Chapter: 10
Study of Reserve Estimation of Construction Materials
From civil engineering point of view, reserve may be defined as a deposit of construction
material. Reserve is the identified economic resources of the total identified resource available.
Topography can aid in the achievement of required construction material. For instance, sand and
gravel in plain area river, rocks in the steep area and so on. Also, the satellite image can be handy
to find the reserve location.
10.1 Types of Reserves
Reserve can be classified into the following types:
a. Proved or measured reserve
The reserve from which the resources are obtained as was estimated is called proved or
measured reserve.
b. Probable or indicated reserve
The reserve for insufficient data is collected or is based on limited data is known as
probable reserve.
c. Possible or inferred reserve
The reserve which is just assumed to exist but may not even exist is known as possible
reserve.
10.2 Estimation to methods of estimation of reserve (Cross section, Isopath, Extended
area and block method)
There are different ways to estimate the reserve. The ways to estimate the reserve are mentioned
below.
a. Cross - section method
This method to find the reserve is conducted with the help of geological map. In this method,
area, thickness, volume, density etc. of the reserve is determined to find the amount of reserve.
Cross section method is the type of conventional estimation technique in which normally a series
of cross sections are constructed to the main trend of the mineralization. A special caution should
be paid to the geologic and mining constraints which limit the estimation. Discrete area may be
defined not only by similar grade in adjacent drill holes but also by the rock type, structural
blocks, ore type, and other parameters considered to have economic and genetic significance.
The procedure for measuring the area and subsequent volume of the proposed mineral resource
is explained by “CHAS. F. JACKSON and JOHN B. KNAEBEL” as follows.
In this method, cross sections of the ore body are prepared on which are plotted the intersections
or projections of mine workings and drill holes. The cross sections may be vertical, horizontal,
or at right angles to the dip, usually parallel to each other, and often are spaced equal distances
apart. Frequently they are taken on lines of drill holes where exploration has been done by
drilling from the surface. Estimates are commonly made from sections normal to the strike of
the ore body. In preparing such sections it may also be necessary to make longitudinal sections,
working one set against the other in interpreting the structure. If the sections are quite similar in
outline the average area, in square meter, multiplied by the distance between them, in meter, will
give the volume, in cubic meter, closely enough for practical purposes:
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V=
(𝑨`𝟏+𝑨𝟐)
𝟐
×H
where, A1 and A2 are the end areas of the block,
H is the perpendicular distance between them, and
V is the volume of block.
If there is a series of sections spaced equidistantly, this formula becomes
V=
(𝑨`𝟏+𝟐𝑨𝟐+𝟐𝑨𝟑+⋯+𝑨𝒏)
𝟐
×H
the common "end-area" formula. Due to the usual irregularity of ore bodies this may never be
actually the case but is often a close enough "approximation for all practical purposes. The
tonnage of the deposit is thereafter calculated by the volume times the overall specific gravity.
b. Isopach method
In this method, the area of reserve is contoured with the block of reserve in different maps like
in cross – section method to find the amount of reserve.
c. Extended area method
In this method, the reserve is estimated by the determination of area only.
d. Block method
This particular method is based on the idea of division of the probable area of reserve. Here, the
reserve area is divided into many blocks and studied individually.
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10.3 Basic information of different quarry sites of limestone and iron in Nepal
Limestone:
It is a type of non-metallic mineral and is very important raw material for making cement. With
the rapid increase of development activities such as construction of roads, bridges, dams,
irrigation cannels, housing complexes, multistory building etc.
The quality of limestone depends on its chemical composition like CaO %, MgO %, SiO2 %,
Al2O3 %, Fe2O % LOI %. Based on chemical composition it is used to manufacture Portland
cement, lime, agrilime, flux for iron and steel industries, agriculture, feed in poultry farm, leather
industries etc.the demand of cement is increasing. Some lime-stone deposits have been identified
in Khotang, Udayapur, Syangja, Palpa, Arghakhanchi, Dang, Pyuthan, Sallyan, Rolpa, Bajhang,
Baitadi, and Darchula, districts.
Preliminary studies indicate that there is a possibility to find more than 2.5 billion tons
of cement grade limestone deposits only in the Lesser Himalayan region and 196 prospecting
licenses of limestone have issued by DMG to private sectors (GoN, 2011). But, in some areas of
Palpa district there is conflict between local people and company due to the unclear minerals
policy
Iron (Fe):
Iron is a metallic mineral. which is the principal metal which is used extensively in
infrastructure development works, and to manufacture steel, heavy machinery equipment, arms,
agricultural tools etc. Iron ores like magnetite (Fe3O4), hematite (Fe2O3), limonite/goethite
(FeO(OH).nH2O) and siderite (FeCO3) occurrences/ prospects/ deposits are known to exist in
more than 88 localities. Some of these ores were extensively mined and smelted in different parts
of Nepal for more than 100 years till 1951 (2007 BS) but none of these mines are in operation
since then.
Iron deposition ores are mostly found in Phulchoki (Lalitpur), Thoshe (Ramechhap),
Labdhikhola (Tanahu), Jirbang (Chitwan), and Dhuwakot (Parbat). Local people had excavated
and used traditionally iron ore since ancient times in different parts of Nepal. But their utilization
was only in the local area. The traditional iron ores were excavated in Baitadi, Bajhang, Jajarkot,
Rolpa, Surkhet, Myagdi, Baglung, Parbat, Chitwan, Ramechhap, Okhaldhunga, Taplejung etc.
The iron ore of Phulchoki has still been commercially utilizing due to its location. However, it
lies in the environmentally sensitive area and suffering from various problems, like the shortage
of power like the electricity and coal for smelting. Thoshe iron deposit was mined in small scale
during the Rana period, now a days the mine has completely closed due to its lack of competition
with processed iron in the market (DMG, 2011; Amayta, 1996; Kaphle, Joshi, & Khan1995
1996, 2006).
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