Analysis Of Surface Settlement Caused By Fine Particles Loss During Seepage

In the underground engineering soil and water loss often induces ground surface settlement,even induced ground collapse,which brings great harm to people's property and life safety,however,there is not much research on the development mechanism and the main influencing factors of surface settlement caused by fine particles loss during seepage in underground engineering.So,in order to understand the mechanism of the underground engineering settlement caused by loss of fine particles during the seepage process,a set of visual test device that can change the blow mouth diameter and simulate gushing of water and sand is designed.This device is used to study the settlement rule of gushing water and sand,under the condition of different content of fine particles,different blow mouth diameter and different hydraulic gradient by the influence law of fine particles loss on ground settlement and its influence mechanism are studied.The results of the study are as follows:(1)When the soil at the bottom of the blow mouth is round,the water inrush from the round mouth and the sand induced settlement,the settlement is circular in the plane,and approximately quadric in the profile,which can be represented by a circular funnel,and the settlement range can be replaced by the influence radius of settlement;(2)When the thickness-to-span ratio is within certain limits,the fine particles is less than a certain value,settlement will happen,more than the certain value,quicksand will happen,the relationship between critical content of fine particle at the time of quicksand and the thickness-to-span ratio show a parabolic curve at the beginning,then maintain level;When the thickness-to-span ratio is more than a certain value,regardless how much fine particles in sand,settlement will not happen;When the thickness-to-span ratio is less than a certain value,regardless how many fine particles in sand,quicksand will happen;When the settlement by the thickness-to-span ratio and content of fine particle interaction,if the thickness-to-span ratio remains the same,the content of fine particles is 35%,the fine particles can fill the pores between the coarse aggregate particles,the soil is in a stable state,without settling;(3)As the soil settling,the diameter and middle depth influenced by settlement and blow mouth diameter is linear relationship;When the hydraulic gradient is more than critical hydraulic gradient,settlement happens,as the soil settling,the diameter and middle depth influenced by settlement and hydraulic gradient is linear relationship;When hydraulic gradient reaches break hydraulic gradient,quicksand happens;When hydraulic gradient is within certain limits,fine particles form soil arch and filters,which preventing particles loss,the soil will not settle;(4)The settlement scope after quicksand is related to the shape damage angle of subsidence surface,which is roughly 9° lager than the natural angle of repose of the soil.