Stability Evaluation Method of Hole Wall for Bored Pile under Blasting Impact

Blasting impact load may be encountered during the construction of some pile foundation projects. Due to the effect of blasting impact, hole collapse can easily occur in the hole-forming stage of pile foundation construction. In order to prevent hole collapse, it is very necessary to evaluate the stability of a pile hole wall before pile foundation construction. The calculation of hole collapse can usually be attributed to an axisymmetric circular hole stress concentration problem. However, the existing collapse failure theory of pile hole hardly considers the effect of blasting impact load. In view of this, this paper proposes the stability evaluation method of a pile hole wall under blasting impact. Compared with the existing collapse failure theory, the proposed method fully considers the effect of blasting impact stress. Using Mohr–Coulomb strength theory and symmetry analysis, the strength condition of collapse failure is established in this work for accurate evaluation of the stability of a hole wall. The proposed stability evaluation method is demonstrated by a pile foundation construction project of a bridge. Moreover, a shaking table test on the pile hole model was performed to verify the proposed method by experimental data. The results indicate the effectiveness and usability of the proposed method. The proposed method provides a feasible way for the stability analysis of a pile hole wall under blasting impact.

Mechanical properties of high-performance concrete under triaxial compression

It is well known that the mechanical properties of a material are related to lateral confinement. In this paper, 60 cylindrical high-performance concrete (HPC) specimens with different concrete strength grades were cast and subjected to a conventional triaxial experiment to study the mechanical properties of the material. The experimental results indicated that the specimens exhibited longitudinal splitting failure patterns under uniaxial compression and inclined plane shear failure patterns under triaxial compression. The stress–strain curves were divided into three stages: an elastic rising stage, a plastic rising stage and a softening descending stage. The application of lateral confining pressure effectively increased the triaxial compressive strength. As the concrete strength increased, the descending stage of the stress–strain curves became steeper, indicating an increase in brittleness. Based on the experimental results, the failure criterion of the HPC was analysed using the Drucker–Prager yield criterion and Kotsovos failure theory. The parameters of the Drucker–Prager yield criterion were determined, and the applicable range of the Kotsovos failure theory was also obtained.

Research on fatigue failure mode and failure theory of rubber

The rubber products are usually used in the condition of periodically complicated stresses, and their anti-fatigue function is simultaneously dependent on their viscoelasticity and the emergence and propagation of cracks directly effecting on the life of rubber products. Therefore, the research on fatigue failure of rubber products has important significance to improve their durability and safety. The research on fatigue failure of rubber has important significance to improve the durability and safety of rubber products. The fatigue failure mechanism of natural rubber was explained from the point of molecular motion theory and phenomenological theory. The application of test research methods in the study of rubber fatigue microstructure and the influence of environmental factors on the fatigue properties of natural rubber were studied, and the future development direction of natural rubber fatigue was also forecasted.

Application of Deterministic Method for Landslide Susceptibility with Deep Learning

A method for estimating landslide susceptibility based on the analytic hierarchy process (AHP) was developed in 2017 as a deterministic method. The objective of this study is to verify the reliability of the proposed method by applying deep learning to improve the applicability of the method. The AHP-based deterministic method comprises eight factors: fines content, soil thickness, porosity, elastic modulus, shear strength, hydraulic conductivity, saturation, and water content. After dividing the testing area into 1 m square grids, eight factors were derived through field and laboratory experiments. The factor of safety was calculated based on the Mohr-Coulomb failure theory. Finally, the input and output values of deep learning were obtained. Bayesian regularization was applied among gradient descents to improve the learning efficiency when applying machine learning. The actual and predicted factors of safety were compared, and they showed excellent reliability in both the training and test phases. This study demonstrates that the AHP-based deterministic method with deep learning is valuable for determining landslide risk areas.

Homogeneous and Isotropic Materials Failure Theory: A Critical Appraisal

The historical status of failure theory is surveyed and found to be close to chaotic. Abandoning that source, the constructive associations and operations that must be required in order to form a viable theory of materials failure are examined in critical detail. The consequent failure theory has been established and its future is discussed.

The Three Controlling Modes of Failure in Homogeneous and Isotropic Materials With Proof Thereof Through Critical Plane Stress Conditions

The recently developed general materials failure theory is specialized to the two-dimensional state of plane stress. It takes a form that is virtually no more involved than that of the Mises criterion. Yet it remains applicable to the entire range of materials types and thus retains that generality. The Mises form has absolutely no capability for generality. This plane stress form of the new failure theory reveals the existence of three independent modes and mechanisms of failure, not two, not four, purely three. The Mises criterion has one mode of failure. These three modes of failure are fully examined. It is verified that these modes of failure under plane stress conditions are exactly the same as those operative in the three-dimensional case. The simple plane stress form of the failure theory has major appeal and likely use as a teaching tool to introduce failure and to help de-mystify the vitally important general subject of materials failure.

Numerical Analyses on the Stability of a Deep Coalmine Roadway Passing through a Fault Zone: A Case Study of the Gugui Coalfield in China

Massive deformation often occurs when deep coalmine roadways pass through a fault zone due to the poor integrity of rock mass and high tectonic stress. To study deformation characteristics of the surrounding rock in the fault zone of a coalmine, a roadway passing through the FD1041 fault zone in China’s Gugui coalfield was investigated in this research. The geo-stress characteristics of this fault zone were analyzed based on the Mohr failure theory. Furthermore, a three-dimensional model for the experimental roadway in the FD1041 fault zone was built and calculated by a numerical program based on the distinct element method. Stability conditions of the roadway, using several types of support methods, were calculated and compared. Calculation results indicated that pre-grouting provides favorable conditions for the stability of a roadway in a fault zone. Finally, an optimized support strategy was proposed and implemented in the experimental roadway. Monitored results demonstrated that the optimized support strategy is appropriate for this fault zone.