Numerical simulation of grooving method for floor heave control in soft rock roadway

Grooving method can restrain the deformation and destruction of surrounding rock by transferring the maximum stress to deep rock,bringing about the effective control for floor heave in soft rock roadway. Based on this important effect,and to discuss the relationship between cutting parameters and pressurerelief effect,this paper carried out a numerical simulation of grooving along bottom slab and two sides of gateway with finite difference software FLAC^（2D）.The results show that the control effect on floor heave in soft rock tunnel can be improved by selecting appropriate cutting parameters.Appropriately increasing the crevice depth in the middle of the floor can improve the stress state of bottom slab by stress transfer. So the floor heave can be more effectively controlled.To lengthen the crevice in the corners of roadway can simultaneously transfer the maximum stresses of bottom slab and two sides to deep rock,and promote the pressure-relief effect.Extending the crevice length and crevice width on both sides within a certain range can decrease the stress concentration in the corners of roadway,and reduce the deformation of two sides.The cutting position beneficial to restrain the floor heave is close to the bottom slab.

A novel method to eliminate the bending-induced collapse of hexagonal honeycomb

A novel grooving method for eliminating the bending-induced collapse of hexagonal honeycombs has been proposed,which lies in determining the appropriate grooving parameters,including the grooving spacing,angle,and depth.To this end,a framework built upon the experiment-based,machine learning approach for grooving parameters prediction was presented.The continuously grooved honeycomb bending experiments with various radii,honeycomb types,and thicknesses were carried out,and then the deformation level of honeycombs at different grooving spacing was quantitatively evaluated.A criterion for determining the grooving spacing was proposed by setting an appropriate tolerance for the out-of-plane compression strength.It was found that as the curvature increases,the grooving spacing increases due to the deformation level of honeycombs being more severe at a smaller bending radius.Besides,the grooving spacing drops as the honeycomb thickness increases,and the cell size has a positive effect on the grooving spacing,while the relative density has a negative effect on the grooving spacing.Furthermore,the data-driven Gaussian Process(GP)was trained from the collected data to predict the grooving spacing efficiently.The grooving angle and depth were calculated using the geometrical relationship of honeycombs before and after bending.Finally,the grooving parameters design and verification of a honeycomb sandwich fairing part were conducted based on the proposed grooving method.