SITE REQUIREMENTS AND LAYOUTS (Contd)
4. Site Parameters -- Carry out further checks on arrival at the proposed
location to ascertain the site suitability for bridge deployment. Although not
exhaustive, consider the following factors:
a. Access routes.
Tie in the access routes at both ends of the bridge where possible to the
existing main road network to reduce preparation and maintenance.
Ensure near and far shores should be approximately of equal height.
Operations are possible provided the difference in shore height does not
exceed 4 ft 3 in. (1.3 m) (10%). Refer to figures 3 and 4 to determine the
difference in near and far shore heights. The shores at the expected bearing
points of the bridge should have a Soil Bearing Capacity (SBC) of 4.5 ton/ft2
(450 kN/m2). Refer to table 1 for the SBC of various soil types. The ground
bearing capacity should have a minimum SBC of 4.5 ton/ft2 (450 kN/m2).
(Additional grillage1 is required if softer shores are to be used.)
Installation of bridge anchorage is recommended but not required for all
soil descriptions listed in table 1 below. Conditions such as SBC of launch
site at far and near shores and local weather conditions should be taken
into account when determining whether to install anchorage. The
installation of bridge anchorage will be at the discretion of the NCOIC.
d. Shore Heights.
The far shore should not be more than 4 ft 3 in. (1.3 m) (10%) higher or
lower than that of the near shore when measured from the projection of the
near shore slope. Refer to figures 3 and 4.
Table 1. Examples of Soil Bearing Capacities (SBC).
Hardpan overlaying rock
Very compact sandy gravel
Loose gravel and sandy gravel, compact sand and
gravelly sand, very compact sand-inorganic silt soils
Hard, dry, consolidated clay
Loose coarse to medium sand, medium compact fine sand
Compact sand clay
Loose, fine sand, medium compact sand-inorganic silt soils
Firm or stiff clay
Loose, saturated sand-clay soils, medium soft clay
1 Grillage Framework of beams and crossbeams built as a foundation for building on soft ground.