Soil arching effect has been widely recognized as one of the most critical factors governing load-transfer mechanism in the design of various geotechnical infrastructures. However, most existing studies on soil arching effects are limited only to the state when soil arching effect is fully mobilized, while the knowledge about the evolution of soil arching effects with relative displacement remains largely unknown. In this study, a series of classical trapdoor tests are conducted to investigate the evolution of soil arching effects with the progressively developed relative displacement for the trapdoor problem. A particle image velocimetry (PIV) technique is employed to measure the progressive development of displacement and shear strain of soil mass. The development of slip surfaces as well as stress transfer in soil mass are studied. The observed evolution of slip surfaces in soil mass is then related to the load-displacement characteristics of the soil mass under various magnitude of surcharge during trapdoor tests. The test results indicate that the triangular and vertical slip surfaces correspond with the minimum and residual values of loosening earth pressure, respectively. Upon the experimental observations, analytical solutions are proposed to predict both the minimum and the residual values of loosening earth pressure acting on top of the trapdoor, where the deflection of principal stress axes is considered. Comparisons between the model predictions with test results are carried out. Good agreement is observed, which validates the proposed theoretical model.

Many uncertain factors in the excavation process may lead to excessive deformations and internal forces of retaining structures; therefore, the design of deep excavations should be adjusted according to real-time monitoring data. This paper presents a case study of dynamic control of excavation deformations. The preliminary design adopted bored piles as retaining structures braced by three levels of steel-reinforced concrete struts, while the final design used only two levels of struts to reduce the construction duration. The final design reduced the safety degree of the project to a certain extent and brought the excavation to a state of emergency. Fortunately, the designers adjusted the excavation sequence based on feedback information from the field monitoring data. In addition, a variety of deformation control measures, aimed at reducing the horizontal displacement of the retaining walls, were used, such as strengthening the chamfer of the retaining structures, adjusting the excavation sequenc...

Large underground voids created by removal of ore are usually backfilled with mill tailings. The stress state in the backfill must be estimated to ensure safety. Most of the existing analytical solutions for estimating stress at any depth within mine fills had adopted the assumption of uniform vertical stress. However, this assumption does not make for a valid hypothesis. This paper presents an analytical solution to estimate the stress state in vertical backfilled stopes with stress patterns of distribution in the fill considered. The trajectory of minor principal stress in the fill from the centerline to the wall was assumed to be either a circular-arc, parabola, or catenary. The direction of the minor principal stress at the centerline was vertical to the centerline, and the direction along the rock mass was determined using the geometrical relationship of Mohr’s stress circle. The stress states of the differential flat elements in the backfill were analyzed through equilibrium considerations. Then, the analytical solution for estimating the stress state in the backfill was obtained. A series of examples are presented and compared with existing analytical solutions and numerical results carried out in ABAQUS (version 6.13). A nonuniform stress distribution across the backfill width is also presented. The vertical normal stress component at the centerline was greater than that along the wall. The stress state in the backfill was affected by the friction angle and cohesive strength of the backfill soils, friction angle at the wall interface, and trajectory of the minor principal stress. A discussion is presented after the comparison of numerical and analytical results and addresses the limitations of the proposed analytical solutions.

In order to sustainably use coal resources and reduce coal mine accidents, the stability evaluation of roadway roofs is particularly important. The existing methods of roof stability evaluation and control application are greatly disjointed, the relationship between roof stability evaluation and early warning control is ignored, and an intelligent evaluation and calculation control system is lacking. Based on the successful application of the roof-cutting non-pillar mining method in various engineering geology and mining conditions, the roof stability evaluation system, mobile intelligent computing system, and engineering application research are carried out. An evaluation index system for roof stability in the roof-cutting non-pillar mining method is established, including the roof rock integrity and the roof-surrounding rock displacement. A comprehensive evaluation method for roof stability grades is proposed based on the coupling of evaluation index grading criteria and improved analytic hierarchy process (AHP) weight assignment. A handheld mobile intelligent platform for roof stability evaluation, roof hazard zone, and control suggestion is developed. The research results have been applied in the coal mine of Hecaogou with good outcomes. This intelligent stability evaluation system will provide an economical and effective approach to achieving sustainable use of coal resources.