http://swrh.whu.edu.cn/dianqing/images/pdf-files/Time-dependent_system_reliability_of_anchored_rock_slopes_considering.pdf

Time-dependent system reliability of anchored rock slopes considering rock bolt corrosion effect

Imprecise probability analysis of steel structures subject to atmospheric corrosion

This paper presents a numerical approach to study the damage evolution of secondary tunnel lining under the combined actions of corrosion of the preliminary support and the creep deformation of the surrounding rock. This improved numerical approach contains three main models for: (1) tensile failure of corroding rock bolt; (2) yielding of corroding supporting steel arch; and (3) elastoplastic damage of secondary tunnel lining. The corroded rock bolt's failure criterion under tension, the yield criterion of a corroded steel arch under combined compression and bending actions were developed and programmed using FLAC3D's FISH language programming. For the secondary lining failure, a Mohr-Coulomb criterion with a damage formulation based on a statistical damage distribution model was adopted. The validity of the models was verified, and the mechanical response of the supporting structures was investigated. The results showed that: (1) a combined strength envelop can reasonably simulate the mechanical behavior of the steel arch under pure compression, pure bending, and compression-bending action; (2) the corrosion fracture criterion of the rock bolt can adequately reflect rock bolt axial force development process of nonlinear increase and decrease, and failure with the increase of axial strain; (3) damage of concrete can be adequately described by the damage constitutive model, with the damage parameters exerting a strong influence on the post-peak behavior of concrete; and (4) the damage level of the plastic zone at the same location in secondary lining for the corrosion yield model is larger than that predicted from the original FLAC3D structural models.

Study on the damage evolution in secondary tunnel lining under the combined actions of corrosion degradation of preliminary support and creep deformation of surrounding rock

Drapery meshes are protection devices installed on a cliff for mitigating rockfall hazard. They can prevent the detachment of rock fragments and control the dynamics of the falling blocks. During their design working life, drapery meshes are subjected to ageing phenomena, corrosion and impact, which can invalidate the purposes of the protection devices. A novel procedure based on a multi-hierarchical assessment of the damages is proposed. The approach is tailored for two technologies well diffused in the Alps. The main components of the system are identified and the effects of each potential damage on the overall behaviour are taken into account through risk analysis approached. A site campaign serving to test the procedure is described. The proposed approach can be modified to consider other drapery mesh installation types.

/pdf/a-quick-assessment-procedure-to-evaluate-the-degree-of-lbklvmsa1p.pdf

A quick-assessment procedure to evaluate the degree of conservation of rockfall drapery meshes

The corrosion of prestressed rock bolts (PRBs) has become a serious problem threatening the durability of prestressed anchorage structures during their service. This paper aims to investigate the corrosion damage mechanisms of the free lengths of PRBs subjected to an aggressive environment. During the experiment period, the corrosion behavior of the rock bolts was analyzed considering the influence of prestress under different pH (4, 5, 6, 7, and 8) amounts and several oxygen flow rates (OFR, 0 cm3/min, 40 cm3/min, 80 cm3/min, 120 cm3/min, and 160 cm3/min). Based on the electrochemical analysis, a corrosion rate (CR) development model of the PRBs related to the OFR was developed. The results indicated that the prestress had a great influence on the corrosion of the rock bolts. In the process of corrosion, the PRBs were in an activated state, and no passivation region was formed all the time. The corrosion degree of PRBs increased remarkably with an OFR ranging from 0 cm3/min to 80 cm3/min, and then it reached a threshold value. Additionally, the CR increment was insensitive to the OFR when the pH value was constant. It was observed that the loss rate of the ultimate elongation was larger than the other mechanical properties such as the ultimate tensile load loss rate and the elastic modulus. The effective stress loss of the PRBs under different conditions indicated that more attention is needed to be given to the specimens immersed in solutions with an OFR greater 40 cm3/min and pH lower than 6.

Corrosion Damage Behavior of Prestressed Rock Bolts under Aggressive Environment

Time-dependent reliability of rock-anchored structures

A research program at the University of Colorado at Boulder investigated time-variant reliability assessment of concrete gravity structures founded on rock for different loading conditions. In the course of this investigation, a methodology was developed for reliability analysis of anchored monolith structures under corrosion effects. This paper presents a brief overview of the methodology for time-variant reliability assessment of existing concrete gravity structures under corrosion effects.

/pdf/reliability-of-anchored-monolith-structures-under-corrosion-5fj4ez7psf.pdf

Reed L. Mosher

Papers

Time-dependent reliability of rock-anchored structures

Reliability of Anchored Monolith Structures under Corrosion Effects