The Research On The Technology And Comprehensive Evaluation Of Soft Soil Foundation In Donggang Expressway

Based on the study of geology,this paper took the Donggang highway as the engineering background,and obtained the basic situation and characteristics of the engineering.The physical properties of the soft soil and the possible adverse effects in the soft soil foundation treatment are analyzed.The numerical simulation of K2 + 250-K2 + 450 subgrade deformation of Donggang highway was carried out by FLAC3D,and the settlement of the subgrade was studied.This paper introduced the reinforcement principle,construction method and construction process of the submerged crushed stone piles and vibro-replacement stone piles,analyzed the monitoring methods of roadbed settlement and the specific requirements of settlement,and determines the evaluation methods and criteria of roadbed settlement.The settlement observation of the K3 +030-K3 + 430 section of the Donggang highway with soft soil subgrade and the K5 + 140-K5 +505 section of the vibrating gravel pile subgrade was carried out.Finally,the genetic algorithm and the fuzzy comprehensive evaluation method were used to evaluate the construction scheme of the vibrating gravel pile in the soft soil roadbed of Donggang highway,and the vibro-replacement stone piles were identified as the soft soil foundation construction scheme to meet the construction requirements.The main work of this paper was following:(1)Donggang expressway was the engineering background,obtained the basic situation and characteristics of the engineering by the geological research.Combined with the engineering,the physical parameters of the soft soil were measured in the laboratory and the field.Then,the engineering properties of the soft soil and the possible adverse effects in the soft soil foundation treatment were analyzed.A more complete design and reasonable process were needed in the soft soil subgrade,and to avoid the unfavorable factors of soft soil foundation,also to ensure the normal use of soft soil foundation and long-term stability.(2)Based on the Moore-Coulomb model,the settlement of the soft soil subgrade of K2 +250-K2 + 450 section of Donggang highway was analyzed by FLAC3D software.This paper introduced the application of Moore-Coulomb criterion in FLAC3D,and establish the three-dimensional numerical model of soft soil roadbed by using the K2 + 250-K2 + 450 section of Donggang highwayas the engineering background.In the middle of the roadbed,the settlement contour line was "oval concave",the maximum horizontal displacement occurred at the left and right foot of the embankment,and the maximum vertical displacement occurred in the middle of the embankment,the maximum vertical displacement was 142.51mm and the maximum horizontal displacement was 39.521mm when the roadbed was completed 5 times.Then,the maximum vertical displacement(settlement)was obtained in the middle of the roadbed,and the settlement contour was "approximate square".The maximum horizontal displacement occurred on the left and right sides of the roadbed.,When the roadbed was completed 5 times the maximum vertical displacement of 45.979mm.Finally,the comparative analysis of the plastic zone of the subgrade with the addition of the gravel pile and the gravel pile was carried out.The results showed that the total volume of the plastic body without the pile is much larger than the total volume of the plastic body of the pile foundation,gravel pile can enhance the carrying capacity of the foundation,the vertical displacement was significantly reduced by 3.1 times.(3)The reinforcement principle,construction method and construction process of submerged crushed stone piles and vibro-replacement stone piles were introduced.Then the monitoring method of roadbed settlement and the specific requirements of settlement were analyzed,also the evaluation method and criterion of roadbed settlement were determined.Finally,the settlement of the K3 + 030-K3 + 430 section of the soft soil roadbed and the K5 + 140-K5 + 505 section of the vibrating gravel pile were measured respectively.The results showed that the settlement of the subgrade was less than 30cm,the maximum settlement was 14.8cm.During the first two months of the subsidence observation,the settlement of the roadbed was larger than that of the later stage,and the later settlement was smaller than the previous period.With the increase of the observation time,the settlement would be smooth.The settlement of soft soil roadbed treated by vibrodite crushed stone was less than that of soft soil roadbed,that was,the stability of soft soil subgrade treated by vibrating gravel pile was better than that of soft soil subgrade.(4)The comprehensive evaluation of vibro-replacement stone piles construction scheme for soft soil subgrade of Donggang highway was carried out by genetic algorithm and fuzzy comprehensive evaluation method.Firstly,the construction scheme evaluation of soft soil subgrade of Donggang highwaywas carried out from the four aspects of standardization and construction fuzzy evaluation matrix,construction judgment matrix,weight calculation and fuzzy evaluation value calculation.Took the first contract section of Donggang highwayAK0+943.150-K6+100.000as the engineering background,and obtained the fuzzy comprehensive evaluation value as follows:line condition,geological and climatic conditions,surrounding building condition,construction condition and economic condition as evaluation index:z(j)= 0.622,The debris pile as a soft soil subgrade construction program was better to meet the construction requirements.