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Lecture 7- Rock Excavation - CEM 602 Construction Methods...

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C E M 6 0 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
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C E M 6 0 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
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C E M 6 0 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 4-5 ft 3 L e c t u r e 7 - R o c k E x c a v a t i o n
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C E M 6 0 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
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C E M 6 0 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
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C E M 6 0 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
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C E M 6 0 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
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C E M 6 0 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 (p-waves) Travel faster than shear waves (s-waves) 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
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C E M 6 0 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
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C E M 6 0 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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