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A new type of retaining wall, the self-balance retaining wall, is introduced in this paper. Based on the stress analysis, the calculation model and method are advanced about the retaining wall. A comparative analysis related to traditional retaining wall is carried out on stress and cost combining with an actual project. The results show that the idea of using upper gravity retaining wall as the resistance of lower retaining wall is clever and reasonable that the self-balance retaining wall has a very wide scope of application relying on the anchor tensile conditions rarely and that the self-balance retaining wall has a great economic value with low cost. The cost of the self-balance retaining wall is 50% compared with the cantilever pile retaining wall under the same conditions which has a good economic effect and application prospect.

China is an eastern country with frequent geological disasters. Since the 1980s, landslide, collapse, debris flow, and other geological disasters showed a trend of increase year by year with the rapid development of economic construction and the influence of natural factor [

A lot of scholars have done a lot of work about slopes (slide) in the aspect of theoretical research [

In order to develop the structure of retaining wall, Ye and Gan [

The self-balance retaining wall is a new type slope supporting structure. The self-balance retaining wall is composed with gravity retaining wall in the upper part of the structure and antisliding pile in the lower part of the structure. This structure form makes full use of the inherent nature of gravity retaining wall. The instruction diagram is shown in Figures

The overall schematic of the self-balancing retaining wall.

Sketch map of the balance of retaining wall.

Gravity retaining wall is characterized by simple structure, large section size, heavier wall body, and simple construction technology. So, the gravity retaining wall is widely used in practical engineering. The gravity retaining walls use the earth pressure against its own gravity function. Its biggest advantage and intrinsic properties are gravity. The self-balance retaining wall is the first to use this resource to expand the gravity from its soil retaining effect to benefit the lower part of the retaining wall. The height of gravity retaining wall should be controlled in the range of 10 m considering the security and economy.

The characteristics of the antislide pile are antisliding ability, good effect of retaining, small disturbance on the stability of sliding body, construction safety, flexible pile position setting, timely supplement sliding resistance, and so on. The self-balance retaining wall makes full use of the advantages of antislide pile with some improvement on traditional antislide pile: firstly, the antislide pile is inclined pile. The angles of deviation of the antipile from the plumb line are about 10~20°. Furthermore, bracket is designed on the top of piles and the pile head coupling beam is set on the bracket. Then, the gravity retaining wall is set on the pile head coupling beam. Finally, in the embankment engineering, the antislide pile under the ground is the straight pile for the convenient installation, while the antislide pile is inclined piles in the process of excavation. The inclined piles, which are the secondary significant creation, greatly reduced the soil pressure.

The self-balance retaining wall is a new type of combined retaining wall. The self-balance retaining wall uses vertical load eccentricity of gravity retaining wall on the lower inclined pile to form a negative bending moment and the angle of inclined piles against sliding of earth pressure to decrease supporting internal force of pile.

The stressed state analysis of the self-balance retaining wall is shown in Figure

Sketch map of self-balancing retaining wall stress analysis.

The bending moment produced by slope thrust at the base of slopes is

The resistance bending moment at the bottom of pile core axis generated by the vertical load of gravity retaining wall and the gravity antisliding inclined pile is

Adjust the unit weight of gravity retaining wall and antisliding inclined pile to make the resistance

The computation of gravity retaining wall using traditional method is not stated here.

The soil pressure of antisliding inclined pile is calculated according to (^{2}); ^{3}); ^{2});

One of the biggest contributions of this new type structure is that there is a dip angle in the antipile. Soil pressure decreases significantly. Take a set of data to calculate the following: slope height is ^{3}, the comprehensive internal friction angle of filling soil ^{2}; calculate the soil pressure

Sketch map of antisliding inclined pile soil stress analysis.

The curve of the soil pressure changing with angle.

The internal force calculation of pile body of antisliding inclined pile upper than the embedded surface is assumed that the embedded part is fixed bearing, the inclined pile is assumed as statically determinate structure, and analysis of stress state is shown in Figures

Soil pressure load bending moment is

The horizontal force of upper gravity retaining wall basement is

The vertical load of upper gravity retaining wall basement is

The weight load of antisliding raking pile is

The internal force moment at

The shear stress at point ^{2}); ^{2}); ^{3}).

The deformation coefficient of pile is firstly introduced when the internal force, displacement, and lateral compressive stress of embedded pile are calculated.

According to the “

According to the “^{−1}); ^{−3}); ^{−4}); ^{−4});

The flexural differential equation of method of “

Introducing the deformation coefficient

The displacement and internal force of any section under the sliding plan is

Equation (

When the pile bottom is fixed,

When the pile bottom is hinged,

When the pile bottom is free,

The flexural differential equation of method of “

Introducing the deformation coefficient

The displacement and internal force of any section under the sliding plan is

Equation (

When the pile bottom is fixed,

When the pile bottom is hinged,

When the pile bottom is free,

The characteristics of self-balance retaining wall are as follows:

Antisliding pile is fastigiated, and the soil pressure is decreased. When the antisliding pile inclines 20°, Coulomb’s earth pressure will decrease 40%.

The gravity of the upper gravity retaining wall is well used. The primary attributes of gravity retaining wall are the gravity. The self-balance retaining wall first utilizes this resource which expands the soil retaining effect from itself to the lower retaining wall with energy conservation and emissions reduction.

The antislide pile bending moment is significantly reduced due to the reduction of soil thrust and force of self-balance.

Reduce embedded requirements of the antislide pile.

Balance problem in construction process. In the fill projects, the balance of self-balance retaining wall is very important. It is different from the other retaining wall and needs balance calculation.

The range of application is as follows: ① the filling slope controlled by Coulomb’s earth pressure and ② the slope with smooth surface of bedrock and without the condition of anchoring; the filling soil slope or half filling soil slope with height of 15–30 m.

An engineering example is used to illustrate the advantages of self-balance retaining wall to the traditional pile plate retaining wall.

The project is located in Chongqing Jiangbei harbour city industrial park zone D “light industrial park D area.” There is a slope with length of 350 m and height of 20 m in the place. Slope position is the original deposit soil. The soil thickness is 15–35 m. The lower bedrock is composed of mudstone and sandstone. The surface of the bedrock is smooth under the slope bottom elevation about 2–10 m. The slope does not have the condition of anchoring. Authors illustrate the application of self-balance retaining wall in the comparison between two schemes. Calculation parameter is given in Table

The design parameter.

Rock property | Natural density^{3} |
Saturated unit weight^{3} |
Cohesive force |
Internal friction angle |
Resistance coefficient^{3} |
---|---|---|---|---|---|

Filled soil | 18 | 20 | 0 | 28 | |

Highly weathered rock | 23.5 | 24.5 | |||

The middle weathered rock | 26.7 | 23.8 | 2490 | 33.6 | 120 |

Calculation parameter is given in Table

The diagram of the balance of retaining wall.

The diagram of retaining wall.

The force of upper gravity retaining wall of self-balance retaining wall is calculated by the traditional method with Leading software 6.0. The soil pressure is calculated according to (

The pile bending moment diagram.

Antislide pile shear diagram.

Antislide pile reinforcement area.

Antislide pile reinforcement area.

The soil pressure to the piles.

As shown in Figures

Comparison of the peak internal force.

Contrastive analysis | The maximum bending moment |
The maximum shear force |
The biggest pile reaction |
---|---|---|---|

Traditional pile retaining wall | 53471.32 | 6144.38 | 3455.30 |

Self-balance retaining wall | 15764.54 | 3678.98 | 2365.12 |

Percent | 29.48% | 59.87% | 68.45% |

As shown in Table

As shown in Figures

The statistics about main work quantities of two kinds of retaining wall is listed in Table

Single pile quantity statistics and cost estimate.

Type of retaining wall | Concrete^{3} |
Reinforcing steel bar/t | Earth cutting/m^{3} |
Rock cutting/m^{3} |
Rubble concrete/m^{3} |
Total |
---|---|---|---|---|---|---|

Self-balance retaining wall | 84 | 11.23 | 16 | 24 | 102.92 | |

Traditional pile retaining wall | 340 | 28 | 40 | 100 | 0 | |

The proportion of saving | 0.75 | 0.59 | 0.6 | 0.76 | 0 | |

Unit price | 500 | 5000 | 200 | 300 | 450 | |

Self-balance retaining wall | 42000 | 56150 | 3200 | 7200 | 46314 | 154864 |

Traditional pile retaining wall | 170000 | 140000 | 8000 | 30000 | 0 | 348000 |

As shown in Table

In fact, this project was completed in 2014, as shown in Figure

The self-balance retaining wall in light industrial zone D.

The self-balance retaining wall is put forward and used in 2003 as a new type of retaining wall. In the last ten years, there have been more than 10 engineering application examples with good effect. The deformation of self-balance retaining wall is much less than that of traditional retaining wall. The features of this technique are as follows:

In the filling slope controlled by Coulomb’s earth pressure, the self-balancing retaining wall has the following remarkable advantages.

The self-balance retaining wall first utilizes this resource which expands the soil retaining effect from itself to the lower retaining wall with energy conservation and emissions reduction.

The antislide raking pile can decrease the soil pressure.

The dependence on the anchor tensile conditions is small or absent.

The retaining wall has a rational stress mechanism and simple mechanical model and can be mastered by designers.

The retaining wall has a low cost and good economic value.

The retaining wall has small deformation and no strict requirement for filling materials.

The authors declare that they have no conflicts of interest.

This work was supported by Projects nos. 0903005203452 and 106112017CDJXY200007 and supported by the Fundamental Research Funds for the Central Universities, Natural Science Foundation Project of CQ CSTC (no. cstc2017jcyjA1250).