Helical piles have received extensive attention in recent years due to its advantages such as convenient construction

load-bearing capacity after installation

and recyclability. However

the previous research was mainly based on the premise of ignoring the installation effect. When the installation effect was considered

researches mainly focused on the degree of disturbance to the relative density of sand. The experimental study of the installation effect in clay is not enough. In response to this problem

a model test was carried out to obtain the load-displacement relationship curves of different types of helical piles. For the helical pile with a single plate

whether the installation effect is considered or not

the variation trends of the ultimate bearing capacity with the increasing of the embedment depth ratio are basically the same

but the ultimate bearing capacity decreases significantly when installation effect is considered. For double-plate pile

after the spacing is greater than 2D

the individual bearing model occurs

and each plate can play its bearing capacity independently. Increasing the number of plates can appropriately improve the bearing capacity

but when the failure model transitions from individual bearing model to cylindrical shear mechanism

the increase of bearing capacity is no longer obvious

and at this moment the critical spacing ratio (S/D)cr is between 1.5 and 2.0. Subsequently

a concept of “disturbance coefficient” is put forward to quantitatively evaluate the reduction of bearing capacity caused by helical pile installation. For the helical pile with a single plate

the disturbance coefficient varies from 0.5 to 0.6 when embedment depth ratio is greater than 4D

and increasing the spacing ratio will lead to an increase in disturbance coefficient ranging from 0.20 to 0.45. For multiple plates

the coefficient lies between 0.4 and 0.6.