Study On Mechanical Properties And Failure Characteristics Of Frozen Soil Rock Mixture

Frozen soil rock mixture refers to a geotechnical material that contains rigid inclusions such as crushed stones and pebbles in frozen soil.It is widely distributed in frozen soil regions and has good mechanical properties,making it often used as an extremely important filling material in engineering construction in frozen soil regions.At the same time,frozen soil rock mixture is also involved in construction projects using artificial freezing methods.It can be seen that research on the relevant characteristics of frozen soil rock mixture is important for the design of frozen soil engineering The quality and safety of construction and the overall project are of great significance.Due to the particularity and complexity of the structure of frozen soil rock mixture,it is very difficult to carry out research on frozen earth rock mixture.Currently,there are relatively few studies on the mechanical properties,strength characteristics,and constitutive models of frozen soil rock mixture.To this end,this paper conducts a combination of experiments and theoretical analysis to study the mechanical properties and failure characteristics of frozen soil rock mixtures with different freezing temperatures,different strain rates,and different rock particle sizes under static and dynamic loading conditions,providing theoretical support for the construction safety of frozen soil engineering.The main work and related achievements are summarized as follows:The uniaxial compression and Brazilian splitting experiments were conducted on frozen soil rock mixtures with different particle sizes（single particle size 5-10 mm,10-15 mm,15-20 mm,and full particle size 5-20 mm）at seven freezing temperatures,namely-10℃,-15℃,-20℃,-25℃,-30℃,-35℃,and-40℃,to analyze the effects of freezing temperature and particle size of rock on the compression and splitting tensile strength of frozen soil rock mixture samples by the RMT-150 rock mechanics testing machine,Furthermore,the evolution process of strain field of frozen soil rock mixture during the Brazilian splitting experiment was reproduced using digital image technology.The experimental results show that under uniaxial compression,the sample will exhibit bulging deformation and then soil and rock peeling,and the fracture surface will become curved and rough;In the splitting experiment,the tensile strain will concentrate in the center of the sample and generate initial cracks,which will crack along the soil soil interface towards the two loading ends and penetrate the sample.The cracks on the surface of the sample are mostly curved and folded;The compression and tensile strengths of the samples exhibit strong temperature sensitivity,and both increase approximately linearly with the decrease in freezing temperature.Using a diameter of 75mm Hopkinson compression bar was used to conduct dynamic compression experiments on frozen soil rock mixture samples with different particle sizes at four freezing temperatures:-10℃,-20℃,-30℃,and-40℃,with strain rates ranging from 257 s^-1 to 634 s^-1.The experimental results show that the frozen soil rock mixture exhibits a completely fractured state and its degree of fragmentation increases with the increase of loading strain rate;Frozen soil rock mixture has obvious strain rate effect and temperature effect,specifically manifested as dynamic brittleness and frozen brittleness,collectively referred to as time temperature equivalence,which represents the significant characteristics of dynamic mechanical properties of frozen soil materials;The frozen soil rock mixture also has a significant size effect.The dynamic compression strength of the single particle size sample decreases with the increase of the particle size of the block rock,with values ranging from 5-10 mm to 10-15 mm and 15-20 mm,respectively.At the same time,the strength of the mixed particle size sample of5-20 mm and the single particle size sample of 10-15 mm are approximately equal.Based on the dynamic compression experimental data of frozen soil rock mixture,and based on the characteristics of this experiment,the calculation method of SHPB energy consumption of frozen soil rock mixture was improved.The relevant characteristics of crushing energy consumption of frozen soil rock mixture samples were analyzed,and the internal relationship between freezing temperature,strain rate,rock particle size,and dynamic compression strength and the crushing energy consumption and crushing effect of frozen soil rock mixture was further studied.The results show that the breaking energy consumption density of frozen soil rock mixture has a linear positive correlation with incident energy,a linear negative correlation with freezing temperature,and a quadratic polynomial relationship with strain rate;The relationship between the crushing energy consumption density and the dynamic compression strength of frozen soil rock mixture is approximately linear,which can directly reflect the essential characteristics of its strength under impact load;The greater the crushing energy consumption density,the more significant the crushing effect.By improving the existing Z-W-T（Zhu Zhaoxiang,Wang Lili,and Tang Zhiping）constitutive model,and based on the experimental conditions and the characteristics of the frozen soil rock mixture,a simplified Z-W-T constitutive relationship equation for the frozen soil rock mixture under different experimental conditions is constructed,which contains the seven parameters of A、α、β、E₀、E₂、θ₂、P_S,the dynamic approximate equivalent constitutive relationship of frozen soil rock mixture is established.Using ORIGIN software,the parameter values of the constitutive relationship were obtained from the dynamic compression experimental data of frozen soil rock mixture,with R²values around 0.9.The obtained stress strain relationship of frozen soil rock mixture is in good agreement with the experimental results,and can well reflect the stress strain relationship before the peak stress of frozen soil rock mixture.Figure[43]Table[8]Reference[97]...