Attachment 5 - Geotechnical Assessment · MCU18/0015

RTI 11/055 Folio B397

“ November 2003 -13- 03632248-001

 

LOOSE SURFACE
SAND FLOWING
DOWN HILL

 
      
    
 

    
   

 

 

 

 

 
 

 

PILE
r
wd Passive K, = Jaterot earth
Pressure pressure cosfficlent
4 Dietrlayflo = 2.77
< Y = soll .density
wd = 18 KN/m>
a KpyH H_« depth of moving sand
| : =3m
@» 28°
Y= 18kN/m?
rT Equivalent Laterol Load on lle:

  

PL 4K nyH? x LSd

 

NOT.TO, SCALE

L ) Equivalent Pils
ee Width (di
. Nh {downstope) Equivalent Pils Width « 15 xd
(ipstope)

—
—e
oe

7.3.2. Shallow Clay / Rock Foundations

 

s Footings supporting structures‘on shallow clay / rock foundations must penetrate through any
7 unsuitable materials to, socket into natural soil comprising either very stiff to hard clay or
dense to very densevcolluvium. Considering the subsurface conditions encountered in the
shallow clay / rock areas, particularly.the probable interlocking of strong diorite cobbles and
boulders, the use of bored piers or conventional strip or pad footings are considered to be

 

ud suitable options.

“ However, due to the presence of loose surface sands, and possibly seasonal groundwater

seepage, contingency’ should be allowed for the installation of temporary liners to support
7 open bored pier holes. Furthermore, due to the presence of strong diorite boulders within the
foundation, the pier boring equipment used must be capable of penetrating such materials (eg.
with a pick attachment).

a Piers which socket into the very stiff to hard clay or dense to very dense colluvium may be
4 designed using an allowable end bearing pressure of 600 kPa for cleaned bases and side
adhesion of 40 kPa.

Conventional strip or pad footings may be used to provide support elsewhere in the shallow
= clay / rock area. Such footings should penetrate through any fill and colluvium to found at
least 200 mm into natural very stiff (or stiffer) clay or medium dense sand. The footings may
be designed using an allowable bearing pressure of 200 kPa.

 

Golder Associates