eChapters

9.1. Balance and Weighing

9.1.1. Principle of Functioning of a Balance

It is one of the important tools used in the laboratory and one should have thorough knowledge about its assembly, use and care, otherwise it may be the initial step for introducing error in any physical or chemical analysis. Every balance has its maximum load limit and sensitivity depending upon its construction.

Essentially balance may be regarded as a rigid beam, BC having a central fulcrum, O and two arms of equal length, d₁, d₂ (Fig.9.1). The both ends of beam have prism edges upon which the balance pans are suspended by means of suitable suspension.

8.1. Law of Mass Action

Gulberg and Waage, the two Norwegian chemists in the year 1864 stated the law of mass action in this form: ‘The velocity of any chemical reaction at any instant at a given temperature is proportional to the active mass of each of the reactants at that instant present in the system, the active mass in a homogeneous system is defined as the number of gram molecule of the substance present per unit volume i.e., the molar volume’.

Mathematical Formulation of the Law of Mass Action

Let us take a simple case of a reversible reaction at constant temperature represented by the equation:

Soil consistency is a term used to designate the manifestation of different physical forces acting within the soil at various moisture levels. The consistency limits, also known as ‘Atterberg Limits’ (Atterberg, 1911; 12) are defined by the water content of the soil to create specified degree of consistency. These limits are – (i) Liquid limit or upper plastic limit, (ii) Plastic limit or lower plastic limit and (iii) Sticky limit.

7.1. Determination of Liquid Limit or Upper Plastic Limit

Equipments and Materials

Liquid limit device (Casagrande, 1932) and accessories, spatula, dish, oven, moisture box, balance, desiccator

6.1. Determination of Hydraulic Conductivity of Saturated Soil: Laboratory Methods

Hydraulic conductivity of a saturated soil indicates the ease with which water is transmitted through the soil pores. If a constant water head (h) is maintained on a saturated soil column of length (L) and the volume of water (V) percolating per unit time (t) through per unit cross sectional area (A) to the other end, then according to Darcy’s Law the rate of flow of liquid or flux (q) is proportional to the hydraulic gradient (ΔH/L) across the length of soil column.

5.1. Determination of Soil Moisture

5.1.1. Determination of Soil Moisture Content by Gravimetric Method (Direct method)

Traditionally water content in soil is expressed as the ratio of the weight of water present in the soil to the weight of dry soil. When this ratio is multiplied by 100, it becomes the percentage of water in the soil sample on dry weight basis.

In natural condition primary soil particles cohere to each other to form a cluster or an aggregate through the cementing action of various agents like organic matter, oxides of iron and aluminium, carbonates, etc. Aggregate analysis tells one about the structural status, pore geometry which in turn influences the movement of air and water in soil, amount of water stable secondary particles (aggregate) as well as the extent of finer particles aggregated to the coarser particles and the erodibility status of surface soil against wind and water.

Methods of Analysis

Among the several methods of aggregate analysis the commonly used methods practiced in agriculture and related fields are wet sieving and dry sieving method of aggregate analysis.

3.1. Determination of Bulk Density of Soil

3.1.1. Determination of Bulk Density of an Undisturbed Soil

Bulk density of soil is expressed as the ratio of the mass (weight) of soil particle to their total volume including the pore space between the soil particles. Alternately, it is the weight of unit volume of dry soil. It is usually expressed in the unit of gram per cubic centimeter (g/cc) or mega gram per cubic meter (Mg/m³). In fine textured soil bulk density varies from 1.00 to 1.60 g/cc, whereas in coarse textured soil from 1.20 to 1.80 g/cc.

2.1. Particle Size Distribution Analysis

Soil is composed of particles of varying size and shape. The expression of the proportion of the different size particles is termed as ‘soil texture’. It is one of the most important basic characters being little changed by cultivation or other practices. Particles are arbitrarily distinguished into following groups on the basis of their diameters.

Soil is a mass of large variability and thus its sampling is the most challenging problem for any soil analyst. Practically, soil sampling is a two step process which includes (i) collection of soil from homogeneous unit and (ii) processing which in turn includes drying, grinding, sieving, mixing, partitioning and storing.

1.1. Sources of Error in Soil Chemical Analysis

Different sources of error involved starting from soil sampling to chemical analysis of a sample can be divided into three main groups:

1. Sampling error : This error results from variability among the different samples drawn from same soil unit with respect to the objective of sampling.
2. Sub-sampling error : This error is due to variability introduced among sub samples of the same soil sample.
3. Analytical error : This error introduced due to variability from one chemical determination to another on same sub sample.

Abstract

The landslides of the hill ecosystems are either due to the natural morphotectonic and morphodynamics processes of the planet earth or due to the anthropogenic effects or due to the combinations of the both. In the Indian subcontinent, the landslides are reported from three major provinces viz: Himalayas, Westernghats and The Nilgiris. While the landslides of the Himalayas are demonstrated to be predominantly due to active tectonics, the landslides of the Westernghats are attributed to excessive weathering and rock fall. On the contrary the landslides of the Nilgiris have been thought to be due to extensive deforestation and the related increase in the pore pressure during rainy seasons. But the studies carried out in the recent years show that not only in the Nilgiris but also in other hill systems of Tamil Nadu, the landslides seem to be related to the recent earth movements. This is very significant in the context of fastly recurring seismicities in South India and hence this aspect warrants detailed studies for landslide mitigation.

Abstract

The analysis of IRS - 1A satellite imagery has indicated the existence of two NE - SW trending sub parallel faults along which the coast is undergoing land subsidence as revealed by the concavity in the shore line, preferential migration of the river systems and the drainage congestion, absence of beach ridges, occurrence of off shore shoal etc. The study has further indicated chains of tectonically induced environmental problems such as ground water logging, coastal zone flooding, storm surges, harbour sedimentation etc.

INTRODUCTION

Coastal zones are always dynamic and active, because of the multivariate morpho tectonic and morpho dynamic processes, viz: tectonic, fluvial, marine and aeolian which act in varying degrees and duration along the coasts. As these geomorphic / morpho dynamic processes act in varying permutations and combinations in different segments of the coasts, the land - ocean interactive phenomenon vary greatly in time and space, which in turn frequently and dynamically alter the coastal environment, and cause fragility to the coastal ecosystems. Further, as the coastal zones act as the junction between the Continents and the oceans, even mild earth movements exhibit exemplified expressions in land - water distribution pattern along the coasts. The green house effect and the much apprehended sea level rise and the disasters like cyclones also contribute in their own way in accelerating such land - water distribution / land - ocean interactive phenomenon.

OBSERVATION

The examination of the IRS - 1A imagery under raw and the digitally enhanced modes vividly display heavy concentration of suspended sediments in certain sectors along the east coast of Tamil Nadu. Such pockets of suspended sediments are seen as long and linear bodies trending parallel to the coast to the strike length of 20 - 30 km and width of 5 - 10 km. Such Phenomenon of suspended sediments concentration are strikingly observed in two sectors. One in between Tuticorin harbour and Vaippar river mouth and the other just at the mouth of Ponnaiyar river along Cuddalore-Pondicherry coast. Both of them are observed along conspicuous (Fig.1& 2) concave coasts.

The resources on the land have started showing sign of faster depletion owing to the population explosion, over exploitation of mineral and water resources and also the improper exploitation and the related wasting of the natural resources. Hence a time has come to search for more and more newer natural resources amongst which the ocean resources gain supreme importance as this treasure is yet to be hunted due to the non - availability of suitable technology for the same.

Such ocean resources mainly include the mineralogical and biological resources. The ocean biological resources, their birth, growth, population and migration greatly depend as chlorophyll content, total dissolved oxygen, total suspended solids, salinity etc. These parameters which constitute the marine environment drastically change in a quick span of time owing to the dynamically changing marine forces.

Abstract

The present study has revealed that the NE-SW and WNW-ESE trending sinistral faults are very active along the Tamil Nadu coast and the same have caused considerable slope modifications along the Coleroon and Karungalar rivers which are well-manifested in the land, water and mudflat distribution pattern. Similarly, the progradation of the land in Vedaranniam nose is due to the rise of Pattukottai-Mannargudi area and the time transgressive modifications of the Vedaranniam backwater indicates the opening up of the N-S trending Pleistocene-Holocene faults.

Abstract

The art of remote sensing has opened up many vistas in the study of river migration as satellite photographs, both in their normal and digitally enhanced modes, vividly show the rivers and their migratory signatures. The rivers migrate for various reasons amongst which tectonic movement is one of the main causes. In the present study an attempt has been made to exhibit the palaeochannel network of the rivers of Western India and integrate them with lineament fabric, so as to understand the Quaternary tectonics of the region. The study has shown that Western India shows considerable signs of Quaternary tectonics.

The great Indian epic ‘Ramayana’ says that ‘Lord Rama’ has tried to cross over the Bay of Bengal so as to reach Sri Lanka from India from three points along the southeastern fringe of the Indian coast. Firstly, he is said to have tried to cross from Vedaranniyam which is mythologically called as ‘Kodiyakkarai’ Secondly from Manamelkudi and finally crossed over to Sri Lanka from Rameswaram Island (Fig.1), as the former two coastal locations were widely separated from Sri Lanka by Bay of Bengal and the Rameswaram Island was nearer to Sri Lanka during that period. But, the recently acquired satellite data shows the huge accretion of sediments and rapid land building activity off Vedaranniyam coast (Fig. 2 and 3). The geomorphic interpretations carried out using IRS 1A imagery and 14^C archaeological dating of such geomorphic features have shown that such ongoing sediment accretion phenomena off vedaranniyam nose might in future connect the Vedaranniyam part of Indian Peninsula with Jaffna Peninsula of Sri Lanka if the sediment accumulation continues unabated. The sediment accretion in this area, therefore, requires detailed studies particularly in the context of the coastal ecosystem (Fig. 1).

Abstract

The Remote Sensing and the followed up field based investigations show that the Tamil Nadu coast, India, is facing series of geoenvironmental problems due to tectonic movements and morphodynamic processes. Such problems pose a challenge to the engineering geologists. The paper discusses such challenging engineering geological problems and plausible remedial measures.

Abstract

The tectonic and the geomorphic features observed along the west coast of the area between Mangalore and Cape Comorin show that the NNW-SSE trending west coast has been carved out by the Western Ghats orogeny and the related NNW-SSE trending release fractures. The sinuosity of the otherwise straight coast line is due to Quaternary cymatogenic arching caused by the thrust related to the northerly movement of the Indian plate. The coast line has further attained peaks, projections and serrations due to the ENE-WSW trending series of Precambrian extension fractures which were reactivated gaining the northeasterly directed forces from the rising Carlsberg ridge. Overall, the west coast is being tectonically evolved even today due to the rise of Carlsberg ridge and the Indian plate movement.

Abstract

There is a consensus amongst the geoscientists that overall there has been progradation along the east and west coasts of peninsular India. However, the present day configuration of the coasts and some of the geomorphologic features such as absence of spit and delta along west coast and absence of major estuaries and petroliferous structures along east coast still remain controversial. The present study, based on the appreciation of certain geomorphological and tectonic features on Landsat imagery and aerial photographs of southern part of Indian Peninsula, suggests that the evolution of the coastline has been mainly controlled by tectonism.

The tapering nature of the coastline is attributed to the Precambrian orographic axis. The serrated nature of the post Precambrian coast line is due to the Precambrian transverse faults, whereas the serrated margin of the post Gondwana, Post cretaceous and post Tertiary coast lines are attributed once again to the Precambrian faults reactivated time and again. During the Quaternary period the coast line has undergone many modifications. The coast line attained sinuosity due to Pleistocene folding which is well manifested by river migration. The coast line was subsequently faulted and shifted with en echelon pattern due to N-S regional compression which is referable to the collision of Indian Plate with Tibetan plate.