Clarifying the time-dependent strength deterioration characteristics of carbonaceous mudstone under dry and wet cycles is of great significance to the design of expressway cut slopes. In this work, we conducted triaxial compression creep tests on carbonaceous mudstone specimens that had undergone different numbers of dry and wet cycles to investigate their creep properties. A function was established between the steady-state viscoplastic creep rate and axial compression. The threshold stress of the steady-state viscoplastic creep rate was assumed as the long-term strength, and the long-term strength deterioration law of carbonaceous mudstone under dry and wet cycles was studied. The results showed that the transient strain, viscoelastic creep, and viscoplastic creep of carbonaceous mudstone increased with the number of dry and wet cycles, and the creep failure stress and transient elasticity modulus decreased. Based on the steady-state viscoplastic creep rate method, the long-term strength of carbonaceous mudstone after n (n = 0, 3, 6, 9) dry and wet cycles was found to be 74.25%, 64.88%, 57.56%, and 53.16% of its uniaxial compression strength, respectively. Compared with the isochronous curve method and the transition creep method, the steady-state viscoplastic creep rate method can more accurately determine the long-term rock strength. The long-term strength of carbonaceous mudstone under dry and wet cycles decays exponentially, and the long-term strength decay rate during the first three dry and wet cycles is about 215 times the average decay rate.

Flowability is a critical indicator of the flow capacity of cement grout, assessing both the performance and engineering applicability of grouting materials. Accurate measurement and evaluation methods benefit the identification and application of these material properties. By combining laboratory experiments with statistical analysis, this paper performs an error analysis and optimizes measurement accuracy for high water-cement ratio cement grout flowability. The research analyzed and discussed the computational errors caused by different testing methods, and clarified that the weakened cohesion of high water-cement ratio cement paste is the reason for the protrusions at local positions along the edge of the liquid surface. The unrepresentative typical diameter further leads to computational errors. Therefore, by transforming the diameter measurement method into an area measurement method, the high-precision image recognition method was proposed to calibrate the liquid surface area, verify the errors between linear diameter measurement and planar area measurement, and propose a predictive model for cement paste flowability. Findings demonstrate that for water-cement ratios exceeding 0.8, traditional methods employing a typical diameter value yield inaccuracies, with errors around 12.3%, which can lead to misleading results. In contrast, the image recognition method effectively compensates for these calculation errors through its high-precision recognition. This study provides an in-depth analysis of flowability measurement errors and optimizes the measurement method, thus offering theoretical support and practical guidance for the precise identification of grout flowability and quality control.