Dewatering, waterproofing and drainage - Tunnel Engineering: Basics and Additional Services for Design and Construction - page 186

Table 5-3 Overview of water transport through rocks [35].

Rock type Water passage type Water flow

Igneous
Intrusive,
for example granite, syenite
gabbro, diorite

joints, fissures, stratum inter-
faces, fractured zones

dependent on jointing, mostly
low

Extrusive,
for example basalt, phonolite,
quartz porphyry

bubble voids, cooling joints
(extensive in basalt)

dependent on jointing, mostly
low

Tuffs,
for example basalt tuff, diabase
tuff, pumice tuff

relatively high porosity, often
jointed

dependent on jointing, mostly
good

Metamorphic,
for example marble, slate

cleavage planes, fractured
zones, joints

dependent on jointing and
cleavage, mostly low

Sedimentary
Clastic sediments,
for example gravel, sand, silt,
clay

pore channels dependent on the pore size, very

good to low

Chemical sediments,
for example gypsum, salt,
limestone, dolomite

caves, chimneys, pipes, splits,
fractures, fractured zones

depending on jointing and
dissolved voids, seldom large
quantities

Biogenic sediments,
carbonate sediments such as
chalk

mostly low porosity, jointed very variable, mostly low

Siliceous sediments,
for example siliceous shale

low porosity dependent on diag-
nesis, jointed

variable, seldom significant

Organic origin
for example peat, lignite, coal,
anthracite

porosity according to the degree
of coal diagnesis (peat 85 %, li-
gnite 50 %), joints in anthracite,
coal, but also lignite

mostly low

Karst water. Karst water deserves particular mention because it is acutely dangerous
to tunnelling. Chemical dissolution and mechanical erosion by percolating rainwater in
joints and bedding planes can create various patterns of branched underground sinkholes,
which can join to form a complicated system of caves and permeate the karst rock mass in
various stories (Fig. 5-1). Cave channels run along weak zones (for example faults), since
the rocks in fault zones are more fractured and susceptible to dissolution and erosion.
The fine veins turn into main veins, which are fewer in number but indicate much larger
caves (Fig. 5-1 a). Karst water networks are mostly found in dolomite and limestone be-
cause this type of connected water vein can only be found in soluble rocks. Karst forma-
tions can be high-level or low-level (Fig. 5-1 b, c). In high-level karst formations, the wa-
ter only remains in the rock mass for the time it takes to percolate and then appears from