Advances in Civil Engineering

Coalbed methane (CBM) has been exploited in the deep area of the coal reservoir (>1000 m). The production of CBM vertical wells is low because of the high in situ stress, large buried depth, and low permeability of the coal reservoir. In this paper, efficient and advanced CBM development technology has been applied in the Libi Block of the Qinshui Basin. According to the characteristics of the coal reservoir in the Libi Block, the coiled tubing fracturing technology has been implemented in four cluster horizontal wells. Staged fracturing of horizontal wells can link more natural fracture networks. It could also expand the pressure drop range and control area of the single well. This fracturing technology has achieved good economic results in the Libi Block, with the maximum production of a single horizontal well being 25313 m³/d and the average single well production having increased by more than 60% from 5000 m³/d to 8000 m³/d. Based on the data regarding the bottom hole pressure, water production, and gas production, the production curves of four wells, namely, Z5P-01L, Z5P-02L, Z5P-03L, and Z5P-04L, were investigated. Furthermore, a production system with slow and stable depressurization was obtained. The bottom hole pressure drops too fast, which results in decreasing permeability and productivity. In this work, a special jet pump and an intelligent remote production control system for the CBM wells were developed; hence, a CBM production technology suitable for the Libi Block was established. The maximum release for the CBM well productivity was obtained, thus providing theoretical and technical support for CBM development with geological and engineering challenges.

The existing pavement performance prediction methods are limited to single-factor predictions, which often face the challenges of high cost, low efficiency, and poor accuracy. It is difficult to simultaneously solve the temporal, spatial, and exogenous dependencies between pavement performance data and maintenance, the service life of highways, the environment, and other factors. Digital twin technology based on the building information modeling (BIM) model, combined with machine learning, puts forward a new perspective and method for the accurate and timely prediction of pavement performance. In this paper, we propose a highway tunnel pavement performance prediction approach based on a digital twin and multiple time series stacking (MTSS). This paper (1) establishes an MTSS prediction model with heterogeneous stacking of eXtreme gradient boosting (XGBoost), the artificial neural network (ANN), random forest (RF), ridge regression, and support vector regression (SVR) component learners after exploratory data analysis (EDA); (2) proposes a method based on multiple time series feature extraction to accurately predict the pavement performance change trend, using the highway segment as the minimum computing unit and considering multiple factors; (3) uses grid search with the k-fold cross validation method to optimize hyperparameters to ensure the robustness, stability, and generalization ability of the prediction model; and (4) constructs a digital twin for pavement performance prediction to realize the real-time dynamic evolution of prediction. The method proposed in this study is applied in the life cycle management of the Dalian highway-crossing tunnel in Shanghai, China. A dataset covering 2010–2019 is collected for real-time prediction of the pavement performance. The prediction accuracy evaluation shows that the mean absolute error (MAE) is 0.1314, the root mean squared error (RMSE) is 0.0386, the mean absolute percentage error (MAPE) is 5.10%, and the accuracy is 94.90%. Its overall performance is better than a single model. The results verify that the prediction method based on digital twin and MTSS is feasible and effective in the highway tunnel pavement performance prediction.

Frost damage is a frequent occurrence in cold regions and can threaten the normal use and structural stability of tunnel engineering projects. To accurately determine the frost heaving force and effectively evaluate the frost damage in cold-region tunnels, an analytical solution for the frost heaving force considering the freeze-thaw (F-T) damage and transversely isotropic characteristics of surrounding rock is presented based on complex variable theory and the power series method. The calculation results indicate that the frost heaving force acts on the lining considering that the transversely isotropic characteristics of surrounding rock are significantly greater than those when assuming the surrounding rock is homogeneous isotropic media. This demonstrates that the transversely isotropic characteristics of surrounding rock have a considerable impact on the frost heaving force and should be considered. The frost heaving force continuously increases as the bedding angle increases from 0° to 90°, and the maximum frost heaving force in the Guanjiao tunnel (the rock mass bedding angle is 30°) of the Xining-Geermu Railway in China is approximately 1.04 MPa. In addition, the influence of F-T cycles on the frost heaving force in cold-region tunnels is investigated based on the analytical solution of the frost heaving force proposed in this paper. The frost heaving force acting on the lining decreases with an increasing number of F-T cycles due to the deterioration of the mechanical parameters of the surrounding rock.

Polymer modified asphalt emulsion (PMAE) has recently been proven to be one of the most effective methods to overcome the common distress of asphalt surface treatments, such as abrasion, rutting, ravelling, and poor durability. Because of the limited research studies about the preparation of PMAE using SBS latex, a new method to prepare SBS latex was developed and the feasibility of using it in preparing SBS latex modified asphalt emulsion (SBS-LMAE) was verified in this study. The optimized swelling parameters for linear SBS solutions were swelling 24 h at the temperature of 50°C with the toluene/SBS (T/S) mass ratios of 2.5 : 1 to 2.0 : 1 which was determined according to the analysis of viscosity and Tyndall effect. After that, the SBS latex with favorable dispersivity and stability was successfully fabricated with the T/S ratio of 2.0 : 1. At last, the well-specified SBS-LMAE was prepared using the fabricated latex and tested for its conventional performances and microstructure. The results show that the SBS-LMAE samples all meet the main requirements of PMAE for microsurfacing and possess appropriate uniformity and stability.

Columnar jointed basalts (CJB) are featured by the joint network of discontinuities, which is hard for geotechnical design and construction. Therefore, investigating the mechanical behaviors of CJB is significant for the long-term use of the engineering structures. In this paper, field research studies, such as the rigid bearing plate tests and acoustic tests, were employed, to obtain the deformation modulus and the acoustic velocity of columnar jointed basalts, and the formula expressed by deformation modulus and acoustic velocity was then established, which would be a useful guidance for the site operation. Based on the monitoring and testing data of CJB, several numerical simulation models with different joint angles and weak thickness were built to further discuss the mechanical behaviors of CJB. The numerical simulation results show that the joint angle of 30° ∼ 60° presents weak antipressure abilities, for the shearing slipping force and interformational sliding are remarkable in them. Besides, the small material property difference is helpful for the compressive strength of rock masses. After adopting the most unfavorable joint angle and width to model the tunneling process in CJB, it suggests that it is easily damaged along the directions of rock joints in CJB when constructing in tunnels.

Based on geological conditions of 3318 working face haulage roadway in Xuchang Coal Mine, as well as the space-time relationship with surrounding gob, theoretical analysis and numerical simulation were used to study the influence of fault structure on the original rock stress of 3318 working face transport roadway. Considering the composite action of the leading supporting pressure of 3318 working face and the structure and the lateral supporting pressure of gob, the stress distribution and deformation law of roadway under the complex and high-stress condition are studied. The results show that, under the superposition of lateral abutment pressure of goaf and abutment pressure of adjacent working face and fault structure, the peak stress of roadway roof and floor moves to the surface of roadway surrounding rock, and its distribution law changes from obvious symmetry to asymmetry; surrounding rock on both sides of roadway forms asymmetric circular concentrated stress area; roof and floor and two sides of roadway show asymmetric characteristics. This reveals the stability characteristics of roadway surrounding rock under the action of multiple perturbation stresses.