| New requirements for resource utilization of bulk solid wastes such as calcium carbide slag,phosphogypsum and red mud are put forward in the 14 th Five-Year Plan.At present,many scholars have conducted experimental studies on the application of calcium carbide slag instead of lime in building materials,but there are few studies on the modification of red clay by calcium carbide slag.Adding calcium carbide slag into soil can not only realize the resource utilization of solid waste,but also realize the local utilization of red clay.This paper studies Guiyang red clay,calcium carbide slag is mixed into red clay for macro and micro tests,and its influence on the characteristics of red clay is explored through bounded water content test,compaction test,unconfined compressive strength test,direct shear test,CBR test,water stability test and dynamic triaxial test.The microscopic mechanism of calcium carbide slag modified red clay was investigated by XRD and SEM.The main conclusions are as follows:(1)After adding calcium carbide slag,the best water content and maximum dry density of the red clay compaction characteristics were not significantly improved compared with the red clay.The liquid-plastic limit index of calcium carbide slag stabilized red clay shows a downward trend with the increase of the content,but the liquid limit of the mixture is still greater than 50%,which does not meet the requirements of Article 3.3.3 of the Code for Design of Highway Subgrades(JTG D30-2015)and cannot be directly used as embankment filler.(2)The unconfined compressive strength of calcium carbide slag stabilized red clay firstly increases and then decreases with the increase of the content.The unconfined compressive strength reaches the maximum value at 9% of the content.The unconfined compressive strength of the mixture increases with the increase of compactness.With the development of curing age,the unconfined compressive strength of the mixture first increases and then tends to be stable.The shear strength,cohesion and internal friction Angle of calcium carbide slag stabilized red clay also increase with the increase of dosage,age and compactness.(3)The CBR value of red clay itself is relatively low.With the increase of calcium carbide slag content and curing age,the CBR value of the mixture keeps increasing and tends to be stable after 14 days of curing.The minimum CBR value of the mixture is 4.14%,which can meet the requirements of the minimum load-bearing ratio of embankment filling of all levels of highway.The water stability coefficient is0.After adding calcium carbide slag,the water stability of the mixture is enhanced,and the maximum water stability coefficient is 0.49.After adding curing agent,the water stability is further enhanced.(4)The dynamic stress and dynamic shear modulus of red clay and carbide slag stabilized red clay increase with the increase of confining pressure and consolidation ratio,while the dynamic shear modulus increases with the increase of confining pressure and consolidation ratio,and the damping ratio decreases with the increase of confining pressure and consolidation ratio frequency.The relationship between dynamic shear modulus,damping ratio and dynamic shear strain of calcium carbide slag stabilized red clay conforms to H-D model.(5)Red clay is loose,and the addition of calcium carbide slag will fill the pores between soil particles and react with red clay to form calcium silicate hydrate and calcium aluminate flocculent colloid.Consolidated with soil particles,the soil will form a new spatial structure,and the original loose structure will become more compact,with better structural strength and stability. |
