Some issues in the theory of soil arch in the geotechnical engineering are brought
forward, including the forms of spandrel, the shape, geometric parameters and microscopic
properties of soil archesetc. From the forming mechanism of soil arches, they are divided into four
types,i. e.directly-forming spandrel, induced-friction spandrel, solum-forming spandrel and
spandrel with different bases. Based on an engineering instance, some primary views on the
geometric parameters of arch shape and arch body are put forward to develop and perfect the theory
of soil arch.