Damage characteristics and damage model for mudstone around driven pile

In view of the insufficient bearing capacity of dynamic driven pile in mudstone foundation, uniaxial and triaxial compression tests of mudstone around the pile 0. 2 m were carried out before and after driving. Based on the statistical damage theory, the damage constitutive model of mudstone affected by pile driving is established. Combined with the field tests data, the bearing capacity of the driven pile and the damage characteristics of the mudstone around the pile are explored. The results show that the average damage of mudstone strength and elastic modulus at 0. 2 m around pile is 28. 2% and 41. 4% respectively. The average shear strength parameters of the moderately weathered mudstone at the pile end after damage are c = 217. 2 kPa and φ = 21. 6°, and φ is only 49. 1% and 51. 4% of the undisturbed strongly weathered and fully weathered mudstone in the same site. The calculated value of the damage model of the stress-strain curve of the mudstone around the pile after driving is in good agreement with the measured value, which verifies the rationality of the model. The characteristic of abnormal bearing capacity is that the pile end bears little force but the settlement displacement of the pile end is significant. The damage of mudstone around the pile caused by dynamic driving is one of the important reasons for the abnormal bearing capacity of driven pile. Mudstone is not easy to recover after damage. It is unreasonable for the mudstone’ s undisturbed mechanical parameters to be used to design and calculate the driven pile of mudstone bearing layer, and recommended to reduce the undisturbed parameters of mudstone according to the damage characteristics. The research results could provide reference for the design, construction and calculation of driven piles in mudstone foundation. © 2024 Chinese Society of Civil Engineering. All rights reserved.