###### Abstract  
Soil structure has significant influences on the mechanical behaviors of natural soils, although it is rarely considered in previous cavity expansion analyses. This paper presents an undrained elastoplastic solution for cylindrical cavity expansion in structured soils, considering the destructuration effects. Firstly, a structural ratio was defined to denote the degree of the initial structure, and the Structured Cam Clay (SCC) model was employed to describe the subsequent stress-induced destructuration, including the structure degradation and crushing. Secondly, combined with the large strain theory, the considered problem was formulated as a system of first-order differential equations, which can be solved in a simplified procedure with the introduced auxiliary variable. Finally, the significance and efficiency of the present solution was demonstrated by comparing with the previous solutions, and parametric studies were also conducted to investigate the effects of soil structure and destructuration on the cavity expansion process. The results show that the soil structure has pronounced effects on the mechanical behavior of structured soils around the cavity. For structured soils, a cavity pressure that is larger than the corresponding reconstituted soils when the cavity expands to the same radius is required, and the effective stresses first increase to a peak value before decreasing rapidly with soil structure degradation and crushing. The same final critical state is reached for soils with different degrees of the initial structure, which indicates that the soil structure is completely destroyed during the cavity expansion. With the increase of the destructuring index, the soil structure was destroyed more rapidly, and the stress release during the plastic deformation became more significant. Moreover, the present solution was applied in the jacking of a casing during the sand compact pile installation and in situ self-boring pressuremeter (SBPM) tests, which indicates that the present solution provides an effective theoretical tool for predicting the behavior of natural structured soils around the cavity. Keywords:cylindrical cavity expansion; elastoplastic solution; structured soils; destructuration effects; pile installation; pressuremeter +
Footnote †: journal:  
_Applied_  
_Acticle_  
**Vol. 2022**  
the influences of stress history and strain hardening/softening on the mechanical behavior of soils around the cavity could not be considered in these solutions [16]. With the development of constitutive models, critical state soil models were introduced into the cavity expansion analyses. For example, Collins and Stimpson [17] proposed the similarity technique based on the Modified Cam Clay (MCC) model for the undrained and drained cavity expansion problems. Later, this solution technique was extended into the bounding surface model [18, 19], the clay and soil model (CASM) [10, 20], the thermoplastic soil model [21], and so on. Because the deviator mean effective stresses were simplified in the above similarity technique, Chen and Abousleiman [22, 23] proposed an exact solution technique for the cavity expansion in MCC soil, following their rigorous definitions. In this framework, many researchers have developed a series of cavity expansion solutions by employing various constitutive models, such as the anisotropic soil model [12, 24, 25] and unsaturated soil model [26, 27]. However, the above-mentioned solutions are suitable for modelling the behavior of reconstituted soils rather than natural structured soils around the cavity because the soil structure was not taken into account. The structure, as one of the most significant features influencing the mechanical behaviors of naturally deposited soils [28], is rarely accounted for in previous cavity expansion analyses. More than a decade ago, several attempts were made to explore the cavity expansion responses in structured soils using a relatively simple constitutive model [29, 30].