Application pillar dam and movable caisson dam technology in building barrier construction to prevent sea water rising and improving flood relief at estuary rivers.

Application pillar dam and movable caisson dam technology in building barrier construction to prevent sea water rising and improving flood relief at estuary rivers.

Application pillar dam and movable caisson dam technology in

building barrier construction to prevent sea water rising

and improving flood relief at estuary rivers

Pro.PhD Truong Dinh Duz; PhD Tran Dinh Hoa; MSc Thai Quoc Hien; MSc Tran Van Thai

Viet nam Academy for Water resource Research

Add: 171 Tay son – Dong Da – Ha Noi

Abstract:

Global climate change is causing terrible disasters such as droughts, floods and sea levels rising To overcome this disaster is much work to do, but first of all, barrier constructions are done to prevent the sea water rising and also keeping fresh water for the national economy development

Due to the characteristics of most estuaries is deep, wide and soft soil therefore traditional technology would be difficult to implement or difficulty in construction Application pillar dam and movable caisson dam technology in building barrier construction at estuary will overcome the difficulties mentioned above, offer high performance in building, Operations, Administration and Maintenance

I Preface

From the ancient times to the present,

most of river barrier works have been

constructed by traditional methods The

works in reinforcement concrete bulk form

with characteristics as shown: bed slab from

1m to 1,5m thick, piers are placed on the

slab, the between of piers is valve gates, pile

system or non pile is placed under bed slab

depending on foundation geology

There are 3 methods for traditional works The first is applied for works which

constructed on bank: Excavating foundation hole, Construction of sluice on bank, Diversion through original river bed, Excavating canal for connecting sluice upstream & downstream and original river after sluice constructed, then earthfill dam is embanked for closure of old river This method is widespread in Vietnam and it is applied for works constructed on bench part

gate Pier Bottom

pile foundation upstream apron Stilling apron

Fig 1: Cross section of traditional works

River

soil Dam

Figure 2: Traditional sluice on bank

The second is applied for sluices constructed on river bed: Excavating of diversion canal

on right/left bank, Embankment of downstream & upstream cofferdam for closure construction site Construction of sluice in dry foundation hole After sluice constructed, Cofferdam must be broken out for flow running through sluice and closing diversion canal This kind of method is done on straight parts of river

The third is applied for construction

of a part of sluice in cofferdam:

Embankment of cofferdam for enclosing a

part of river, Construction of a part of

sluice in cofferdam, Diversion through a

part of remain river of original river After

completing sluice construction, cofferdam

must be broken out, Diversion through

constructed part of sluice, Embankment of

cofferdam for construction of the remainder part of sluice This method is used for construction

of works on wide part of river

The traditional method has advantage of being easy control in construction, skill in design

and construction However, diversion construction is complex if these methods are applied to works on Mekong delta or large river regions, and the weakness which are very difficult to over come has occurred at living resident zones as : Big quantity, a lot of construction land area occupied, Environment effected, some sites are difficult for construction and high cost The methods are difficult to apply to the regions

of cropping pattern transition

II Movable caisson dam technology

The idea of technology was given from 1992 - 1994 In the year of 2003, this technology

was continued to study in the ministry level subject “Design study and production of movable

caisson dam for economic structure transition on the Mekong delta “ In 2004 year, the

permission of experiment production with this technology was given at ministry level DAĐL-

CofferDam Diversion canal

Figure 3: Construction of traditional sluice on river

bed

Barrier CofferDam

Figure 4: Diversion sluice through river

construction for 7 sluices of Omon-XaNo project was applied this technology by the Ministry of Agriculture and Rural Development (MARD) and two sluices named Minh Ha &Rach Lum of Tran Van district, Ca Mau province were also successful in the year of 2007

The movable caisson dam technology was not only evaluated at the Vifotec award in

2006 and the invention exclusive right degree given in 2007, but also at the award of excellent technology among 5 awards on August 2007 given by the decision of ACECC – Asian Civil Engineering Coordinating Council

II.1 Technological principle and structure of movable caisson dam

a Principle:

Slump stabilization: Application of optimal structure with light slab beam for bed stress smaller than allowable stress of weak bed, and the bed treatment is not necessary accordingly

Slide, overturning stabilize: Using bed earth friction with bed of works and sluice side earthfill with side wall

Permeable stabilization: Following the horizontal border principle under the bed of works Erosion stabilization: Enlargement of sluice span for speed after sluice smaller than allowable erosion speed of weak original

earth, and so, the simple consolidation is

only necessary

b Structure of works:

Form 1 (Hermetic float box):

Bed and pillar in box form with side

slab structure and optimal bearing frame

Material for production of movable caisson

dam is normal one such as reinforcement

concrete, steel, composite Movable caisson

dam bed box is divided a lot of gallery spans Each works can be included 1 barge with valve spacing from 4 to 30m or many barges connected each other by watertight structure depending on the width of river

Form 2 (side slab box): Bed box and pillar with side slab unit structure, both of upstream and downstream of sluice are location for installation of valve or slot, sluice body and slot at two heads, these made a box with open on face and water tight around faces, so that the sluice can be floated on the water surface and movable to construction site

Figure 5: Cross section of movable caisson dam

The gates using for this works can be Clape, segment, self acting, rubber, vertical lift gates…

c Construction solutions:

* Caisson dam manufacture:

- This dam is manufactured in factory

or precast hole, or on earth mound where

land clearance is not necessary

- Installation of valve gate and

operation equipment

- Diversion water into precsat hole

to float dam to construction site

* Erection work:

- Excavation of foundation hole:

- Chief cost price, expenditure for the dam is less 40% than traditional works in the same condition Investment level for traditional method is around 800 million VND per 1m sluice while only 250 million VND per 1 m sluice for caisson dam technology Taking Phuoc Long dam

in Bac Lieu province as one example on its price of 8 billions VND for traditional method and only 2.3 billions for caisson dam technology

- The method has both of science and economic significances on caisson dam’s movable ability in case of changing construction site by crop production transition demand, and it can be reused works structure, even expenditure is not necessary for breaking out work

- Backward dam can be replaced by temporary one but it will be waste and environment pollution, during only 10 years of dam management, the expense for temporary dam is the same expenditure as for construction of one movable caisson dam

b Technical output:

- Movable caisson dam technology has opened one more new direction of river barrier technology and promoted new technology development in construction of river barrier works

- Using bearing ability of original bed for works construction without weak foundation treatment costly

- Optimizing its structure, saving materials, Thông Lưu dam as one example It was constructed with traditional method with around of 1500m³ reinforcement concrete, but with movable caisson dam technology, the Thong Luu dam was completed with the amount of 180m³ reinforcement concrete

Figure 6: Phước Long dam for salty protection

- This dam is constructed and

erected on river, so that it is not

necessary to move houses, make

compensation…If traditional method

was applied in dam construction, the

above-mentioned work must be done

- The new technology should

meet tide zone economic development

requirement for improving living

standard and contributing on social

stable at coastal regions

-The new technology brings higher output in construction at underdevelopment transportation zones material transportation is very difficult at zones with complex natural topographic conditions as Ca Mau peninsula where is remote area

- Movable characteristic of caisson dam meets open planning, future economic development for contributing the national agricultural modernization

- Environmental pollution is not occurred at zones where broken out temporary dam Natural environmental landscape is not changed by using movable caisson dam technology (construction diversion and plan are not need to be done…)

- Environmental protection and flood drainage capability at caisson dam site are better than traditional and temporary dam sites by spacing open

- The types of present works and difficulties at Ca Mau peninsula can be solved by movable caisson dam technology but not by others

III Pillar dam

III.1 Definition of pillar dam

Pillar dam is type of works on river, its duty is water source regulation Pillar dam is constructed on river bed The water drainage and river bed are about the same width, bearing by pillar laid on pile system, beam supports valve which placed on two pillars, permeable protection

by grooved pile under valve supported beam erosion protection by rock cover

Water pressure by the difference between upstream and downstream which is received by valve gate and together with loading capacity on bridge, all, transmitted into pillar, then continued down to foundation pile system Such type of works for water barriering and regulation

is called pillar dam

III.2.Design principle of pillar dam

1 Works stable by pile system fixed into earth bed of river It can be used reinforcement concrete, pipe, or filling piles depending on field conditions Pillar dam is bearing big vertical loading capacity, because of in pillar dam there are a lot of piles for bearing cross loading

Fig construction of sluices in foundation hole Cà Mau

capacity Consequently, the construction of pillar dam should be combined with construction of bridge

2 Permeable protection according to the principle of sheet pilling vertical bounder, but not bed sheet

3 Enlarging sluice span for increasing flood drainage capacity, flow speed is reduced and equal delivered at tail of downstream in order making it smaller permissive scouring flow speed

of bed earth, so that spillway consolidation can be minimized (consolidation by rock cover is enough)

Sluice is placed on right main flow, construction diversion through river, it is no need to construct dam for river closing and diversion canal Quantity of land compensation is less

III.3 Structure of Pillar dam

a Supported pillars

The pillar is main bearing component which

made by pile system This system is fixed

into bed, the pile can be compacting, filling

Supporting is placed on the pile system,

pillar is placed on the supporting Spacing

between pillars is from 5 m to 40m

depending to field requirement Supporting

pillars are constructed in flow by blockade

of steel slab pile supporting frame, coffer

dam is not round embanked and construction

diversion canal is excavated Structure of

supported pillar is shown in fig 8

b Beam supporting valve

Structure of the beam is single one,

the beam is chocked on two pillars, it

receives a part of water pressure from valve

gate and the pressure is transmitted into supporting pillar, beam supporting valve together with two pillars at both sides make 3 faces against valve gate Beam supporting valve can be precasted

on dry place, then, put together into position or in-situ beam in blockade of steel slab pile supporting frame

pile foundation Antiseepage

upstream apron Lowerbeam

Gate

Figure 8: Cross section of pillar dam

Dam permeable is protected by groove slab fixed deeply into bed earth following stand permeable bounder The groove is made of steel, steel covered composite or reinforcement

concrete Groove is compacted along river cross section, under supporting pillar, valve site and on bedside where much permeability Edge of groove surface is connected with valve supporting beam tightly

Two types of permeable protection: Type of coupling into water Two holes on pillar are remained for installation of groove supporting beam Groove for permeable protection is compacted at the centre of two groove supporting beams and two ears of groove are chocked on these beams which make the same height for grooves for water tight between groove head and valve supporting beams All of groove piles, valve & valve gates make a water tight plane which separates upstream and downstream of sluice

Type of construction in place

Type of valve beam is constructed in place at surround frame, groove supporting beam is not necessary but the head of groove pile is connected directly into valve supporting beam concrete

d Structure of scouring protection

Width of pillar dam is nearly the same as river’s, so the water level difference between before and after dam of flood flow is very small Flow

through pillar dam is nearly the same bridge’s, flow speed is

nearly the same river’s, therefore long, thin concrete

reinforcement spillway as traditional structure is not

necessary but method of flow consolidation by rock cover is

necessary for protection of before and after sluice

connection part which effected by vortex flow after dam

pillar Downstream is not effected by scouring with the

condition to be V ≤ [V] in which V is after dam flow

mean speed, [V] is permission non-erosion speed of bed

earth

Erosion protection textile is spread directly on bed

surface at upstream and downstream sides Beams and concrete reinforcement frames are used to keep the textile, Erosion protection concrete slabs, rock covers can be used to make diffuse walls

by concrete beams which lay on piles

e Valve gate and control devices

Figure 9: T type of putting together

construction

Figure 10: In-situ construction type

The type of valves such as Clape, buoy can be used for intercepting dam with type of pillar Rotation axis is under these valves, When valve opens , its axis is bed earthen , it is not obstacle for flood discharge and it is not effected by floating, windy, waves and plane, automatic, radial valve gates can be used For type of rotation axis under valve, its axis is fixed into valve supporting concrete reinforcement beam to transmit bearing down and reduce moment which impacts on supporting pillar, thus pillar size is reduced Spacing of these vales can be enlarged to be 20÷40m, but it is difficult for reparation work

III.4 Construction method

- Construction under water The hammer with its capacity of 2.5 – 3.5 ton is used to compact piles on floating platform, this hammers are used widespread in Viet Nam For big dams, supporting pillar foundation can be treated by big dimension pipe or filling pipe

- Construction of pile platform and supporting pillar are done in steel slab around frame or face down bucket

- Permeable protection groove piles are done under water by crane, compacted hammers (Shake hammer can be combined) on

floating platform

- Valve supporting concrete

reinforcement beam is placed in site (at

location of each dam span) or on floor, then

using jack, winch, and crane to move them

down to their position Steel standard

framework should be used to reduce errors in

construction of concrete, pile framework

system, pillar framework and supporting

beam framework

- Valve gate and rotation axis

supporting steel framework: comprehensive

installation of valve gate is done before moving them to their location by crane, winch, and kick

on floating platform or floor

- Transportation bridge beams are installed by crane laying on barge or one kind of beam plunge machine

III.5.Design works following pillar dam and its economic output

II

Figure 11: Cross section of Dinh river Dam in Ninh

Thuan province

- Cui river sluice consists of 2 gates, width of each gate is 7.5m the difference of water level is 3m All of principle and idea of pillar dam are experimented, its construction is carried out under water However, its economic output is not so high by its size is small

- Hiền Lương sluice in Tư Nghĩa district, Quảng Ngãi province, its cost is 200 million VND per/1 0 m wide Hiền Lương sluice has span with 64m wide, the sluice consists of 16 automatic gates with 4m wide for each, water level difference is 2m, bridge 4m, H13-X60 Total cost is 11 billions VND, Cost saving is 12 billions VND

- Thao Long weir in Hue city with its biggest size in Viet Nam consists of 15 spans, Bxh = 480.5x4m, bridge spacing is 33m, bridge surface is 10m, weight H30-XB80 Clape valve with its under axis of 31.5m wide, water level difference is 1.2m Control by hydraulic cylinder, construction cost is 115 billions DVN and this method is 100 billions less than traditional method

Figure 12: Completed Thảo Long Dam

- Year of 2006, the institute was commissioned to apply the technology for 7 O Mon - Xa

No works instead of designed traditional works but it is very difficult to have plane for construction in Can Tho province by the Water resources construction and investment board No.10 under the Ministry of Agriculture and Rural development (MARD)

III.6 Advantages of pillar dam:

- Be sure of with works is nearly the same flood discharge capacity as without works, it means that environment is little changed due to upstream without inundation Thanks big flood discharge section, so downstream river is nearly not changed

- Works is constructed right on river, cofferdam and diversion are not necessary to construct, therefore, permanent and temporary land compensation is not necessary

- Construction of works can combine with construction of big size water resources and walk Transportation Bridge works, so social-economic aspect is meaningful, and separation in construction is protected in order protection of lavish money in infrastructure construction

- Reasonable structures are applied, build quantity is reduced accordingly, the river is larger, the cost is cheaper

III.7 Conclusion

In the situation of the water resources which will be able to be limited by increasing demand of water using at upstream of Red and Cuu Long rivers On other hand, the climate on the earth is hotter and hotter, thaw on North Pole, sea water level rises high, and it is estimated that in the year 2050, sea water level will be able to be risen from 35cm – 50 cm According to forecasting, Vietnam is one among five countries to bear big loss when sea water level rising The salinity intrusion protection and fresh water storage works should be constructed to against heavy losses by phenomenon of slump earth and sea water level rising On the base of the above-mentioned results, from now on, this technology will be studied completely to barrier large river estuarine and deep water head as Ham Luong, Cai Lon rivers

Reference

[1] Pillar dam experimental production project report; Thao Long project design profile; Movable caisson dam experimental production project; movable caisson dam subject