Effects of Joint Spacing on Static Bearing Capacity of Rock Foundations in the case of Punching Failure

In this paper, using distinct element method, static bearing capacity of rock foundations containing one, two or three joint sets is investigated in the case of punching failure. The effect of joint spacing is incorporated in the analyses using a dimensionless factor, named spacing ratio (SR). Different values for SR are selected and variation of bearing capacity versus SR is monitored. Then, the magnitude of SR in which the bearing capacity is not changed significantly, is determined. The findings show that for SR30, joint spacing does not affect bearing capacity, significantly. Hence, SR=30 can be used as a criterion for analysis of rock foundations either as an equivalent continuum or a discontinuous medium. Using this criterion, it will tend to greatly reduce the time required for bearing capacity analysis of rock foundations

Analysis of non-linear strain-softening behaviour around tunnels

This paper studies the influence of non-linear stress-strain of post-failure on the ground response curve of a circular tunnel excavated in rock mass. Thus, the influence of variations of both the quality of rock mass and the confining stress around the tunnel due to the advancement of the tunnel face are addressed on the value of drop modulus. A new procedure is presented to obtain the softening parameter and its critical value, and the accuracy and practical application of the proposed procedure are shown through examples. The effects of variable drop modulus and the value of the critical softening parameter on the ground response curve are investigated. The results show that, to obtain a ground response curve, the variable drop modulus (non-linear behaviour) in the post-failure region can be approximated by a constant drop modulus (linear behaviour post-failure) if it is calculated by using both quality of rock mass before failure and the average value of confinement stress within the plastic regio

Bearing failure modes of rock foundations with consideration of joint spacing

AbstractIn this study, two main failure modes of jointed rock foundations consisting general shear failure and failure due to excessive deformation are discussed. For each of these two modes, the method of determining ultimate bearing capacity is presented and the effect of joint spacing is also examined. For the former mode, an upper bound method of limit analysis is employed, while for the latter one, distinct element numerical modeling is used to investigate the effect of joint spacing on the bearing capacity. The calculations are performed for a rock mass containing two orthogonal joint sets that the orientation angle of the first joint set is 15°, 30° and 45° to the horizontal, respectively. A non-dimensional parameter called “Spacing Ratio” (SR) is used to examine the effect of different joint spacing. This study shows that in the case of general shear failure mode, joint spacing does not have significant effect on the bearing capacity. In the failure mode induced by excessive deformation of the rock mass, for SR<30, increasing the SR results in decreasing the bearing capacity, however, for SR>30, the joint spacing does not significantly affect the bearing capacity

Effect of life review therapy with spiritual approach on the life quality among cancer patients

Background: Cancer as a global problem can affect different aspects of a patient's life. The number of people of all ages suffering from cancer is increasing. Psychological problems and reduction in quality of life are the most important issues among cancer patients. Therefore, the purpose of this study was to determine the effect of life review with spiritual approach on the life quality in cancer patients. Materials and Methods: This clinical trial study was performed on 80 cancer patients in Kashan. Patients were randomly assigned to the two equal groups: the experimental and control groups. The quality of life questionnaire, EORTC QLQ - C30, was completed for both groups before the intervention. Then, six sessions of individual counseling on life review therapy with spiritual approach were held for the experimental group. One week after the last session, the quality of life questionnaire (EORTC QLQ - C30) was completed for both groups again. Results: The mean quality of life scores changed from 27.5 in pretest to 75 in posttest for the experimental group, and from 33.75 in pretest to 21.87 in post-test for the control group. According to the results, the quality of life in the experimental group has significantly increased after the implementation of life review. Conclusion: Life review therapy with spiritual approach can improve quality of life in cancer patients. Therefore, this treatment can be used as an effective way to improve the life quality of these patients

A simplified model to study the behavior of pre-tensioned fully grouted bolts around tunnels and to analyze the more important influencing parameters

This paper develops an analytical method to obtain distribution of the axial force in the pretensioned fully grouted rockbolts around a circular tunnel. For his purpose, the axial force along the bolt is calculated by the assumption of rigid connection between the bolt and rock mass. To include the effect of relative shear displacement, the condition of end boundaries of bolt is focused on i.e. the reduction of the force on the bolt head is calculated through modeling of the flexibilities of its component (washer, plate …) and tunnel surface. Then, this force is simulated by applying a fictitious compressive force on the bolt head. The distribution of this fictitious force along the bolt is obtained to subtract from that of rigid connection. According to a case study, the theoretical prediction of axial force in the passive cases is comparable to the in-situ measured data. The magnitude of pre-tensioning force, delay in installing of bolts, stiffness of bolt head, and rockbolt density are considered as parameters to perform the sensitive analysi

Ultimate bearing capacity of jointed rocks as homogenous media

In this paper, the bearing capacity of a jointed rock foundation was investigated using the code UDEC. The models include two joint sets with variable orientations and different joint spacing. Three values for orientation and joint spacing were selected and bearing capacity analysis was performed for each case. The results obtained from the numerical analyses were compared with the existing solutions in which both the rock matrix and joint properties are considered and then, the ranges in which the UDEC simulation takes the best agreement with the existing methods are specified. In other part of this paper, the effect of joint normal and shear stiffnesses on the bearing capacity was investigated. Results of this part show that the joint normal and shear stiffnesses don't have very significant effects on the bearing capacity of rock masses. The results obtained in this research show that by increasing the number of joints beneath the foundation, the bearing capacity will be reduced

Rock pillar stress analysis to obtain effective dimensioning and guarantee the mining void stability

In the room and pillar mining method, dimensioning of the pillars is of fundamental importance. Nowadays, the area of influence method is typically used for dimensioning of the pillars; however, over-dimensioning or critical stability conditions can happen in this method. A parametric analysis with three-dimensional numerical modelling was carried out to study the stress conditions of rock pillars in details. This helped to identify a critical point, where the minimum local safety factor was reached, at the corners of the pillar close to the roof of the mining room. Through the estimation of the major principal stress at the critical point, it was possible to evaluate the minimum local safety factor through the geometric and geomechanical parameters of the problem. The dimensioning of the pillars through the local safety factor at the critical point helps to avoid over-dimensioning and static problems, which can occur when simplified calculation methods are used. The use of the proposed figures can allow a fast pre-dimensioning of the pillars, leaving the more detailed numerical modelling only for the found geometric configuration