The performance and safety of a geotechnical engineering system are affected by uncertainties. The purpose of Reliability-Based Optimization (RBO) is to find a balanced design that is not only economical but also reliable in the presence of uncertainties. Numerous reliability optimization techniques have been proposed. In this study, the Artificial Bee Colony (ABC) algorithm is employed for reliable optimization of a geotechnical engineering system. The proposed ABC-RBO method combines ABC and First Order Reliability Methods (FORM). Optimization is performed with ABC, while the reliability analysis is performed with FORM, incorporating Excel solver. The proposed method is verified by two geotechnical engineering examples and compared with other methods, and shown to be robust, accurate, and feasible.

Determination of the geomechanical parameters and in situ stress of petroleum reservoir rocks by hydraulic fracturing is critical in performing fracturing operations and reservoir simulation in petroleum engineering. Many uncertainties are associated with the determination of petroleum geomechanical parameters and in situ stress because of the complexity and nonlinearity of hydraulic fracturing and the variation of rock properties. Inverse analysis is commonly used to determine petroleum geomechanical parameters, but conventional analysis does not allow the uncertainty to be considered. This study proposes a probabilistic inverse analysis method that integrates numerical simulation, Bayesian theory and a multi-output support vector machine (MSVM) to determine in situ stress, geomechanical parameters, and related uncertainties. Furthermore, this study tried to establish the relationships between those parameters and numerically simulated borehole pressure. The proposed method was verified by a numerical example in which the uncertainties in the values of the Young’s modulus, Poisson’s ratio, and in situ stress were modeled as random variables. Compared with the traditional inverse analysis methodology, the proposed method was found to improve the accuracy of maximum in situ stress to 45% and 5% with and without considering the poroelastic effects, respectively. Using the parameters determined by probabilistic inverse analysis, the simulated borehole pressure agreed closely with the measured pressure, indicating that the MSVM model reproduced the relationship between the geomechanical parameters and borehole pressure reasonably well. An analysis of the effect of the uncertainty of borehole pressure showed that estimates of the geomechanical parameters are greatly improved by decreasing the error in monitoring borehole pressures.

Rock crack propagation is an important direction in the analysis of rock mechanical properties. However, due to the opacity of rock mass, crack evolution process cannot be directly observed. In this study, a heterogeneous anisotropic transparent rock made by mixture randomly distributed different sizes molten quartz sand and pure epoxy resin. This study aims to provide an intuitive and useful method of observing the characteristics of crack evolution, also crack evolution process is recorded by a high-speed camera based on Split-Hopkinson pressure bar (SHPB) tests. The results show that: change of internal color is monitored during loading, which confirms the visualization of internal crack evolution. Failure occurs along the loading direction, and many cracks are distributed in the center of the sample. When the main crack passes through the broken glass sand, it directly passes through the glass sand, and when it passes through the unbroken glass sand, it extends along the edge of the glass sand. Particle flow code(PFC) is used to simulate crack propagation process of transparent rock sample in the SHPB test, and the process is divided into four stages: no crack, crack initiation, crack coalescence, and crack stability. When the final failure of the sample occurs during loading course, tensile cracks account for 78.3% of the total cracks and shear cracks account for 21.7%. Furthermore, fracture of the sample is dominated by tensile action. Stress—strain curve and failure mode of numerical simulation are in good agreement with laboratory test. The visualization of rock crack propagation is helpful to the follow-up study of hydraulic fracturing of roadway and debonding of bolt.

To research the internal load transfer behavior and failure mechanism of a bird’s nest anchor cable anchoring structure based on a pull-out test, a bond-slip failure model is established on the basis of statistical damage theory, and the distribution formula of shear stress at anchorage agent–rock interface is deduced. Combined with theoretical analysis, bird’s nest anchor cable pulling out test and particle flow code (PFC) numerical simulation test, as well as axial force distribution of the cable and shear stress distribution of its interface, help reveal its load transfer behavior and failure mechanism. Results show that: (1) The established bond-slip model can reflect the internal load transfer behavior and failure process of bird’s nest anchor cable anchorage structure. (2) The shear stress of the anchorage agent interface increases exponentially to the peak value and then decreases exponentially to the residual strength. The process is repeated at every location of the anchorage agent interface. The curve of the axial force and shear stress of the bird’s nest anchor cable is a negative exponential distribution with anchorage depth, and the maximum value occurs at the load end. (3) The crack of the anchorage agent interface extends from the load end to the other end and finally cuts through the whole interface. Rock mass generates radial cracks by the split effects of the bird’s nest. The failure mode is a combination of the debonding slip of the interface and the shear failure of the rock mass. The shear stress distribution and failure mode of the anchor structure are basically consistent according to laboratory tests and simulation tests, and PFC2D better reflects the internal load transfer behavior, failure mechanism, and failure process of the bird’s nest anchor cable under tensile loads.

Interface slip is one of the main failure forms of an anchor structure, but the debonding slip process of rockbolt cannot be directly observed under impact load, so it is important to study the failure mechanism of the interface debonding of an anchor structure. For this purpose, a kind of transparent similar rock-anchoring structure and a new rockbolt impact load test system were developed. The debonding process of the anchor structure was carried out based on the system and Particle Flow Code (PFC) simulation test. The main conclusions are as follows: Axial force of rockbolt decreases progressively from the load end to the other end, but the shear stress of the interfaces increases at the early stage and then decreases. The majority of shear stress is at I interface compared to shear stress at II interface. The crack in the transparent sample occurs first in the middle of the sample, then extends to the local position of the two interfaces and finally penetrates all cracks, and the debonding failure mode is dual-interface mixed. According to laboratory tests and PFC simulation tests, the crack growth process can be divided into three stages. The results of the PFC simulation tests are similar to those of the laboratory impact tests of rockbolt.