ĐỊA CHẤT THỦY VĂN VÀ THOÁT NƯỚC MỎ BÀI GIẢNG MÔN HỌC nhieu.dcct@gmail.com 23/09/2009 11:00:23 AM nhieu.dcct@gmail.com 23/09/2009 AM 11:00:23 nhieu.dcct@gmail.com 23/09/2009 AM 11:00:23 nhieu.dcct@gmail.com 23/09/2009 AM 11:00:23 nhieu.dcct@gmail.com 23/09/2009 AM 11:00:23 nhieu.dcct@gmail.com 23/09/2009 AM 11:00:23 nhieu.dcct@gmail.com 23/09/2009 AM 11:00:23 Saltwater contamination due to excessive well pumping nhieu.dcct@gmail.com 23/09/2009 AM 11:00:23 Sinkholes in Urban Settings nhieu.dcct@gmail.com 23/09/2009 AM 11:00:23 nhieu.dcct@gmail.com 23/09/2009 AM 11:00:23 10 Aquifer Characteristics Let’s Let s consider an aquifer instead of a column We are interested in the rate, and also the amount of water that can be transmitted Q = -KA (( h / L) 109 nhieu.dcct@gmail.com 23/09/2009 12:56 CH Q = -KA ( (h / L) Need Mechanism to Compare p Aquifers q Assume Unit Width Assume Hydraulic Gradient of Plug Into Darcy’s Law Transmissivity y T = KB T = transmissivity (L2/T) K = hydraulic conductivity (L/T) B = saturated thickness of aquifer (L) Measure of the amount of water that can be transmitted horizontally through a unit width by the full f saturated thickness off the aquifer f under a hydraulic gradient of 23/09/2009 12:56 CH 110 nhieu.dcct@gmail.com When We Pump A Well Where Does the Water Come From? Storage g coefficient or storativity y ((S)) volume of water that a permeable unit will absorb or expel from storage per unit surface area per unit change in head Unconfined System Drainage of the Pores Specific Yield 111 nhieu.dcct@gmail.com 23/09/2009 12:56 CH Confined System If potentiometric surface changes, water will be expelled p or stored But Pores aren’t aren t Draining? Where is the Water Coming From? 112 nhieu.dcct@gmail.com 23/09/2009 12:56 CH Think of a Tire Filled with air under pressure we release it System is Elastic it is still filled with air Skeleton If pressure increases, Mi Mineral l skeleton k l t will ill expand d Water will contract P If pressure drops, Mineral skeleton will contract Water will expand P Expansion p of Water Wh P When Pumping i Reduce the Pressure nhieu.dcct@gmail.com Water 113 Compaction of the 23/09/2009 12:56 CH Aquifer Skeleton Specific Storage (Ss) elastic storage coefficient amount of water per unit volume of a saturated formation that is stored or expelled from storage owing to compressibility of the mineral skeleton and pore water per unit head change Ss = wg( + n) w = density of water g = acceleration of gravity  = compressibility of aquifer skeleton n = porosity  = compressibility of water What contributes more to storage, compressibility of water or compressibility of 23/09/2009 matrix?12:56 CH 114 nhieu.dcct@gmail.com Compressibility of Geologic Materials (m2 N-1) Clay Sand Gravel Shales Sandstones Limestones Igneous/Metamorphic Water ate ((B)) 115 nhieu.dcct@gmail.com 10-6 to 10-8 10-7 to 10-9 10 10-88 to 10-10 10-9 to 10-10 10-10 to 10-11 10-10 to 10-11 10-11 4.4 x 10 0-10 23/09/2009 12:56 CH Storage Coefficient The storage coefficient (S) consists of two components: pore fluid draining of the aquifer water released from compressibility p y of aquifer q For confined aquifers, there is no draining of the pores, so all storage comes from the compressibility component Ss = specific storage (1/L) S = Ss b b = saturated thickness (L) S < 0.005 For unconfined aquifers, most of the water is from draining, contribution t ib ti ffrom compressibility ibilit iis very smallll iin comparison i S = Sy + Ssb usually, Sy >> Ssb S ~ Sy nhieu.dcct@gmail.com Sy = specific yield b = saturated thickness (L) Ss = specific storage (1/L) 116 to 0.30 23/09/2009 12:56 CH S: 0.02 Homogeneous vs Heterogenous Variation as a function of Space Homogeneity – same properties in all locations Heterogeneity hydraulic properties change spatially 117 nhieu.dcct@gmail.com 23/09/2009 12:56 CH Isotropy vs Anisotropy Variation as a function of direction Isotropic same in direction Anisotropic changes with direction 118 nhieu.dcct@gmail.com 23/09/2009 12:56 CH Regional Flow In Humid Areas: Water Table Subdued Replica of Topography In Arid Areas: Water table flatter 119 nhieu.dcct@gmail.com 23/09/2009 12:56 CH Water Table Mimics the Topography Subdued replica ep ca o of topography opog ap y Q = -KA (( h / L) L) Need gradient for flow If water table flat – no flow occurring Sloping Water Table – Flowing Water Fl Flow typically t i ll flflows ffrom hi high h tto llow areas Discharge occurs in topographically low spots 120 23/09/2009 12:56 CH nhieu.dcct@gmail.com Discharge vs Recharge Areas Discharge Upward Vertical Gradient Recharge Downward Vertical Gradient 121 nhieu.dcct@gmail.com 23/09/2009 12:56 CH Di h Discharge Recharge Topographically High Areas D Deeper U Unsaturated t t dZ Zone Flow Lines Diverge nhieu.dcct@gmail.com 122 Topographically Low Areas Sh ll Shallow U Unsaturated t t dZ Zone Flow Lines 23/09/2009 Converge 12:56 CH Contours Reflect Gradient and Direction of Flow Gaining Stream nhieu.dcct@gmail.com 123 Losing Stream 23/09/2009 12:56 CH ... nhieu.dcct@gmail.com 23/09/2009 AM 11:00:24 38 Viện Khoa học Xã hội Nam nhieu.dcct@gmail.com 23/09/2009 AM 11:00:24 39 Sạt lở mỏ đá D3 Thủy điện Bản Vẽ 0,5triệu m3, 18 người chết nhieu.dcct@gmail.com... nhieu.dcct@gmail.com 23/09/2009 AM 11:00:24 40 nhieu.dcct@gmail.com 23/09/2009 AM 11:00:24 Trượt đường đắp vào cầu 41 nhieu.dcct@gmail.com Sạt lở mái23/09/2009 dốc nền11:00:24 AM đường đắp Thái Lan 42 nhieu.dcct@gmail.com