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Under strong winds, newly transplanted trees can tilt or fall, causing economic losses and injuries. Therefore, studying the wind resistance of trees and methods to enhance their wind resistance is of great significance. In this study, 3D simplified models of spruce were built before and after the installation of support frames in them. The trees were 8 m in height, 4 m in crown diameter, with a trunk diameter of 0.3 m at the base. Corresponding mechanical properties were assigned to the models and fluid-solid interaction was numerically simulated. The results showed that without support, the displacement of the spruce treetop, shear stress on branches, and bending moment at the base increased with increasing wind speed. At a wind speed of 20 m.s-1, the maximum shear stress in the transverse direction of spruce was 2.6 MPa, exceeding 85% of its transverse shear strength. This indicates that there is a possibility of shear failure in the tree with the failure point at the junction of the primary branch and the main stem. Supporting the tree at 1/8, 2/8, and 3/8 of its height reduced the displacement of the treetop, shear stress on branches, and bending moment at the base, ultimately lowering the risk of shear failure and falling. When the support frame was placed at 2/8 of the tree's height, the shear stress on the tree was minimized, reducing the risk of branch breakage by 50%. However, the part of the tree above the support frame had an increased wind-induced oscillation frequency compared to the unsupported tree, reducing the tree's stability and increasing the risk of branch breakage owing to prolonged high-frequency vibration. Numerical simulation of wind-induced tree response is highly customizable, and its results have reference value for studying wind resistance of trees and designing support frames for trees. [ABSTRACT FROM AUTHOR]

In order to study the influence of different forms of defects on the stress of lining structure, through the model test, different forms of defects were simulated, and the changes of bending moment, axial force and safety factor at different parts of lining structure were analyzed. The results showed that the defects at the connection between the side wall and the inverted arch increased the bending moment and axial force at the middle of the lining arch waist and the inverted arch, and decreased the bending moment and axial force at the vault. According to the different forms of defects, the effects on different parts of the lining were different. When there were only concrete shrinkage defects or unconnected steel defects, the main influence parts of lining structure were haunch and side wall. When the two defects coexisted, the middle part of vault and inverted arch would also be greatly affected. The influence of concrete loose defects on the safety factor of lining structure was generally greater than that of unconnected defects of steel bars. The main influence areas were arch waist and side wall. When the two defects coexisted? the safety lector at the middle of arch waist and invert decreased obviously 3 which was 52.03% and 32.40% respectively. The effect of defects on the safety factor at the middle of the hance and inverted arch was greater than that at the vault and side wall. During construction? the quality of concrete pouring here should be strictly controlled to ensure the strength after forming, and the pouring thickness can be appropriately increased to make it have a higher safety reserve. [ABSTRACT FROM AUTHOR]

In order to study the damage mechanism of shield segment structure of shield tunnel with small curvature radius, based on practical engineering cases, a fine lining segment model considering segment joints and inter-ring joints was established to reveal the segment damage mechanism in the construction stage of shield tunnels with small curvature radius. The results showed that the axial force, shear force, positive bending moment and Mises stress of the segment all peaked at the inner and outer arch waists when the shield tunnel with small curvature radius was constructed in the turning section. The arch waist position of segments were more likely to be damaged during the excavation process. When the rectification angle of the jack thrust increased, the overall tunnel deviated to the outside. The outer side of the shield tunnel waist was more obviously affected, since the offset of outer arch waist was significantly larger than that of inner arch waist. The numerical simulation was consistent with the field observation of segment damage, which could provide reference for practical engineering. [ABSTRACT FROM AUTHOR]

Relying on the open excavation subway foundation pit project of Aixihu in Nanchang, the excavation of the foundation pit was numerically simulated by ABAQUS software. The reliability and applicability of the numerical model were verified by comparing the numerical calculation and field monitoring results of the horizontal displacement of the diaphragm wall, supported axial force, surface settlement. The bending moment variation law of diaphragm wall during excavation was analyzed. The research showed that there was a significant difference in the bending moment between the earth facing side and the excavation side of the diaphragm wall, the excavation side was tensioned as a whole and the earth facing side was compressed as a whole. The maximum bending moment of the excavation side was 2.3 times than that of the earth facing side. In the original design scheme, the main reinforcement on both sides of the diaphragm wall was symmetrically reinforced, and there was a large optimization space in the design scheme; the effect of crack control was not good only by increasing the amount of reinforcement. Under the condition of constant excavation depth and internal support spacing, after the asymmetric reinforcement optimization of the existing design, the reinforcement amount on the earth facing side and excavation side was reduced by 38.3% and 11.4% respectively, and the load sharing characteristics of the structure were more reasonable, which could greatly reduce the use of reinforcement, so as to reduce the project investment and construction scale. [ABSTRACT FROM AUTHOR]

A lateral loading model box was used to carry out model tests under two cases: the tunnel was located in loess (case 1) and penetrated by potential sliding surface in loess (case 2). The stress characteristics of tunnel lining in the process of slope deformation were studied, and the laws of slope deformation, pressure change of tunnel surrounding rock and lining moment change were analyzed. Results showed that the surrounding rock near the slope side of the tunnel lining was easy to form a void zone under the two cases. The maximum width of the void zone was about 1 cm in case 1 and close to 2 cm in case 2. The void zone in case 2 was much larger than that in case 1, with a relative increase of 100%; Compared with case 1, the peak value of lining bending moment in case 2 increased significantly, with a relative increase of 159.33%, and the maximum increase was located in the area near the side arch foot of the slope. The slide of the potential sliding surface in the slope significantly increased the possibility of tunnel lining damage. [ABSTRACT FROM AUTHOR]

Comparing to the roof and door, the two ribs of coal mine roadways are relatively weaker and have more deformability. The large deformation of the coal-mass in the ribs have significant effect on the roadway stability. Based on the practical case of severely deformed ribs and by considering its deformability, an analytical model of roof beam with Winkler foundation is built. Hereby the characteristics of bending moment and reflection have been studied. The foundation rigidity of coal mine roadway is revealed and the rib-control support principle is proposed. By employing reinforcement in the ribs, the foundation rigidity of the ribs will increase, and the deformation and failure of the ribs will directly controlled by the reinforcement. The stability of roof and floor is reinforced via the foundation rigidity effect. The foundation rigidity and the rib-control support principle of coal mine roadway are analyzed and validated by means of numerical simulation and field tests. The results show that under the effect of the vertical concentrated stress over ribs, the coal-mass is notably compressed and the roof strata bend and sag along with it. The foundation rigidity has great effect on roof deformation which makes it the key influencing factor. Under the conditions of identical roof support, the reinforcement in the ribs will not only reduce the convergence and failure extent of the ribs during roadway development and retreat mining, but also effective control the deformation and failure of the roof and the floor, which makes it an effective method to improve the roadway stability. This study has improved the understanding of the importance of rib support in roadway ground control, and revealed the support mechanism of rib-control. [ABSTRACT FROM AUTHOR]

In view of the asymmetrical deformation failure in the mining roadway at a steeply inclined special thick coal seam, some field observations, mechanical modeling calculations and numerical simulation analysis were used to reveal the asymmetrical deformation failure mechanism after the excavation of the roadway in steeply inclined coal seams. The stress field after the excavation of the roadway and the distribution characteristics of the plastic zone were analyzed. A new support and reinforcement scheme for the retractable U-shaped steel and asymmetric prestressed anchor(cable)support was proposed. The study shows that:(1) the asymmetrical failure of the roadway is characterized by the subsidence, slippage, and internal expansion along the bedding of the hard rock strata along the side of the coal body; the subsidence of the top of the side of the hard rock is greater than that of the coal side and the central axis of the roadway inclines to the coal side. (2) The asymmetric deformation mechanism of the roadway is that, under the effect of nonuniform load, the angle and size of the counterforce of the shoulder angle support on both sides of the roadway arechanged. The reaction force of the hard rock lateral support is greater than that of the coal side. Also the inclination angle of the coal side is larger than the side of the hard rock. The side rock of the hard rock layer slides, sinks, and expands along the bedding under the action of small angle and large stress, and the side of the coal body is pushed out of the drum under the action of nearly vertical angle force. (3) The bending moment of the roadway from the side of the hard rock to the side of the coal body is increasing all the time. The shear force appears to increase first, then decrease and then increase, and the direction changes in the second increase. The position of the direction change is the offset position of the roadway axis inclining to the side of the coal body. The axial force appears as a parabola,decreasing first and then increasing. The optimum and reasonable section of the roadway under non-uniform load acts is the"asymmetric three-hinged arches". (4) The retractable U-shaped steel and asymmetric prestressed anchor(rope) support are proposed, focusing on reinforcing the lateral support of the roadway coal body and the top support on the side of the hard rock. [ABSTRACT FROM AUTHOR]