NATM or New Austrian Tunneling Method has been for long time under scrutiny. Many disagree that was “NEW” in 1957 (Kovari 2003, Jaeger 1979) when it was introduced by L. von Rabcewicz. Many more have disagreed with the term “METHOD” such as Kovari 1993. The term “NEW” was introduced by Rabcewicz to distinguish what he … Continue reading NATM is it New, Austrian or a Method?
When tunnels are excavated with conventional drill and blast operations or via mechanical excavation for softer material, the quickest way to support is the use of shotcrete. This method is called Sprayed Concrete Lining (SCL) in the UK and in other countries it is named as New Austrian Tunneling Method (NATM). In reality NATM is … Continue reading Fiber reinforced shotcrete or wire mesh for tunnel support
Things to remember when using the Mohr – Coulomb failure criterion: The linear failure envelope is just an approximation to simplify calculations The failure envelope is stress dependent and will produce some kind of curvature if shear strength tests are executed in much different confining stresses (fig 1, from Duncan and Write, 2005). According … Continue reading Mohr – Coulomb failure criterion continued
This is something that all geotechnical engineers should know but it is surprising how many do not! Just a brief overview of how the Mohr – Coulomb strength criterion came about. The Mohr – Coulomb criterion is the outcome of inspiration of two great men, Otto Mohr born on 1835 and passed away on 1918 … Continue reading The Mohr – Coulomb strength criterion
One of the largest mine landslides in Utah is presented in this story by ksl.com. Also read the relevant blogs: Slope stability and scale effects, Slope failures, landslides and mines
In previous entries the issue of stiff fissured clays and the time to failure was briefly touched. The design of such slopes is not a trivial matter and requires significant knowledge of soil mechanics, geology, hydrogeology etc. One additional issue mentioned (one that sometimes is neglected) is the scale effect. This was presented in the … Continue reading Slope stability and scale effects
On 11 of April 2013, around 9:30 p.m. a large slide (maybe the largest) in the northeast section of the Kennecott mine occured (fig 1). The slide was preceded by slope movements that reached ~50mm per day. Two major questions could be raised, why this slide occurred and could it have been predicted before hand … Continue reading Slope failures, landslides and mines
Lately the subject of sinkholes has appeared on press due to a fatal incident in Florida USA and several incidents in Samara Russia. In the first case a man sleeping in his bedroom in Tampa Florida, disappeared when a 5 – 10m diameter sinkhole opened suddenly under his house. The estimated depth of the sinkhole … Continue reading Sinkholes: Is it a natural or man induced hazard?
Coming back to the issue of stiff fissured clay slopes, one very important question is the standup time of a slope excavated or formed (natural erosion etc) with higher inclination than the one that would be the outcome using fully softened shear strength. Skempton (1970) in his paper “First time slides in over consolidated clays”, … Continue reading How long can stiff fissured clay slopes stand?
IAEG (International Association for Engineering Geology) organizes the XII Congress that will be held in Torino (Italy) from 15 to 19 September, 2014. The topic of the IAEG XII Congress is: “Engineering Geology for Society and Territory” and aims to explore and analyze the role of Engineering Geology. There are four main themes offered … Continue reading IAEG XII Congress: Engineering Geology