Soil thermal conductivity is a dominant parameter of an unsteady heat-transfer process, which further influences the stability and sustainability of engineering applications in permafrost regions. In this work, a laboratory test for massive specimens is performed to reveal the distribution characteristics and the parameter-influencing mechanisms of soil thermal conductivity along the Qinghai–Tibet Engineering Corridor (QTEC). Based on the measurement data of 638 unfrozen and 860 frozen soil specimens, binary fitting, radial basis function (RBF) neural network and ternary fitting (for frozen soils) prediction models of soil thermal conductivity have been developed and compared. The results demonstrate that, (1) particle size and intrinsic heat-conducting capacity of the soil skeleton have a significant influence on the soil thermal conductivity, and the typical specimens in the QTEC can be classified as three clusters according to their thermal conductivity probability distribution and water-holding capacity; (2) dry density as well as water content sometimes does not have a strong positive correlation with thermal conductivity of natural soil samples, especially for multiple soil types and complex compositions; (3) both the RBF neural network method and ternary fitting method have favorable prediction accuracy and a wide application range. The maximum determination coefficient (R²) and quantitative proportion of relative error within ±10% ( $P_{\pm 10\%}$ ) of each prediction model reaches up to 0.82, 0.88, 81.4% and 74.5%, respectively. Furthermore, because the ternary fitting method can only be used for frozen soils, the RBF neural network method is considered the optimal approach among all three prediction methods. This study can contribute to the construction and maintenance of engineering applications in permafrost regions.

The comprehensive understanding of the variation law of soil thermal conductivity is the prerequisite of design and construction of engineering applications in permafrost regions. Compared with the unfrozen soil, the specimen preparation and experimental procedures of frozen soil thermal conductivity testing are more complex and challengeable. In this work, considering for essentially multiphase and porous structural characteristic information reflection of unfrozen soil thermal conductivity, prediction models of frozen soil thermal conductivity using nonlinear regression and Support Vector Regression (SVR) methods have been developed. Thermal conductivity of multiple types of soil samples which are sampled from the Qinghai‐Tibet Engineering Corridor (QTEC) are tested by the transient plane source (TPS) method. Correlations of thermal conductivity between unfrozen and frozen soil has been analyzed and recognized. Based on the measurement data of unfrozen soil thermal conductivity, the prediction models of frozen soil thermal conductivity for 7 typical soils in the QTEC are proposed. To further facilitate engineering applications, the prediction models of two soil categories (coarse and fine‐grained soil) have also been proposed. The results demonstrate that, compared with nonideal prediction accuracy of using water content and dry density as the fitting parameter, the ternary fitting model has a higher thermal conductivity prediction accuracy for 7 types of frozen soils (more than 98% of the soil specimens’ relative error are within 20%). The SVR model can further improve the frozen soil thermal conductivity prediction accuracy and more than 98% of the soil specimens’ relative error are within 15%. For coarse and fine‐grained soil categories, the above two models still have reliable prediction accuracy and determine coefficient (R²) ranges from 0.8 to 0.91, which validates the applicability for small sample soils. This study provides feasible prediction models for frozen soil thermal conductivity and guidelines of the thermal design and freeze‐thaw damage prevention for engineering structures in cold regions.

The traditional methods of treating and disposing waste drilling fluid are encountering severe challenges with the tightening of environmental regulations in China. Commonly used chemical destabilization technology needs to be improved, and treating processes are required to be optimized and updated. This paper details a laboratory investigation on two waste water-based drilling fluids (a high-density drilling fluid and a reservoir drilling fluid) from the rig sites, as well as the corresponding treatment and disposal process design. The laboratory work focused on a solid-liquid separation technique on the basis of chemical flocculation and centrifugation. According to the properties of each waste drilling fluid, different flocculants were added to initiate chemical flocculation. The effects of type and concentration of flocculants as well as treating conditions (including sulfuric acid, dilution ratio, centrifugal speed and agent adding sequence) on the degree of separation were comprehensively investigated. To apply the separation technology in various fields, two integrated processes for collective and in-site treatments were designed and discussed respectively. The results showed that the correct combination of inorganic and polymeric flocculants can lead to a great degree of separation. In particular, a novel flocculant based on modified starch exhibited excellent performance. The molecular weight of polymeric flocculant substantially influences treatment efficiency, which can be explained by the combination of adsorption-bridging and sweep-flocculation mechanisms. Adding sulfuric acid to the waste drilling fluid in treatment is beneficial to solid-liquid separation due to the reduction of electrostatic repulsion between solid particles. Molecular weight of flocculant is also a crucial factor influencing the separation effectiveness and rate. For the two waste fluids studied, the optimal treating conditions were proposed. The weight fraction of separated liquid phase reached higher than 80% and the liquid content of the solid phase was lower than 30%. Detailed analysis and discussion of the advantages of this process were presented. Preliminary field practice of this technique exhibited its satisfactory performance. This highly-integrated technique based on novel chemical agents, rational design and high-efficiency equipment is helpful to deal with the increasing technical and environmental challenges. The information provided in this work offers a reference to relevant researchers, designers and engineers.

The rock strata traversed by frozen shafts in coal mines located in western regions are predominantly composed of weakly cemented, water-rich sandstones of the Cretaceous system. Investigating the rheological damage behavior of saturated sandstone under frozen conditions is essential for evaluating the safety and stability of these frozen shafts. To explore the damage evolution and creep characteristics of Cretaceous sandstone under the coupled influence of low temperature and in situ stress, a series of triaxial creep tests were conducted at a constant temperature of −10 °C, under varying confining pressures (0, 2, 4, and 6 MPa). Simultaneously, acoustic emission (AE) energy monitoring was employed to characterize the damage behavior of saturated frozen sandstone under stepwise loading conditions. Based on the experimental findings, a fractional-order creep constitutive model incorporating damage evolution was developed to capture the time-dependent deformation behavior. The sensitivity of model parameters to temperature and confining pressure was also analyzed. The main findings are as follows: (1) Creep deformation progressively increases with higher confining pressure, and nonlinear accelerated creep is observed during the final loading stage. (2) A fractional-order nonlinear creep model accounting for the coupled effects of low temperature, stress, and damage was successfully established based on the test data. (3) Model parameters were identified using the least squares fitting method across different temperature and pressure conditions. The predicted curves closely match the experimental results, validating the accuracy and applicability of the proposed model. These findings provide a theoretical foundation for understanding deformation mechanisms and ensuring the structural integrity of frozen shafts in Cretaceous sandstone formations of western coal mines.

Asphalt concrete has been widely used in various fields, and now most of the urban roads have taken asphalt concrete pavement. Because of the way of channelization and the braking force of the vehicle, the road surface of the special road needs to bear greater shear stress, so the road section and the section of the platform usually adopt different pavement structures. In this paper, two kinds of pavement structures are numerically simulated, and the deformation and stress of two kinds of pavement structures under vehicle loading are compared and analyzed.