Study Of Active Earth Pressure Of The Retaining Wall Under Non-limite State Considering RB Displacement Mode

With the rapid development of economy, all kinds of infrastructure construction is rapid increasing. Retaining wall as a supporting structure, is widely used in various kinds of infrastructure construction. At present, when the retaining wall is designed, the classical Rankine’s and coulomb’s earth pressure calculation method still continue to be used. however, the calculation method of classical Rankine’s and coulomb’s earth pressure has a lot of defects.First: In most cases, the soil behind retaining wall is in the limit state rather than a limit state. Especially in active cases, the earth pressure of non-limit state is bigger than the earth pressure of limit state. Therefore, the earth pressure of limit state tends to make the retaining wall structure be dangerous. Second:Classical earth pressure theory does not take into account the effect of different displacement model of retaining wall and the different displacement under same displacement mode in the size and distribution of earth pressure. Third: In the classical earth pressure theory, friction angle has been regarded as a constant.But, in fact, the friction angle between wall and soil and the internal friction of soil is gradually increased with the increase of soil deformation. Fourth: In theclassical earth pressure theory, earth pressure along wall height is linear distribution. However, a large number of experiments and field measured data have confirmed: Earth pressure along wall height is nonlinear distribution.In view of the above reasons, this paper uses ANSYS to establish the elastic-plastic finite element model of the retaining wall, the soil behind retaining wall and foundation. Segment displacement constraint method was used to simulate the non-limit state of retaining wall of RB displacement mode.We analyze the displacement field, the plastic zone, the coefficient of active earth pressure and the active earth pressure result of the finite element, calculate the active earth pressure under non-limit state coefficient with the modified earth pressure calculation formula of coulomb. Finally, we compare the calculation results of finite element and formula, improve the rationality of he modified earth pressure calculation formula of coulomb and give the following conclusions:(1)The relative displacement zone of the sandy soil behind retaining wall under non-limit state is the approximate fan; the horizontal displacement zone increases with the increase of wall displacement ratio, internal friction angle and poisson ratio of back fill sand and decreases with the increase of external friction angle and elastic modulus.The vertical displacement of soil which is close to the upper part of the retaining wall increase and have a tendency to collapse with the increase of wall displacement ratio. The vertical displacement of soil which is close to the upper part of the retaining wall decrease and don’thave a tendency to collapse.(2)The plastic zone of the Sandy soil behind retaining wall under non-limit state is the approximate triangle; the plastic zone increases with the increase of wall displacement ratio, elastic modulus of back fill sand and decreases with the increase of internal friction angle, external friction angle and poisson ratio of back fill sand.(3)The coefficient of active earth pressure of retaining wall of RB displacement mode under non-limit state decreases In the bottom of a retaining wall,because of the friction effect of the soil and the foundation. The coefficient of active earth pressure increases with the decrease of the height of retaining wall; decreases with the increase of wall displacement ratio, internal friction angle, external friction angle and elastic modulus of back fill sand; increases with the increase of poisson ratio.(4)The earth pressure of retaining wall under non-limit state along wall height is nonlinear distribution; the active earth pressure and the resultant force decreases with the increase of wall displacement ratio, internal friction angle,external friction angle and elastic modulus and increases with the increase of poisson ratio of back fill sand; the height of resultant force point decrease and became stable with the increase of wall displacement ratio, internal friction angle and elastic modulus of back fill sand, decrease with the decrease of external friction angle, decrease with the increase of poisson ratio.(5)We calculate the active earth pressure, the curvature of active earthpressure distribution, the resultant force of active earth pressure, and the height of resultant force point under non-limit state coefficient with the modified earth pressure calculation formula of coulomb. At the same time, we compare the calculation results of formula and finite element, find them fairly consistent on the whole and verify the validity of the calculation results.