CASE STUDY OF EXCAVATION AND DEWATERING TECHNOLOGY (GROUP 7)

SITE INVESTIGATION BNC31803 INDUSTRIAL CASE STUDY

EXCAVATION AND DEWATERING TECHNOLOGY GROUP 7

GROUP MEMBERS: NO

NAME

MATRIC NUMBER

1

MOHAMAD ARMIN HAKIMY BIN MOHD NASHARUDIN

AN190077

2

MUHAMAD HAZIQ BIN ABDUL MUTI

AN190158

3

ARIEF FIRDAUS BIN BAKHARY

AN190082

4

SITI AMINAH BINTI MANSOR

AN190074

Group Members:

MOHAMAD ARMIN HAKIMY BIN

ARIEF FIRDAUS BIN BAKHARY

MOHD NASHARUDIN

MUHAMAD HAZIQ BIN ABDUL MUTI

SITI AMINAH BINTI MANSOR

TABLE OF CONTENT

PAGE NUMBER

NO. CONTENT 1.

Introduction

1

2.

Problem Analysis

3

3.

Modern Tool Usage

9

4.

Project Management & Finance

18

5.

Conclusion

26

6.

References

27

1. PROJECT BACKGROUND AND INTRODUCTION Rosha trade complex is located in north of Tehran, Iran. The site area for construction is 1978m2 .It has 17 floors that 7 of them are located below ground level and 10 floors are located above ground level. The totally area of the building is 31319 m². In the fig. 1 situation of trade complex is shown. The building, when finished, will be the largest trade complex in Dezashib vicinity. As shown in figure2 the site has five sides (north, east, south-east, south, west), and located between Lavasani and Ammar streets. Depth of excavation is 20m. Commercial complex with 20-meter excavation in the built-up area of northern Tehran is the case presented here. Clayey gravel with a high density characterises type C Tehran alluvium, which is the site of this project. However, sandy clay with limited plasticity was found in some of the site's soil strata.

Figure 1: Rosha trade complex situation

1

Figure 2: Site Plan of Rosha Project (Dimension in meter0

PROBLEM STATEMENT • • •

•

An existence of three multi-story buildings on the perimeter of the site.

An active support system was required to limit the displacements to an acceptable level.

Unexpectedly, additional examination revealed that prior works downstream had blocked an abandoned qanat (subterranean hand-dug water conveyance tunnel), and the water discharge from the qanat into the area had caused the rise in the water table.

Some of the soil layers encountered in the site consisted of sandy clay with low plasticity.

2

2. PROBLEM ANALYSIS Formulation of an effective excavation support system with description of the components & mechanism. i.

Anchored retaining wall

It's a good idea to use soil nailing or anchoring systems in conjunction with a soldier pile system to stabilize excavations. The use of this stabilizing device in this project increased the resilience of the excavation to failing Due to the presence of three multi-story structures on the site's periphery, an active support system was required to keep displacements to a manageable level. This was accomplished by the use of anchored-solider piles beneath the buildings and regular anchors on the other sides. In between, soil nails were used to supplement the support structure. Two parameters were taken into account when designing the excavation wall stabilising system. First, there is the limit equilibrium approach, which analyses the equilibrium of a soil mass that tends to slide down under the effect of gravity.

Transitional or rotational movement is taken into account on an expected or known possible slip surface beneath the soil bulk. This method is based on a comparison of forces (moments or stresses) that resist mass instability and those that cause instability (disturbing forces).

The analysis of two-dimensional sections is done on the assumption of plain strain conditions. This technique implies that linear (Mohr-Coulomb) correlations between shear strength and normal stress on the failure surface dictate the shear strengths of the materials along the possible failure surface. The analysis yields a factor of safety, which is defined as the ratio of available shear resistance (capacity) to that necessary for equilibrium.

The finite element method was utilised to assess excavation stability as the second method.

The finite element method (FEM) (or its practical application, finite element analysis (FEA)) is a numerical methodology for finding approximate solutions to partial differential equations (PDE) and integral equations. The solution strategy is based on either completely eliminating the differential equation (steady state problems) or converting the PDE into an approximating system of ordinary differential equations, which are then numerically integrated using standard techniques such as Euler's method, Runge-Kutta, and so on.

PLAXIS 8.2 software was used in this study to estimate the lateral and vertical displacement of surrounding buildings and streets. This technique analysis is critical in situations where nearby structures are sensitive to vertical and lateral displacement, such as next to a skyscraper.

3

Figure 3: West wall finite element design using PLAXIS

Figure 3: West wall limit equilibrium design using GeoStudio2007

4

ii.

GWT Condition with Soil Properties

The scenario shown here is a privately financed commercial complex with a 20-meter excavation in northern Tehran's built-up area. The project is situated on Tehran alluvium type C, which is primarily clayey gravel with a high density. However, some of the soil strata found on the site were sandy clay with low plasticity. Table 1 shows the mechanical characteristics of the soil layers. Six metres below the surface, the groundwater table was discovered. As a result, the water table in the area had risen unexpectedly.

Table 1: Soil Properties of The Case Study

5

Demonstration of an effective groundwater management approach with description of the components & mechanism.

❖ Originally, the ground water table was initially encountered at a depth of 6m below surface. This was very unexpected, and additional research revealed that an abandoned qanat (subterranean hand-dug water conveyance tube) had been blocked by earlier projects downstream, causing the water table to rise. As a result, one of the first jobs was to lower the ground water level so that excavation could commence. ❖ Pumping on a permanent basis could be considered to reduce the ground water table.

However, because competent qanat diggers were readily accessible, it was decided to sink a series of interconnected wells around the site to collect and direct ground water into a slightly sloped, newly dug qanat 3 metres below the foundation level. ❖ The water in the well was then bulged with a drilling tool to encourage flow back and forth through the filter, while undesired fines flowing within the sump were cleaned before the submersible pump was attached because of the area's advantageous geography, it was easy to link the qanat to a sewage tunnel some 300 metres downwards. ❖ Figure 4 depicts a perspective view of the drainage wells and connected tunnels.

Figure 4: The layout of drainage wells and the interconnection tunnels ❖ The hand digging of wells and qanats on central Iran's dry plateaus is well documented. The qanat was always started at the outlet point and made its way up to the target water table in the foothills. It is now possible to start the conveyance system from the so-called mother-well (head-well) downhill using electrical pumps. ❖ The procedure described above proved successful in lowering ground water levels and is now being considered for use in another project. The removal of water from the excavation's walls enabled for the project's regular design method to be carried out. ❖ However, the ability of the soil to allow such operations is an indication of the alluvium's cohesion or cementation. Routine sampling and laboratory studies, however, are unable to detect cohesiveness in the coarse-grained strata of Tehran alluvium.As a result, somewhat expensive in-situ shear tests in underground galleries have become standard practice in major excavations.

6

Comparison of Method Evaluation of option

EDUCTOR SYSTEM

QANAT SYSTEM

Description

An eductor is a device that works on the venturi effect for pump operation. It is a type of jet pump used to pump out liquid/sediments where the suction head is too low for the normal pump to operate.

Qanats are underground tunnel systems that bring infiltrated groundwater, surface water, or spring water to the earth's surface using only gravitational force. Qanats have been used for irrigation and drinking water for centuries worldwide, particularly in the Middle East and North Africa and Central and West Asia.

OSHA Requirement

Yes

Yes

Personal Safety

High Risk

High Risk

Availability of Materials

Local

Local

Foundation Requirement

No

No

7

Advantages and Limitation of Solution

Eductor System Advantages -

-

-

-

-

Assists with close well-spacing in soils with low permeability, or vacuum is useful Once the system has been adjusted, minimal upkeep and fine-tuning are necessary.

Suitable for deep excavations that are not constrained by suction lifts

Limitation -

For high-volume applications, this is a problem.

-

Due to the dual supply/return line and associated piping/valving, this process is more time consuming.

Pump stations may demand more power than normal.

-

Due to the vacuum formed in the borehole, it is useful for dewatering stratified soils.

Installation from a sub-cut bench is unnecessary with ground elevation installation.

Qanat System Advantages -

-

-

-

-

Limitation

Exploits ground-water as a renewable resource, in contrast to the simple well Educes water loss from seepage and evaporation.

-

It is difficult to continually maintain and repair old Qanat systems.

-

Delivers large quantities of water to the surface without the need for using a pump and an energy supply.

Obtain energy source from this system

-

Flooding can destroy, or deposit sediment into, the vertical shaft and main channel.

Qanat specialists are usually too old or have passed away.

-

Qanats were a major contributor to the cholera epidemics of the 19th century.

water is filtrated naturally through the earth so a Qanat can deliver cold fresh water with low pollution in a hot dry climate.

8

3. MODERN TOOL USAGE 3.1 Anchored Retaining Wall In the case of non-cohesive and cohesive soils, anchored cast-in-situ and/or precast/cast-in-situ reinforced concrete walls are employed. A wall can be made up of numerous longitudinal levels that are stacked one on top of the other. One level of longitudinal stages is sufficient if the wall height does not exceed 6 m. Walls that are taller than 6 metres are built in two or three tiers of longitudinal stages. Each horizontal segment level can be up to 4 metres high, with a total height of 10 to 12 metres for the corresponding wall portion. The entire height of the wall is determined by the needed slope protection height.

Between individual levels, horizontal segments up to 1 m wide should be planned, serving the structure's construction, dewatering, and maintenance.

If the slope height exceeds 10–12 m, a 3 m wide berm between the individual wall parts must be designed. The berm is used for the structure's construction, dewatering, and maintenance. The thickness of the anchored wall must be at least 40 cm and no more than 60 cm (to allow the anchor force to be transferred). When anchored prefabricated slabs are planned, the weight of the slabs must be considered, as they will be transported to the site and erected. For transportation reasons, the slab dimensions are also limited. The foundation is only required for erection at the construction stage in this type of anchored wall.

This type of anchored wall is used to protect slopes of non-cohesive and cohesive mediumgrade soils. Because of the less favourable soil properties compared to anchored walls, this wall type's horizontal segments are limited to a maximum of 3 m. Such walls are built from the top down, beginning with the top of the wall and ending with the foundation, resulting in a very complex execution method. The walls are made up of horizontal segments in several levels with a maximum height of 3 m and sections that are 6–7 m long. By skipping sections on a chessboard system, work can be done on several sections in a single vertical segment.

The height of such walls is limited to about 10 metres for aesthetics and functionality. When a higher wall height is needed to protect a cut, an intermediate berm should be built first, followed by one of the wall types listed above.

Figure : Anchored wall constructed from above downwards

9

3.2 Eductor system

The eductor dewatering method consists of a series of small diameter wells with a nozzle/venturi (eductor body) driven by an at-grade pumping station. Eductor wells are extremely low-maintenance and cost-effective because they only require minor adjustments after initial startup. In low permeability soils, eductors are commonly used to pump less than 200 GPM. Because there are no suction lift limits, this method is ideal for deep excavations.

Eductor systems are pressurised closed-loop systems that use a high-pressure supply water stream and nozzle/venturi to create a localised low-pressure (vacuum) zone at the well's bottom. The vacuum draws groundwater into the system through a foot-valve that connects to the return stream and directs it to a recirculation tank.

A gravity discharge line collects excess water from the network (groundwater), and a jet pump pulls water from the same tank to supply water to the system. Suction lift isn't a problem with this method, and it can handle air without losing prime. However, it is incapable of handling large amounts of water.

• • • • •

•

Eductors are closely spaced (5-15ft), small diameter wells Mix between deep wells and wellpoints Each well is equipped with an eductor body (nozzle/venturi setup) near the bottom Installed to depths ranging from 20ft to 80+ ft depending on the project/geology Requires a supply & return piping system and highpressure jet pump to deliver supply water Multiple eductors can be powered by a single pump.

10

3.3 Eductor System Installation.

1.

2.

3.

4.

5.

6.

7.

8.

9.

Jet/Drill boreholes at spacing designed for excavation Install eductor screen/casing into boreholes and place filter pack/annular seal Develop the well Install the pressure and return pipes and eductor bodies Connect eductors to pressure & return pipes with high-pressure hoses Set the eductor pump station & tank Optimize, monitor, and adjust the system Lower water table Excavate

11

3.3 SOIL CONDITION

Figure: Soil Condition on Site

Figure: Groundwater Level (6m below the surface)

12

Figure: Site Excavating with Retaining wall

Figure: Anchored Support System

13

Figure: Groundwater Table After Dewatering

Figure: Groundwater Table Result

14

3.5 Adaptation for Eductor System

•

Useful in low permeability soils when close well spacing is required, or vacuum is beneficial

•

Low maintenance/tuning required once the system is optimized

•

Not limited by suction lift - Suited for deep excavations

•

Useful for dewatering stratified soils due to vacuum created in the borehole

•

Ground elevation installation eliminates the need to install from a sub-cut bench

•

They are flexible in level and layout

•

Stable in operation and Able to run dry without damage

3.6 Limitation for the Eductor System •

Volume limited, not typically suited for high volume applications

•

More labor-intensive due to dual supply/return line & other piping/valving

•

Pump stations can have higher power requirements

15

Proposal of operational efficiency & good practices to ensure optimised productivity & safety i.

Anchored Retaining Wall

The construction of anchored walls is based on the fact that ground anchors take the horizontal force, while the concrete structure serves as a foundation for the realisation of pressures and forces.

The use of contact concreting in the construction of anchored walls is a common feature. As a result, a typical drainage of filter layers behind the wall, as is the case with gravity walls, is not possible. Drainage concrete made of single grain size aggregate or drainage geo-textiles are used behind the wall for this purpose.

During contact concreting, drainage geo-textiles also prevent concrete and soil mixing. If there is a lot of water on the back of the wall, horizontal drainages must be built into the slope and connected to the wall drainage system.

Slopes with anchored walls must be sufficiently dewatered. On the top of the wall and on the top of any future vertical segments, channels or ditches must be planned for this purpose. The entire drainage system must be designed using hydrological and hydrotechnical data.

After the wall is built, the next type of supervision (superintendence) takes over, with the goal of ensuring the retaining/supporting structure's safety, serviceability, and durability.

The legislator has prescribed the maintenance and operation plan, which is a component part of the technical documents, for this purpose.

The maintenance and operation plan is a systematically organised document that includes photos, drawings, and texts in the form of guarantees, certificates, lists, schemes, instructions, and other similar documents that establish rules for the use and operation of the constructed or reconstructed structure and built-in installations, allowing the owner to properly maintain his structure.

Advantage of anchored retaining walls: • • • •

Mostly used for slope protection and earth retaining works of deep excavations.

Thin walls or very light structures can be designed in combinations with anchored walls.

Anchored walls are one of the most economical system of earth retention.

Combination with sheet piles, cantilever retaining walls, piled retaining walls etc are very much useful for very deep excavations to provide a safe working area.

16

ii.

Eductor System

Eductor dewatering systems work to control pore water pressure in low permeability soils so this method of dewatering is best suited for sites with soils such as silts and fine sands.

Like the deepwell systems, the eductor (or ejector) system is based on wells that are drilled to lower the groundwater level to provide stable working conditions. Eductors use air within the wells to produce a vacuum to draw water out of the soil.

The eductor system is commonly used in areas where soil permeability is low. It works particularly well in deep excavations with stratified soils. The eductors are spaced close together, similar to the array in wellpoint systems, but only one stage is needed to achieve drawdowns of up to 100 feet.

A venturi draws groundwater into the well screen and up to the surface with this system.

The well casing is formed by a large diameter pipe, while the return line is formed by a smaller inner pipe in the single pipe packer system. Water is forced through the nozzle and venturi at high pressure along the annulus between the two pipes.. The groundwater is then recovered through the well and into the return pipe, giving fine-grained soils a stabilising effect. iii.

•

•

• •

Settlement ponds and tank To remove sediment from water by settlement, the water must be left undisturbed (i.e., not moving) for an extended period of time. As a result, particles can fall out of suspension. They fall out at a rate proportionate to particle size, with finer particles taking longer to settle.

Settlement ponds and tanks must be large enough to accommodate particles to settle for an extended amount of time. This may necessitate the use of series ponds or tanks, baffles, or some other means to extend through flow and moreover treatment to account for the effect settlement.

In this construction settlement ponds and series of tanks are used as the treatment and disposal of contaminated water from the wider construction site Reason of chosen practices is caused by contaminated water can arise from dewatering of excavation.

17

4. PROJECT MANAGEMENT AND FINANCE

The limitation of urban ground space is becoming increasingly problematic as the socioeconomic system develops, modern industrialization and urbanization improves, and the population grows. Dewatering technology has evolved throughout time, resulting in newer and more advanced dewatering systems. Electroosmosis wellpoints were first utilized in dewatering in 1930. The multistage wellpoint, ejector wellpoint, and deep wellpoint have all been developed in response to the growing dewatering depth. (Yiqun, 2017) A construction environmental management plan's objective is to detail how a construction project will prevent, minimise, or mitigate consequences on the environment and surrounding area.

4.1 Control in surface water at construction site: a) Surface water runoff from the surrounding areas should be kept out of the excavation by sloping the earth away from it or constructing dikes around the top of it. To manage water runoff and decrease surface erosion, dikes and ditches can be built on the slopes of an excavation. Runoff into slope ditches can be removed by pumping from sumps constructed in these ditches, or it can be conveyed in a pipe or lined ditch to a central sump at the excavation's bottom and pumped away.

Dikes at the top of an excavation and on slopes should have at least 1 foot of freeboard above the maximum elevation of the water to be impounded, a crown width of 3 to 5 feet, and side slopes of 1V on 2-2.5H. b) A provision must be included in the design of a dewatering system for collecting and pumping out surface water so that the dewatering wells and pumps are not swamped. Controlling surface water within the diked region will not only prevent stoppage of the dewatering process, which might potentially jeopardize the excavation's stability, but will also prevent harm to the construction operations and reduce work interruption. The duration and season of construction, rainfall frequency and intensity, area size, and surface soil type are all factors to consider when selecting and designing a surface water control system.

18

Excavation operations are one of the most dangerous construction tasks, resulting in accidents among construction workers. A serious approach towards accident prevention is needed.

Sloping the ground, benching the ground, shoring the trench with supports such as planking or hydraulic jacks, and sheltering the trench with a trench box should all be appropriately applied at all times. Other excavation safety precautions involve: • •

Collapsing should be avoided by hammering the sides or supporting them with blankets.

Materials from the excavation should be stored a safe distance away from the excavation to prevent the chance of them falling on people.

•

Adding barriers to the excavation is a necessary precaution to prevent individuals from falling into the excavation.

Mechanical equipment should be avoided in places where there are subsurface services, and instead spades and/or shovels should be used.

Flooding can be avoided by installing adequate pumping equipment, which allows any water that penetrates into the excavation to be immediately pumped out to a safe area.

Make certain that employees are using personal protective equipment.

Make sure there are a safe entrance and exit and provide cave-in protection. Workers need protective systems or equipment while inside trenches with a depth of five feet or more ( 15m)

• • • •

Before employees can operate on or near excavations, OSHA requires employers to put protective measures in place to ensure their safety. Here are some examples of excavation safeguards: • • •

• • •

Structural ramps - whether for the exclusive use of people or of equipment around excavations, structural ramps must be erected to a competent person's design.

Employees who are not just working near excavations but are also exposed to public traffic must wear high-visibility vests or garments with similar reflective material.

Mobile equipment operators who do not have easy view of the edge of excavations should be able to observe warning signals such as barricades that indicate their approach to excavations.

Testing - The atmosphere in and around excavations must be examined to ensure that it is safe even before employees are permitted to operate on the site.

Emergency equipment — In the event of an emergency, equipment such as stretchers, harnesses, and so on should be ready.

Regular inspections - Daily inspections by certified competent personnel can assist reinforce the excavation safety protection installed for employees. Inspections performed prior to the start of a shift can detect and rectify potential safety hazards.

19

4.2 Technology Efficiency Eductor systems have been demonstrated to be effective in draining and regulating groundwater in difficult environments, resulting in dry, safe, and stable working conditions.

They can work at depths of more than 20 feet, which are not possible with traditional wellpoint systems. Around them, they can successfully depressurize impermeable soil formations such as clays and silts. With pressurized water, a single pumping station may activate and regulate up to 100 wells. When high-pressure water is pumped into the well, it passes through a nozzle and Venturi at the bottom, providing the vacuum needed to lift the groundwater and perform 90-foot draw downs.

Ejector systems connect many wells with a single pumping station and are often utilized when groundwater must be lowered more than 5 meters, commonly in low-permeability soil. They can be employed at close spacing in certain scenarios. The ejector (also known as eductor) system elevates the well water with a nozzle and venturi fed by high-pressure water, and hence is not restricted to suction lift. This allows for the use of common pumps and close spacing of wellpoints, as well as the capacity to dewater to larger depths of up to 30 m (100 ft) or more with a single stage.

Eductor Dewatering Systems are a cost-efficient choice for low-permeability soils, soil stabilization by vacuum in fine-grained, sandy soils, and produce effective results with the use of only one pump. The eductor well method of dewatering is similar to the wellpoint method in that high-pressure water is used instead of vacuum to draw water out of the wellpoints.

Because the depth of the building site exceeds 20 metres, the eductor system performs well in dewatering the soil below the water table.

The technical efficiency demonstrates that the eductor system can lower the water table from depths of 10-45 m in a single stage. The efficiency of such a system, however, is lower than that of other pumping systems. They become commercially competitive in relatively low permeability soils. Eductor well systems can be highly effective in low permeability silty sands, silts, and clays where pore water pressure control is critical. Because of the poor permeability of the aquifer, jet-eductor wellpoint or ejector systems are most useful for dewatering deep excavations when the volume of water to be pumped is relatively small.

20

General comparation for dewatering system: Wellpoint system

• easy installation, and • it’s relatively cheap and flexible, being practical and effective under most • soil and hydrologic conditions • This method is ideal for buildings with deep basements and is effective in sands and sandy gravels

Sump pumping system

• the simplest, cheapest, and most effective dewatering method. a risk of collapse of the sides as “the groundwater flows towards the excavation with a high head or a steep slope”. In finegrained soils, such as silts and fine sands, there is also a risk of instability which may result in ground movements and settlement.

Deep well system

deep excavation is needed, and a large quantity of groundwater is required to be removed, dewatering may be done by constructing deep wells in soils or rocks where permeability is between moderate (e.g., sands) to high (e.g., gravels).

Eductor system

•

cost-efficient choice for low-permeability soils, soil stabilization by vacuum in finegrained, sandy soils, and produce effective results with the use of only one pump

•

specialist technique used in low permeability soils such as very silty sands, silts, or clays. Eductors are typically used to help stabilize the side slopes and soil in the excavation area.

Figure: Different of Dewatering method depending on grin size distribution

21

4.3 Cost Effectiveness In a standard comparison of dewatering methods, sump pumping dewatering system is less expensive than other dewatering systems. Because gravity is the dominant playing force, this is the most popular and cost-effective way of dewatering. However, because the depth of this building site exceeds 20 feet, sump pumping is not a feasible dewatering option for the excavation.

In the case of the wellpoint system, many processes are required to reach depths greater than 5m. When close spacing is necessary, wellpoint systems are particularly cost-effective.

However, as a vacuum-type device, their efficiency is limited to 15-20 ft of usable suction lift and depth. This technique is limited to a depth of 15 metres, indicating that the excavation conditions are insufficient. Because deep well pumps are costly, they are only used for major projects. The organic Chemicals include epoxy resin, polyester resin and other resins are used in which method of dewatering of the foundation trenches.

Eductor systems are exceptionally low-maintenance and cost-effective, requiring only minor adjustment after first activation. This is due to the vacuum pump technology employed in the eductor system.

•

When more than five well points are required to meet extraction targets, the water is less than roughly 25 feet deep during pumping conditions, and the ground water is in a low permeability formation, vacuum pumps are typically used. A common header system with drop tubes in numerous wells is vacuumed by a single pump. When 15 or more well points are required, vacuum pumps are very cost-effective. A vacuum pump that includes an air/water separator, vapour controls, and a sump can cost anywhere between $10,000 and $25,000. Although vacuum pumps require more maintenance than electric or pneumatic submersibles, their life-cycle costs may be lower in some instances.

22

Figure: sample of eductor dewatering system cost estimation (Basana,2012)

23

Sheet pile vs anchoring system cost estimation Cost effectiveness is critical to compare the health and cost consequences of various therapies impacting the same health outcome. It can also be used to determine how much an intervention might cost (per unit of health gained) when compared to an alternative intervention.

For the support system, we have included the estimated costs for the sheet pile and anchoring system below to compare the cost effectiveness of both solutions. Based on the comparison, sheet piling has a lower cost required for support system installation than anchoring system.

The anchoring system could be just as effective as the pile sheet system. However, the cost of the anchoring method is prohibitively expensive. A good construction not only delivers on the effectiveness of the construction methods used, but also on the cost.

Support system

Total cost estimation

Anchoring system

1 000 000 USD

Sheet Pile system

up to 1 200 000 USD (Russell Hart,1990)

24

Figure: Cost estimation for sheet pile construction

Figure: Cost estimation for anchoring system (john s wolhope, 2015)

25

5.0 Conclusion In deep excavation of more than -20 meters of depth, the appropriate method and solution in each perspective of construction are necessary in preventing any damage toward the building construction, workers and presence building around the perimeter of the construction site. Groundwater affects the project whenever excavation must take place below the water table. Under certain conditions, unsuitable dewatering methods might cause damage to adjacent properties and result in third-party litigation. In this project, an eductor dewatering system is employed to lower the level of the groundwater table for the deep excavation, which can reach a depth of -20 metres. Ejector dewatering technology have been found to enhance ground conditions to depths of 50 metres. The eductor system was chosen for this project due to its technology, cost effectiveness and low risk. This report includes the comparation of cost and technology efficiency for the selected dewatering system, eductor system with the other dewatering system used globally.

The geotechnical conditions of the excavation site, as well as the safety of the excavation surroundings and nearby structures, greatly influence the selection of an acceptable support structure system and dewatering system to be implemented in an urban excavation.

Thus, due to various conditions such as varied geotechnical conditions and the presence of different surcharges due to nearby structures, selecting a suitable dewatering system for all projects is not practicable. For this study, the sheet pile method is used for the project's support system as it improves excavation resistance to collapse with low-cost consumption. Sheet pile support system has been proven as one of the most advance and contains high effectiveness.

The appropriate temporary drainage is also applied in as a control measures placed on construction sites to appropriately manage stormwater runoff. To protect the workers in construction site, safety measures are also been highlighted and need to be taken seriously as excavation construction are contain high potential of hazard.

26

6.0 REFERENCES 1. Missouri University of Science and Technology Scholars' mine. (n.d.). Retrieved January 17, 2022, from https://scholarsmine.mst.edu/cgi/viewcontent.cgi?article=3354&context=icchge 2. Miller, E. (1988, August 31). The eductor dewatering system. GROUND ENGINEERING. Retrieved January 17, 2022, from https://trid.trb.org/view/307498 3. Deep well dewatering systems for excavations -operations and design. The Constructor.

(2021, October 13). Retrieved January 17, 2022, from https://theconstructor.org/construction/deep-well-dewatering-excavation/17442/ 4. Eductor dewatering system. Griffin Dewatering. (2021, December 3). Retrieved January 17, 2022, from https://griffindewatering.com/dewatering/eductor-dewatering-system/ 5. Coker, A. K. (2007, September 2). Ejectors and Mechanical Vacuum Systems. Ludwig's Applied Process Design for Chemical and Petrochemical Plants (Fourth Edition).

Retrieved January 17, 2022, from https://www.sciencedirect.com/science/article/pii/B9780750677660500154 6. The design of groundwater control systems using the observational method. Géotechnique. (n.d.). Retrieved January 17, 2022, from https://www.icevirtuallibrary.com/doi/pdf/10.1680/geot.1994.44.4.727 7. Abhishek, A. (2020, June 5). What is an Eductor and how does it work. ShipFever.

Retrieved January 17, 2022, from https://shipfever.com/what-is-an-eductor/ 8. What are Deepwells? What are Deepwells? | Project Dewatering. (n.d.). Retrieved January 17, 2022, from https://project-dewatering.co.uk/technical_information/article/what-aredeepwells 9. Broms, B. B., 1988. Design and Construction of Anchored and Strutted Sheet Pile Walls in Soft Clay. Singapore, Missouri University of Science and Technology, Scholar's Mine. construction drilling Inc., 2016. construction drilling. [Online] Available at: http://condrill.ca/services/shoring-walls-cofferdams-cut-off-walls/soldier-pilewalls/ [Accessed 19 September 2017].

10. Russell, H. 1990 Cost Estimate for Sheet Piling Installation United States Environmental Protection Agency [June 22, 1990] https://semspub.epa.gov/work/05/233032.pdf 11. Griffin2018Marketing. (2017, October 27). 5 Reasons to Use Eductor Systems for Complex Rehabilitation. Griffin Dewatering. https://griffindewatering.com/5-reasonsuse-eductor-systems-complex-rehabilitation/ 12. Scottish Environment Protection Agency & Scottish Environment Protection Agency.

(2009). Temporary Construction Methods, Engineering in the Water Environment, Good Practice Guide. SEPA.https://www.sepa.org.uk/media/150997/wat_sg_29.pdf

27