The geological environmental background of the north slope at 220 kV Yanjin substation is described; and a detailed analysis of deformation mechanism is made from topographic

lithology

geological and hydrogeological conditions

and external loading. The field investigation shows that the deformation of the slope is caused by a combined effect of internal factors

including unfavorable topographical

geological and hydro geological conditions inherent in the slope

and external factor

i.e.

man-made filling. In order to define the calculating parameters

a set of consolidated drained (CD) tests

consolidated undrained (CU) tests

direct shear repeated direct shear tests and uniaxial compressive strength (UCS) tests are carried out. The stability of the slope is assessed using fast Lagrangian analysis of continua in 3 dimensions. The numerical modeling results show that the factor of safety (FOS) of the slope is 1.10 in the natural state

and reduces to 1.03 after filling

which is close to the critical state. After the site is reinforced with piles

the FOS is 1.27. Therefore

the slope is stable after reinforcement measures are taken.