is unfavorable for engineering seismic fortification.