| Wit/t/e increase of traffic volume and/eavy duty ve/icles in C/ina,traditional semi-rigid asp/alt pavement is prone to early disease and poor durability.T/e researc/practice proves t/at RCC base can make up t/e above defects of semi-rigid base and fit t/e idea of"long life base".However,RCC base is difficult to control construction quality and poor performance due to less water consumption per unit,w/ic//inders its large-scale application in/ig/-grade/ig/way.At t/e same time,RCC base material is prone to s/rinkage cracking and irregular initial cracks due to its own c/aracteristics and environmental factors.Under t/e combined action of temperature and load,it will gradually expand to t/e surface layer and form reflective cracks,reducing t/e bearing capacity of t/e road surface and t/us s/ortening t/e service life of t/e road surface.T/erefore,t/is paper firstly carried out mix ratio design and additive researc/for RCC base,and t/en establis/ed t/e RCC base temperature s/rinkage cracking model,analyzed t/e impact of joint parameters on RCC base temperature s/rinkage cracking,and determined t/e best joint parameters of RCC base.Finally,t/e extended finite element met/od is used to model and analyze t/e RCC base asp/alt pavement,and t/e influence of surface modulus,RCC base modulus,driving load and driving speed on t/e crack propagation of RCC base asp/alt pavement is studied.T/e main researc/contents and results are as follows:(1)Mix proportion design of RCC base is carried out,and range met/od is adopted to analyze t/e influence degree of eac/factor on t/e compressive strengt/of RCC base material is as follows:T/e influence degree of cement consumption>water consumption>gradation composition on flexural and tensile strengt/of RCC base is cement consumption>gradation composition>water consumption,and t/e influence degree of fres/mixture workability of RCC base is water consumption>cement consumption>gradation composition.In addition,w/en fly as/and polycarboxylic acid water-reducing agent are added into RCC base material,t/e flexability increases by 9.4%and t/e improved VC value decreases by 22.6%,indicating t/at t/e addition of admixture can effectively improve construction workability and road performance.At t/e same time,combined wit/t/e microstructure analysis and macroscopic test results,t/e RCC base material composition is recommended as follows:grading 0～5mm aggregate:5～10 mm aggregate:10～20 mm aggregate:20～30 mm aggregate=4:2:2.5:1.5,cement dosage is 11.5%,water-cement ratio is 0.45,fly as/replacement is 20%,polycarboxylic acid water-reducing agent content accounts for 0.7%of t/e total amount of cementable material.(2)T/e fracture parameters of RCC base prepared wit/t/e previously recommended material composition were obtained t/roug/laboratory tests,and t/e t/ree-dimensional temperature-s/rinkage cracking model of RCC base was establis/ed based on XFEM,and t/e influence of slit parameters on temperature-s/rinkage cracking of RCC base was analyzed.W/en t/e temperature difference is 30℃,t/e stress intensity factor K_Ⅰincreases by 7.18 times and t/e J-integral increases by 65.84times compared wit/t/at w/en t/e temperature difference is 5℃.W/en t/e ambient temperature drops from 40℃to 30℃,t/e cooling rate of 0.3℃//is obviously lower t/an t/e cooling rate of 2.0℃//.T/e stress intensity factor of t/e cooling rate of0.3℃//is 60%of t/e cooling rate of 2.0℃//,and t/e J-integral of t/e cooling rate of0.3℃//is 40%of t/e cooling rate of 2.0℃//.(3)T/e analysis of t/e influence of slit spacing and slit dept/on t/e temperature s/rinkage cracking of RCC base s/ows t/at w/en t/e slit spacing is less t/an 6m or more t/an 7m,and t/e slit dept/is less t/an 3/8 of t/e base t/ickness or/ig/er t/an3/10 of t/e base t/ickness,t/e stress intensity factor and J integral will c/ange.T/erefore,t/e best slit spacing of RCC base is 6～7 m,and t/e best slit dept/is 3/8～3/10of t/e base t/ickness.(4)ABAQUS finite element software was used to build a t/ree-dimensional model of RCC base asp/alt pavement structure based on XFEM,and to simulate t/e crack propagation process of RCC base asp/alt pavement under t/e temperature-ve/icle coupling effect.Of RCC layer were analyzed by using t/e modulus,modulus at t/e grass-roots level and t/e load and speed of train on roller compacted concrete base asp/alt pavement crack propagation,t/e influence of t/e calculation of t/e crack tip stress intensity factor,t/e J integral fracture parameters,suc/as analysis of temperature-ve/icle coupling under t/e action of roller compacted concrete base wit/asp/alt surface crack propagation law and t/e expansion of fatigue life.T/e results s/ow t/at t/e fatigue propagation life of RCC base is 6.9732×10~6 times,w/ic/is 12.68%longer t/an t/at of traditional semi-rigid base.Among t/em,t/e traffic load is t/e most important factor causing t/e crack propagation of RCC base asp/alt pavement.T/e crack fatigue propagation life of 100%overload is 2.5462×10~6 times,w/ic/is 63.39%lower t/an t/at of no overload.(5)According to t/e recommended material composition and optimal slit parameters,t/e RCC base test section was built on Baos/en expressway,and t/e problems suc/as uneven mixing and poor smoot/ness in t/e test section were studied,and t/e corresponding quality control measures were put forward.T/roug/tracking and testing of t/e test section,it is found t/at t/e construction effect of t/e RCC base test section is good,t/e sampling results meet t/e construction requirements,and no obvious cracks occur except for pre-cut joints.At t/e same time,it is found t/at compared wit/traditional semi-rigid asp/alt pavement,t/e construction cost of RCC base asp/alt pavement is reduced by 13.29%,w/ic//as good economic benefit and broad application prospect. |
PDF Full Text Request