In the construction of essential structures for the determination of the mechanical properties of large-scale heterogeneous fractured rock soils, people usually rely on the results of more representative large-scale field testing when assigning expected performances. Such large-scale field testing is conducted with the help of concrete stamps or rock pillars, usually with a square in plan outsole, for compression and flat shear, in galleries or in open sites. However, there are drawbacks: the complexity in the implementation and interpretation of the testing data, low informativeness, etc. Due to the rectangular shape of the stamp, a very uneven stress state is implemented at its base during shear. In order to eliminate these drawbacks in 1979 V.L. Kubetskiy offered the method of the ring loading, in which the square base of a stamp (a pillar) was replaced by a ringone, and the shift was carried out by applying a torque load to the stamp. This gives the possibility to realize various stress-strain state in the soil massif, to provide a more uniform contact stress diagram at its base, to obtain technological advantages and additional information during the experiment and to interpret the experimental data more reasonably and reliably using more modern models. Adescription of the method, loading schemes, developed field and laboratory equipment, results and interpretation of field experiments using isotropic and transversally isotropic soil models is given. The ways of method modernization using inventory installations are described. Taking into consideration that the common trend of improving the methods of geomechanical testings is aimed to increase the accuracy and informativity and at the same time to decrease the labor intensity, the method of ring loading which is being improving nowadays is still competitive.
Evaluation of nitrogen requirement and efficiency of rice in the region of Yangtze River Valley based on large-scale field experiments
