Dynamic Stress Concentration of Underground Lined Cavities in Different Distance under Incident Plane SV Wave

A series solution for dynamic stress concentration of underground lined cavities in different distance under incident plane SV waves is given by wave function expansion method. The infinite series is cut and calculated under the required precision. The lining includes rigid lining, unlined cavities, flexible lining. The numerical results show that the distance between cavities has an important impact on the dynamic stress concentration factor and the interaction between two cavities greatly amplifies the dynamic stress concentration. With the distance increases the dynamic stress concentration factor turn smaller gradually and tend to the distribution case of one cavity; The rigidity of lining also has great effect on the dynamic stress concentration which is highest for the rigid lining, second for unlined cavities and is lowest for the flexible lining.

Temperature and surface forces in excised rabbit lungs

This study was designed to determine whether the effects of temperature on lung pressure-volume (PV) curves were influenced by the state of the surface lining at the time of warming or cooling. In successive runs, temperature was varied (21, 37, or 5 degrees C) with lung gas volume fixed at either 55% total lung capacity (TLC) or 0% TLC (degassed), followed by PV curves to TLC. Peak inflation volume in a given lung was made identical at all temperatures. The starting pressure at 55% TLC remained fixed during temperature changes, whereas peak pressure ranged from 24 cmH2O at 37 degrees C to 40 cmH2O at 5 degrees C. However, below 75% TLC all deflation curves differed by less than 1 cmH2O, and the lowest recoil occurred at 5 degrees C. At 0% TLC, a similar dispersion in pressures appeared at TLC. However, on deflation, recoil at 37 degrees C was always less than at 21 degrees C, whereas at 5 degrees C a drastic shift to the right occurred. First-cycle hysteresis and midinflation pressure also increased with cooling. Thus, with cooling, the spreading and adsorption of surfactant during lung expansion are inhibited, and during deflation aggregation is greatly facilitated, accounting for the above results. When an already spread surface is cooled, then expanded, as at 55% TLC, the more rigid lining causes some rise in peak pressure at TLC but little change elsewhere. However, when lungs are degassed and then cooled, the aggregated surfactant spreads extremely poorly, leading to greatly increased recoil throughout the cycle. Changes in pressure at TLC may depend considerably on tissue effects.

Gravitational Stresses on Deep Tunnels

Gravitational stresses around a horizontal tunnel opening are determined by means of Muschelišvili’s complex variable method for solving two-dimensional elasticity problems. The tunnel is located at a large but finite depth underneath the horizontal ground surface. It has the shape of a general ovaloid, including the rounded-cornered square, the ellipse, and the circle as its special cases. The surrounding material is assumed to be elastic, isotropic, and homogeneous. Two problems are solved. In one problem an unlined tunnel is considered, which has a boundary free from external stresses. In the other the tunnel has a rigid lining, and a perfect bond is assumed to exist between the lining and the surrounding material so that the displacements at the boundary are zero.