ROAD AND RAILWAY CONSTRUCTIONfischersz/Education/Road and railway construction/Rail… · ROAD AND...
Transcript of ROAD AND RAILWAY CONSTRUCTIONfischersz/Education/Road and railway construction/Rail… · ROAD AND...
ROAD AND RAILWAY CONSTRUCTION
MSC COURSE
2016/2017 AUTUMN SEMESTER
RAILWAY SUBSTRUCTURE
SZÉCHENYI ISTVÁN UNIVERSITY Dr. Ferenc HORVÁT professor
1. SET-UP OF RAILWAY TRACK SUBGRADE
1.1 Railway track cross section – single track S
up
ers
tru
ctu
re
Su
bg
rad
e
1. SET-UP OF RAILWAY TRACK SUBGRADE
Single track just after renewal
Single track in operation
Substructure: Generally each part of the railway track belongs to substructure, which has to fulfil
the tasks as below:
- to implement of the railway track position in space,
- to tolerate the forces generated by traffic,
- to give protection against weather influences, meteoric water and groundwater,
- to ensure transition over / under natural and artificial hindrances,
- to ensure connection conditions of level crossing,
- to help to fulfil the tasks of railway service and track maintenance.
Railway track earthwork: The platform upon which the track superstructure is constructed. Mostly
made out of soil material. Task: to distribute the dead weight of railway track and traffic loads.
Top of subgrade: Top level of the compacted earthwork on planned level and with planned
inclination.
Subsoil: Natural soil under earthwork.
Retaining structure: Structure designed to restrain soil to unnatural slopes.
Groundwater level (m): the level of the water table, the upper surface or top of the saturated portion
of the soil or bedrock layer that indicates the uppermost extent of groundwater. It can be expressed
as a height above a datum, such as sea level, or a depth from the surface.
Standard level of groundwater: the measured maximum height + 0,5 m.
Soil replacement: Unacceptable soils (e.g. organic soils, frost sensitive soils) must be removed and
replaced by an acceptable soil.
1.2 Basic definitions
1. SET-UP OF RAILWAY TRACK SUBGRADE
Subgrade improvement: In cases where the subgrade is too weak or has to low stiffness, the
resulting high cost of track maintenance may dictate the need to improve the subgrade conditions.
Alternatives are as below:
o modification of the subgrade properties without removal or disturbance (e.g. grouting),
o modification of properties by reconstruction (e.g. compaction, replacement, admixture
stabilization),
o strengthening of subgrade (e.g. with asphalt concrete layer).
1. SET-UP OF RAILWAY TRACK SUBGRADE
Railway earthwork has to be designed and constructed on the basis of following principles:
- it has to fulfil his task during his lifespan with safety,
- it has to be stable during the construction period and in his final condition as well,
- it can be used for the planed goals economically,
- it has to be avoided the appearance of unacceptable deformations on earthwork surface,
- it has to be resistant against influences of weather, meteoric water and groundwater,
- it has to be technically harmonized with the other constructed adjacent facilities of railway track
(e.g. electric cable conduit, catenary supports),
- it needs only few maintenance and/or repair works in operation,
- it must comply with the environmental and esthetic aspects.
In plan of railway track earthwork has to be determined the requirements of load bearing capacity
and usability correctly.
In support layer of ballasted track has to be avoided or compensated the sharp change in stiffness
(e.g. section between ballasted and ballastless (e.g. mass spring system = MSS) track.
1.3 Formation
1. SET-UP OF RAILWAY TRACK SUBGRADE
2. IMPACTS ON RAILWAY SUBGRADE
2.1 Basic definitions
Action (F)
a) Set of forces (loads) applied to the structure (direct action);
b) Set of imposed deformations or accelerations caused for example, by temperature changes,
moisture variation, uneven settlement or earthquakes (indirect action).
Effect of action (E)
Effect of actions (or action effect) on structural members, (e.g. internal force, moment, stress, strain)
or on the whole structure (e.g. deflection, rotation).
Permanent action (G)
Action that is likely to act throughout a given reference period and for which the variation in
magnitude with time is negligible, or for which the variation is always in the same direction
(monotonic) until the action attains a certain limit value.
Variable action (Q)
Action for which the variation in magnitude with time is neither negligible nor monotonic.
Accidental action (A)
Action, usually of short duration but of significant magnitude, that is unlikely to occur on a given
structure during the design working life.
Geotechnical action
Action transmitted to the structure by the ground, fill or groundwater.
Static action
Action that does not cause significant acceleration of the structure or structural members.
Dynamic action
Action that causes significant acceleration of the structure or structural members.
Quasi-static action
Dynamic action represented by an equivalent static action in a static model.
Load arrangement
identification of the position, magnitude and direction of a free action.
Load case
compatible load arrangements, sets of deformations and imperfections considered simultaneously
with fixed variable actions and permanent actions for a particular verification.
Limit states
States beyond which the structure no longer fulfils the relevant design criteria.
Ultimate limit states
States associated with collapse or with other similar forms of structural failure.
Resistance
Capacity of a member or component, or a cross-section of a member or component of a structure, to
withstand actions without mechanical failure e.g. bending resistance, buckling resistance, tension resistance.
2. IMPACTS ON RAILWAY SUBGRADE
Strength
Mechanical property of a material indicating its ability to resist actions, usually given in units of
stress.
Reliability
Ability of a structure or a structural member to fulfil the specified requirements, including the design
working life, for which it has been designed. Reliability is usually expressed in probabilistic terms.
Serviceability limit states
States that correspond to conditions beyond which specified service requirements for a structure or
structural member are no longer met.
Characteristic value of an action (Fk)
Principal representative value of an action.
Representative value of an action (Frep)
Value used for the verification of a limit state. A representative value may be the characteristic value
(Fk) or an accompanying value (Fk)
Design value of an action (Fd)
Value obtained by multiplying the representative value by the partial factor f.
Combination of actions
Set of design values used for the verification of the structural reliability for a limit state under the
simultaneous influence of different actions.
2. IMPACTS ON RAILWAY SUBGRADE
Stress
Effect of action in a part of supporting structure (e.g. inner force, moment, strain, deformation) or in a
whole structure (e.g. inclination, turning-off).
Zone under pressure
Part of subgrade / natural ground / foundation, attacked by loads originated from railway traffic.
Maintenance
Set of activities performed during the working life of the structure in order to enable it to fulfil the
requirements for reliability.
Repair
Activities performed to preserve or to restore the function of a structure that fall outside the definition
of maintenance.
2. IMPACTS ON RAILWAY SUBGRADE
2.2 Permanent, variable and accidental actions
2.2.1 Permanent load (dead load)
Dead load of railway track has to put on the loaded surface as like an evenly-distributed load.
Dead load in case of ballasted track, if Vd 200 km/h (Vd = design load):
- single track 12,5 kN/m2, in a width of 4,5 m,
- double track 12,5 kN/m2, in a width of 8,5 m.
Load width has to set symmetrically to the track axle (single track) or line axle (double track).
In case of mass spring system the dead load has to be calculated from data of structural geometry
and density of materials used.
2. IMPACTS ON RAILWAY SUBGRADE
2.2.2 Load of vehicle
Static design load signed LM 71 (above)
and equivalent load (below),
parallel with the longitudinal axis of the
track
Equivalent evenly-distributed load,
perpendicular to the longitudinal axis
of the track
Connected line load 80 kN/m can be changed
on a surface load 26,7 kN/m2, with a width of 3
m.
2. IMPACTS ON RAILWAY SUBGRADE
2.2.3 Extraordinary load
Extraordinary loads is the seismic load in case of high earthwork and retaining structure.
2.2.4 Extras
In normal condition in case of geotechnical facilities it isn’t necessary to take account the
temperature effects.
But in case of retaining structures we have to take account the temperature effects, if the harmful
temperature stresses can’t be avoided.
The effect of the longitudinal loads generated by railway vehicles (e.g. breaking) can be neglected,
except supporting and retaining structures (e.g. abutment).
2. IMPACTS ON RAILWAY SUBGRADE
2.2.5 Calculation of dynamic load
Qdyn = (1 + t·s)·Qstat
s = n ·
n = 0,1 … 0,3 (depends on condition of track)
= 1 + (v-60)/140 (velocity factor)
t = 3 (distribution factor, calculation accuracy 99,7%)
2. IMPACTS ON RAILWAY SUBGRADE
2.3 Propagation of vehicle loads
Source material: Lichtberger: Track Compendium
2.3.1. Loaded surfaces and compressive stresses
2. IMPACTS ON RAILWAY SUBGRADE
2.3.2 Vertical stresses in layer construction under the sleeper
Source material: Lichtberger: Track Compendium
2. IMPACTS ON RAILWAY SUBGRADE
2. IMPACTS ON RAILWAY SUBGRADE
2.3.3 Vertical stresses in layer construction under the sleeper, taking account the adjacent
sleepers as well
Material source: Göbel: Der Eisenbahnunterbau
2. IMPACTS ON RAILWAY SUBGRADE
Vertical stresses on plane of ballast and on plane of subgrade
2. IMPACTS ON RAILWAY SUBGRADE
Compressive stress on the subgrade is generated by vehicles (track’s dead load can be negligible).
Function of compressive stress against the depth can be calculated according to C. Esveld with
formula as below:
2421
12
)21(
2
zb
zb
z
barctg
pz
p = compressive strength on the bottom plane of sleeper (N/mm2),
b1 = width of sleeper on the bottom plane (mm),
z = depth under the bottom plane of sleeper (mm).
Parameters in calculations:
rail 54E1,
static axle load: 225 – 250 kN,
sleeper type LM, b1 = 280 mm,
k = 770 mm,
C = 0,1 N/mm3,
track condition: very good – good – bad.
2. IMPACTS ON RAILWAY SUBGRADE
Standard compressive stress on subgrade,
axle load Q = 225 kN
Standard compressive stress on subgrade,
axle load Q = 240 kN
2. IMPACTS ON RAILWAY SUBGRADE
Deformations on plane of subgrade under the sleepers
2. IMPACTS ON RAILWAY SUBGRADE
2.3.4 Spreading of stresses generated by railway vehicle in track
Approximate assumption
2. IMPACTS ON RAILWAY SUBGRADE
Regulation at DB (German Railways)
At strength calculation the loads have to be taken in account
- in inner zone under pressure: dynamic loads,
- in outer zone under pressure: quasi-static loads.
2. IMPACTS ON RAILWAY SUBGRADE
3. SERVICEABILITY LIMIT STATE OF SUBGRADE
Railway subgrade is suitable in regard of serviceability limit, if
- it can take the deformations generated by railway traffic,
- the geometrical inaccuracy of the rails caused by these deformations can be repaired by main-
tenance works,
- it can take the vibrations caused by railway traffic,
- don’t occur vibrations threating the safety of railway traffic,
- vibrations don’t cause damages in superstructure (e.g. fracture in elements of fastenings).
Acceptable deformation in one renewal cycle, in case of ballasted track
4. SET-UP OF RAILWAY EARTHWORK
Set-up of railway earthwork: shape and dimensions according to standards
Materials and qualities
Construction technologies
Quality supervisions
4.1 Set-up of cross section
With the cross sectional set-up of earthwork all shape and dimension requirements have to be
ensured, which are necessary for its stability, for the safety of railway traffic, and for the suitable
behaviour of track in operation.
Determining factors of cross sectional dimensions:
- planning velocity of the track (e.g. width of track bench depends on velocity),
- dimensions of clearance chart,
- number of tracks and distance between track centres,
- horizontal track geometry (e.g. curve radius),
- height of superelevation,
- track characteristic (fishplated or CWR),
- set-up of superstructure (e.g. type of rail, length of sleepers, etc.),
- dimension of efficient ballast thickness,
- width of ballast shoulder and inclination of ballast slope,
- requirements of protection layer (e.g. thickness),
- cross inclination of plane of subgrade,
- dewatering requirements (e.g. ditches),
- set-up of connecting facilities (e.g. platform),
- place demand of maintenance works (e.g. ballast material storage on track bench),
- placement requirements of facilities along the track (e.g. catenary masts).
4. SET-UP OF RAILWAY EARTHWORK
sk = top of rail
v1 and v2 = width of ballast shoulder (in curv can be different)
p = width of track bench
e% = cross inclination of protection layer
m = superelevation
a = efficient thickness of ballast
kv = thickness of protection layer
k1 and k2 = side widths on subgrade
k = total width of subgrade
1:n = inclination of slope
am = depth of ditch
asz = width of ditch
T = distance between track centres
Cross section, fill and cut, single ballasted track,
straight, no superelevation
4. SET-UP OF RAILWAY EARTHWORK
Inclination of plane of subgrade / protection layer is 4-5%.
In case of single track the direction of inclination of subgrade plane has to be (as far as possible)
equal with direction of superelavation. Change in inclination direction can be executed at bridge or
level crossing. Length of transition section is 5 m.
Inaccuracy of the plane of subgrade / protection layer can be not greater than 20 mm, on a base with
length of 4 m.
Inaccuracy of slope surfaces can be maximum 50 mm.
Inaccuracy of height of subgrade can be ±30 mm, in case of height of protection layer can be not
greater than ±20 mm.
4. SET-UP OF RAILWAY EARTHWORK
Constant length of sleeper at design is 2,60 m.
4. SET-UP OF RAILWAY EARTHWORK
Cross section, fill and cut, single ballasted track,
in curve with superelevation
4. SET-UP OF RAILWAY EARTHWORK
Cross section, fill and cut, double ballasted track,
straight, no superelevation
Cross section, fill and cut, double ballasted track,
in curve with superelevation
Condition after more years operation
4. SET-UP OF RAILWAY EARTHWORK
Layer structure of railway track
Thickness „kv” of protection layer has to be calculated based on geotechnical report. Minimum
thickness is 15 cm.
4. SET-UP OF RAILWAY EARTHWORK
Differences among ballasted and ballastless (mass spring system) tracks
4. SET-UP OF RAILWAY EARTHWORK
Cross section at ÖBB (Austrian Railways), single track with higher speed
(„Hochleistungsstrecke”)
4. SET-UP OF RAILWAY EARTHWORK
Bevágásoknál/töltéseknél:
ak 3,00 m nem kötött talajoknál
5,00 kötött talajoknál
h >2,00 m: t = 1,5 h 0,20 m
h > 2,00 m: t = 3,00 m
1) 0,40 m v 160 km/h
2) acél vezetéktartó oszlopoknál 0,95 m
3) az adatok B70 típusú betonaljakra
és a tervezett sk. értékre vonatkoznak
4) építési tűrés 0,05 m
5) a zárójeles értékek helyszűke esetére vonatkoznak,
és ha a kábeleket a padkán kívül helyezik el
3,80 (3,50)
Ív belső
oldal
Ív külső
oldal
Ív belső
oldal
Ív külső
oldal
Ív belső
oldal
Ív külső
oldal
Vágánytengely - koronaél
távolsága
a5), m
Vágánytengely - alaptest
legkisebb távolsága
b5), m
Padkaszélesség
(kerekített értékek)
c5), mKorona-
szélesség
bPI5), m
Túlemelés
u, mm
3,80 (3,50)
3,80 (3,50)
3,80 (3,50)
3,80(3,50)
3,90 (3,60)
4,00 (3,70)
4,10 (3,80)
0-20
25-50
55-100
105-160
3,65 (3,50) 0,95 (0,65)
1,00 (0,70)
1,10 (0,80)
1,15 (0,85)
0,95 (0,65)
0,90 (0,60)
0,90 (0,60)
0,85 (0,55)
3,75 (3,60)
3,85 (3,70)
3,95 (3,80)
3,65 (3,50)
3,65 (3,50)
3,65 (3,50)
3,65 (3,50)
11,60 (11,00)
11,70 (11,10)
11,80 (11,20)
11,90 (11,30)
2,502,202,202,50
2,80 2,80
c
b
a a
b
4,70
bpit
Kábelcsatorna
vasúti pályatesten
kívüli elhelyezésnél
h
sk
~ 1,05)
Kisajátítási határ
ak
t
1:n h
0,20
0,051)0,051)
1,202)
0,45
1:n
Kábelcsatorna
0,731:201:20
0,35
1,202) 0,051)
Cross section at DB (German Railways), V ≤ 200 km,
double (reconstructed) track
4. SET-UP OF RAILWAY EARTHWORK
2,502,202,202,50
2,80 2,80
cc
a
b b
a
4,70
bpit
Kábelcsatorna
vasúti pályatesten
kívüli elhelyezésnél
h
sk
~ 1,0
Kisajátítási határ
ak
t
1:n h
0,20
0,052)0,052)
0,751)
0,45
Bevágásoknál/töltéseknél:
ak 3,00 m nem kötött talajoknál
5,00 kötött talajoknál
h >2,00 m: t = 1,5 h 0,20 m
h > 2,00 m: t = 3,00 m
1) 0,75 m = beton feszítőoszlopok esetén,
tartóoszlopoknál 0,55 m
2) építési tűrés 0,05 m
3) zárójeles értékek, ha a kábeleket
a padkán kívül fektetik
3,65 (3,50)
Ív belső
oldal
Ív külső
oldal
Ív belső
oldal
Ív külső
oldal
Ív belső
oldal
Ív külső
oldal
Vágánytengely - alaptest
legkisebb távolsága
a3), m
Vágánytengely - koronaél
távolság
b, m
Padkaszélesség
(kerekített értékek)
c, mKorona-
szélesség
bPI, m
Túlemelés
u, mm
3,65 (3,50)
3,65 (3,50)
3,65 (3,50)
3,65 (3,50)
3,75 (3,50)
3,90 (3,75)
4,05 (3,90)
0-20
25-50
55-100
105-160
13,30
13,40
13,55
13,70
4,30
4,30
4,30
4,30
4,30
4,40
4,55
4,70
1,30-1,35
1,35-1,40
1,40-1,45
1,45-1,50
1,30-1,25
1,30-1,25
1,40-1,25
1,40-1,25
1:n
Kábelcsatorna
0,731:201:20
0,35
Cross section at DB (German Railways), V = 250 km,
double track, new construction
4. SET-UP OF RAILWAY EARTHWORK
Cross section at station
4. SET-UP OF RAILWAY EARTHWORK
4.2 Density and load bearing capacity of railway earthwork
4.2.1 Density of railway earthwork
4. SET-UP OF RAILWAY EARTHWORK
Requested density values (according to Hungarian regulation):
- in protection layer Tr = 98%,
- in barrier layer Tr = 96%,
- below the barrier layer Tr = 94%,
- in backfill of engineering structures Tr = 98%,
- other places Tr = 92%.
4.2.2 Control of load bearing capacity
Measurement of load bearing capacity
4. SET-UP OF RAILWAY EARTHWORK
Static measurement and evaluation
according to Hungarian Standard
2
5,67
2
3,0300
43
243
24
)21(
2 sssDp
sDpstatE
= Poisson’s ratio
p = loading stress (kPa)
D = diameter of loading plate (m)
s2 = measured setting in second loading (mm)
4. SET-UP OF RAILWAY EARTHWORK
Static measurement and evaluation
according to German Standard DIN 18 134
Calculation of Ev2
modulus: (Poisson’s
ratio = 0,21)
Ev2 = (1,5 r ) / s
German EV2 ≠ Hungarian E2 stat
4. SET-UP OF RAILWAY EARTHWORK
Measurement of density and load bearing capacity
by light falling weight deflectometer
4. SET-UP OF RAILWAY EARTHWORK
The small-plate light falling weight deflectometer
measures
- the conventional dynamic modulus, as the bearing
capacity;
- and it is able to calculate the degree of compactness
from the compaction curve generated as the result of the
drops.
Tool is allowed to use only in case of coarse-grained soils
for purpose of qualification.
Correlation between values of static and dynamic modulus
Results of comparison measurements
Material source: Mérnök Újság, 2003/4
4. SET-UP OF RAILWAY EARTHWORK
Correlation between requested values of EV2 and EVd
according to German regulation of Ril 836
y = 0,2344x + 21,719
R2 = 0,9844
0
10
20
30
40
50
60
0 20 40 60 80 100 120 140
EV2
EV
d
Quotient EV2 / EVd is not constant. In case of fine-grained changes between 1,5 and 3,5. It
depends sharply on water content and compactness.
Numerous comparison measurement proved that the rate in case of coarse-grained soils used
for protection layer is EV2 / EVd ≈ 2. Conditions of validity:
- thickness of protection layer 30…50 cm,
- compactness correspond to Ril 836,
- dynamic measurement is executed after compaction with minimum 6 hours.
Material source: Göbel – Lieberenz: Handbuch Erdbauwerke
4. SET-UP OF RAILWAY EARTHWORK
Modulus
Velocity (km/h)
V 40 40 - 80 81 - 120 121 - 160 161 - 250
E2stat
(MPa) 50 60 80 100 120
Edin
(MPa) 35 35 40 45 50
Requested values of E2 stat and Ed modulus in Hungarian regulation
Negative deviation is prohibited.
Values regard on upper plane of protection layer and in absence of it for the upper plane of the
subgrade.
Pairs of values of E2stat and Edin summarized in table above are not allowed to get pairs of values
with correlation! There is a great difference between two measuring methods: static plate test and
light falling weight test. During static loading the pore-water pressure has stopped partly. In dynamic
measurement pore-water can cause significant increase in load bearing capacity.
4. SET-UP OF RAILWAY EARTHWORK
Geotechnical cross section in German regulation Ril 836
4. SET-UP OF RAILWAY EARTHWORK
Requested values in Ril 836 (DB)
4. SET-UP OF RAILWAY EARTHWORK