Geotechnical Engineering

DHARM

830 GEOTECHNICAL ENGINEERING

for satisfactory operation of machines, as it can be furnished only by the manufacturers of the
machinery.

Barkan (1962) proposed the following values from his observation on the performance
of machines:

Table 20.1 Permissible amplitudes (after Barkan, 1962)

S.No. Type Permissible Amplitude

(mm)

1. Low speed machinery (500 rpm) 0.2 to 0.25


2. Hammer foundations 1 to 1.2


3. High speed machinery:
   (a) 3000 rpm
   (i) Vertical vibrations 0.02 to 0.03
   (ii) Horizontal vibrations 0.04 to 0.05
   (b) 1500 rpm
   (i) Vertical vibrations 0.04 to 0.06
   (ii) Horizontal vibrations 0.07 to 0.09

2.50

1.25

0.50

0.25

0.125

0.050

0.025

0.0125

0.0050

0.0025

100 200 500 1000 5000 10000

Frequency(cpm)(Log scale)

Amplitude(mm)(Log scale)

Danger to structures

Caution to structures

machines foundations

Line for machines and

Trouble some to persons

Severe to persons

Easily noticeable to persons

Barely noticeable to persons

Not noticeable to persons

Fig. 20.18 Allowable limits for vertical amplitudes (after Richart et al., 1970)
For foundations of sensitive equipment such as calibration test stands and precision
machines, the design criteria should be established either by the manufacturer or by the user
himself. Permissible bearing pressures for soil should be evaluated by adequate sub-soil
exploration and testing in accordance with IS: 1892 and IS: 1904 or other relevent standards.