Applied Geology: Engineering, Hydrogeology and Environmental Geology
What the domain covers
Applied Geology: Engineering, Hydrogeology and Environmental Geology tests how geological materials behave in construction, how groundwater occurs and moves, and how mining and development affect the environment. Expect aquifer terms, Darcy's law, bearing capacity, landslides and pollution.
Core rules
- Engineering properties include porosity, permeability, strength, compressibility and bearing capacity. Weak shales, expansive clays and weathered basalt require careful foundation design.
- An aquifer stores and transmits water; an aquitard transmits slowly; an aquiclude is impermeable; an aquifuge is neither porous nor permeable. The water table is the upper limit of saturation in an unconfined aquifer.
- Groundwater flows from high to low hydraulic head. Darcy's law is Q = K i A, where Q is discharge, K is hydraulic conductivity, i is hydraulic gradient and A is cross-sectional area.
- Environmental issues include groundwater over-abstraction, saline intrusion, mine drainage, waste leachate and landslide hazard.
Worked example
An aquifer has K = 10 m/day, hydraulic gradient i = 0.01 and cross-sectional area A = 100 square metres. Using Darcy's law, Q = 10 times 0.01 times 100 = 10 cubic metres per day. The reasoning keeps units consistent and uses the hydraulic gradient, not the depth to water table. A higher K or steeper gradient would increase discharge.
Traps
Porosity is not permeability; a clay may be porous but nearly impermeable. In a confined aquifer the potentiometric surface, not the water table, indicates head. Do not confuse specific yield with total porosity. Over-abstraction can cause subsidence and saline intrusion.