The comparison study of the monopole tower foundation using CPT and laboratory data in Gresik district, East Java-Indonesia

In the millennial era, the development of information and communication technology is very fast, one of the telecommunications infrastructure is a monopole type telecommunications tower. This type of tower is one of 3 types of telecommunication towers whose main construction is made of steel. The monopole structure is supported by a tread foundation, which is one type of shallow foundation. The main factor in the design of the tread foundation is the bearing capacity factor. Calculation of foundation bearing capacity can be done directly in the field using Sondir data (CPT) and indirectly using laboratory data. In this study a study was conducted to compare the carrying capacity of monopole foundations between field data methods in the form of Sondir data or CPT with result data. Soil tests in the laboratory calculated with the Terzaghi formula. The research location was carried out in Gresik Regency, East Java Province, Indonesia at 3 sites, namely: Mojosarirejo, Kembangan Kebomas and Setromenganti. The results of the comparison of the calculation of the bearing capacity of the foundation (Q) at the Mojosarirejo site with the type of sandy soil. value of QSondir < 9.58 % of Qterzaghi. At the Krembangan Kebomas site with brown clay and gravely clay, the Q value was < 69.93 % of the Qterzaghi and at the Setromenganti site with brown clay soil type with the influence of water level depth – 1 m, the Q value was < 27, 62% of Qterzaghi. From the comparison of the average calculation in the 3 study locations, the bearing capacity of QSondir treads foundation is 26.50 % smaller than Qterzaghi, so the use of Sondir data is more accurate for use in tread foundation planning and provides greater security assurance for the tower foundation structure. monopole type

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Determination of bearing capacity of shallow foundations without using superposition approximation

Canadian Geotechnical Journal ◽

10.1139/t02-105 ◽

2003 ◽

Vol 40 (2) ◽

pp. 450-459 ◽

Cited By ~ 18

Author(s):

D Y Zhu ◽

C F Lee ◽

K T Law

Keyword(s):

Bearing Capacity ◽

Field Method ◽

Ultimate Bearing Capacity ◽

Shallow Foundation ◽

Closed Form Expression ◽

Safe Side ◽

Superposition Approximation ◽

Bearing Capacity Factor ◽

Rigorous Procedure

The Terzaghi superposition assumption has been widely used to determine the bearing capacity of shallow footings. Although this assumption always errs on the safe side, a rigorous procedure to calculate the bearing capacity is still of engineering value. This paper presents such a procedure that is free from errors as a result of the superposition assumption. It demonstrates that the ultimate bearing capacity can be precisely expressed by the Terzaghi equation, except that the bearing capacity factor Nγ is dependent upon the surcharge ratio. A recently developed numerical method, i.e., the critical slip field method, is used to calculate the modification coefficient for modifying Nγ. It is found that this modification coefficient increases with the surcharge ratio at small values of surcharge ratio and then remains constant for large values of surcharge ratio. However, the errors invoked by the superposition assumption do not exceed 10%. On the basis of numerical calculations, a simple closed-form expression of the modification coefficient is proposed that yields the theoretically rigorous ultimate bearing capacity. In the later part of the paper, errors in bearing capacity calculations owing to the use of conventional procedures are analyzed. It is concluded that the continued use of conventional procedures is justified, but the inherent errors should not be neglected in assessing the performance of shallow foundations.Key words: shallow foundation, strip footing, ultimate bearing capacity, critical slip field.

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A numerical study of the bearing capacity factor Nγ

Canadian Geotechnical Journal ◽

10.1139/t01-023 ◽

2001 ◽

Vol 38 (5) ◽

pp. 1090-1096 ◽

Cited By ~ 27

Author(s):

D Y Zhu ◽

C F Lee ◽

H D Jiang

Keyword(s):

Bearing Capacity ◽

Numerical Solutions ◽

Numerical Study ◽

Limit Equilibrium ◽

Failure Surface ◽

Shallow Foundation ◽

Capacity Factor ◽

Foundation Engineering ◽

Base Angle ◽

Bearing Capacity Factor

Values of the bearing capacity factor Nγ are numerically computed using the method of triangular slices. Three assumptions of the value of ψ, the base angle of the active wedge, are analyzed, corresponding to the following three cases: (1) ψ = ϕ, the internal friction angle; (2) ψ = 45° + ϕ/2; and (3) ψ has a value such that Nγ is a minimum. The location of the critical failure surface is presented and the numerical solutions to Nγ for the three cases are approximated by simple equations. The influence of the base angle on the value of Nγ is investigated. Comparisons of the present solutions are made with those commonly used in foundation engineering practice.Key words: shallow foundation, bearing capacity, bearing capacity factor, limit equilibrium.

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Seismic Bearing Capacity Factor Considering Composite Failure Mechanism

International Journal of Geotechnical Earthquake Engineering ◽

10.4018/ijgee.2018010104 ◽

2018 ◽

Vol 9 (1) ◽

pp. 65-77

Author(s):

Swetha S Kurup ◽

Sreevalsa Kolathayar

Keyword(s):

Bearing Capacity ◽

Failure Mechanism ◽

Static Analysis ◽

Limit Equilibrium ◽

Failure Surface ◽

Shallow Foundation ◽

Capacity Factor ◽

Composite Failure ◽

Seismic Bearing Capacity ◽

Bearing Capacity Factor

This article describes how the design of shallow foundation needs complete knowledge about bearing capacity. During earthquakes additional lateral force acts at the foundation bed which reduces the bearing capacity. Most of the literature present either the pseudo static analysis or assume a planar failure surface to estimate seismic bearing capacity factors. Here, a pseudo dynamic approach that considers the time dependent effect of earthquake loading is employed. A composite failure surface has been considered for a more realistic estimation of seismic bearing capacity. New expressions were formulated to arrive at the seismic bearing capacity factor, considering the forces acting on the failure wedge based on the limit equilibrium approach. The effect of soil friction angles and the seismic peak of horizontal ground accelerations on the seismic bearing capacity were studied using the proposed method. It was observed that present pseudo-dynamic analysis with a composite failure mechanism gives lower values of seismic bearing capacity factors when compared to pseud- static analysis.

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