The excavation of a foundation pit can exert a notable impact on the underlying tunnel. This research paper aims to analyze and synthesize measured deformation outcomes caused by foundation pit excavation on the underlying tunnel. The paper employs a two-stage analysis approach to derive the calculation formula for additional stress and the deformation control equation of the adjacent tunnel under the influence of foundation pit excavation. Subsequently, the Hermite spectrum method is applied to transform the deformation control equation of the underlying tunnel into a set of linear equations, enabling the determination of the deformation curve. To verify the precision of the theoretical calculation method, a comparative study is conducted between theoretical results and actual measurements. Moreover, a sensitivity analysis of crucial project factors is performed. The research findings reveal minimal disparity between theoretical calculation outcomes and measured deformation of the underlying tunnel, thus affirming the accuracy and rationality of the theoretical calculation formula. The excavation of the foundation pit leads to an uplift deformation in the underlying tunnel, resulting in an “n”-shaped deformation profile. Notably, the stiffness of the foundation soil and the depth at which the tunnel is buried emerge as pivotal factors influencing the deformation of the underlying tunnel. As the stiffness of the foundation soil and the depth of tunnel burial increase, the uplift deformation gradually diminishes, albeit within a restricted range of reduction.

The relationship between moisture transportation and efflorescence in sodium hydroxide- or sodium silicate-activated fly ash/slag geopolymers was investigated. The results show that the efflorescence products are sodium carbonate hydrates, mainly composed of natron, heptahydrate, trona and sodium carbonate. The efflorescence induces compressive strength loss, water absorption increases and pore structure degradation in the geopolymer. When the curved surface of a geopolymer cylinder is covered with plastic film, the moisture transportation drives the free alkalis to the top surface to initiate efflorescence. In comparison, the efflorescence occurring on the curved surface of an uncovered geopolymer cylinder results in a more intensive alkalinity loss. For the uncovered geopolymers prepared with sodium hydroxide activator, efflorescence deposits are formed on the lower half of cylinder. A low capillary absorption capacity developed in the pore structure can only drive the moisture to the middle of cylinder, which is confronted with the drying front. More efflorescence products are formed on the upper half of the uncovered geopolymer cylinder prepared with sodium silicate activator. A relatively higher capillary absorption capacity, developed in the more compact pore structure, transports the moisture from the bottom to the top of cylinder, so no drying line is observed in the cylinder.