Use of the Standard Penetration Test to Assess the Liquefaction Potential for Mingalardon, Okkalapa and Dagon Townships, Yangon Area
                                                                            Ei Ei Mar#1, Kyaw Htun*2
          #West Yangon Technological University, Department of Engineering Geology, Yangon Technological University
                                                                              [email protected]
The study area lie between North Latitude 16° 49´ and 16° 58´ and East Longitude 96° 4´ and 96°8´. This thesis is mainly targeted on Mingalardon, Okkalapa and Dagon townships. The surface drainage pattern is dendritic pattern. In research area, hilly area, ridge area, and low lying flat plain are found. The studied area is composed of alluvium derived from Irrawaddy Formation and Pegu Group. Geologically, the area is complicated by numerous folding system of rock unit of Bago Yoma. These are the Hlawga anticline, and Yangon-Mingarladon anticline. The largest fault of this area is Mingarladon Fault. Joint are common in the competent beds of the Thudugan Sandstone unit. Acscording to the result of the bore hole data, the clayey silt (CL) soil is found almost everyplace of the study area. High plasticity CH soil type is found in Dagon and Okkalapa. Liquefaction is one of the catastrophic of earthquake related hazards. It is generally said that soil layers which need liquefaction analysis are ones which distribute within mainly GL- 20 meters or adjacent according to past earthquake experiences and flow chart of liquefaction analysis. Because of continuity of loose saturated sandy layer, most of liquefied soil layers in which liquefaction occurred have less fine content within 35%. However, even if it has fine content more than 35% some liquefaction cases are reported in case clay content, Pc (clay content) ≤ 20% or Ip ≥ 15%, therefore such cases have also been analyzed. According, even though it is silt layer, which has low plasticity and high water content which is close to liquid limit can be liquefied. Groundwater is found in the unconsolidated layer of alluvium sediments along the Ngamoeyeik creek and surrounding area. The movement of groundwater is generally from east to west. Yangon area falls in the moderate to strong earthquake with intensity of 7 MM to 8 MM (Modified Mercali scale).
Keywords- Liquefaction, Standard Penetration Test, Cyclic Stress Ratio, Cyclic Resistance Ratio, Safety Factor against Liquefaction