Dynamic behavior of marine deposited clay under the simulated circular tunneling construction disturbances

The marine deposited clay will bear a series of complex stress paths caused by shield construction. This will change macroscopic and microcosmic mechanical properties of the marine deposited clay. A lot of evidence from engineering practice showed that geotechnical model parameters ignored soil stress path characteristics, leading to over- and underestimations of soil deformation and strength. Safety risks for tunnel shield construction are significantly posed. To better understand and accumulate macroscopic and microcosmic parameters of marine deposited clay under shield construction stress path, the stress path of marine deposited clay surrounding the tunnel was obtained by using the C. Kirsch analytical solution theory in this study. Scanning Electron Microscopy (SEM) and Mercury Injection Porosimetry (MIP) tests were carried out to obtain and compare the microstructure characteristics of marine deposited clay within and without shield construction stress path, and the microscopic parameters of approximate void ratio, peak aperture, probability entropy of pore orientation were quantitatively analyzed. The loading stress path was simulated by triaxial test, and the graded dynamic triaxial test was carried out to analyze the development of dynamic shear modulus and the stress–strain relationship feature. The correlations between macroscopic parameters of dynamic shear modulus, and microscopic parameters of approximate pore ratio, peak aperture, and probability entropy of pore orientation, were established, which provided a reference for revealing the microscopic deformation mechanism of marine deposited clay.