A generalization of the original peridynamic framework for solid mechanics is proposed. This generalization permits the response of a material at a point to depend collectively on the deformation of all bonds connected to the point. This extends the types of material response that can be reproduced by peridynamic theory to include an explicit dependence on such collectively determined quantities as volume change or shear angle. To accomplish this generalization, a mathematical object called a deformation state is defined, a function that maps any bond onto its image under the deformation. A similar object called a force state is defined, which contains the forces within bonds of all lengths and orientation. The relation between the deformation state and force state is the constitutive model for the material. In addition to providing a more general capability for reproducing material response, the new framework provides a means to incorporate a constitutive model from the conventional theory of solid mechanics directly into a peridynamic model. It also allows the condition of plastic incompressibility to be enforced in a peridynamic material model for permanent deformation analogous to conventional plasticity theory.

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Stiffness is one of the basic performance parameters for railway track. The efficient and accurate stiffness measurement has been considered as the foundation for further development of railway engineering, and therefore has great theoretical and practical significance. Based on a summary of the connotation and measurement of track stiffness, the state of the art of measurement methods for track stiffness was analyzed systematically. The standstill measurement of track stiffness can be performed with the traditional jack-loading method, impact hammer method, FWD (falling weight deflectometer) method, and track loading vehicle method. Although these methods can be adopted in stiffness measurement for a section of railway track, they are not desirable owning to small range and low efficiency. In the recent 20 years, researchers have proposed many methods like unbalancedloading laser displacement method, deflection basin deformation rate method, and eccentricity excitation method to continuously measure track stiffness; however, these methods have drawbacks like poor accuracy, low speed, and insufficient data analysis. In this work, the merits and demerits of these methods were summarized, and optimization suggestions were presented. Based on the wave transmission mechanism and principle of vibration energy harvesting, an overall conception on continuous measurement of stiffness and long-term stiffness monitoring for special sections was proposed.

The Nankai Trough of Japan is one of the most active seismic zones in the world. In order to understand the mechanisms of great interplate earthquakes and the tectonics, the seismic activity, the focal mechanism solutions were analyzed in detail in this research. Based on the geometry of slabs and status of stress within the slabs, the Nankai Trough can be divided into two parts, the eastern (Shikoku and the Kii peninsula) and the western (Kyushu) part. The seismic slab of the Philippine Sea plate subducts with shallow dip angels between 10~ 22° and its leading edge reaches down only to about 60~85km depth beneath Shikoku and the Kii peninsula. However, the seismic slab with a dip angle of 40° subducts down to about 160km depth beneath Kyushu. Two types of seismogenic stress field exist within the slabs of the Philippine Sea plate in the eastern and western parts of the Nankai Trough. The stress field of down‐dip compression type can be seen in the region beneath the most of Shikoku and the Kii peninsula. On the other hand, the stress field of down‐dip extension type within the slab is dominant beneath Kyushu. The analysis results of gravity, GPS, heat flow and other geophysical data suggest that the tectonic properties in the eastern part differ from the western part. Two types of characteristics of seismotectonics and intraslab stress field in the same trough might be related to the differences of slab age in the eastern and western parts.

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