Volume Deformation Characteristics And Pore Pressure Growth Model Of Coral Soil

Coral sand is a kind of special soil with many pores,many edges and corners,fragile and other properties.It is a kind of broad gradation soil with distribution from silt to gravel sand and even larger particles.It is widely used in the global distribution and island reclamation.Several serious coral sand earthquake liquefaction phenomena have occurred in history.For example,coral sand liquefaction caused by the magnitude 8.1 earthquake in Guam,USA in 1993 caused the surface rupture and lateral slip of Apra port for several hundred meters.The 2006 magnitude 6.7 earthquake in Hawaii caused extensive liquefaction and ground damage to coral sand,both artificially filled and naturally deposited,at the Kawaihae port.A magnitude 7.0 earthquake in Haiti in 2010 caused catastrophic damage to the coral sand foundation of Port au-prince.However,it is generally believed that coral sand has higher anti-liquefaction strength than quartz sand,and the liquefaction possibility of coral sand is still controversial.At present,many scholars have carried out studies on the liquefaction characteristics of coral sand,but they are limited to silt and fine sand.In fact,due to different distances from the blowing-pipe mouth,the particle size distribution of the blowing-pipe site varies greatly.The area of the blowingpipe mouth is dominated by gravel and gravel,while silt and fine sand are mainly deposited far away from the blowing-pipe mouth.At present,relevant researches mainly focus on silty sand and fine sand.This paper takes the coral sand of a reef in the south China sea as the research object,explores the basic physical properties of the coral sand,and studies the liquefaction characteristics,volume deformation characteristics and pore pressure growth trend of the coral sand under different particle sizes.The main work and results are as follows:(1)The basic physical properties of coral sand were tested,and it was found that the particle shape of coral sand was irregular and there were many pores.The calcium content of coral sand was obtained by elemental analysis,and the crushing potential of coral sand was about 2.16% before and after the maximum dry density test.(2)A total of 36 sets of dynamic triaxial tests were carried out for coral sand with different particle gradation and different relative densities.The effects of gradation,effective consolidation pressure and cyclic stress ratio on dynamic pore pressure,dynamic strength and dynamic strain were analyzed.(3)The volume deformation characteristic test of coral sand was carried out.Through the loading and unloading rebound test of GDS dynamic triaxial meter,it was found that there was critical shear strain in the cyclic loading process,and the unloading point had a certain influence on the recoverable volume strain,and the components of the volume consistent equation were obtained.(4)According to the test results of volume deformation characteristics,the calculation parameters of martin-fin-seed pore pressure strain model were given,and the measured and calculated values of pore pressure were compared.The results showed that the model could better describe the pore pressure growth of coral sand.