CRREL

Modeling Ice Passage Through

an Auxiliary Lock Chamber With

a Submergible Lift Gate

Jon Zufelt, John Rand and Gordon Gooch June 1993
Abstract

River ice from the Des Moines and Fox Rivers combines with that of the

Mississippi during spring breakup, resulting in massive ice accumulations

upstream ofLock and Dam 20 on the Mississippi River. The accumulations in

the upper lock approach area cause considerable delays to navigation, as ice

must be passed through the lock chamber to clear the approach. Aphysical

model study was conducted to determine the effects of using the existing

auxiliary lock chamberto pass ice.The auxiliary lock chamberwas fitted with

a submergible lift gateat itsupstream endthat could be lowered topass iceand

clear the upper lock approach area. Model tests were conducted with real and

plastic ice material tosimulate the brash ice conditions encountered during lowflow prototype winter conditions. The submergible lift gate worked well in

clearing ice accumulations from the upper lock approach. It was necessary to

disturb the accumulation and keep it from refreezing by simulating towboat

movement or high volume point source air bubblers to thoroughly clear the

approach area.

For conversion ofSI metric unitstoU.S./British customary unitsofmeasurement

consult ASTM Standard E380-89a, StandardPracticeforUse oftheInternational

System ofUnits, published by the American Society for Testing and Materials,

1916 Race St., Philadelphia, Pa. 19103.

This report is printed on paper that contains a minimum of 50% recycled

material.
Special Report 93-15

US Army Corps

of Engineers

Cold Regions Research &

Engineering Laboratory

Modeling Ice Passage Through

an Auxiliary Lock Chamber With

a Submergible Lift Gate

Jon Zufelt, John Rand and Gordon Gooch June 1993

Prepared for

U.S. ARMY ENGINEER DISTRICT, ROCK ISLAND

Approved for public release; distribution is unlimited.
PREFACE

This report was prepared by Jon Zufelt, Research Hydraulic Engineer; John Rand,

Research General Engineer; and Gordon Gooch, Civil Engineering Technician, of the Ice

Engineering Research Branch, Experimental Engineering Division, U.S.Army Cold Regions

Research and Engineering Laboratory.

Funding for this research was provided by the U.S. Army Engineer District, Rock Island,

under contract no. NCR90-0030, Modeling Ice Passage Through Auxiliary Lock Equipped with

Submergible Lift Gate.

Steven F.Daly and Dr.Jean-Claude Tatinclaux technically reviewed the manuscript of this

report.

The authors express their appreciation to Charles Schelewa and Peter Stark for their

assistance in construction of the model.

The contents of this report are not to be used for advertising or promotional purposes.

Citation of brand names does not constitute an official endorsement or approval of the use

of such commercial products.
CONTENTS

Preface i

Introduction 1

Model design and construction 4

Model calibration 6

Submergible gate hydraulics 7

Model testing program 10

Results 11

Conclusions and recommendations 12

Literature cited 12

Abstract 15

ILLUSTRATIONS

Figure

1. Location map of Lock and Dam 20, Mississippi River 1

2. Plan view of Lock and Dam 20, Mississippi River 2

3. Severe ice jam at Lock and Dam 20, Mississippi River 3

4. Plan view of IEFResearch Area showing model of Lock and Dam 20

as constructed 4

5. View looking upstream at the main and auxiliary lockchambers and

submergible lift gate 5

6. View of the completed model looking downstream at the approach

area and dam 6

7. Prototype velocity measurements taken October, 1990 6

8. Velocity vector plot of flow configuration in the model following

calibration 7

9. Velocity vector plot for open water conditions with a lift gate

submergence of 1 ft 8

10. Velocity vector plot for open water conditions with a lift gate

submergence of 2 ft 8

11. Velocity vector plot for open water conditions with a lift gate

submergence of 3 ft 9

12. Percentage of total river flow passing through auxiliary lock

chamber vs. vertical lift gate submergence 10

13.Typical location of ice arch formed in the upper lock approach of

the model 11

TABLES

Table

1. Average monthly lockages for 1990-1992 2

2. Model submergible lift gate hydraulics 9

3. Testing matrix 10

in
Modeling IcePassageThrough an AuxiliaryLock Chamber

With a Submergible Lift Gate

JON ZUFELT, JOHN RAND, AND GORDON GOOCH

INTRODUCTION

Thisreport examinesicepassageat Lockand Dam

20 on the Mississippi River using a scale physical

model. The model study was conducted to determine

the effectiveness of using a submergible lift gate to

pass icefrom the upper lockapproach area through

the auxiliary lock and downstream.

Lock and Dam 20 is one of the structures making

up the Inland Waterway NavigationSystem of the

Upper Mississippi RiverBasin. It is located at River

Mile 343.2 (miles upstream from the mouth of the

Ohio River)on the MississippiRivernear the city of

Canton, Missouri (Figure 1).The Lock and Dam 20

pool extends approximately 21 miles (34 km) up

stream to Lock and Dam 19 at Keokuk, Iowa. Con

struction of Lock and Dam 20 began in November,

1932, and was completed in November, 1935. The

facility was placedintooperationon 9June1936. The

structure is owned and operated by the Rock Island

District of the U.S.Army Corps of Engineers.

The structure actually contains two navigation

locks. The main lock is located on the Missourishore

and is 110 ft (33.5 m) wide and 600 ft (183 m) long.

The auxiliarylock was designed to be 110ft wide by

360ft (33.5 by 110m) long but was never completed

(Figure 2). The main lock is equipped with miter

gates at its upstream and downstream ends,but the

auxiliary lock was only equipped with an upstream

miter gate.Themaximum liftthrough the lockis 10.5

ft (3.2m). The river guard wall upstream of the locks

is actually a series of sheet pile 'cells' with a bridge

superstructure built on top of them. The superstruc

ture extends below the water surface and thus pre

vents ice passage from the upper approach area

through the cells. During the 1940s the unobstructed

spacebetweenthe firstcelland the riverward auxil

iary lockwall wasincreased from5.0to23.0 ft (1.5 to

7 m) in an effort to clear debris and ice from the lock

Iowa \ ^->. City ( ^. )

\ r t~

^_s_^Mollne

^Cf

IOWA \j)\

fc=/"Vv q. f Land D CltumwaN^X- Burlington 4 18

^§ If

\^ a Jr Illinois

MISSOURI "A ^\

KeokukM'LandD

ILandD

Canton41 20 I

N

nn» Quincy LandDf 1

21 <k

Figure 1. Location map ofLock and Dam 20, Mississippi

River.

approach area. While this has proved somewhat

helpful for minor debris accumulations, it has not

been effective for ice.

The dam has a total length of 2294 ft (700 m),

which consists of 150 ft (45.7 m) of non-overflow

earthen dike on the Illinois shore and 2144 ft (653.5

m) of gated structure between the earthen dike and

the locks.There are 43 gates in the dam: 40are fainter

gatesand threeare rollergates. Thethreerollergates

arenonsubmergible; they are20fthighand 60ftwide

(6.1 by 18.3 m)and are located nearmidchannel. The

40fainter gatesmeasure20ft high by 40ft wide (6.1
3

12 Roller

Tainter Gates Gates

ttttttW3

Flow

28

Tainter Gates

ttt rr rrr r r rr

N

I M I l

Figure 2.Plan view ofLock and Dam 20, Mississippi River.

by 12.2 m). Gates 1, 2,17,18,42, and 43 are also ca

pable of being submerged 3 ft(0.9 m) below the nor

mal crestelevation of480.0 ft (146.3 m).Thelayout

of the gates is shown in Figure 2.

The normal navigation season for Lockand Dam

20 is February through December, but lockages do

occur all year. The average number of tows transit

ing the lock each month for the years 1990-1992are

given in Table 1. River traffic generally declines

through December as the river freezes over and re

mains very low through January and February.Dur

ing thesemarginaltimes, theentirerivermaybecov

ered with iceexceptfor a ship trackcut through the

ice corresponding to the 9-ft-(2.7-m-) deep naviga

tion channel. Traffic picks up again during March

and remains high through spring, summer, and fall.

Ice problems at Lock and Dam 20 are twofold.

During the period when the river is partially cov

ered or when only a ship track exists in an ice-cov

ered river, brash ice flowing downstream ispushed

into the lockapproach by downbound tows.Thisice

can fillthe entire approach area and must be locked

through justas a tow and barges would be.Another

method ofclearingthe lockapproach isto divert the

incoming ice away from the approach and toward

the dam, where it can be passed over or under the

dam gates. During most of the winter, however, the

discharge in the river is very low. This results in small

dam gate openings that are insufficient to passice.

Towboatssometimesuse theirpropellerwash todi

rect iceout of and away from the lockapproach and

toward the dam gates. To assist ice movement, the

towboats are often requested to keep a section of the

icecover broken from the approach area to the dam

gates.

As spring approaches and temperatures rise, the

icecoveron the river begins to break up. Higher dis

chargesare oftenassociated with thespringbreakup

Table 1. Average monthly lock

ages for 1990-1992.

Month Numberof lockages

January 12

February 43

March 340

April 419

May 464

June 465

July 533

August 524

September 401

October 401

November 361

December 143
Figure 3. Severe ice jam at Lockand Dam 20, Mississippi River.

period and thus necessitate largergateopenings at

thedam thatfacilitates icepassage. Manyofthetribu

taries also break up at nearly the same time as the

Mississippi River, causing largeice runs that move

downriver. The Des Moines River is a large tribu

tary that enters the Mississippi just downstream of

Lock and Dam 19. The Des Moines often breaks up

and runs into the Mississippi, causing very severe

accumulations and jams at Lock and Dam 20 (Fig

ure 3). These large amounts of ice can become

grounded in the pool upstreamofthe dam, cutting

off navigation forseveral daysuntilthe jam canbe

cleared.

Ice problemssuchas thesearenot unique, asevi

dencedby the response toa surveyon ice problems

at navigation facilities conductedbyCRREL (Zufelt

and Calkins 1985). Similar problems exist at many

locations on the Mississippi, Ohio, Illinois, and

Monongahela rivers. These facilities have devised

manyways to dealwith the problems ofice in the

upperlock approach and ice passage through navi

gation dams. Submergible tainter gates have been

used with success at several locations on the Illinois

Waterway. Submergible tainter and submergible

roller gates have been usedon theMississippi River.

On the Ohioand Monongahela Rivers, facilities have

modified their upstream emergency lock closure

bulkheads to act as overflow weirs. These bulkheads

are placed in the auxiliary lock chamber and both

theupper and lower lock gates areopened, with the

resultthat the ice passesoverthebulkhead, through

the lock, and downstream.

The Rock Island District (RID) contacted the Ice

Engineering Research Branch ofCRREL following

the particularly troublesome winterseason of1990-

91, which was plagued with ice problems at Lock

and Dam 20. RID was interested in improving ice

passage at thefacility, particularly during the win

terlow-discharge periods. The Ice Engineering Re

search Branch had recently completed a physical

modelstudyofice passage problems atStarved Rock

Lock and Dam on the Illinois Waterway for RID

(Gooch et al. 1990). In that study, CRREL recom

mended the installation of two submergible tainter

gates to increase ice passage through thedam and

reduce iceaccumulationsin theupper lockapproach.

Since the auxiliary lock of Lock and Dam 20 was

never completed andwaswithin the upper approach

area, itappeared thatpassing ice through theauxil

iary lock chamber would be very effective in clear

ing theupper approach. Itwas decided tophysically

modela vertical gatestructureat the upstreamend

ofthe auxiliary lock thatcouldbe submergedto pass

icefrom the upper lockapproach.
Ice Supply Flume

^

—J x-*- Drain

Figure 4. Plan viezv oflEF Research Area showing model ofLock and Dam 20as constructed.

4

Main Lock Chamber

Auxiliary Lock

^O OOOO

Guard S^&% Dam

Gates

Wall

MODEL DESIGN

AND CONSTRUCTION

The physical model of Lockand Dam 20was con

structed in the refrigerated research area of the Ice

Engineering Facility at theU.S. ArmyColdRegions

Research and EngineeringLaboratory(USACRREL).

Therefrigerated research areaisa large, unobstructed

room measuring 80by 160ft (24.4 by 48.8 m) with a

refrigeration system capable oflowering theairtem

perature in the room to -10°F (-18°C). Water can be

delivered from a 60,000-gallon (230-m3) sump

through a variety of pipelines and pumps to the

model areaat dischargesup to5ftVs (0.14 m3/s). A

large icesupply flume measuring 16ft wide, 140 ft

long, and 1.5 ft deep (4.9 by 42.7 by 0.46 m) is lo

cated along one wall of the research area and can be

used to further cool the water coming into a model

or to form icesheetsthat can then bebroken up and

fed into a model. A trough islocated along theop

positewallto return the water to thesump. An over

head crane system capable of bidirectional move

ment provides accessto any area of the model with

out the need forscaffolding, catwalks, or theirsup

ports, which would obstruct flow or ice movement

in the model. Figure4 shows a plan view of the re

search area with the Lock and Dam 20 model as con

structed.

Since the main objective of the study was to de

terminetheeffectiveness ofthesubmergible gateand

icemovement in the upper lockapproach area where

vortices and other three-dimensional flow effects

were possible, it was decided to construct an

undistorted model in which the horizontal and ver

tical scales are equal. The Lock and Dam 20 model

was therefore designed and constructed as an

undistorted, sectional, Froude scale model, at a scale

of 1:25.

The scale of a model is represented by the ratios

of its horizontal (H) and vertical(V) lengths to that

of the prototype

(lh) »^fk

R Uh).

and (Lv)R =(-^ (1)

ThesubscriptsR, P,and M refer to ratio,prototype,

and model, respectively.The vertical length ratio is

usually equal to the depth ratio. For an undistorted

model, (LH)R = (LV)R = LR and the model is charac

terized simply by the length ratio LR. The accelera

tion due to gravity is the same for both the proto

type and the model, resulting ingR = 1.

Froude model similarity requires that the Froude

numberofthemodel and prototype beequalor that

their ratio beequal to unity:

FrR=-FrM _ V

FrP V^rT^

B-=l

where Fr = the Froude number

V = water velocity

g = accelerationdue to gravity

h = water depth.

(2)
Substituting //R = LR and gR = 1 into eq 2 above, the

velocity and discharge scales then become

VR={h~R = fL„

Qr =arvr =l£vr =lr/2

(3)

(4)

where ARis the area ratio.

The scalechosen for a physical model is bounded

on the high side (large model) by the space and

pumping capacity available aswellascost. Minimum

scales (small models) are dependent on the measure

ment accuracy required and the need to avoid vis

cous and surface tension effects. There was an op

portunity for additional costsavings for thismodel

study since the Starved RockLockand Dam model

study had just been completed and the model had

not yetbeendemolished. TheStarvedRock Lock and

Dam physical model was a 1:25 scale undistorted

physical model that included the lock structure, a

section of ungated dam, and three of the 10 tainter

gates (Gooch et al. 1990). The Starved Rock lock

chamber was also the same width as the main lock

chamber and was located in a similar position to the

dam as Lock and Dam 20.Bychoosing a scale of 1:25

for the Lockand Dam 20 physical model, it was pos

sibleto use the existing (StarvedRock) model pump

and pipingsystem, inletand outletworks, lockcham

ber, lock gates, and filling ports, and the dam sill.

This saved a considerable amount of time, and the

cost for demolition of the old model and construc

tion of the new model was reduced by 50%.

By choosing thislength scale, however, thewidth

ofthemodel was limitedto the rightbank,lockcham

bers, and the first 13of the 44gates on the dam. This

included the first12tainter gatesand the firstroller

gate. Asmentioned above, the main purposeof the

model study was to investigateice passage during

periodsoflowflowduring winter.Under thesecon

ditions,the river istypically frozenover completely

exceptfora continually rebroken shiptracknear the

right bank leading into the lockchamber. The win

ter discharge to be modeled was approximately

39,000 ftVs (1100 m3/s) and, at this dischargelevel,

the gateoperating schedule calls forgates1-12,17,

and 18 to be opened 3 ft (91 cm) and gate 19 to be

opened 2 ft (60 cm).Since the main area of interest

was the lockapproach area and the firstfew tainter

gates, it wasnot necessary tomodeltheentiredam.

Detailed hydrographicsurveysprovidedthedata

necessaryformodeling the riverbedupstream from

the dam. Construction drawings provided informaFigure 5. View looking upstream at the main and auxiliary lock chambers and submergible lift gate.
^fniin,,,

Figure 6. View ofthe completed model looking dozonstream atthe approach area anddam.

tion for the auxiliary lock, sheet pile cells,

and dam gates. Model construction entailed

the fabrication and placement of plywood

templates at 4-ft (1.2-m)spacing upstream

of the lock and dam. The area between the

templates was then filled with sand and

smoothed before being covered with a 3-

in.-(76-mm) thick concrete cap. The sheet

pile cells,auxiliary lock structure, and dam

piers were fabricated with poured concrete.

The dam tainter gates were constructed of

wood and plastic. Since the model tests

were to be conducted at a single, low win

ter discharge, the dam gates were con

structed as non-operable overflow weirs

rather than operable underflow-type gates.

The vertical lift gate in the auxiliary lock

chamber was simulated with a sharpcrested aluminum plate that could be raised

and lowered. Figure 5shows the main and

auxiliary lock chambers and the submerg

ible lift gate looking upstream at the ap

proach area. Figure 6 shows the completed

model looking downstream at the approach

area and dam.

MODEL CALIBRATION

The model was calibrated by matching

a detailed set of prototype velocity mea

surements taken during low-flow, open

water conditions during late October, 1990.The lo

cations of the velocity measurements are shown in

Figure 7; they included the upperlock approach and

the spaces between the cells of the river guard wall.

= 1 ft/s Prototype Velocity

Figure 7.Prototype velocity measurements taken October, 1990.

Theprototype velocities were taken at approximately

1 ft (30 cm) below the water surface, to simulate the

velocity of free drifting ice.For the locationsbetween

the cells, the depth of measurement was increased
= 1 ft/s Prototype Velocity

Figure S. Velocity vector plot offlowconfiguration inthe modelfal

lowing calibration.

ice movement in the lock approach area, we

decided to calibrate the model by closely

matching the prototype velocities inside and

immediately outside of the lock approach

area. The flow was further adjusted by plac

ing roughness elements and flow alignment

structures at the model inlet and on the bed

immediately upstream of the lock approach.

Velocities were matched within 10% for all

the calibration locations except for the two

points immediately upstream of the main

lock, where a large eddy developed in the

model. In general, the flow approaches the

lock parallel to the shore and is diverted to

ward the dam, accelerating as it flows

through the openings between the cells. It

then passes through the dam in a nearly nor

mal direction. The general flow configuration

is presented in Figure 8 as a velocity vector

plot.

Water level in the upper pool of the model

was measured by point gauges and the model

discharge by an in-line flow meter. Two-di

mensional velocities were measured using a

Marsh McBirney electromagnetic flow meter

oriented to the x-y plane of the overhead

crane system. Still photography and video

coverage were also used to document the

model calibration and testing.

to6 ft (1.8 m) due to the blockage ofsurfaceflowby

the submerged wall connecting the cells. The dis

charge in the river during the velocity measurements

averaged 37,500 fP/s (1060 m3/s), with the upper

pool elevation at 479.75 ft (146.2 m) and the lower

pool elevation at 471.8ft (143.8m).

If the entire width of the river had been modeled,

it can be seen from eq 4 and the model scale of 1:25

that the model discharge to stmuLste 37,500 ftVs

(1060 m3/s) in the prototype would be 12 ftVs or

approximately5400 gal/min (0.33 m3/s).Thisvalue

is well above the pumping capacity of the research

area.Byreducing the model width to thefirst13gates

of the dam, it was possible to reduce the pumping

requirements. We wanted to run several tests with

real icein the model, but at large pump discharges a

considerable amount of heat is added to the water,

which quickly melts the ice in the model and affects

the results. The maximum pumping rate possible to

avoid melting the icein the model is approximately

1350 gal/min(0.085 m3/s). This pumping rate would

require closingthe outer gates with only the firstsix

gates of the dam open. Sincethe primary interest was

SUBMERGIBLE GATE HYDRAULICS

Experience at other lock and dam facilities has

shown that submergible gates can satisfactorily pass

brash ice when the submergence is at least equal to

1.5 times the ice piece thickness. Thermally grown

sheet icethickness would not be expected to be more

than 2 ft (61 cm) for the upper Mississippi River in

the vicinity of Lock and Dam 20, but frazil deposi

tion could result in significantly thicker ice.The Rock

Island District suggested that the model gate be op

erable up to submergences of 8 ft (2.4m). The proto

type submergible lift gate would be located in the

auxiliary lock chamber upstream from the upper

miter gate and would be either a sharp-crested or

ogee-crest gate; it would allow ice passage by sub

merging the crestbelow the upstream pool elevation.

The model gate was constructed as a sharp-crested

weir that spanned the entire width of the auxiliary

lockor 110-ft(33.5-m) prototype. The discharge over

the model gate is given by the weir equation as:

Q=2/3SCdV?gH 3/2

(5)
= 1 ft/s Prototype Velocity

- 1 ft/s Prototype Velocity

Figure 9. Velocity vector plotfor open water conditions

with a lift gate submergence of1ft.

Figure 10. Velocity vector plotforopen water conditions

with a lift gate submergence of2ft.
where Q = discharge

B = width

Cj = weir coefficient of 0.69

g = acceleration due to gravity

H = submergence of the weir.

To maintain the upper pool at elevation 480.0when

the prototype submergible lift gate is lowered, it

would be necessary to partially or completely close

one or more of the prototype dam tainter gates. The

model dam gates were constructed as sharp-crested

weirs that could be partially or completely blocked

over their width to simulate tainter gate closure. It

was assumed that the lock operator would choose

to close the dam tainter gates closest to the lock, so

this was also done for the model. Using eq 5 above,

the discharges at gate submergences of 1,2, and 3 ft

were calculated, along with the amount of closure

necessary for gates 1 and 2 on the dam. These are

given in Table 2.

Detailed velocitymeasurements were made in the

model for open-water lift gate submergences of 1,2,

and 3 ft for comparison against existing conditions.

These are presented in Figures 9 through 11. It can

be seen from these figures that lowering the submerg

ible liftgate eliminates the eddy in front of the auxil

iary lock chamber, reduces the size of the eddy in

front of the main lock chamber and also increases

the velocity of flow through the lock approach. The

flow coming into the lock approach passes through

Table 2. Model submergible lift gate hydraulics.

Gatesubmergence

(prototype ft)

Modeldiscliarge

(gal/min) (m3/s)

Closureofdam

gate 1 (%)

Closureof dam

gate 2 (%)

1 60 0.038 l) 28

2 165 0.010 67 0

3 300 0.019 100 2S

MM

= 1 ft/s Prototype Velocity

Figure 11. Velocity vectorplotforopen water con

ditions with a liftgatesubmergence of3ft.
1 | 1 | 1 | 1 i " to

30

Dam ^^^^ ^ — 3C

•>

0)

1

TO 20 - 6C

O

(0

5 -

40

10

-

Gate^-^^^

—r~i , i , i i

20

n

4 6

Gate Submergence (ft)

to

Figure 12. Percentage oftotal river flow passing through

auxiliary lock chamber vs. vertical lift gate submergence.

the auxiliary lock instead of between the cellsof the

river guard wall. Figure12shows the percentage of

the total river flow of 37,500 ftVs (1060 m3/s) that

would be passing through the auxiliary lock vs. the

dam gates at lift gate submergences up to 8 ft.

MODEL TESTING PROGRAM

The velocity of flow through the upper lock ap

proach area is increased by lowering the submerg

ible lift gate. To determine if ice passage is also in

creased, several tests were conducted using both real

and plastic ice materials.

For these tests, the upper lock approach area was

filled with icematerial. The submergible liftgate was

then lowered, the appropriate closures were made

at the first two dam tainter gates, and the model was

observed to determine if the ice would pass through

the auxiliarylock, therebyclearingthe upper lockap

proach. Testswerealsorun in whichicewas fedinto

the clear approach area to see if ice arches would

form. Foralltests, the prototype discharge washeld

constant at 37,500 ftVs (1060 m3/s) with an upper

pool elevation of 480.0 ft. Variables for the testing

program werethe type and sizeofice, the submerg

ible lift gate setting, and methods of disturbing the

ice cover to reduce refreezing of the brash ice accu

mulation. Table 3 presents the testing matrix.

Three types of icewere used in the testing:plastic

blocks, plastic beads, and real ice. The plastic ice

materials are formed of polyethylene with a specific

gravity of 0.92. The dimensions of the blocks are 4

in. by 4 in. by 1/4 in. thick (34 by 34 by 6.3 mm),

which simulates prototype ice floes 8 ft (2.4m) on a

side and 6 in. (15 cm) thick. The beads are approxi

mately cylindrical in shape with a diameter and

length of 3-4 mm or a prototype size of 4 in. (100

mm), simulating brash ice.The real ice was formed

in the ice supply flume and then broken into ran

dom-sizedpieces generally ranginginsizefrom2 to

9 in. (51 to 229 mm) or prototype sizes of 4 to 20 ft

(1.2 to 6.1 m). Thicknesses ranged from 0.5 to 1.5 in.

(13to 38 mm) or prototype thicknesses of 1 to 3 ft (30

to 90 cm). During tests with real ice, the air and wa

ter temperature were kept near freezing to prevent

excessive melting or refreezing of the ice over time.

Typically, therealicewould archacross the open

ing of the upper lock approach. Three methods of

disturbing the ice cover or accumulation in the up

per lock approach were used:

Table 3. Testing matrix.

Test Ice thickness, Ice size. Gatesetting. Disturbance

no. Ice type prototypeft (cm) prototypeft (m) prototypeft (in) method

1 beads 0.3 (10) 0.3 (10) 1.0 (0.3) none

2 real 0.5 (15.2) 4-8 (12.2-24.3) 3.0 (0.9) none

3 real 1.5 (45.7) 10-20 (30.5-61) 3.0 (0.9) barge

4 blocks 0.5 (152) 8 (24.3) 3.0 (0.9) none

4A beads 0.3 (10) 0.3 (10) 3.0 (0.9) none

5 real 1.0 (30.5) 4-8 (12.2-24.3) 3.0 (0.9) manual

6 real 1.0 (30.5) 10-20 (30.5-61) 3.0 (0.9) barge

7 real 0.5 (15.2) 8-12 (24.3-36.6) 3.0 (0.9) manual

8 beads 0.3 (10) 0.3 (10) 3.0 (0-9) none

9 blocks 0.5 (15.2) 8 (24.3) 3.0 (0.9) none

10 real 1.0 (30.5) sheet 3.0 (0.9) none

11 real 0.57 (17-4) 8-12 (24.3-36.6) 3.0 (0.9) barge

12 real 0.82 (25) 8-12 (24.3-36.6) 3.0 (0.9) bubbler

13 real 0.82 (25) 8-12 (24.3-36.6) 3.0 (0.9) bubbler

14 real 0.82 (25) 8-12 (24.3-36.6) 8.0 (24.3) bubbler

10
1) A model barge constructed at the model scale

was pulled or pushed through the arched accumu

lation.

2) The accumulation was manually disturbed by

gently moving a few of the ice pieces at the center of

the arch with a pole.

3) A line bubbler and two point-source bubblers

were installed on the bed of the model and operated

to continually disturb the arch.

Following the bead tests,minor amounts of plas

tic beads remained in the model that were then fro

zen into the sheet icecover grown for the real icetests.

The effects of those beads on the outcome of the real

ice tests are negligible.

Test 10 was conducted with a sheet ice cover over

the entire model to determine the effect of an ice cover

on the water velocity. Small holes were made in the

icecover,and velocity was measured at a prototype

depth of 3.0 ft (90 cm).

RESULTS

The three model ice materials responded differ

ently for several reasons. The beads are small, simu

lating prototype ice that would be about the size of

brash ice or smaller. This ice would be ex

pected to pass easily through the auxiliary

lock and over the submergible gate. The

beads did pass through the upper approach

easilyfor all gate settings,even the 1-ft(30.5-

cm) submergence test. The beads are also

cohesionless, which reduces the chances that

arches would form in the model. The plastic

ice blocks simulated larger ice floes8 ft (2.4

m) on a side. Although the larger size facili

tates arching, the blocks are also cohesionless and regular in shape, which inhibits

arching. The real ice consistently formed

arches in the upper approach. Their irregu

lar shapes allowed the ice pieces to "key"

into each other more easily than did the

square plastic blocks.Sinceair temperatures

in the research area were kept near freezing,

the real ice pieces tended to freeze together

and had to be rebroken before the start of

each test.

Theeffects of the liftgate submergenceon

theicemovementin theupper approachwas

minor except very closeto the gate itself.Pre

liminary tests showed that a submergence

greater than 1.0 ft (30.5 cm) would be neces

sary for the real ice tests, as the larger and

thicker ice pieces would lodge on the gate.

The 3.0-ftsubmergence was chosen as a typical pro

totype setting as this would be able to pass ice up to

2.0 ft (61 cm) thick easily. Midwinter tailwater ele

vations require gate settings of 3.0 ft (90.5cm) or less

on the dam tainter gates in order to prevent scour. It

was assumed that similar limits would exist down

stream ofthe submergibleliftgate.Thegate was sub

merged to 8.0 ft (2.4m) prototype to assess its effec

tiveness in dislodging ice arches that formed in the

upper approach. The increase in velocitythrough the

approach was not sufficient to dislodge the arches.

The icearches that formed in the upper approach

were primarily located just upstream of the entrance

into the auxiliary lock, extending from the tip of the

bullnoseor midlockwallto the riverguard wall (Fig

ure 13). In two instances, a secondary arch formed

across the entire approach area at the bend in the

river guard wall. The arches only formed during the

real ice tests,although one did form for a very short

time during a test with the plastic blocks. Labora

tory studies have investigated the ratio of the open

ing width to iceblocksize and incomingiceconcen

tration that results in ice arch formation. Tatinclaux

and Lee (1978) looked at the arching ofboth plastic

and realice blocks across an opening. Applying their

work to the model configuration, it would be necesFigure 13. Typical location ofice archesformed in the upper lock

approach ofthe model.

1 1
sary to have a plastic ice block surface concentration

coming into the upper approach area of greater than

100%to cause arching. The larger size and irregular

shape of the real ice pieces made arching easier. For

the tests where the approach was initially clear and

icewas fed into the model, concentrations were gen

erally low enough to prevent arches from forming,

even with the real ice.

As mentioned earlier, three methods were used

to disrupt the arches that formed in the upper ap

proach. The manual method would not be possible

to implement in the prototype and was used initially

to determine if the ice would continue to keep mov

ing through the approach once the arch had been dis

turbed. Unfortunately, this was not the case,as arches

would consistentlyreform at approximately the same

location. The barge simulated river traffic that would

be expected during that time of year, typically lim

ited to single-width tows with two or three barges.

The barge was slightly more effective when moving

downstream, as it pushed much of the ice that was

upstream of the arch into the approach. This reduced

the concentration of ice remaining upstream of the

approach and delayed the reformation of another

arch.

Because it can be hours or days between lockages

during midwinter, it was decided to test air bubblers

as a means of keeping the ice arches disturbed. The

arches formed at nearly the same location each time,

so the placement of two high-volume point-source

bubblers was sufficient to keep the ice moving

through the approach. These point-source bubblers

only needed to be pulsed once an arch had formed.

The line bubbler described above was also tested to

see if it would be useful in preventing arch forma

tion. While it initially broke the arch, its continual

operation actually imparted an upstream velocity to

the surface that inhibited ice passage and assisted in

reforming the arch slightly upstream of the bullnose.

It was then necessary to pulse the point-source bub

bler to break the reformed arch. The line bubbler was

very successful in keeping ice out of the main lock

gate area during tests when the approach was ini

tiallyclear.Thecombinationof the two bubblers kept

the icepassing through the approach area easily and

consistently.

CONCLUSIONS AND

RECOMMENDATIONS

The model study showed that a submergible lift

gate located in the auxiliary lock chamber of Lock

and Dam 20 on the Mississippi River could greatly

improve ice passage at the facility. A gate submer

gence of 3 ft (90.5cm) proved to be sufficient to pass

ice and thereby clear the upper lock approach area

without a detrimental loss of pool. Byusing the aux

iliary lock for icepassage, it becomes unnecessary to

keep an ice-free channel from the upper approach to

the dam or to request assistance from tows to use

their propeller wash to direct ice from the upper ap

proach toward the dam gates. This method of ice

passage will be especially helpful during periods of

low flow during January and February when only a

ship track exists in an otherwise intact ice cover. Ice

moving or being pushed down the ship track ahead

of tows will be pushed into the lock approach but

will be easily passed over the submergible lift gate

in the auxiliary lock chamber. This will eliminate the

need forseparate ice lockages and reduce the poten

tial for damage to the main lock gates.

The model tests did show that ice in the upper

approach would arch across the opening and that

some form of disturbance was necessary to keep the

ice moving over the submergible lift gate. This could

easily be accomplished by towboat traffic.There are

periods during midwinter when river traffic is very

light, however, when rather large accumulations

could arch across the upper lock approach. The

model tests showed that strategically placed highvolume, point-source air bubblers could be used to

disturb the ice accumulation and keep it from arch

ing or to disrupt arches that have already formed.

The tests also showed that an air bubbler placed at a

45° angle from the end of the bullnose to the land

wall in an upstream direction would act as a deflec

tor and keep ice from entering the main lock gate

area. This would reduce damage to the main lock

gates and operating machinery as well as eliminate

the need for any ice lockages.

It is recommended that when the submergible lift

is installed, a series of field tests be conducted to de

termine whether ice arching is a problem in the pro

totype as it was in the model. If arching does occur,

tests with high-volume, point-source air bubblers

should be conducted to determine their optimum

position in the upper approach. The use of air bub

blers to keep the ice arch from forming may elimi

nate the need for towboat assistancealtogether.

LITERATURE CITED

12

Gooch, G., J. Rand, B. Hanamoto and J. Zufelt (1990)

Model ice passage through submergible and non-
submergible tainter gates. USA Cold Regions Re

search and Engineering Laboratory, Special Report

90-39.

Rand, J., J. Zufelt and G. Gooch (1991) Modeling

ice passage through an auxiliary lock chamber

equipped with a submergible lift gate. Contract Re

port to the U.S. Army EngineerDistrict, RockIsland.

Tatinclaux, J.C. and CL. Lee (1978) Initiation of ice

jams—A laboratory study. Canadian Journal ofCivil

Engineering, 5(2): 202-212.

13

U.S. Army Engineer District, Rock Island (1980)

Upper Mississippi River Basin, Mississippi River

Nine Foot Channel Navigation Project Reservoir

Regulation Manual, Appendix 20—Lock and Dam

No. 20. U.S. Army Engineer District, Rock Island,

Corps of Engineers, Rock Island, Illinois.

Zufelt, J. and D. Calkins (1985) Surveyof iceprob

lem areas in navigable waterways. USA Cold Re

gionsResearch and EngineeringLaboratory,Special

Report 85-2.
REPORT DOCUMENTATION PAGE

Form Approved

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1. AGENCY USE ONLY (Leave blank)

4. TITLE AND SUBTITLE

2. REPORT DATE

June 1993

3. REPORT TYPE AND DATES COVERED

5. FUNDING NUMBERS

Modeling Ice Passage Through an Auxiliary LockChamber With a

Submergible Lift Gate Contract No. NCR90-0030

6. AUTHORS

Jon Zufelt, John Rand, and Gordon Gooch

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

U.S. Army Cold Regions Research and Engineering Laboratory

72 Lyme Road

Hanover, New Hampshire 03755-1290

8. PERFORMING ORGANIZATION

REPORT NUMBER

Special Report 93-15

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

U.S. Army Engineer District, Rock Island

P.O. Box 2004

Rock Island, Illinois 61204-2004

11. SUPPLEMENTARY NOTES

12a. DISTRIBUTION/AVAILABILITY STATEMENT

Approved for public release; distribution is unlimited.

Available from NTIS, Springfield, Virginia 22161

10. SPONSORING/MONITORING

AGENCY REPORT NUMBER

12b. DISTRIBUTION CODE

13. ABSTRACT {Maximum 200 words)

River ice from the Des Moines and Fox Rivers combines with that of the Mississippi during spring breakup, resulting in

massive ice accumulations upstream of Lock and Dam 20 on the Mississippi River. The accumulations in the upper lock

approachareacauseconsiderable delaysto navigation, as icemustbe passed through thelockchambertocleartheapproach.

A physical model study was conducted to determine the effects of using the existing auxiliary lock chamber to pass ice.The

auxiliary lock chamber was fitted with a submergible lift gate at its upstreamend that could be lowered to pass ice and clear

the upperlockapproacharea.Modeltests wereconducted withrealand plasticicematerialtosimulatethebrash iceconditions

encountered during low-flowprototype winterconditions. The submergible lift gate worked well in clearing ice accumula

tions from the upper lock approach. It was necessary to disturb the accumulation and keep it from refreezing by simulating

towboat movement or high volume point source air bubblers to thoroughly clear the approach area.

14. SUBJECT TERMS

Auxiliary lock chamber

Ice passage

Lift gate

17. SECURITY CLASSIFICATION

OF REPORT

UNCLASSIFIED

NSN 7540-01 -280-5500

Navigation lock

Physical model

River ice

18. SECURITY CLASSIFICATION

OF THIS PAGE

UNCLASSIFIED

River transportation

Submergible lift gate

19. SECURITY CLASSIFICATION

OF ABSTRACT

UNCLASSIFIED

15. NUMBER OF PAGES

20

16. PRICE CODE

20. LIMITATION OF ABSTRACT

UL

Standard Form 298 (Rev. 2-89)

Prescribed by ANSIStd. Z39-18

298-102