Navigation Locks




    Types of Navigation Locks

  Classification of Locks

  Main Items of a Navigation Lock

  Time of Filling or Emptying of a Lock

  Hydraulic Design of locks

  Dimensioning & Structural Design

  Detailed Drawings



General Layout

a)      Dam

b)      Regulator

c)      Navigation Lock

Objective: navigating boats or ships at canal locations having different water surface levels

Types of Navigation Locks according to Lock Chamber:


i.                  Movable Lock Chamber

ii.               Fixed Lock Chamber


Type I:  Navigation Locks with Movable Lock Chamber

1- Moving Basin Chamber


Single Floating Basin

Double Floating Basin

■ In this type of locks, the lock chamber is constructed of steel plates supported with a truss system of steel members


The lock chamber moves vertically between the US & DS water levels


Two gates for each lock chamber are installed at the directions facing the US & DS sides of the navigation canal


The chamber gates are facing the two ends of the channel US & DS sides of the lock chamber

II- Elevator Lock Moving on Inclined Floor


Lock Chamber: A steel container (chamber) constructed on a truss of steel members and moving through rollers on inclined floor


III Vertical Elevator Locks




a)    lock gate

b)    elevator gate

c)     tower column

d)    elevator chamber

e)     chains

f)      fixed ring

g)    retaining wall

h)    US abutments

i)       DS abutments

j)      Grooves for temporary US gates

k)    Grooves for temporary DS gates

L)     Counter weight

Type II: Navigation Locks with Fixed Lock Chamber

►In this type, the lock chamber is composed of fixed constructed elements

►The water filling this type of locks moves vertically between the US and DS water levels; inside the lock chamber

►A system of side water tunnels or (side culverts) is constructed for this purpose


 Classification of Navigation locks with fixed Basins

a) According to layout


a)      Adjacent to a heading up work as Regulator; Weir or Dam

b)      On a separate canal;

c)      At intersection of a water way with a sea


b)     According to Change of US & DS Water Levels 

     ► Gates (a) are working when HWL is at left side of canal

          ► If position of high & low water levels are exchanged, then the working

              gates are (b) and gates (a) are totally opened (not working)



c) According  to location relative to regulator or weir


a)                  Adjacent to a heading up work as regulator; weir or dam

b)                  On a separate canal

c)                  At intersection of a waterway with the sea




d)According to density of Navigation

► Length of working chambers may be 100m, 200m or 300m according to

               length of boat(s) sailing through the lock

          ►In case of heavy density navigation, 2 parallel chambers may work

             simultaneously either in one or in 2 directions




e)According to different lengths of lock chamber

For water consuming, the working lock chamber should be of suitable

              length of the sailing boat(s)



f) For very light Navigation Density

Lock chamber is designed long enough to take many boats in one trip

            Lock chamber is constructed of natural canal bed and side slopes

            The only constructed elements are the thrust walls supporting the US and the DS gates





g) According to difference between US and DS water levels (stepped Locks)

    i) Mitre gates



ii) Rolling gates


Some Common Dimensions of boats


Type of Boat

Length (m)

Width (m)

Draft (m)





Steam boats












Sail boats






Dimensions of Lock Chamber


Type of Lock

Length (m)

Width (m)

Depth (m)

First class lock




Locks on River Nile




Locks on Nile branches (2nd class)




Locks on Main Canals (3rd class)




Small water ways






1- head bay            2- tail bay           3- lock chamber        4- U.S.W.L of navigable channel             5-  D.S.W.L of navigable channel        6- gates           7- floor level     8- gate recess in floor        9- side culverts        10- side walls

Floor Bed of Lock Chamber


Same Bed level at US and DS of Lock

            ►Same gate dimensions and design

►Same wall lengths

Different Bed level at US and Ds of Lock

            ►Different gate dimensions at US & DS

            ►Different wall heights


        Main elements at U.S of lock with a drop in floor level



A lock of different Bed levels & different types of gates





Time taken by a boat sailing through the Lock


  1. 1.        filling (or emptying) Lock Chamber               5 – 10 min(needs opening of sluice gates

                of US side culverts)

  1. 2.      Opening of US gates to Enter the Lock            1          min


1.      3.      Boats to enter into chamber                            8 – 10   min


4.      Closing US gates                                           1           min

1.       5.      Emptying (or filling) Lock chamber            5 – 10 min(needs opening of sluice gates

                of DS side culverts)



1.      6.     Opening DS gates                                         1       min


1.      7.      Boats to leave Lock chamber                       6 – 8 min




1.      8.     Close DS gates                                              1       min


         Total time                                                             28 – 42 min




A         Average time taken for sailing a boat

         from the US to the DS through a lock              30 – 40 min


        Time taken depends on: dimensions of lock chamber; head between US & DS water levels; efficiency of opening & closing system of gates; efficiency of the mechanical system of controlling the valves of side culverts



 Determination of time of filling (or emptying) a lock chamber:











►The time of filling of the lock chamber is divided to steps;

►First starts with the beginning of opening the side culverts until it is completely opened; i.e. area of opening of the culvert is variable

►Second starts when the area of side culverts is completely opened and ends when the water level inside and outside the lock chamber is equal

a1= area of side culvert = ac

t1 = time of complete opening of side culverts, in seconds

discharge through culvert x  time

                             = volume of filled water in chamber

Q dt = A dh

Cd a (2gh)0.5 dt = - A dh


But:   or    



By Emptying:

time = 0            at area = 0        &         head = H

time = t at area = a        &         head = h

time = t1           at area = a1       &         head = H1


h is the head at any time t

a is the area of the opening of side culvert at head h and time t

H1 is the head when the side culvert is completely opened







then from head = H1 to head = 0;          Cd, a1, (2gh)0.5 dt = -A dh



from 1 & 2



 where T is the total time of emptying of chamber in seconds



  Different types of feeding systems










a)     culvert (or tunnel) at floor                            

b)     sluice gate at thrust wall

c)     longitudinal culverts along landing wall

d)    cross pipes (or openings) above the floor level





Cross section of lock chamber showing types of feeding sections





Sluice gates installed in lock gates to accelerate the process of filling









Shapes of side culverts (cross-sections)



Some Common Dimensions


Type of Boat

Length (m)

Width (m)

Draft (m)





Steam boats












Sail boats





Dimensions of Lock Chamber


Type of Lock

Length (m)

Width (m)

Depth (m)

First class lock




Locks on River Nile




Locks on Nile branches (2nd class)




Locks on Main Canals (3rd class)




Small water ways








Relation between Time of filling, Areas and Velocities


General Plan for a Combined Structure, Showing Elements of

a Regulator and a Lock



1- Floor         2- landing wall           3- thrust wall        4- guide pier         5- U.S. gates       6- D.S. gates        7- side culvert

8- swing bridge (lift bridge)            9- wing wall        10- temporary grooves        


Details of Floor Recession



Dimensioning of Locks



      = USWL – DS(floor)L + 1.0m





Check of Stability of Lock Elements


The structural elements of this type of locks (which is mostly adopted in Egypt) are:


1.                 Thrust walls

2.                 Retaining walls; which work as wing walls at the US & DS of the structure, landing walls that are retaining the soil behind the lock chamber

3.                 Guide pier, for unsymmetrical locks

4.                 Floor

5.                 Gates


   1.         Check of Stability of the Thrust Walls

► The critical part of a thrust wall that should be checked for overstressing, overturning, is that where the gate hinges are installed, besides the earth pressure outside the lock and the water pressure from the other side inside the lock

► Then, the other part of the thrust wall should be safe for the design dimensions of the concerned part.


   Cases of Loading of thrust wall 

a)          during operation (lock chamber is full)

i-                   lock gates are opened (treated as landing wall or guide pier)

ii-                 lock gates are closed (earth pressure from outside is neglected for most critical case)

Critical Case: Closed gates


a)   During Operation

Forces acting on walls: 1) water pressure U1 at DS of the gate, 2) water pressure U2  at US of the gate, 3) reaction force from the gate acting on the wall at the upper hinge location, 4) own weight


Critical case (b); closed gates:

In order to get the reaction force R acting on the wall,

Get the triangle of forces at the level of the upper hinge

The three forces in equilibrium are: water pressure on the gate, reaction force from the neighboring gate

First; the reaction force R should be determined

Get the water pressure acting on the gate

P = Pο * Lg (water pressure at the hinge level)




Where: Lg = gate width

          Hw = height of water acting on the gate

          H = DS water depth (if any)

y` = height of resultant Pu


Concerning the bottom level (floor level),

at which the lower hinge joining the gate to the

wall is installed, and knowing that the level of

 the upper hinge is 0.50m above

the water level, then;



by taking moments for the forces acting

 on the wall at the floor level, then;




b)     During Repair (dry Lock)


G = weight of the steel gate

    =  (200-300)  kg  per square meter of gate

    = Lgate * Hgate * (200-300)  kg

Hgate = water depth                                                    

+ 0.50m (for recession below bed level)

            + 0.50m (upper hinge is 0.50m

above water level)

                                                                                   Taking moments at the lower

                                                                                    hinge level, z


                                                                                      R*h = G* Lg /2

                                                                                  Reaction R can be determined



Gate may take any position

Case of fully opened gives only My

Case of completely closed gives Mx & My


        Forces acting in this case are:

  1. i)                    earth pressure; (with or without water table)

  2. ii)                  reaction force from the gate at the upper hinge

  3. iii)                 own weight

           Then, by taking moments for the forces acting

            on the wall at the floor level;                                     





2.     Check of Stability of Retaining Wall (Landing Wall )

q       dimensions are put for the wall

q       different cases of loading should be studied

q       check of the stresses is made at least

                  for the most critical case

q       the wall is checked for overturning

                   and overstressing

q       these dimensions are for pl concrete


q       in case of RC structure is chosen,

             Egyptian RC code should be applied                


Critical Case: During Repair

                               i.e. Chamber empty


►acting forces on the wall :

q     Earth pressure (soil is saturated)

q     Own Weight



2.     Check of Stability of Guide Pier

  (for unsymmetrical lock)

Cases of loading:

i)       during operation;

water pressure from both sides

ii)     during repair;

water pressure from side of regulator and chamber is empty from the other side


Critical Case: During Repair                                               


        ►acting forces on the wall :

o       Water pressure

o       Own weight





Check of Stability of Lock Floor


Loads & forces acting on a lock:

Earth and surcharge above sloping walls (landing walls + thrust walls); earth pressure;  water pressure; weight of floor; weight of water in chamber; uplift pressure; weight of walls

For locks constructed of Pl. concrete;

Floor thickness  = 0.25 span + 0.5 (Head)0.5

Where, span is the chamber width, Head is the difference between US & DS water levels

For locks constructed of Pl. & reinforced concrete (mixed type);

Floor thickness = 0.667  of the thickness of pl concrete types (empirically),

In this case, the thickness of RC slab = 0.4 – 0.6 m with dowels between the two layers and the rest of thickness is of pl. concrete.

Cases of loading:

a)      During operation :            min. water level in chamber with max. GWL

b)      During repair :                  empty chamber + max GWL

c)      Just after construction : empty chamber + dry earth (no uplift)

Soil Reaction on Floor


Francis Simplification

For the determination of stresses in the floor, assume the soil reaction as a combination of the 2 assumptions

1- First, assume floor thickness empirically

2- Determine the soil reaction, assuming it as a rigid body

3- To get the modified soil reaction according to Francis assumption, get

*        assuming:

*        Area of  (1) {uniform stress distribution below the floor} =

*                  Area of (2) {uniform stress distribution below the floor}

*   4- At section b-b,                                                                     

*        the  shearing force = 0 (for Max B.M.),

*        the reaction force R inside the floor section is horizontal

*        & equal to the earth pressure;

5- Taking moments at point “o” ,

    Then,  x = M/N, e = (M/N) – (t/2); where “t” is the floor

    thickness, “e” is the eccentricity




a      a)   Loads and Pressure Distribution for Case of Symmetrical

 l        lock Chamber



    b )  Loads and Pressure Distribution for Case of Unsymmetrical lock Chamber 




*   = friction coefficient between floor

*          material and soil

*       = 0.5

2- taking moments for all forces at “m”

 to get e, 

3- Get the stress distribution diagram f1 & f2 (as before), then, get the modified stress diagram;


For check against sliding;

N= ∑ w – Uplift ;  ∑ ( horizontal forces) = E;

FS (factor of safety) = (∑N) . μ / E

Then, by taking moments about “m”,

line of thrust should be drawn for the whole section of chamber

                       b = x

after determination of stress diagram distribution (4), check the stresses through the floor section “t”

get the moments M at point “n” for one half of the lock chamber for all loads, forces & soil reaction “f1 – f3” diagram




Lock Chambers of natural Bed & RC landing Walls



Different Structural Types of locks