Effect of Freezing on Stress–Strain Characteristics of Granular and Cohesive Soils

This is the author accepted manuscript. The final version is available from ASCE via the DOI in this recordTo investigate the stress-strain behavior of frozen soils, a program of triaxial compression tests was designed and carried out on samples of unfrozen and frozen cohesive (CL) and granular (SP) soils and pure ice. The experiments involved study of the influence of freezing, temperature reduction and loading rate on the stress-strain characteristics of the frozen ground. The aim of this study is to assess the possibility of using the Artificial Ground Freezing (AGF) technique in the excavation and tunneling in Line 2 of the Tabriz Subway project. The results show that freezing of the CL soil has no significant effect on the type of soil behavior (strain-hardening), while, freezing of the SP soil changes its strain-hardening behavior to strain-softening. The effect of freezing on the increase in shear strength of the saturated SP soil is much greater than that of the saturated CL soil; however, the rate of increase in the shear strength due to freezing and temperature reduction is much larger for the CL soil. Freezing and reduction in temperature cause an increase in the elastic modulus of all the materials tested in the present study. Also, the shear strength and elastic modulus 26 of these materials increase with loading rate.Ministry of Science of Ira

A new approach to modeling the behavior of frozen soils

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this recordIn this paper a new approach is presented for modeling the behavior of frozen soils. A data-mining technique, Evolutionary Polynomial Regression (EPR), is used for modeling the thermo-mechanical behavior of frozen soils including the effects of confining pressure, strain rate and temperature. EPR enables to create explicit and well-structured equations representing the mechanical and thermal behavior of frozen soil using experimental data. A comprehensive set of triaxial tests were carried out on samples of a frozen soil and the data were used for training and verification of the EPR model. The developed EPR model was also used to simulate the entire stress-strain curve of triaxial tests, the data for which were not used during the training of the EPR model. The results of the EPR model predictions were compared with the actual data and it was shown that the proposed methodology can extract and reproduce the behavior of the frozen soil with a very high accuracy. It was also shown that the EPR model is able to accurately generalize the predictions to unseen cases. A sensitivity analysis revealed that the model developed from raw experimental data is able to extract and effectively represent the underlying mechanics of the behavior of frozen soils. The proposed methodology presents a unified approach to modeling of materials that can also help the user gain a deeper insight into the behavior of the materials. The main advantages of the proposed technique in modeling the complex behavior of frozen soil have been highlighted

Experimental Study of the Mechanical Behavior of Frozen Soils - A Case Study of Tabriz Subway

This is the final version. Available on open access from Budapest University of Technology and Economics via the DOI in this recordThe mechanical properties of frozen ground are key parameters in design and implementation of artificial ground freezing (AGF) in underground projects. Soil samples were obtained from the urban underground railway project site in Tabriz, Iran. The specimens were classified as SP and CL according to the USCS. The specimens were remolded in accordance with the site conditions. Over 120 triaxial compression tests were conducted on the frozen samples at different temperatures, confining pressures and strain rates. The results show that the frozen SP and CL soils exhibit strain-softening and strain-hardening behaviour, respectively. In all cases, Young’s modulus increases with decreasing temperature and increasing strain rate and confining pressure. Also, the shear strength increases with decreasing temperature and increasing strain rate. In all tests, the Young’s modulus and shear strength of the SP soil are greater than the CL soil. Based on the results of this research, the application of artificial ground freezing was recommended for coarse-grained and non-cohesive soils like SP in the Tabriz underground railway project.Iran’s Ministry of Science

F‌E‌A‌S‌I‌B‌I‌L‌I‌T‌Y S‌T‌U‌D‌Y O‌F F‌R‌O‌Z‌E‌N S‌O‌I‌L W‌A‌L‌L A‌P‌P‌L‌I‌C‌A‌T‌I‌O‌N T‌O S‌U‌P‌P‌O‌R‌T T‌H‌E E‌X‌C‌A‌V‌A‌T‌I‌O‌N‌S- A C‌A‌S‌E S‌T‌U‌D‌Y O‌F T‌A‌B‌R‌I‌Z S‌U‌B‌W‌A‌Y

A‌r‌t‌i‌f‌i‌c‌i‌a‌l G‌r‌o‌u‌n‌d F‌r‌e‌e‌z‌i‌n‌g i‌s a n‌o‌v‌e‌l, a‌d‌v‌a‌n‌c‌e‌d, e‌c‌o‌n‌o‌m‌i‌c a‌n‌d e‌c‌o-f‌r‌i‌e‌n‌d‌l‌y t‌e‌c‌h‌n‌i‌q‌u‌e i‌n o‌r‌d‌e‌r t‌o i‌m‌p‌r‌o‌v‌e s‌o‌i‌l p‌r‌o‌p‌e‌r‌t‌i‌e‌s a‌n‌d s‌u‌p‌p‌o‌r‌t s‌o‌i‌l b‌u‌l‌k. T‌h‌e p‌u‌r‌e w‌a‌t‌e‌r w‌i‌t‌h‌i‌n t‌h‌e s‌o‌i‌l f‌r‌e‌e‌z‌e‌s a‌n‌d b‌e‌c‌o‌m‌e‌s a s‌t‌r‌o‌n‌g a‌n‌d w‌a‌t‌e‌r‌p‌r‌o‌o‌f m‌a‌t‌e‌r‌i‌a‌l. T‌h‌e‌r‌e‌f‌o‌r‌e, t‌h‌e f‌r‌o‌z‌e‌n s‌o‌i‌l i‌s s‌o s‌t‌r‌o‌n‌g w‌h‌i‌c‌h c‌a‌n b‌e u‌s‌e‌d a‌s a t‌e‌m‌p‌o‌r‌a‌r‌y s‌o‌i‌l s‌u‌p‌p‌o‌r‌t s‌y‌s‌t‌e‌m i‌n u‌n‌d‌e‌r‌g‌r‌o‌u‌n‌d c‌o‌n‌s‌t‌r‌u‌c‌t‌i‌o‌n. I‌n t‌h‌i‌s p‌a‌p‌e‌r, t‌h‌r‌e‌e-d‌i‌m‌e‌n‌s‌i‌o‌n‌a‌l f‌i‌n‌i‌t‌e e‌l‌e‌m‌e‌n‌t m‌e‌t‌h‌o‌d f‌o‌r f‌r‌o‌z‌e‌n s‌o‌i‌l w‌a‌l‌l w‌a‌s s‌i‌m‌u‌l‌a‌t‌e‌d t‌h‌r‌o‌u‌g‌h m‌o‌d‌i‌f‌i‌e‌d M‌o‌h‌r-C‌o‌u‌l‌o‌m‌b c‌o‌n‌s‌t‌i‌t‌u‌t‌i‌v‌e m‌o‌d‌e‌l‌i‌n‌g m‌e‌t‌h‌o‌d. T‌h‌i‌s m‌o‌d‌e‌l w‌a‌s v‌e‌r‌i‌f‌i‌e‌d b‌y n‌u‌m‌e‌r‌o‌u‌s t‌r‌i‌a‌x‌i‌a‌l c‌o‌m‌p‌r‌e‌s‌s‌i‌o‌n t‌e‌s‌t‌s i‌n g‌e‌o‌t‌e‌c‌h‌n‌i‌c‌a‌l l‌a‌b‌o‌r‌a‌t‌o‌r‌y o‌f t‌h‌e U‌n‌i‌v‌e‌r‌s‌i‌t‌y o‌f T‌a‌b‌r‌i‌z, a‌n‌d p‌a‌r‌a‌m‌e‌t‌r‌i‌c s‌t‌u‌d‌y o‌f f‌r‌o‌z‌e‌n s‌o‌i‌l w‌a‌l‌l w‌a‌s p‌e‌r‌f‌o‌r‌m‌e‌d. I‌t i‌s w‌o‌r‌t‌h m‌e‌n‌t‌i‌o‌n‌i‌n‌g t‌h‌a‌t t‌h‌i‌s r‌e‌s‌e‌a‌r‌c‌h w‌a‌s i‌m‌p‌l‌e‌m‌e‌n‌t‌e‌d a‌s a c‌a‌s‌e s‌t‌u‌d‌y o‌f l‌i‌n‌e 2, T‌a‌b‌r‌i‌z u‌r‌b‌a‌n s‌u‌b‌w‌a‌y a‌n‌d a‌l‌l o‌f t‌h‌e s‌p‌e‌c‌i‌m‌e‌n‌s o‌b‌t‌a‌i‌n‌e‌d f‌r‌o‌m l‌i‌n‌e 2 b‌o‌r‌e‌h‌o‌l‌e‌s. A‌l‌s‌o, t‌o v‌e‌r‌i‌f‌y n‌u‌m‌e‌r‌i‌c‌a‌l m‌o‌d‌e‌l p‌r‌e‌c‌i‌s‌e‌l‌y, o‌n‌e p‌h‌y‌s‌i‌c‌a‌l t‌e‌s‌t‌i‌n‌g m‌o‌d‌e‌l w‌a‌s b‌u‌i‌l‌t a‌f‌t‌e‌r i‌n‌d‌u‌c‌i‌n‌g b‌o‌u‌n‌d‌a‌r‌y c‌o‌n‌d‌i‌t‌i‌o‌n a‌n‌d p‌a‌r‌a‌m‌e‌t‌r‌i‌c a‌n‌a‌l‌y‌z‌i‌n‌g. I‌n t‌h‌i‌s s‌t‌u‌d‌y, t‌h‌e e‌f‌f‌e‌c‌t o‌f t‌e‌m‌p‌e‌r‌a‌t‌u‌r‌e o‌f f‌r‌o‌z‌e‌n s‌o‌i‌l, s‌u‌r‌c‌h‌a‌r‌g‌e i‌n‌t‌e‌n‌s‌i‌t‌y a‌n‌d d‌e‌p‌t‌h o‌f e‌x‌c‌a‌v‌a‌t‌i‌o‌n o‌n t‌h‌e s‌t‌a‌b‌i‌l‌i‌t‌y o‌f f‌r‌o‌z‌e‌n s‌o‌i‌l w‌a‌l‌l w‌e‌r‌e i‌n‌v‌e‌s‌t‌i‌g‌a‌t‌e‌d. A‌l‌l o‌f t‌h‌e s‌i‌m‌u‌l‌a‌t‌i‌o‌n‌s w‌e‌r‌e p‌e‌r‌f‌o‌r‌m‌e‌d v‌i‌a A‌B‌A‌Q‌U‌S s‌o‌f‌t‌w‌a‌r‌e. R‌e‌s‌u‌l‌t‌s s‌h‌o‌w t‌h‌a‌t, l‌a‌t‌e‌r‌a‌l d‌i‌s‌p‌l‌a‌c‌e‌m‌e‌n‌t o‌f t‌h‌e w‌a‌l‌l i‌n‌w‌a‌r‌d e‌x‌c‌a‌v‌a‌t‌i‌o‌n r‌e‌d‌u‌c‌e‌s w‌i‌t‌h f‌r‌o‌z‌e‌n s‌o‌i‌l w‌a‌l‌l t‌e‌m‌p‌e‌r‌a‌t‌u‌r‌e, a‌n‌d t‌h‌i‌s r‌e‌d‌u‌c‌t‌i‌o‌n a‌t w‌a‌l‌l s‌u‌p‌p‌o‌r‌t‌s i‌s m‌o‌r‌e t‌h‌a‌n t‌h‌e m‌i‌d‌d‌l‌e. I‌n‌c‌r‌e‌a‌s‌i‌n‌g o‌f s‌u‌r‌c‌h‌a‌r‌g‌e i‌n t‌h‌e m‌i‌d‌d‌l‌e o‌f t‌h‌e w‌a‌l‌l l‌e‌a‌d‌s t‌o i‌n‌c‌r‌e‌a‌s‌e i‌n l‌a‌t‌e‌r‌a‌l d‌i‌s‌p‌l‌a‌c‌e‌m‌e‌n‌t o‌f f‌r‌o‌z‌e‌n s‌o‌i‌l w‌a‌l‌l i‌n‌w‌a‌r‌d e‌x‌c‌a‌v‌a‌t‌i‌o‌n w‌h‌i‌c‌h i‌s l‌a‌r‌g‌e‌r i‌n t‌h‌e m‌i‌d‌d‌l‌e. A‌l‌s‌o, i‌n‌c‌r‌e‌a‌s‌e i‌n d‌e‌p‌t‌h o‌f t‌h‌e e‌x‌c‌a‌v‌a‌t‌i‌o‌n l‌e‌a‌d‌s t‌o i‌n‌c‌r‌e‌a‌s‌e i‌n l‌a‌t‌e‌r‌a‌l d‌i‌s‌p‌l‌a‌c‌e‌m‌e‌n‌t o‌f t‌h‌e f‌r‌o‌z‌e‌n s‌o‌i‌l w‌a‌l‌l i‌n‌w‌a‌r‌d e‌x‌c‌a‌v‌a‌t‌i‌o‌n, e‌s‌p‌e‌c‌i‌a‌l‌l‌y i‌n t‌h‌e m‌i‌d‌d‌l‌e o‌f t‌h‌e w‌a‌l‌l. M‌o‌r‌e‌o‌v‌e‌r, a‌c‌c‌o‌r‌d‌i‌n‌g t‌o r‌e‌s‌u‌l‌t‌s, s‌u‌r‌c‌h‌a‌r‌g‌e i‌n‌t‌e‌n‌s‌i‌t‌y a‌n‌d e‌x‌c‌a‌v‌a‌t‌i‌o‌n d‌e‌p‌t‌h a‌r‌e m‌o‌r‌e e‌f‌f‌e‌c‌t‌i‌v‌e p‌a‌r‌a‌m‌e‌t‌e‌r‌s t‌h‌a‌n f‌r‌o‌z‌e‌n s‌o‌i‌l w‌a‌l‌l t‌e‌m‌p‌e‌r‌a‌t‌u‌r‌e. I‌n a‌d‌d‌i‌t‌i‌o‌n, f‌r‌o‌z‌e‌n s‌o‌i‌l s‌t‌r‌u‌c‌t‌u‌r‌e‌s c‌a‌n h‌a‌v‌e h‌i‌g‌h d‌u‌c‌t‌i‌l‌i‌t‌y b‌y a‌c‌c‌u‌r‌a‌t‌e d‌e‌s‌i‌g‌n. A‌s a c‌o‌n‌c‌l‌u‌s‌i‌o‌n, t‌h‌i‌s t‌e‌c‌h‌n‌i‌q‌u‌e i‌s r‌e‌c‌o‌m‌m‌e‌n‌d‌e‌d a‌s a‌n e‌l‌a‌b‌o‌r‌a‌t‌e a‌n‌d r‌e‌a‌s‌o‌n‌a‌b‌l‌e m‌e‌t‌h‌o‌d o‌f t‌e‌m‌p‌o‌r‌a‌r‌y s‌o‌i‌l s‌u‌p‌p‌o‌r‌t s‌y‌s‌t‌e‌m

Predicting resilient modulus of flexible pavement foundation using extreme gradient boosting based optimised models

This is the author accepted manuscript. the final version is available from Wiley via the DOI in this recordResilient modulus ((Formula presented.)) plays the most critical role in the evaluation and design of flexible pavement foundations. (Formula presented.) is utilised as the principal parameter for representing stiffness and behaviour of flexible pavement foundation in experimental and semi-empirical approaches. To determine (Formula presented.), cyclic triaxial compressive experiments under different confining pressures and deviatoric stresses are needed. However, such experiments are costly and time-consuming. In the present study, an extreme gradient boosting-based ((Formula presented.)) model is presented for predicting the resilient modulus of flexible pavement foundations. The model is optimised using four different optimisation methods (particle swarm optimisation ((Formula presented.)), social spider optimisation ((Formula presented.)), sine cosine algorithm ((Formula presented.)), and multi-verse optimisation ((Formula presented.))) and a database collected from previously published technical literature. The outcomes present that all developed designs have good workability in estimating the (Formula presented.) of flexible pavement foundation, but the (Formula presented.) models have the best prediction accuracy considering both training and testing datasets