|FINITE ELEMENT ANALYSIS OF WEAK ROCK UNDERCUT REINFORCED WITH SOIL NAILS
A hard rock cavern is usually self-standing and stable with a full crown. However, for an undercut in very weak to weak limestone, additional support was required to make it stable and safe.
This paper presents a case study of using soil nails to stabilize an undercut in weak sedimentary rock supporting a traffic deck foundation. The undercut behavior was analyzed with a finite element program for both Ultimate Limit State stability and Serviceability Limit State taking into account the soil nails. The analyses confirmed the need for soil nails to stabilize the undercut under traffic loads applied at the top and was used to adopt soil nail pattern.
Modelling aspects, undercut behavior and movement monitoring results are presented and discussed in this paper. Total monitored movements after 2 years were about 40% of predicted movements.
Effect of flexural and axial stiffness of plate elements onto soil nail axial load was also investigated.
Neglecting flexural stiffness resulted in slight load redistribution with load reduction in heavier loaded nailsof less than 5%, which is not significant for practical purposes. Further parametric analysis of influence of flexural and axial stiffness on the axial force indicated changes in the axial force of up to 5% which is also not significant for practical purposes. This is in agreement with methodologies for soil nail design adopted in standards and engineering manuals.
Undercut, Finite Element Analysis, Weak Rock, Soil Nails.
|PIJESAK KAO GEOTEHNIČKI MATERIJAL KOD STABILIZACIJE KOSINA
Pijesak, veoma jeftin materijal, rijetko se koristi u svrhu stabilizacije kosina. Stabilnost kosina najčešće predstavlja složen inženjerski poduhvat, kako zbog složenosti radne sredine tako i zbog velikih investicionih troškova.
U radu je prikazano istraživanje mogućnosti upotrebe kvarcnog pijeska, kojeg na Rudniku Šikulje ima u ogromnim količinama, u svrhu izgradnje nasipa kao geotehničke konstrukcije. Nasip ima ulogu da stabilizira unutrašnje odalgalište. U radu su prikazane varijante miješanja pijeska sa drugim materijalima kao industrijski otpad i portland cement. Urađene su mješavine pijeska, sa bijelim i crnim morem iz Tvornice sode Lukavac, glinom sa Rudnika Šikulje i cementom iz Tvornice cementa Lukavac. Utvrđena je optimalna geotehnička konstrukcija koja se sastoji iz glavnog i pomoćnog nasipa. Glavni nasip bi se radio od kvarcnog pijeska, čija je cijena ugradnje relativno niska.
Drugi, pomoćni nasip bi se gradio od niskokvalitetnog betona čije bi komponente bile rovni kvarcni pijesak i cement.
odlagalište, kosina, površinski kop, geotenička konstrukcija, mješavine matrerijala, kvarcni pijesak
|DEVELOPMENT OF “LUMPED MASS DAMPER MODEL“ TO PREDICT FAILURE TIME AND VELOCITY OF LANDSLIDE
The authors developed a simulation model using viscous damping to predict the moving velocity of landslide before it reaches a strain limit and named this model „Lumped mass damper model“. Even if LMDM is very simple model based on the motion equation incorporating viscous damping, it is clarified that the analysis of landslide behavior using this LMDM is suitable method to predict the velocity and further displacement of landslides induced by not only increasing groundwater level but also by terrain modification. Furthermore, LMDM is newly improved using tank model for prediction of landslide displacement corresponding to rainfall. As a result of a lot of case studies on landslide displacement using LMDM analyses, it is found that the results of LMDM analyses are closely related to observation data of displacement up to a certain time, however they deviate after this time point. These deviation points might represent the limit strains. In order to solve this probelm of deviation, the authors modified LMDM with introduction of reduction functions on φ and Cd parameters. There is a possibility to predict not only moving velocity of landslide but also failure time of landslide using analysis results by this modified LMDM.
Lumped mass damper model, Moving velocity, Displacement, Damper, Mass system model, Reduction function
| HARMONIZING ENGINEERING GEOLOGY WITH ROCK ENGINEERING FOR ASSESSING ROCK SLOPESTABILITY: A REVIEW OF CURRENT PRACTICE
Progresses in understanding, analysis and control of rock slope movements have been the result of interdisciplinary efforts involving engineering geologists and rock engineers. In addition to rock engineeringmethodologies, the inputs from engineering geology are absolutely a fundamental to any rock slope design. This paper aims to emphasize the importance of harmonizing engineering geology with rock engineering on stability ofnatural and engineered rock slopes. The main engineering geological factors featured in the design and construction of rock slopes, role of engineering geological and hydrogeological conceptual models and their combination with the stability analysis methods used in rock slope engineering, input parameter selection, current back-analysis techniques and movement monitoring methodsare briefly discussed through some real cases selected from practice and on hypothetical examples.
Rock slope stability, engineering geology, rock engineering, back-analysis, movement monitoring, slope design, engineering geological model, hydrogeological conceptual model