What is an “Expansive Soil”?
Expansive soils contain minerals such as smectite clays that are capable of absorbing water. When they absorb water they increase in volume. The more water they absorb the more their volume increases. Expansions of ten percent or more are not uncommon. This change in volume can exert enough force on a building or other structure to cause damage.
Cracked foundations, floors and basement walls are typical types of damage done by swelling soils. Damage to the upper floors of the building can occur when motion in the structure is significant.
Expansive soils will also shrink when they dry out. This shrinkage can remove support from buildings or other structures and result in damaging subsidence. Fissures in the soil can also develop. These fissures can facilitate the deep penetration of water when moist conditions or runoff occurs. This produces a cycle of shrinkage and swelling that places repetitive stress on structures.
How Many Buildings are at Risk?
Expansive soils are present throughout the world and are known in every US state. Every year they cause billions of dollars in damage. The American Society of Civil Engineers estimates that 1/4 of all homes in the United States have some damage caused by expansive soils. In a typical year in the United States they cause a greater financial loss to property owners than earthquakes, floods, hurricanes and tornadoes combined.
Even though expansive soils cause enormous amounts of damage most people have never heard of them. This is because their damage is done slowly and can not be attributed to a specific event. The damage done by expansive soils is then attributed to poor construction practices or a misconception that all buildings experience this type of damage as they age.
The Dissertation on Earthquake Performance of Reinfoced Concrete Buildings
I would also like to thank Nejat Bayulken for helping with my questionnaire and Luke Murgatrody and Sammuel Gracey for helping to correct my grammatical errors. I wish to acknowledge my classmates; Robert Leeming, Simon Yallop. Sagar Rasioni and Gianni Spagnolli , who were always ready to help in any time during dissertation research. At last, many thank all those at Middle East Technical ...
Expandable, Shrink-Swell, Heavable Soils?
Expandable soils are referred to by many names. “Expandable soils”, “expansive clays”, “shrink-swell soils” and “heavable soils” are some of the many names used for these materials.
Expansive Soils Map
The map below shows the geographic distribution of soils which are known to have expandable clay minerals which can cause damage to foundations and structures. It also includes soils that have a clay mineral composition which can potentially cause damage.
How to Interpret the Map
The map above is meant to show general trends in the geographic distribution of expansive soils. It is not meant to be used as a property evaluation tool. It is useful for learning areas where expansive soils underlie a significant portion of the land and where expansive soils might be a localized problem.
All construction projects should include a soil analysis to identify the types of soil present and determine their expansive properties. Local occurrences of expansive soils can be found in all of the soil categories shown on this map.
Why Do These Soils Expand?
Soils are composed of a variety of materials, most of which do not expand in the presence of moisture. However, a number of clay minerals are expansive. These include: smectite, bentonite, montmorillonite, beidellite, vermiculite, attapulgite, nontronite, illite and chlorite. There are also some sulfate salts that will expand with changes in temperature. When a soil contains a large amount of expansive minerals it has the potential of significant expansion. When the soil contains very little expansive minerals it has little expansive potential.
Changes in Moisture Content Trigger Damage
When expansive soils are present they will generally not cause a problem if their water content remains constant. The situation where greatest damage occurs is when there are significant or repeated moisture content changes.
The Essay on Soil Profile
Soil forms the surface layer of the earths crust. The development of soil is a constructive process in where disintegrated material resulted from weathering of rocks and minerals get converted into the soil body. Soil profile is the vertical section of soil showing the various layers from the surface to the unaffected parent material. The soil contains three main layers. The surface soil or that ...
The Bottom Line
It is possible to build successfully and safely on expansive soils if stable moisture content can be maintained or if the building can be insulated from any soil volume change that occurs. The procedure for success is as follows:
* Testing to identify any problems
* Design to minimize moisture content changes and insulate from soil volume changes
* Build in a way that will not change the conditions of the soil
* Maintain a constant moisture environment after construction
Expert assistance is needed to do these things successfully.b
11. Pakistan
SANDY SOILS IN WEST PAKISTAN
by
M. Alim Mian
Soil Chemist
Soil Survey Project of Pakistan
Lahore
11.1 INTRODUCTION
West Pakistan has a total area of 312 000 mi2 (about 800 000 km2) and supports a population of about 60 million. It lies between latitudes 23° and 37° north and longitudes 61° and 76° east. There are three broad physiographic divisions: (i) the mountainous area, (ii) the Indus plains and (iii) the Thar desert. The mountainous area covers more than two-thirds of the total area on the western side. The Indus plains occupy an area of about 80 000 mi2 (205 000 km2), whereas the Thar deser covers about 25 000 mi2 (64 000 km2).
11.2. CLIMATE
West Pakistan has an arid to semi-arid subtropical continental climate. According to the precipitation data, 67% of the area receives rainfall/snow below 10 inches (250 mm), 24% between 10 and 20 in (250 and 500 nun), 5.3% between 20 and 30 in (500 and 750 mm) and only 3.7% area gets rainfall above 30 in (750 mm).
The highest precipitation occurs in the north-east and decreases rapidly in the south-west direction. The rainfall/snow is greatly variable in time as well as space. In the area east of the Indus above two-thirds of the annual rainfall is received during summer, mainly in July, August and September, the remaining one-third occurring during winter months. May and June are the hottest months when the maximum temperature may rise to 113°F (45°C.)In the area west of the Indus river about two-thirds of the precipitation occurs in winter and the remainder in summer. The hilly areas in the west and north have mild summers and severe winters.
The Term Paper on Different Types of Soils in India
1. Black soils The principal region of black soils is the Deccan plateau and its periphery extending from 8°45’to 26o north latitude and 68o to 83o45′ east longitude. They are formed from Deccan basalt trap rocks and occur in areas under the monsoon climate, mostly of semi-arid and sub-humid types. The overall climate of black soil region may be described as hot and dry summer, 40-100 ...
11.3 SANDY REGIONS
There are three sandy regions in West Pakistan. The location of these regions is shown on the accompanying map. The potential, use and management problems of each region are described below.
11.3.1 Thal Sandy Area
The Thal is the most important sandy region in the country. It occupies an area of some 9 000 mi2 (23 000 km2) between the Indus and Chenab rivers. It presents a complex pattern of alluvial deposition of sandy materials in Late Pleistocene, mainly by the Indus river and locally by the Chenab; progressively followed by wind resorting of the sediments into various forms of sand ridges; resorting and further deposition of sandy materials by water within spill channels passing through the sandy ridges; locally, modification of the sand ridges by river action; deposition of silty and clayey sediments by river spill channels; and present-day wind resorting of the sandy materials and locally, dune formation.
Most of the area is under longitudinal sand ridges; their size and orientation is variable depending upon wind regimes of the localities where they occur. The inter-ridge valleys have loamy soils under a semi-arid climate, but sandy loam soils in the arid area (classification: yermosols, FAO/Unesco; typic camborthids, USDA).
The sand ridges are several feet higher than the valleys between them and have developed sandy soils. The subsoil is firm when dry and is slightly brighter than the surface soil or the sub-stratum. The proportion of fines in the sandy soils is higher under the semi-arid climate as compared to the ones under the arid condition, (classification: calcaric regosols, FAO/Unesco; ustipsamments and toripsamments in semi-arid and arid regions respectively, USDA).
The sandy soils of Thal are used at present for raising crops as well as for grazing. In the northern part of this region where annual rainfall is more than 10 in (250 to 300 mm), most of the area is sown to dry-farmed gram (Cicer arietinum) and mustard (Brassica juncea).
The sandy soils in the arid part are exclusively used for grazing. In considerable areas over-grazing has transformed the surface of the sand ridges into shifting sands.
The Essay on Soil Pollution 2
Soil is a natural body consisting of layers (soil horizons) of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics.[1] Soil is composed of particles of broken rock that have been altered by chemical and environmental processes that include weathering and erosion. Soil differs from its ...
Around 1947, canal irrigation was introduced in the northern and western parts of this region. Subsequently, the irrigation was extended to areas further south. This development has affected the use and management of sandy soils in a number of ways.
i. In spite of the fact that the main canal was lined with bricks to check exclusive seepage losses, a rapid rise in watertable was noticed. This can be attributed to large-scale seepage losses from the unlined distributaries, water courses and also over-irrigation of highly permeable sandy soils having sandy substrata. There are some places where the sand ridges can be seen surrounded by marshes. In areas close to the main canals and where the sand ridges are not well marked, the sandy soils were subjected to high watertable and salinization.
ii. Irrigated valley bottoms were extended into the sandy ridges by disturbing the sandy soils and their sandy substrata, and then spreading the material on the loamy soils. In many places this caused deep burial of the productive soils with unproductive sand.
iii. The pressure of population has been responsible for bringing large areas of sandy soils under irrigation in this region. The flood irrigation has severely impoverished the soils of their nutrients by excessive teaching. Before irrigation the sandy soils were sown to gram which has a deep root system and builds up the nitrogen content of the soil. Cultivation of other crops under irrigation has incapacitated those soils from producing gram. This may also be due to the use of nitrogenous fertilizers only, causing acute deficiencies of phosphorous in the soil. Under these conditions the yields of other crops, especially wheat, sugarcane and guara (Cyamopsis psoralioides) are showing a steep decline and the plants indicate nutrient deficiency symptoms of all sorts. The irrigated sandy soils in Thal are going to pose a serious fertility problem in the coming years.
iv. The uncultivated sandy soils had a fair cover of vegetation under natural conditions and were used for grazing. In areas where valley soils are irrigated, the natural vegetation is rarely found in an undisturbed state, much of the original vegetation having been subjected to cutting, lopping and over-grazing. This has given rise to formation of active dunes which may pose a serious threat to the adjoining irrigated interdunal valleys.
The Essay on Soil
Soil, superficial covering of most of the earths land area; an aggregation of unconsolidated mineral and organic particles produced by the combined action of wind, water, and organic decay. Soils vary widely from place to place. The chemical composition and physical structure of the soil at any given location are determined by the kind of geologic material from which it originates, by the ...
11.3.2 Thar Sandy Area
The Thar is the most extensive sandy region in the country. It comprises the deserts of Cholistan and Thar, a band of about 50 mi wide and extending over a distance of some 500 mi in the south-east, along the Indian border. It covers about 25 000 mi2 (64 000 km2).
The Thar is actually the western part of the Rajputana sandy desert of India. The origin of the sand is not certain. The oldest part is probably older than the Last Glacial period, in view of the elevation of the sand ridges far above the probable levels of the Indus and Sutlej in the Late Pleistocene. The landscape consists of mainly stabilized hilly sand plain, with longitudinal ridges in the south but alveolar (honey combed) and transverse ridges in the north. The sands are calcareous, rich in weatherable minerals and typically pale brown. They contain less mica, but more quartz than the sands of the Indus river and its tributaries.
The Thar has two distinct climatic zones, i.e. the southern semi-arid zone and the northern arid part. The semi-arid part has well developed soils. The interdunal valleys have loamy soils with a fair amount of organic matter. The subsoils are brighter in colour than the surface soil or the substratum. Towards the southern side the rainfall increases and the temperatures are mild due to the influence of the Arabian sea. These soils are under cultivation for growing sorghum (Andropogon sorghum).
The sandy soils in the semi-arid part occur on the sandy ridges. The soils are sands and loamy sands with bright subsoils. The sandy ridges are 100-200 ft (30-70 m) higher than the interdunal valleys. Very little cultivation is practised on the sandy soils. Natural vegetation provides some grazing for cattle and sheep. Over-grazing and lopping of natural vegetation is the major problem. The crests of the sandy ridges have been transformed into shifting sand dunes.
The arid part of the Thar is far more extensive than the semi-arid part. In this area the interdunal valleys have sandy loam and sandy soils. Due to scanty and uncertain rainfall no cultivation is practised. The sandy ridges have sandy soils and about 10% of their surface is shifting sand. This entire area provides some grazing for cattle and sheep.
The Essay on White Beach Water Sand Surface
Living on the beautiful island of Okinawa, there was a lot to experience at the White Beach. I remember the overwhelming site I behold with each visit. My memory consisted of the blue sky, pure sand, intense sun, noticeable breeze and sparkling water. For me, White Beach was my place to gather peace of mind. Everything the beach had to offer I would take in. I look back now and miss the occasions ...
The main problem of this great region is the scarcity of water. Only after the rains cattle and sheep herds find their way into the interior of the area and stay there as long as drinking water is available in ponds. These ponds are located on such sites where substratum is tight enough to hold water and can collect considerable run-off from large areas. Areas close to the water points are severely grazed whereas the remote areas are probably under-utilized. After the ponds dry out, the herds move away from the interior towards the margins, partly depending upon the adjoining irrigated floodplains for their supplies of water and fodder. Groundwater in most of the area is highly saline and unfit even for drinking. There are a few narrow belts of land where groundwater is sweet. The exact location and extent of such areas needs investigation. The information would be very useful in the development of this large region.
11.3.3 Western Sandy Desert
The western sandy desert comprises four units separated by hill ranges. These sandy areas together occupy an area approximately equivalent to that of the Thal. The sands of this desert are also of alluvial origin, deposited as sandy piedmont slopes, mostly of Holocene age. The climate is extremely arid and soil development is virtually nil. The vegetation covers less than about two percent of the total area. Almost the entire area is in the form of shifting sand dunes and the reworking by wind is continuing. Groundwater as well as surface water is very scarce and often brackish. So this area has little potential for development.
11.4 CONCLUSION
The extensive sandy soils in West Pakistan have a potential mainly for grazing. The soils occurring in the semi-arid zone of Thal as well as Thar are partly used for grazing and partly for dry-fanning of crops such as gram, mustard, guara (Cyamopsis psoralioides) and sorghum. The soils within the arid zone are exclusively used for grazing. The present use seems to be most suitable under the local conditions.
In Thal where sandy soils occur in close association with irrigated loamy soils, the cropping patterns of the irrigated area should be changed in favour of the crops that have a low water requirement and could also provide feed, fodder and hay for the cattle and sheep during the period when the un-irrigated sandy soils are not able to provide grazing but need rest. The grazing potential of the sandy soils should be developed as a part of the development potential of the irrigated loamy soils, for the production of cattle and sheep.
Canal irrigation cannot be extended to additional areas of Thal due to the unfavourable relief and sandy nature of the soils. In such areas, pockets of usable groundwater exist and efforts have been made to irrigate isolated patches of loamy soils here and there. Due to the extreme aridity, and desiccating winds, the cost of production of sugarcane and wheat is very high in terms of irrigation water. The agriculture in such areas should be entirely complementary to the cattle and sheep production, and only such crops should be grown which would provide feed, fodder and hay for the animals. Similarly, in Thar desert grazing potential could be realized by extending canal irrigation to loamy soils in the desert margins for the production of feed, fodder and hay. This could supplement the forage on the sandy soils.
Irrigation of sandy soils in West Pakistan has remote possibilities, because there is a great disparity between land and water resources in the country, there is far more land than water. Water is insufficient to meet the requirement of even good quality land. The country has to think in terms of maximum returns per unit of water rather than per unit area. Sandy soils have a much lower potential than many other soils presently lying barren for want of irrigation. Their economic utilization is related to their favourable capacity for conserving scanty rainfall in a more efficient manner for the growth of natural vegetation for grazing or dry-farmed crops.