Study On Engineering Characteristics Of Expansive Soil Improved By Construction Rubbish And Reasonable Structure Form Of Subgrade

Based on the construction of the Chengbei Expressway in Jingzhou City,this paper conducts an experimental study on the engineering characteristics of the construction waste improvement expansive soil construction based on the comprehensive utilization of construction waste generated by house demolition during the road construction process and the expansive soil distributed along the road.Based on regional meteorological data,a numerical simulation calculation and analysis of the reasonable structure form of the construction waste-improved expansive soil subgrade were carried out,and areasonable subgrade structure suitable for Jingzhou area was recommended.Through research,it effectively solves the practical problems of lack of high-quality fillers and difficulty in handling construction waste during the construction of the road.The mainresearch contents and results are as follows:(1)Through the analysis of indoor compaction test,strength test and expansion-shrinkage test,the mechanical properties and expansion-shrinkage characteristics of samples with different construction waste mixing ratios and different gradation designs are discussed.When the gradation combination I is used and the mixing ratio is 40%,Construction waste expansive soil has better strength characteristics and expansion and contraction characteristics and meets the specifications.(2)In the case of the best combination and mixing ratio,the samples are prepared according to the 94% compaction degree,and compared with the 3%,5%,and 7%cement modified soils of the same compaction degree for strength and expansion and contraction characteristics.Tests show that the strength of construction waste modified soil is higher when not immersed in water.The strength reduction after immersion is greater than that of cement-modified soil,and the swelling amount is higher than thatof cement-modified soil,but it is significantly lower than that of plain soil.(3)Carry out 16 sets of sample compression consolidation tests to analyze the impact of construction waste mixing ratio and gradation on compression characteristics.The results show that with the increase of the construction waste mixing ratio,the compressibility of the construction waste mixed soil decreases.The construction waste mixing ratio of 30% to 40% belongs to the transition interval.When the construction waste mixing ratio is less than 30%,the compression characteristics When the influence is small,the compression characteristic changes obviously when it is higher than 40%.Among the 4 particle size combinations,particle size combination I has the lowest compressibility under the same mixing ratio.(4)Choose the optimal particle size combination Ⅰ,40% mixing ratio,94% compaction sample with the same compaction plain soil and 3%,5%,7% cement modified soil to compare the compression characteristics,the test shows that the building Thecompressibility of garbage-improved soil is significantly reduced,and the initial porosity ratio of the sample is lower.(5)Indoor penetration test,dry-wet cycle test,compaction degree and water content on strength test of construction waste expansive soil,the results show that the construction waste modified soil is more permeable than the same compaction plain soil and cement modified soil;Dry-wet cycle will reduce the compaction degree and strength of the construction waste-improved soil;the compaction degree and water content will affect the strength of the construction waste-improved soil,but the influence of the contrast soil is lower.(6)According to the roadbed humidity conditions and the meteorological data in Jingzhou area,combined with the results of the dry-wet cycle test and the water stability test,numerical simulation tests such as the thickness of cladding clay,gravel soil cushion,geotextile seal,etc.were carried out.The results showed that: 50 cm The gravel cushion with poor thickness gradation can completely block the groundwater.Due to the large permeability coefficient of the construction waste improvement soil,if the measures of laying impermeable geotextile and cladding clay on the top of the road bed are not taken,the conditions of continuous rainfall There will be large deformation under the ground,and the internal humidity of the subgrade will change greatly,which is extremely unfavorable for the construction waste improvement of the expansive soil subgrade material.When the roadbed structure with impermeable geotextile and 2m thick cladding clay and gravel cushion is used on the top of the roadbed,the internal humidity of the roadbed will remain very small under relatively unfavorable rainfall conditions,which can effectively maintain the internal humidity of the roadbed stable.