Temel mühendisliğinde presyometre metodu

Abstract

Po = the horizontal earth pressure in terms of total stress at the depth at which the pressuremeter test was carried out k = a bearing capacity factor Based mainly on experimental evidence and experience, it has been found that the factor k has no unique value, but varies from about 0.8 to 9 depending primarily upon 1) the type of soil and 2) the relative depth of embedment of the foundation. It also depends to a lesser extent on 3) the shape of the foundation and 4) the way in which it is installed. Adhesion or friction along the sides of a foundation such as a pier or a pile is proportional to the net limit pressure, but the physical properties of the surface in contact with the soil are also important, as is the method with which the foundation is installed. Furthermore, designing foundations by using pressuremeter method assumes that there exists a good agreement between the actual performance of structures and the bearing capacity and settlement predictions based on the pressuremeter modulus. The allowable bearing capacity can be calculated from the formula: F where F : safety factor Pi *: net limit pressure And the settlement, s, is usually estimated from the equation: B s = q * 9EM 2B0(Xd- r+od0B On where q* : the net average bearing stress B : the width of the footing B0 : a reference width, usually 60 cm Xd, X: : shape factors which depend on the length to width ratio of the foundation a : rheological factor only for very large foundations and rafts has it been found necessary to modify settlement predictions based on this equation; in other words, for the majority of cases only the pressuremeter modulus is required and not consolidation or other test results. In addition to Em, however, the factor a plays an important role since it varies from 1/4 to 1 depending upon the types of soil and its condition. xxi As a result, the advantages of the pressuremeter method in foundation design are such that it must come into ever increasing use. Those who arrange, control, or pay for foundation engineering services will have to have a basic yet critical understanding of the pressuremeter method. For this reason the pressuremeter and foundation engineering will be useful to architects, construction engineers, and project managers as well as soil mechanics and foundation specialists. Their acceptance of the method will be a further milestone in its development. xxn Po = the horizontal earth pressure in terms of total stress at the depth at which the pressuremeter test was carried out k = a bearing capacity factor Based mainly on experimental evidence and experience, it has been found that the factor k has no unique value, but varies from about 0.8 to 9 depending primarily upon 1) the type of soil and 2) the relative depth of embedment of the foundation. It also depends to a lesser extent on 3) the shape of the foundation and 4) the way in which it is installed. Adhesion or friction along the sides of a foundation such as a pier or a pile is proportional to the net limit pressure, but the physical properties of the surface in contact with the soil are also important, as is the method with which the foundation is installed. Furthermore, designing foundations by using pressuremeter method assumes that there exists a good agreement between the actual performance of structures and the bearing capacity and settlement predictions based on the pressuremeter modulus. The allowable bearing capacity can be calculated from the formula: F where F : safety factor Pi *: net limit pressure And the settlement, s, is usually estimated from the equation: B s = q * 9EM 2B0(Xd- r+od0B On where q* : the net average bearing stress B : the width of the footing B0 : a reference width, usually 60 cm Xd, X: : shape factors which depend on the length to width ratio of the foundation a : rheological factor only for very large foundations and rafts has it been found necessary to modify settlement predictions based on this equation; in other words, for the majority of cases only the pressuremeter modulus is required and not consolidation or other test results. In addition to Em, however, the factor a plays an important role since it varies from 1/4 to 1 depending upon the types of soil and its condition. xxi As a result, the advantages of the pressuremeter method in foundation design are such that it must come into ever increasing use. Those who arrange, control, or pay for foundation engineering services will have to have a basic yet critical understanding of the pressuremeter method. For this reason the pressuremeter and foundation engineering will be useful to architects, construction engineers, and project managers as well as soil mechanics and foundation specialists. Their acceptance of the method will be a further milestone in its development. xxn Po = the horizontal earth pressure in terms of total stress at the depth at which the pressuremeter test was carried out k = a bearing capacity factor Based mainly on experimental evidence and experience, it has been found that the factor k has no unique value, but varies from about 0.8 to 9 depending primarily upon 1) the type of soil and 2) the relative depth of embedment of the foundation. It also depends to a lesser extent on 3) the shape of the foundation and 4) the way in which it is installed. Adhesion or friction along the sides of a foundation such as a pier or a pile is proportional to the net limit pressure, but the physical properties of the surface in contact with the soil are also important, as is the method with which the foundation is installed. Furthermore, designing foundations by using pressuremeter method assumes that there exists a good agreement between the actual performance of structures and the bearing capacity and settlement predictions based on the pressuremeter modulus. The allowable bearing capacity can be calculated from the formula: F where F : safety factor Pi *: net limit pressure And the settlement, s, is usually estimated from the equation: B s = q * 9EM 2B0(Xd- r+od0B On where q* : the net average bearing stress B : the width of the footing B0 : a reference width, usually 60 cm Xd, X: : shape factors which depend on the length to width ratio of the foundation a : rheological factor only for very large foundations and rafts has it been found necessary to modify settlement predictions based on this equation; in other words, for the majority of cases only the pressuremeter modulus is required and not consolidation or other test results. In addition to Em, however, the factor a plays an important role since it varies from 1/4 to 1 depending upon the types of soil and its condition. xxi As a result, the advantages of the pressuremeter method in foundation design are such that it must come into ever increasing use. Those who arrange, control, or pay for foundation engineering services will have to have a basic yet critical understanding of the pressuremeter method. For this reason the pressuremeter and foundation engineering will be useful to architects, construction engineers, and project managers as well as soil mechanics and foundation specialists. Their acceptance of the method will be a further milestone in its development.