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Unformatted text preview: C E M 6 2 C o n s t r u c t i o n M e t h o d s CEM 602 Construction Methods Lecture 7 Rock Excavation 1 L e c t u r e 7 R o c k E x c a v a t i o n C E M 6 2 C o n s t r u c t i o n M e t h o d s Ripping Rock 2 L e c t u r e 7 R o c k E x c a v a t i o n C E M 6 2 C o n s t r u c t i o n M e t h o d s Rippers • Rippers are special tools attached to crawler tractors • Rippers vary in configuration for different tractor sizes • Variation is in configurations and linkage design change penetration depth and attach angle • Large tractors with significant power and tractive force can have penetration depth of 45 ft 3 L e c t u r e 7 R o c k E x c a v a t i o n C E M 6 2 C o n s t r u c t i o n M e t h o d s Rippers • Ripper have a narrow profile and are pulled by the tractor to loosen soil • Motor grades and some loaders can also by equipped with rippers 4 L e c t u r e 7 R o c k E x c a v a t i o n C E M 6 2 C o n s t r u c t i o n M e t h o d s Rippers • Recent advancement that increase the ability to rip rock – Heavier and more powerful tractors – Improvements in rippers (Impact rippers) – Better instruments for determining rock rippability 5 L e c t u r e 7 R o c k E x c a v a t i o n C E M 6 2 C o n s t r u c t i o n M e t h o d s Determining Rippability • First step in rock excavation is determining rock rippability (can be plowed) • Rippability is determined first before deciding on drilling and blasting • Evaluation of rippability involves determining the rock type and density – Igneous rocks (Granite and Basalt) are impossible to rip – Sedimentary rock is easier to rip because of its layers 6 L e c t u r e 7 R o c k E x c a v a t i o n C E M 6 2 C o n s t r u c t i o n M e t h o d s Determining Rippability • Physical characteristics that favor ripping – Fractures, faults, and joints – Weathering – Brittleness and crystalline structure – High degree of stratification or lamination – Large grain size • Rippability of most rock types is related to speed at which siesmic (sound) waves travel through the rock • The method used for determining rippability 7 L e c t u r e 7 R o c k E x c a v a t i o n C E M 6 2 C o n s t r u c t i o n M e t h o d s Determining Rippability • Refraction seismographic methods depend on Snell’s law which determines how a wave refracts when it passes the boundary between two materials • Compression waves (pwaves) – Travel faster than shear waves (swaves) – Reflects and/or refracts across the boundary depending on velocity of material • Refracted waves travel along the boundary and not to lower layer 8 L e c t u r e 7 R o c k E x c a v a t i o n C E M 6 2 C o n s t r u c t i o n M e t h o d s Determining Rippability • Measuring the refracted waves allows seismic velocity to be determined 9 L e c t u r e 7 R o c k E x c a v a t i o n C E M 6 2 C o n s t r u c t i o n M e t h o d s Determining Rippability • Rocks with low velocity (less than 7000 ft/sec) are rippable...
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This note was uploaded on 03/17/2012 for the course CEM 602 taught by Professor Amrkandile during the Spring '10 term at American University in Cairo.
 Spring '10
 AmrKandile

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