Shallow Foundation

Shallow foundations Shallow foundations are those founded near to the finished ground surface; generally where the founding depth (Df) is less than the width of the footing and less than 3m. These are not strict rules, but merely guidelines: basically, if surface loading or other surface conditions will affect the bearing capacity of a foundation it is ‘shallow'. Shallow foundations (sometimes called ‘spread footings') include pads (‘isolated footings'), strip footings and rafts.Shallows foundations are used when surface soils are sufficiently strong and stiff to support the imposed loads; they are generally unsuitable in weak or highly compressible soils, such as poorly-compacted fill, peat, recent lacustrine and alluvial deposits, etc. Pad foundations Pad foundations are used to support an individual point load such as that due to a structural column. They may be circular, square or reactangular. They usually consist of a block or slab of uniform thickness, but th ey may be stepped or haunched if they are required to spread the load from a heavy column.Pad foundations are usually shallow, but deep pad foundations can also be used. Strip foundations Strip foundations are used to support a line of loads, either due to a load-bearing wall, or if a line of columns need supporting where column positions are so close that individual pad foundations would be inappropriate. The main area of strip foundation are buildings with heavy walls (brick, concrete, stone), and heavy floor slabs. Strip foundation is located on the perimeter exterior walls, and placed under the supporting inner walls of buildings or other areas with increased load.Also strip foundation is well-suited for homes, which is planned to create basement, garage or basement. Strip foundation is also suitable in the case of a possible slight deformation of the base. Typically, strip footing located below the level of soil freezing at 20 cm of sandy soil You can lay the strip foundation a nd higher levels of freezing, but not more than 60 cm from ground level. For deep-freezing and highly swelling soils usually strip foundation shall not apply. Process itself strip foundation construction is simple, on the other hand it requires a fairly high cost of materials and work on the construction of the foundation.There are criteria for the minimum thickness of the foundation, which can be used building a house. Thus, the minimum thickness of reinforced concrete strip foundation – 10 cm of concrete – 25 cm, rubble concrete foundation – 35 cm, well and laying of natural stone – 50 cm in the construction of strip foundation to be also take into account the permissible load on the soil under the foundation. For clay soils at a depth of 80 cm load should not exceed 2 kg/cm2. In addition to pouring the foundation concrete mixtures, often strip foundations erected using ready-made foundation blocks or bricks.This speeds up the process of building a foun dation. It should also be noted that during the construction of strip foundation is an opportunity to save money raising the foundation to the full depth only during the construction of heavy structures. There is still the most reliable option strip foundation remains solid foundation, more time-consuming and requires prior creating formwork and reinforcement training design to increase strength strip foundation. And in this case, the valves must be connected to each other by welding. Raft foundationsRaft foundations are used to spread the load from a structure over a large area, normally the entire area of the structure. They are used when column loads or other structural loads are close together and individual pad foundations would interact. A raft foundation normally consists of a concrete slab which extends over the entire loaded area. It may be stiffened by ribs or beams incorporated into the foundation. Raft foundations have the advantage of reducing differential settlements a s the concrete slab resists differential movements between loading positions.They are often needed on soft or loose soils with low bearing capacity as they can spread the loads over a larger area. Deep foundations * Piles Deep foundations are those founding too deeply below the finished ground surface for their base bearing capacity to be affected by surface conditions, this is usually at depths >3 m below finished ground level. They include piles, piers and caissons or compensated foundations using deep basements and also deep pad or strip foundations. Deep foundations can be used to transfer the loading to a deeper, more competent strata at depth if unsuitable soils are present near the surface.Piles are relatively long, slender members that transmit foundation loads through soil strata of low bearing capacity to deeper soil or rock strata having a high bearing capacity. They are used when for economic, constructional or soil condition considerations it is desirable to transmit lo ads to strata beyond the practical reach of shallow foundations. In addition to supporting structures, piles are also used to anchor structures against uplift forces and to assist structures in resisting lateral and overturning forces.Piers are foundations for carrying a heavy structural load which is constructed insitu in a deep excavation. Caissons are a form of deep foundation which are constructed above ground level, then sunk to the required level by excavating or dredging material from within the caisson. Compensated foundations are deep foundations in which the relief of stress due to excavation is approximately balanced by the applied stress due to the foundation. The net stress applied is therefore very small. A compensated foundation normally comprises a deep basement. Types of pilePiles are often used because adequate bearing capacity can not be found at shallow enough depths to support the structural loads. It is important to understand that piles get support from both e nd bearing and skin friction. The proportion of carrying capacity generated by either end bearing or skin friction depends on the soil conditions. Piles can be used to support various different types of structural loads. End bearing piles End bearing piles are those which terminate in hard, relatively impenetrable material such as rock or very dense sand and gravel.They derive most of their carrying capacity from the resistance of the stratum at the toe of the pile. Friction piles Friction piles obtain a greater part of their carrying capacity by skin friction or adhesion. This tends to occur when piles do not reach an impenetrable stratum but are driven for some distance into a penetrable soil. Their carrying capacity is derived partly from end bearing and partly from skin friction between the embedded surface of the soil and the surrounding soil.

Why was Malthus wrong about Japan?

Today Japan is a highly developed first world country with a vast population and a booming economy. The demographic history of Japan and how it reached this renowned economic status has been the focus of much theorising and has engaged the minds of many demographers, economists and historians for centuries. Japan is unique in the way its population has changed and its economy has developed without the stimulus of overseas markets. It does not boast the best physical landscape, being 85 percent mountainous, and it is not well endowed in terms of resources. Despite these negative attributes however, Japan has developed, and to such an extent it can now boast one of the worlds leading economies. Indeed Japan was the only country outside the western world to have developed at a similar rate. In the 18th century a Swedish doctor, P. Thunberg commented on Japan, ‘Of all the countries that inhabit the three largest parts of the globe, the Japanese deserved to be ranked first, and to be compared with the Europeans. ‘ (Modern Japan, P. Duus. ) It stands to reason therefore that Japan's history merits such a wealth of discussion amongst academics. Part of Japan's success as a country has to be attributed to its longstanding political regime. For centuries Japan was an empire ruled by an emperor based at Kyoto. From the 12th century however Japan was governed by Shogun (military leaders) who oversaw the day-to-day life of the Japanese people. The emperor, in effect, was under house arrest, taking a submissive role being more of a spiritual leader to the people. The year 1600 saw an important event for the political governing of Japan. It was in this year that a battle (Sekigahara) established the supremacy of the Tokugawa family as ruling shoguns. From 1600 to 1868 this family ruled and these 268 years of Japan's history became known as the Tokugawa period. It is this period that is of fascination to many demographers as during this time Japan experienced stagnation in its population but it also seemed to be the onset of its economic success. From the early 18th century to the Meiji restoration in 1868 Japan's population stayed at around 33 million. It is this 150-year period of stagnation that is of interest to studiers of the demographic history of Japan. There is also much discussion as to whether the population as it was, was inextricably linked to economic growth or vice versa. Searches for explanation of population trends date back centuries. One of the earliest and probably the most famous explanation of observed population figures in the world in general, was put forward by the Rev. Thomas R. Malthus in the 18th century. In 1798 Malthus's ‘Essay on Population' was published, in which he wrote at length on past, present and future population trends of mankind. His most famous stance on population levels was that ‘population, when unchecked increases in geometrical ratio; subsistence only in an arithmetical ratio. (Malthusian Population Theory, McCleary. ) He believed that mans (sic) power to produce population is greater than his power to produce subsistence, thus meaning that that the population of a country was constantly held in check by misery and vice. From this a simple model is produced illustrating the point that if populations increases; food prices will increase; real income will decrease; and thus mortality will increase (figure 1. ) The ultimate check according to his works was the want of food, but this was never an immediate check except in the case of actual famines. The constant checks can be classified into two sets, preventative and positive. Positive checks are multifarious and include such components as exposure to the elements, epidemics, war, plagues, famines and extreme poverty. The preventative checks can be further sub-classified into vice and non-vice. According to Malthus however, there is only one preventative check that can be classified as vice and this is moral restraint. The consideration of moral restraint was a latter thought from Malthus, added to his ‘essay' in 1803. From this a more optimistic model of possibility was constructed (Fig 2. ) The two checks vary inversely from one another and can be in operation with varying affect according to the society in which there are operational. The situation as it was in Japan must have had some constituent that caused the observed trends in population. If Malthus's theory is believed to have been operational in Japan then some sort of check was holding the population at its stagnated rate. Japan, unlike Europe at the time was a closed system. Emigration was unheard of and likewise nobody entered the country. Internal migration was also low, although would not have affected population figures. This was mainly due the Tokugawa establishing a period of isolation, cutting Japan off from the rest of the trading world. In terms of Japans population this meant that migration was not responsible for the stagnation, therefore according to Malthus it must be due to high mortality rates and/or moral restraint alone. Malthus travelled to various European countries to study their population trends in order to supplement the work in his first essay. He did not however make it as far as Asia, but did manage to comment on Japan and China in his work. He tended to make generalisations about Japan based on his thoughts about China, believing that in both of these countries moral restraint was not practiced, as it was only adapted to Western Europe. His work led him to believe that in Japan and China marriage was universal and occurred at a very young age. Taking this into account, Malthus attributed positive checks on population to the cause of the stagnation the Tokugawa period. Included in the positive checks Malthus believed occurred in Japan was the act of infanticide or ‘mabiki', literally meaning ‘thinning out. ‘ Again he depicted Japan as being similar to China, but whether he was wrongly casting aspersions about Japan or whether infanticide was one of the components accountable for the population trends is another area that has been widely debated. Many people in this field of work since Malthus have devised various explanations as to the cause of Japans stagnation, and many have been curious as to whether Malthus was right about Japan. In order to deem Malthus right or wrong on this topic information on fertility and mortality levels as well as the marriage system and evidence of infanticide is needed. Early studiers of Japan's history found a way of gathering such information. During the Tokugawa period a registration system, known as Shumon Aratame Cho, was devised (mainly for tax reasons) that recorded births, deaths and other such information for villages in Japan. By studying, what were tantamount to an early form of census, family reconstitution is possible and a better idea of the overall demographic change at that time in Japan is given. Generations of population historians have performed village studies and different generations have varying ideas about the trend in population. The first generation of population historians believed Malthusian checks to be in action in Japan. Subsequent work has questioned this conclusion and many other avenues of thought have been opened up. Levels of fertility are related to marital patterns. This is an area that Malthus had decidedly definite views on in Japan. A control on marriage may have been responsible for the stagnation experienced between 1700 and 1850. This kind of population control may have been conducted in Japan in order to yield positive benefits from lower fertility levels, managed food prices and improved real incomes. Malthus believed that nuptuality in China and Japan was universal and occurred at a young age. He did not believe that controls on marriage could occur in Japan as outside Western Europe h thought that ‘the passion between the sexes is necessary' and cannot be overcome (Malthusian Population Theory, McCleary. From studies of nuptuality records (including components such as age at marrying and proportion of people ever married) it is shown that marriage was universal in Japan but was not at such an early age as it was in China. If nuptuality levels for Japan are compared with England and China for the same time period, then Japan falls somewhere in the middle (see fig 3. ) Universal marrying would suggest high levels of fertility but as discussed this was not the case in Tokugawa Japan. The issue of marrying at a later age can account for low levels of fertility, and possible reduced fecundability in women. Other factors can be attributed to fertility levels and many studies have been carried out in this area. T. C Smith, part of a later generation of population historians, conducted a study of a village which he named ‘Nakahara,' to give an overall general pattern of what was occurring in Japan at this time. Smith looked at fertility levels of the village and constructed fertility curves to examine the possibility of infanticide. The curves showed low levels of fertility, and were convex suggesting that there was an absence of birth control in the village. This adheres loosely to the standard levels of fertility at the time; although the figures in question were lower (fertility levels were naturally low in Tokugawa Japan, lower than pre-industrial Europe. ) Smith believed that the low levels of fertility were due not only to factors such spacing and lactational amenorrhea, as put forward by some of his contemporaries (e. g. Cornell), but also to the practice of infanticide. If Smith's study is consistent with the rest of Japan, then Malthus's theory would be true. However fertility curves alone do not prove beyond doubt that infanticide was occurring. L. Cornell believed the reasons for the low levels of fertility could be explained by factors other than infanticide. She believed the low level of fertility in general in Japan was a result of cultural rather than structural patterns. One of the main reasons put forward for this was the long lactation periods of Japanese mothers. It is biologically proven that the longer the lactation period after birth the harder it is for a couple to conceive their next child. This, Cornell attributes to the observed low fertility levels. Another reason put forward is migration patterns of males in villages at that time, causing a reduction in fecundability. Migration to castle towns, where employment had a large pulling power, was seasonal in villages and as a result of long periods of migration, fecundability decreased and fertility was kept at a low level. Cornell believed that these factors not deliberate controls on family size by the practice of infanticide as other academics believed, caused low levels of fertility in Japan. This was brought about by controls on society by over-riding cultural trends. Smith however, had evidence other than fertility curves to support his claim about infanticide. He studied the sex bias in families in Nakahara to add weight to his argument. He believed that the sex of the next child in a family was enforced by infanticide. Assumptions are easily made that this practice accords with the widely heard of folklore that males were the preferred sex in Japanese households, therefore one would expect the sex ratio to be male biased. However Smith found from his studies that the sex of the next child was not biased to males. He tabulated the evidence, which showed that in a family with predominantly male children, the next child was more likely to be female, and in families that had equal number of male and female children, the next child was most likely to be a male. The opposite was true in families with predominantly female children. However sex selectiveness was not found in other studies, for example in a study by Hayami, there was no evidence of sex selectiveness in families. Smith used this evidence to suggest that infanticide was a means of family limitation in Japan. Another piece evidence he found for the practice of infanticide was that small landholders had fewer children than large landholders, suggesting that family limitation was practiced as a long-term plan, so as to not put financial on the existing family and to maintain living standards. This idea has been rejected however by other authors such as Hanley and Yamamura who believed that infanticide was not only practised by peasants and poor families, but also by the rich who chose to limit their family in order to husband assets. Many authors speculate that infanticide was also practiced to limit the number of male heirs in a family and lessen the competition for family headship. On the matter of infanticide in Japan, contrasting ideas make it difficult to conclude if Malthus was correct in his assumption. However what can be concluded is that villages would have undoubtedly varied in their practices and beliefs. From a persons study of one village it would be wrong to conclude that infanticide was or was not practised in general in Japan. What would be a fair assumption would be to say that infanticide probably was operational in some areas and not in others. However it seems unlikely that infanticide alone, occurring in some areas would lead to the stagnated population that occurred in Japan at this time. Other checks on population must now be looked at to prove or disprove Malthus's theory. It is a given that fertility levels were low in Tokugawa Japan, so according to Malthus mortality must be a contributing factor of the population stagnation. From the Shumon Aratame Cho it is difficult to gain an idea of mortality levels, especially infant mortality. It has been estimated (Cornell) that by as late as 1926 a quarter of all deaths in Japan were infants. In the early Tokugawa period death rates were high and fluctuating. The life expectancy at birth at this time was in the low thirties. Epidemics as a constant check, proposed by Malthus, occurred regularly in Japan; however by about the 16th century the population was large enough to support such disasters. There were also some wide spread famines, particularly bad ones occurring in the 1730's, 1780's and the 1830's, which obviously would have made a dent in population figures. However there is a tendency for populations to recover quickly from famines, and many people would have simply moved away from the area. These two Malthusian checks seem not to have had a large impact on death rates, suggesting Malthus was wrong about Japan in this case in point. Death rates not associated with widespread disasters, must also be take into account. Mortality levels were generally higher in the cities, of which there were about 200 at this time, than in the countryside. An increase in the number of people living in cities could account for a high national mortality level; however improvements in the standard of living meant that death rates actually decreased in these areas. It seems that in this period of Japan's history contrasting factors were at work keeping the death rates at a constant level. Warfare decreased at the beginning of the Tokugawa period, lowering death rates; but epidemics were introduced, increasing the rates. Similarly death rates increased slightly as cities grew, but the improvements of living standards combated this increase. Malthus was correct in the sense that checks on population were occurring in Tokugawa Japan, however he did not account for the fact that Japan with a completely different culture and set of traditions from Europe, would have had different ‘checks' on the population working in opposition to the ones he proposed. A picture is now appearing of life in Tokugawa Japan. Fertility levels were low; mortality levels were high and fluctuating at the start of this period but then decreased towards the end. These two demographic variables can account in part for the population remaining constant for so many years, but it is not exactly in accordance with what Malthus thought about Japan. In reality Japan was much more akin to England in terms of its demography than China. Malthus was wrong in this case as well. He presumed Japan to be dissimilar to European countries and because of its locality in relation to China, to be much more alike it neighbouring country. Malthus had some general thoughts on population, not specific to Japan, but which are also wrong in Japans case. Malthus believed that ‘man (sic) does not like hard work', and this is why subsistence cannot take keep pace with population. This would ultimately lead to a positive check on population, which Malthus did believe was occurring in Japan. From the time of the Tokugawa period to present day, the people of Japan have shown to have been hardworking, which is represented in the level of their economic success today. From the 17th century agriculture was the main employment sector in Japan. During this century agriculture took off at a vast rate and began to keep pace with the growing number of mouths. As the population slowed and productivity continued to increase, the per capita food supply also increased. Small-scale cultivators dominated the agricultural economy in Tokugawa Japan, but this was only the starting point of the economic transitional change in Japan. By the late Tokugawa period, ‘proto-industrialsation', a term referring to the production of goods for distant markets was underway. New technologies spread and output of products such as soy sauce, bean paste and vegetable oil was a substantial proportion of all non-agricultural output. Proto-industialisation was concentrated in rural areas, which meant migration to large cities slowed, which in turn would have affected mortality rates, as mortality was consistently higher in these areas. In this case Malthus was also wrong in his assumptions about Japan. The population did not grow in a geometric ratio whilst the subsistence only grew in an arithmetical ratio. In fact quite the opposite occurred during the Tokugawa period in Japan. Overall it seems Malthus was wrong in most of his assumptions about Japan, such as universally low ages of marriage, moral restraint not being practised and widespread infanticide. However he did touch upon factors that operated in Japan as they did in many other countries at that time, such as family limitation and preventative checks affecting population numbers. In fact given the very little first hand knowledge Malthus actually knew about Japan, the only way his speculations could have been correct would have been purely by chance, which as highlighted is the not the case. Malthus was incorrect in his assumptions about the extent to which population-influencing factors occurred in Japan. Never the less he gave many population historians a foothold to further investigate the demographics of historic Japan.