Study On Soft Ground Improvement For Highway In Mountain Area

With the further construction of highways, which are the foundations of thesustained development of the national economy, there are increasing weak soilfoundations in special areas. And soft foundation in mountain area occupies animportant place in the weak soil foundation in our country. As yet there are nocriterion and ripe techniques that can be referenced to improve soft foundation inmountain area. Therefore, it is important to develop new methods for improving thesoft foundation in mountain area.There are two primary characteristics of soft foundation in mountain area: Firstly,the topography of vale in mountain area is comparatively low, drainage is impeded,and the soil, on which there is certain thickness of silt whose physical mechanicsindexes are very bad, is usually in a state of saturation and over saturation;secondly,construction environment in mountain area is worse and there are some difficulties inmaterial transport and power supply. In this case, the conventional soil stabilizingtechniques can not be referenced for the improvement of soft foundation in mountainarea. The conventional technical characteristics should be combined with soiltexture in mountain area and concrete conditions in engineering geology, theirapplicability should be researched and technical reform should be carried out, andeven new methods should be developed in some conditions.Based on the field tests of Gan-ding highway, three new methods to improve softfoundation in mountain area are developed according to computer simulation andmodel tests.(1) The technical research of blasting toe-shooting method to improve the softfoundation. According to the basic theory of soil mechanics and explosion mechanics,the action mechanism of blasting toe-shooting method on land has been presented andthe charge quantity function under certain thickness of silt has been educed;based on fieldtest, technology system and quality detection system of the construction of blastingtoe-shooting method on land having been advanced and every phenomenon during test hasbeen analyzed.(2)The technical research of soil-cement pile and geogrid compositefoundation to improve the soft foundation. Based on finite element emulation andcentrifugal model test, the action mechanism of this composite foundation has beenadvanced and every character of pipe and geogrid has been analyzed;according tofield test construction technology system and quality detection system of thiscomposite foundation have been advanced.(3) The technical research of multi-types-pile composite foundation toimprove the soft foundation. The load transfer behavior of multi-type-pipe compositefoundation and the character of subsidence deformation have been analyzed by use ofFEM;according to field test construction technology system and quality detectionsystem of this composite foundation have been advanced.The results of theoretical analyses and field test show that the three new methodsto improve soft foundation in mountain area can satisfy the requirements of bearcapacity and deformation, can be used in special construction environment andprovide new feasible methods to improve soft foundation under special condition.