Calculation Points on Sheet Pile Wall Structure in Soft Soil Water

1. Three Types of Calculation

A. The whole sheet pile wall structure must meet construction requirements in strength and stablity. In calculation, we should consider the worst construction condition and flowing water pressure from above riverbed to river surface, water foce when ships passing by and in tide situation. Pressure from below the riverbed to sheet pile end is combined by hydrostatic pressur and positive earth pressure.

B.  Because of three layers steel waling system, the whole weight is on the sheet pile, we must calculate the vertical load of sheet pile wall.

C. Because of soft soil with deep excavation, the base of sheet pile wall must do stability calculation mainly including Pile Sand Welling and  Base Bumping Calculation.

2.   Establish Calculation Model

 

Use Infinite softwarelike Midas Civil, sheet pile is modeled or simulated by pile units, support and waling system is simulated by beam units.

3、Notes on Base Stability Calculation

 

3. 1　Pile Sand Welling in Base End Calculation

In the pumping of base end, it easily brings danger of pipe sand welling, we should calculate in simplized way. The rule of calculation is by the enough sheet pile embeded depth t to increase water flow length and reduce upward water force. The frequently used calculation formula for non-sandwelling is : K·i·γ≤γ

In this formula：

K-Safe Coeffcient (less than 2 is required) ;
I—hydraulic gradient;
i = h′/(h1+ t) ;
γ—Water Weight ;
γb —Soil Effective Weight

3.2  Base Bumping Calculation

After deep excavation in soft soil foundation pit, under the water pressure and unbalanced soil pressure inside and outside, there may be bumping situation at the end of soft base,  we can claculation by slip surface way, the frequently used fomula is :

Slip Moment：Md=γMH（x2/2）
Stable Moment：Mr=x∫π/2+α0 SM(xdθ), α＜π/2

In this formula：
α=atg(b/h);
h – the height of bottom inside support against to concrete casting height
b – Haft length of base end;
SM -shear strength without watering in slip surface

Note: the article is from  Calculation Points on Sheet Pile Wall Structure in Soft Soil Water