Formulas for tunnel crown settlement and horizontal displacement measurement are presented in this paper according to the theory of tunnel displacement as measured by a total station with three-dimensional (3D) coordinate measurement and with remote distance measurement (RDM). Comparison tests using 3D coordinate measurement, RDM, and traditional measurement (i.e., precision levels and tape extensometers) were conducted at a tunnel construction site. Tests showed that measurement of displacement by a total station is more convenient than that by traditional methods. Measurement of crown settlement by a total station with 3D coordinate measurement produces an error, which accounts for a 13% difference in total crown settlement. The accuracy of horizontal displacement measurement by a total station with 3D coordinate measurement is weak compared with RDM and traditional methods. Three-dimensional coordinate measurement is therefore not suitable for tunnel horizontal displacement. Tunnel displacement measurement by a total station with RDM obeys the law of curve and so meets the demand of construction monitoring attained by traditional methods. Use of a total station with RDM is the best method for measuring tunnel displacement, especially in tunnels with weak surrounding rock.

Freeze‐thaw cycle is a type of fatigue loading, and rock stress relaxation under freeze‐thaw cycles takes into account the influence of the freeze‐thaw cycle damage and deterioration. Rock stress relaxation under freeze‐thaw cycles is one of the paramount issues in tunnel and slope stability research. To accurately describe the mechanical behaviour of stress relaxation of rocks under freeze‐thaw, the software element is constructed based on the theory of fractional calculus to replace the ideal viscous element in the traditional element model. The freeze‐thaw damage degradation of viscosity coefficient is considered. A new three‐element model is established to better reflect the nonlinear stress relaxation behavior of rocks under freeze‐thaw. The freeze‐thaw and stress relaxation of rock are simulated by ABAQUS, the relevant model parameters are determined, and the stress relaxation equation of rock under freeze‐thaw cycle is obtained based on numerical simulation results. The research shows that the test results are consistent with the calculated results, indicating that the constitutive equation can better describe the stress relaxation characteristics of rocks under freeze‐thaw and provide theoretical basis for surrounding rock support in cold region.

Firstly, I‐RPT ultrasonic detector was used to test the wave velocity of karst limestone with different initial microstructure and water content. Then, RMT‐150B rock testing machine and DS2‐16B acoustic emission system were used to test the acoustic emission (AE) under uniaxial compression. Mechanical properties and AE characteristics were obtained during rock failure. The detailed relationship between stress‐strain and AE characteristics was studied in this paper. Research results indicated the following: (1) For samples with many primary fissures and defects, wave velocity in dry state was larger than that in its natural state. From natural state to saturated state, the wave velocity tended to increase. For samples with good integrity, wave velocity increased with increasing of water content. (2) In the dry state, the samples presented tension failure. In saturated state, the samples presented tension‐shear failure. For samples with cracks and good integrity, samples showed brittle failure. For samples with many corrosion pores which showed ductile damage under natural and saturated state, the spalling phenomenon was enhanced under saturated state. (3) With increasing of water content, the peak stress and AE peak reduced dramatically. In brittle failure, AE peak could be considered a sign of failure. In ductile failure, AE activity decreased gradually with the decrease of stress. (4) The mechanical properties and AE characteristics corresponding to four main fracture propagation types were also discussed.

The impacts of various aggregate particle sizes and cement contents on the internal structure of pervious concrete were investigated. Accordingly, test blocks with different aggregate particle sizes and cement contents were dissected and photographed. Subsequently, the captured images were processed using the ImageJ software (1.53i) to analyze the profiles of the test blocks and identify the internal mesoscopic parameters of the pervious concrete. This study discusses the relationship between microscopic parameters and macroscopic factors based on experimental results. It also fits functional equations linking the permeability coefficient with pore parameters, matrix parameters, and compressive strength. The results indicated that, as the aggregate size increased, the internal pore diameter of the pervious concrete increased, whereas the total area and width of the cement matrix decreased. This resulted in a low permeability coefficient and high compressive strength of the test block. Increasing the cement content in pervious concrete reduced the porosity and increased the width and area of the internal matrix. Consequently, the permeability coefficient decreased, and the compressive strength of the test block increased.