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17. In all these cases borings might, and probably would judging from the experience gathered on this railway, where borings were taken in many of the cuttings, give the most fallacious results. In the first two cases it is evident that any borings taken might either hit or miss the boulders or rock, while in the latter case a uniform stratum of rock being met with, the engineer might, and possibly would, feel confident that all below it was rock, the exact contrary being the case.
18. Trial pits, if sufficiently numerous, would of course give more trustworthy results, but the great expense of sinking them would, I submit, be utterly incommensurate with any benefit derived, as the following considerations will, I think, amply show.
19. Under a Schedule contract, or if the work be executed departmentally, payment would of course only be made for the quantities of rock and earth actually excavated.
20. The experience upon this, railway has proved that, in consequence of the much greater quantity of excavation necessary, accompanied with the expense of removing of alips, which are of course much more liable to occur in earth, than in rock cuttings, the decrease in the amount of rock met with, as compared with that scheduled, has not resulted in any corresponding saving in the cost of earthwork. In illustration of this point I annex copy of paragraph 3 of my last half-yearly report, No. 31 of 12th February last.
"A.-EARTHWORK executed up to 31st December last.
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represent the comparative value of rock and earth excavation, actually cost more than that of a rock cutting. This is evident from the following figures.
Messrs. Nowell & Co.'s scheduled price for rock excavation per cubic yard is Rs. 1·70,
or 2-83 times their price of 60 cents per cubic yard for earth excavation.
Cutting No. 60 on the Haputale extension, scheduled as rock, and calculated to a formation width of 15 feet with slopes of to 1, contains 4,469 cubic yards, and its cost would, therefore, be Rs. 7597-30; had this cutting been through earth, requiring a formation width of 18 feet with slopes of 1 to 1, its contents would have been, had the surface of the ground been level in a direction transverse to the cutting, 8,122 cubic yards; the average transverse slope of the ground is, however, 30°, and this causes an increase of about 60 per cent. to the contents, thus raising the total quantity to be excavated to 12,995 cubic yards, or 292 times the quantity of the cutting if calculated as being rock, and this quantity at 60 cents per cubic yard amounts to Rs. 7,797, or Rs. 199-70 above the price set down for it as a rock cutting.
22. An examination of the annexed diagrams, being the actual cross sections of the ground at 5 miles 49 chains, a point in cutting No. 60 on the Haputalé extension, will render clear to an unprofessional person the enormous increase to earthwork quantities upon a railway caused by the steep sidelong or transverse slope of the ground:--
Rock Earth
Total
-
Up to 80th June 1884.
During half-year ending 31st December 1884.
Totalic 31st December
1884.
Contract Quantity.
Cabic yards.
Cubic yards.
660,667 1,980,964
28,853
88,706
Cable yards. 688,920 2,019,600
Cabic yards.
1,044,794
1,879,882
2,041,521
67,059
2,708,680
2,424,626
"The sums paid for earthwork are as follows:-
Book
Earth
Total
Up to 80th June 1084.
During half-your
ending 31st December 1884.
Total to 31st December 1904.
Contract Amount.
Rs. 1,122,964 1,188,878
2,311,637
Ba
48,200
23,228
Ba. 1,171,164 1,211,796
1,776,150 887,899
71,423
2,382,960
1,804,049
"And the corresponding per-centages of contract amount paid are :--
Book Earth
Up to 80th June 1894.
During half-your
anding 31st Desember 1884.
Towels to Sist
Dovember 1904.
63.92 143-56
9.71 2.01
65.08
146.87
"The total quantity of rock and earth excavation taken together, executed up to 30th June last, is thus shown to be 2,708,580 cubic yards, or 111:30 per cent. of the total contract quantity, while the amount paid is Rs. 2,382,960, or 91:51 per cent. of the contract sum for earthwork."
On examination of these figures it will be seen that, although up to 81st December 1884, only 65.93 per cent. of the scheduled quantity of rock had been excavated, yet the expenditure upon rock and earth excavation, taken together, amounted to 91-51 per cent. of the contract sum for those items.
21. Again, in extremely steep ground the excavation of an earth cutting, setting aside any risk of slips, may, assuming that Messrs. Nowell & Co.'s contract prices
Had the ground been level transversely, the area would have been the sum of the arena of the portions coloured red and blue, or 528-50 square feet, bat owing to the transverse slope of the ground, the actual ares to be excavated is the sum of the areas of the portions coloured red and green, or 862.80 square feet, an increase of 4'541 per cent.
1 32333.
Soals, 20 foot to 1 inok.
FIGURE No. 1.
Rock Cutting base, 18 fest.
Slope, to 1.
PUBLIC RECORD OFFICE
།
Reference :---
miniminim ITPELLICO. 882
PUBLIC RECORD OFFICE, LONDON
|ALLY WITHOUT PERMISSION OF THE BE REPRODUCED PHOTOGRAPHIS, || COPYRIGHT PHOTOGRAPH——NOT, 10
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