液限ωL：流动状态与塑性状态的分界含水量。
Liquid limit (wL)： water content when state change occurs from plastic to liquid;
塑限ωP：塑性状态与半固体状态间的分界含水量。
Plastic limit (wP) –water content when state change occurs from plastic to semisolid;
缩限ωs：半固体状态与固体状态间的分界含水量。
Shrinkage limit-water content when state change occurs from semi-solid to solid states.
Measures of liquid and plastic limit values can be obtained from laboratory tests.
液限和塑限的值可以从实验室测试中获得。
Water-related geotechnical issues:
•Changes engineering behavior and properties of soil and rock
改变土壤和岩石的工程特性
•Flow into excavations
流入基坑
•Wells
井
•Stability of cut slopes and embankments路堤
路堑边坡和路堤的稳定性
•Uplift forces on buried structures
地下结构的浮力
•Seepage failures
渗流破坏
•Chemical transport
化学传输
What makes ground water move?
–Differences in hydraulic head (the height to which water will rise in an open pipe)
压力水头的差异（开口管道中水上升的高度）
•How fast it moves depends on:
–How easily water can move through the aquifer含水层(hydraulic conductivity)
–The area available for water to move through
fundamental conceptions
(1) Hydrostatic Groundwater Condition (静水条件)
Pore-water pressure (孔隙水压力) at a depth z below the water table where
u=γw ·z 
γw (kN/m3) is unit weight of the water (水的重度)
z (m) is depth (深度) of the water below water table
(2) Total head (总水头)
H=u/γw +z
where h is total head, u/γw is pore-water pressure head and z is elevation head Two piezometers ( 测压计) are installed at A and B. At hydrostatic groundwater condition, levels in both piezometers will be the same, i.e. hA= hB. （水静止）总水头=压力水头pressure head+位置水头potential head
(2) Hydraulic head水头（总水头）
Hydraulic head or piezometric head is a specific measurement of liquid pressure above a geodetic（测地学的）datum. It is usually measured as a liquid surface elevation, expressed
in units of length, at the entrance (or bottom) of a piezometer. In an aquifer（含水层）,it can be calculated from the depth to water in a piezometric well(a specialized water well),and given information of the piezometer’s elevation and screen depth. Hydraulic head can similarly be measured in a column of water using a standpipe piezometer by measuring the height of the water surface in the tuber elative to a common datum（基准面）.The hydraulic head can be used to determine a hydraulic gradient（梯度）between two or more points.
(3) Groundwater flow
Water will flow from A to B if there is a difference between the water levels in the piezometers (in this case hA> hB).
(4) Hydraulic gradient水力梯度
The hydraulic gradient is a vector gradient between two or more hydraulic head measurements over the length of the flow path. A dimensionless无量纲hydraulic gradient can be calculated between two points with known head values as:
Where i：is the hydraulic gradient(水力梯度) (dimensionless无量纲tabletotal函数),
dh：is the difference between two hydraulic heads (Length, usually in m or ft), and dl：is the flow path length between the two piezometers (Length, usually in m or ft)
达西定律（H. Darcy’s law）
Two families of curves:
•Flow lines流线 –Path that water would flow
•Equipotential lines等位线、等势线 –Lines of constant total head
Rules for constructing flow nets:
•Flow occurs in the direction of maximum drop in total head.
–Flow lines and equipotential lines should intersect at 90 deg.
•Cells formed by the flow lines and equipotential lines should have a uniform length to width ratio
Characteristic of stress distribution
the slope of line of geostatic stresses is unit weight；
自重应力分布曲线的斜率为重度。
Geostatic stresses vary linearly with depth in the homogeneous（均质的）soil mass;

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