BE-02 Open Cut Method: Embedment Zone

Minimum Trench Width Calculation in the US for Various Pipe Materials

How to Calculate the Minimum Trench Width for Vitrified Clay Pipes?

Trenches for Vitrified Clay Pipe (VCP) installation shall be excavated to a width that will provide adequate working space, but not more than the maximum design width, according to [ASTM C12-07].

There is no single formula that is applicable for minimum trench width calculation for VCP. Trench width is mainly one factor to compute loads caused by backfilling to determine the supporting strength of VCP.  The factors taken into consideration to determine the vertical external load on a closed conduit due to backfill materials  (Marston Equation) are:

• Depth of backfill cover over the top of the pipe.

• Width of trench measured at the level of the top of the pipe.

• Unit weight of backfill.

• Values for frictional characteristics of the backfill material.

Table: 

Example of trench width for VCP installed in gravel is documented in the load tables the [VCP Engineering Manual]
    Trench Width At Top Of Pipe (in) for GRAVELS (GW, GP, GM, GC) Kμ' = 0.165
Diameter VCP [in]   18 24 30 36 42 48 54 60 72 84 96 108 120 132 144
6                              
8                              
10                              
12                              
15                              
18                              
21                              
24                              
27                              
30                              
33                              
36                              
39                              
42                              
48                              

 

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