Bearing Capacity Of Rock Mass Research Articles

Distinct element simulation of ultimate bearing capacity in jointed rock foundations

In this paper, distinct element method numerical modeling is applied to evaluate bearing capacity of strip footing rested on anisotropic discontinuous rock mass. As yet, a little work has been carried out to investigate the effect of joint set orientation on the bearing capacity of rock mass. Generally, the overall behavior of rock mass under loading is very complicated and such analysis should include deformation determination, sliding along discontinuities and failure of rock material. Failure mechanism of rock mass depended on both geometrical parameters of joint sets and strength parameters of rock mass. In this research, it is assumed that rock mass contains one joint set, and therefore the anisotropy in bearing capacity and rock behavior is only due to the existence and orientation of the joint set. In this study, by assuming constant strength parameters and using Mohr–Coulomb failure criterion for the single joint set and nonlinear Hoek–Brown failure criterion for rock material, variation of the bearing capacity values and the type of failure mechanism of rock mass with different joint set dips is investigated. The obtained results indicate that the ultimate bearing capacity of rock mass containing one joint set varies between 27 and 86 % of intact rock.

Comparative Bearing Capacity Analysis of Spread Footing Foundation on Fractured Granites

It is evident from several studies that ultimate bearing capacities calculated by traditional methods are conservative and subjective. For large civil structures founded on spread footings, cost-effective and safer foundation could be achieved by adopting optimum ultimate bearing capacity values that are based on an objective and pragmatic analysis. There is a pressing need to modify the existing methods for accurate estimation of the bearing capacities of rocks for spread footings. In practice, foundation bearing capacities of rock masses are often estimated using the presumptive values from Building Officials Code Administrators, National Building Code, and methods adopted by the American Association of State Highway and Transportation Officials. However, the estimated values are often not realistic, and site-specific analyses are essential. In this study, geotechnical reports and drill-log data from successful geotechnical design projects founded on a wide range of granites in eastern Tennessee were consulted. Different published methods were used to calculate ultimate bearing capacity of rock mass. These methods included Peck, Hansen and Thornburn, Hoek and Brown, Army Corps of Engineers, Naval Facilities Engineering Command, and Terzaghi's general bearing capacity equations. Wide variation was observed in the calculated ultimate bearing capacity values, which ranged over about two orders of magnitude. Only two of the methods provided realistic results when validated with plate-load test data from similar rocks.

Limit analysis solutions for the bearing capacity of rock masses using the generalised Hoek–Brown criterion

This paper applies numerical limit analyses to evaluate the ultimate bearing capacity of a surface footing resting on a rock mass whose strength can be described by the generalised Hoek–Brown failure criterion [Hoek E, Carranza-Torres C, Corkum B. Hoek–Brown failure criterion—2002 edition. In: Proceedings of the North American rock mechanics society meeting in Toronto, 2002]. This criterion is applicable to intact rock or heavily jointed rock masses that can be considered homogeneous and isotropic. Rigorous bounds on the ultimate bearing capacity are obtained by employing finite elements in conjunction with the upper and lower bound limit theorems of classical plasticity. Results from the limit theorems are found to bracket the true collapse load to within approximately 2%, and have been presented in the form of bearing capacity factors for a range of material properties. Where possible, a comparison is made between existing numerical analyses, empirical and semi-empirical solutions.

２次元弾性解と個別要素解析によるトンネル支保特性曲線の考察

Active mobilization of bearing capacity of rock mass surrounding an underground opening characterizes the NATM (New Austrian Tunneling Method) concept of supporting. There have been many attempts to give quantitative expressions for this capacity but no one has ever completely solved the question. In the first part of this paper the theoretical relations between support pressure and tunnel wall displacements are briefly discussed. We derive a simplified solution of a circular lined-tunnel in an elastic ground under the plain strain for full-slip and no-slip conditions. These two conditions at the ground-lining interface make it possible to explain the effects of shear stress transmission and relative shear displacement. The lateral free-field ground stresses for this solution are restricted to a fixed value of the vertical stresses (σV*=-p, σH*=-kp). An actual tunnel opening is excavated and supported after the load corresponding to the free-field stresses. We introduce an assumption of the actual “excavation unloading” conditions that occur during tunneling. By advancing this derivation, the strict solution is utilized successfully to construct a theoretical characteristic curve of tunneling. The characteristic curve shows clearly the bearing capacities of a tunnel lining, the surrounding ground and the total by using an index, “relative-support-stiffness”.The elastic theory of the stress distribution around tunnels demonstrates that the deviatoric stresses are maximum at the periphery of the excavation. Therefore, the rock mass may yield in the overstressed zone surrounding the excavation. Discussion here should include the dependence of the characteristic curve on the zone of yielded ground and the discontinuity in the ground. We have carried out numerical simulations for a discontinuous ground with Distinct Element Modeling. The realistic ground reaction curves by the analyses are examined with the theoretical solution derived above. We will learn that while the ground may work, more or less, as a load bearing structural component to the load corresponding to the free-field stresses, overestimation must be avoided.

Corrigendum to “Ultimate bearing capacity of rock masses based on the modified Hoek–Brown criterion”

Corrigendum to “Ultimate bearing capacity of rock masses based on the modified Hoek–Brown criterion”

Ultimate bearing capacity of rock masses based on the modified Hoek–Brown criterion

Ultimate bearing capacity of rock masses based on the modified Hoek–Brown criterion

Ultimate bearing capacity of rock masses : A. Serrano & C. Olalla, International Journal of Rock Mechanics & Mining Sciences, 31(2), 1994, pp 93–106

Ultimate bearing capacity of rock masses : A. Serrano & C. Olalla, International Journal of Rock Mechanics & Mining Sciences, 31(2), 1994, pp 93–106

Ultimate bearing capacity of rock masses

The determination of the ultimate bearing capacity of spread foundations on rock masses has traditionally been considered taking into account previous experience, using empirical criteria or applying local or national codesAR1]. This paper defines a methodology for bearing capacity quantification based on the Hoek and Brown rock failure equations and by applying the characteristics method for resolving the differential equation systems which govern the stress field. Reference is made to the works of both Sokolovskii [3] and Serrano [4] in solving the plasticity problem. Three different regions of the characteristic lines are considered, two of which are of the Karman type, the third being of the Prandtl type. The boundary conditions defined by the external load system and the geometrical configuration are incorporated, allowing for a closed form solution. In this paper, gravity rock masses will not be considered. Therefore, the required data are: the type of rock, the uniaxial compressive strength of the intact rock and the Bieniawski classfication (RMR parameter). To facilitate an overall understanding of the procedure, and example problem is solved showing how the initial data are used and illustrating the intermediate steps involved.

The Vane Test in Organic Soils: Discussion

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