Water Treatment Plant in Nigeria

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Geological Engineering investigations in situ and Geotechnical Engineering solutions to support the realization of the third lot of the Water Treatment Plant in Calabar, Nigeria

Luciano Blois PhD Chartered Engineer MICE, MASCE Professor of Engineering and Safety of Excavations, Faculty of Applied Sciences and Technologies, “Guglielmo Marconi” Telematic University of Rome, Italy [email protected]

ABSTRACT This paper shows the results of the Geological-Engineering investigations in situ and the Geotechnical-Engineering solutions to support the building of the third lot of the Water Treatment Plant, located in Calabar, Cross River State, Republic of Nigeria. In order to characterize the litho-stratigraphic succession and a geotechnical profile of the subsoil in Calabar, three different geognostic investigations have been carried out: surface, subsurface and laboratory investigations. The aim of the paper is to validate the use of the 3D subsurface geological-geotechnical modeling to optimize the design and the Engineering structures of the Water Treatment Plant. The results of the

four Bore Holes, drilled for a total length of 64 m and of the five Cone Penetration Tests, set up to a depth of 22,40 m from the surface, were analyzed to develop a geological/geotechnical model. Approximately twenty-two soil samples have been obtained. The variability of qc (cone resistance in kPa); e0 (initial void ratio); Eeod (compressibility modulus in kPa); Dr (relative density);  (friction angle); cu (undrained shear strength in kPa); for the clayey sand and gravelly sand were spatially described and the influence of these parameters on the immediate and consolidation settlements of the treatment plant was also highlighted.

KEYWORDS:

Geotechnical Investigations; Engineering Geology; Litho-stratigraphic; Settlements; Foundations; Micropiles; Finite element analysis; Water Treatment Plant; Calabar; Cross River State, Republic of Nigeria.

INTRODUCTION By an International Bank loan to the Cross River State Government in South-Eastern Nigeria, an Urban Water Scheme involving construction of New water treatment units, storage tanks and new pipe networks is presently being carried out at Calabar, the capital of Cross River State by a Consortium of three international contractors (Consortium-Impregilo-Bakolori-Associates) of Lugano (Switzerland), handling the different aspects of the job. The water treatment plant site is located in Calabar.

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In the 8th May 1999, the C.I.B.A. Consortium indented on me for a technical consulting about the solutions of the geotechnical problems of the construction of the third lot of the Water Treatment Plant in Cross River State Calabar. The geotechnical consulting started by the examination of the four Bore Hole (B.H. 1, B.H. 1A, B.H. 2, B.H. 3) drilled in the site of the Water Treatment Plant in Calabar, obtaining the stratigraphy of the site. The lithostratigraphic model and the geotechnical profile, demonstrated by the CPT test, showed that the subsoils in Calabar, even if appropriate to support the weights of the Water Treatment Plant, were susceptible to a settlement that did not allow the use of surface foundations to guarantee the perfect functionality of the Water Treatment Plant. Regarding the accomplishment of the geotechnical investigations in situ, the following objectives have been achieved: 

The definition of the geomorphologic and geological genesis of sediment and the detailed litho-stratigraphic profiles of the underground foundation, with particular attention to the existence of draining layers (continuous) in the case of fine grain soils;



The depth of soils layers and of the suitable thickness from the plant altitude;



The geotechnical characteristics of the underground foundation by using the elastic modulus in terms of stressdeformations (Es), the shear resistance in terms of the effective stress (c‟ and φ') and the undrained shear strength (Cu). In addition, geotechnical profiles of the underground foundation have been reached with particular attention to the existence of stiff and soft layers;



The evaluation of the immediate settlements and the consolidation settlements of underground foundation, under the load of the Water Treatment Plant, by using the elastic modulus in terms of stress-deformations (Es); the compressibility modulus (Eoed), and the decrease of the volume of the soil for loss of water due to the equatorial climatic conditions of Calabar. Moreover the following aspects have been considered:



The presence of low permeable soils with the consequent absolute vertical settlements;



The presence of the underground water and its possible interaction with the volume of subsoil, interested by the loads of the foundation of the Water Treatment Plant;



The selection of a better type of foundation;



The absolute vertical settlements induced by the underground foundation of the Water Treatment Plant;



The induced absolute vertical settlements among adjacent Clarifiers;



The selection of the executive foundation technology.

CLIMATIC CONDITIONS The Calabar Water Treatment Plant area is situated in the tropical forest of southern Nigeria, at east of the delta of the Niger river (approximately latitudes 4°30' N and longitudes 7°50' E). The climate is warm and very humid for the most of the year, with an average maximum temperature of 30°C (Celsius or Centigrade) and a recorded maximum of 43°C (Celsius or Centigrade).

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Figure 1: Water Treatment Plant Area CALABAR Located at about 5.00°N 8.40°E. Height about 63m / 206 feet above mean sea level.

Table 1: Average Temperature

(Source: derived from 583 months between 1909 and 1960) CALABAR Located at about 4.97°N 8.32°E. Height about 12m / 39 feet above mean sea level.

Table 2: Average Maximum Temperature

(Source: derived from 407 months between 1903 and 1950) In general, the area has two seasons, a wet season from April to October and a dry seasons from November to March. The Harmattan, a dry dust-laden wind blowing from the Sahara desert to the Gulf of Guinea, blows generally between the end of November and the middle of March. The annual average rainfall is about 3000 millimeters: the rainy season last from April to October but it is also usual to have some shower in all months. CALABAR Located at about 5.00°N 8.40°E. Height about 63m / 206 feet above mean sea level.

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Table 3: Average Rainfall

(Source: derived from 921 months between 1895 and 1973) Applying Koppen-Geiger (1953) climate classification, the Climatic type is valued as tropical rainy forest. The maximum value of humidity can be about 98% and the minimum about 62%. The Maximum value of humidity rarely coincide with the maximum value of temperature. The prevailing wind blows east and north-east, veering sometimes from south and Southwest.

WATER BALANCE Applying the method of Thorntwaite and Mather (The Water Balance, 1955), the water balance of subsoil has been calculated, for every month and for every year. CALABAR Located at about 5.00°N 8.40°E. Height about 63m / 206 feet above mean sea level.

Table 4: Water Balance

The parameters, shown in the table above, have the following meaning: °C average maximum temperature; R average rainfall; Ep potential evapo-transpiration; R-Ep effective rainfall; PLw cumulative potential loss water; FC field water capacity of soil = 150 mm for clayey sand soil; ELw effective loss water; Er real evapo-transpiration; Dw water deficit and Sw water surplus.

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The results of water balance are the following: 

from January to March the water deficit in the subsoil is estimated about 208 mm;



from May to November the water surplus in the subsoil is estimated about 1241 mm, refilling the underground water and consequently the rivers;



from January to March, the soil suffers the decrease of volume due to the desiccation, reaching the contact among the single soil grains;



from May to November, the soil suffers the rapid increase of volume due to the absorption of the rain, reaching to saturation;



due to the repetition of the annual cycle of desiccation and hydration of the soil, in this area the constructions with shallow foundations are not preferred.

GEOMORPHOLOGICAL CHARACTERISTICS The site is located in the Cross Rivers State Water Board, in Calabar metropolis. Calabar, the capital of Cross River State, is a seaport on an estuary of the Gulf of Guinea. The Calabar Water Treatment Plant is situated in a area which can be described as fairly flat by the orographic, altimetric and geomorphologic characteristics. The site for the water treatment units (consisting of aerators, sedimentation tank, filter and clarifiers) is located between 70.20 m. and 66.40 m above mean sea level, with big trees, shrubs and grasses. The whole treatment plant area presents a bland inclinations, included between a minimum 3 % and a maximum of 5%. The area, characterized by a warm and humid climate, is influenced by the dominant morphological agents like rain and temperature, determining intense chemical alteration processes that transform the feldspatis of igneous rock, present in the mineral clay, in a unstable and spongy lateritic soil characterized by a notable thickness (Clayey Silt Sand). This morphogenesis, associated with the hydrological dynamic of the Cross River and the associated processes of erosion and sedimentation, especially in river estuary, explains how the river sediments of Clayey Sand and Gravelly Sand have been founded in the underground of Calabar treatment plant area. To control the erosion of Cross River Shoreline and to provide an adequate protection to the city's waterfront, in 1987 the Federal Ministry of Works of Nigeria proposed and realized a US $5 million Project to build 4 km of waterfront to obtain the following objectives: 

the monitoring of the erosion;



the study the cases of erosion;



the identification of potential reclamation sites to enhance the economic feasibility of the project;



the feasibility studies and preliminary engineering designs for erosion control and protection works.

GEOLOGICAL CHARACTERISTICS The area investigated is located in Calabar River side of the Niger Delta, Southeastern Nigeria, it extends from the southern margin of the Oban Massif in the east to the line of the Niger delta in the west. Geologically, Calabar is underlain by the Benin Formation; one of the Formations of the Tertiary - Recent sediments of the Niger Delta (Short and Stauble, 1967) and is locally referred to as Coastal Plain Sands. The treatment plant area is characterized by an pronounced thickening of the Coastal Plain Sand sediments and the Charcort fault demarcates the beginning of the Niger Delta Basin. The Benin formation is the terminal

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stratigraphic unit of the three formations that make up the Niger Delta. Its type section according to Allen (1967) is made up of fine-grained, poorly cemented sands and gravels with clay and shale intercalation. The type section of the Coastal Plain Sands according to Allen (1967), is made up of fine grained sands, pebbles moderately sorted with local lenses of fine grained poorly cemented sands and gravels with clay and shale intercalations. The sands are sub angular to well rounded. although there are local variations of the type section. In addition the tectonism associated with the movement along the Charcort fault and the events of the spread caused the block faulting that results in the direction NW - SE.

Figure 2: Geological Map of Calabar (Edition 1957, Sheet 85, G.S.N.)

PROGRAMME AND RESULTS OF INVESTIGATION The analyzed program has been carried out in two steps: the first is about the execution of the 4 Bore Holes (B.H. 1, B.H. 1A, B.H. 2, B.H. 3) and the second about the five CPT (cone penetration tests) at a variable depth of about 16,6 m. for the CPT 4 and at about 26,4 m. for the CPT 5. The drillings were undertaken in Calabar from the 20/01/1999 to 30/01/1999 and the CPT tests from the 07/06/1999 to 08/06/1999 by the “TREVI Foundations” company. On the basis of the results of the Bore Holes and the CPT tests, the litho-stratigraphic model was realistically defined and the geotechnical profile of the subsoil of the area of the clarifiers, the filters and the reagent.

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Figure 3: Surveying program map: location of bore holes and cone penetration tests

Table 5:

LITHO-STRATIGRAPHIC CHARACTERISTICS The Calabar Treatment Plant area is characterized from a litho-stratigraphic of Clayey Silt Sand soil alternated with Clayey Sand and Gravelly Sand. The genesis of these soils can be classified as recent. As follows, it is illustrated a short description of the different lithotypes forming the litho-stratigraphic profile of the subsoil of the treatment plant area. The description of the litho-stratigraphic profile of the subsoils in the treatment plant area, reported in attached, is generated by using firstly the correlation between the five Cone Penetration Tests and the Four Bore Holes, and finally the reconstruction of the litho-stratigraphic sections. The analysis of the investigations shows a remarkable uniformity of the soil layers. The litho-stratigraphic results are depicted in the following table, from the top of the soil to the bottom succession:

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Table 6: Soil profile

The most significant results of these investigations and the suitability laboratory tests are cited in the tables attached in this paper. The final result of the correlations between the five Cone Penetration Test and the four Bore Hole of the preceding investigations, is the reconstruction of the litho-stratigraphycs section in the 3D subsurface geologicalgeotechnical modeling Stereo-Block-diagram, represented in this paper.

GROUND WATER The underground water resources of the treatment plant area and its magnitude depends on the geological formations. In the Oban Basement, for example, the underground water gets moving in a discontinuous way. In addiction the main sedimentary rocks are more significant for the ground water potential. In accordance with the aim of the investigation, two piezometer have been used, one into CPT – 1 until 22.00 m below the ground level and the second in the CPT – 5, until 14.10 m below the ground level. The readings of the piezometers, performed on July 10, 1999, show that there is no ground water but just damp on the bottom of the piezometer used in the CPT – 5. However, no ground water was found in the preceding geotechnical investigation in situ.

GEOTECHNICAL CHARACTERISTICS The CPTs were performed using the 20 tons equipment mounted on the wheels. The equipment consists of a thrust machine, comprising a hydraulic jacking unit of nominal 200KN. The equipment is furnished with a 2 mechanical cone penetrometer having a base area of 1000 mm and an apex angle of 60°. The cone penetrometer has a friction sleeve attached on top has and with 2

an area of 1500 mm . With this arrangement, we can measure both the lateral and the end resistance of the encountered soils. For every investigation a Cone Penetrometer Test was performed with the Dutch 20 tons penetrometer until the impossibility to the penetration, called “refusal”. Every twenty centimeters in depth, a Cone Penetrometer Test (CPT) has been performed to obtain the geotechnical parameters for the most significant soil strata in terms of Qc (point resistance) and Fr (friction resistance). Therefore, the Calabar treatment plant area is characterized litho-stratigraphically. The table below presents the depths of termination of the 5 CPTs performed at the treatment plant site:

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9 Table 7: The depths of termination of the CPTs

The table below shows the following geotechnical profiles from the top of the soil to bottom of the subsoil: Table 8: Clarifiers (Parameters)

In brief, among the six strata identified, the second, the third and the fifth are considerably compressible and susceptible to an immediate settlement and consolidation. The fourth strata has a variable width, with good geotechnical characteristics, even if less than those in the sixth layer. There are further information obtained by regarding the settlement through the laboratory test like the consolidation tests and unconfined compression tests. Table 9: Filters

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Figure 4: Litho-Stratigraphic and Geotechnical section between CPT-4 - CPT-1

Figure 5: Litho-Stratigraphic and Geotechnical section between BH-1 - CPT-2 - CPT-3

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Figure 6: Litho-Stratigraphic and Geotechnical section between CPT-3 - BH-2 - CPT-5

Figure 7: Litho-Stratigraphic and Geotechnical section between CPT-5 – BH-3

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Figure 8: Litho-Stratigraphic and Geotechnical section between CPT-5 – CPT-4

Figure 9: Litho-Stratigraphic and Geotechnical section between CPT-4 – CPT-3

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Figure 10: Litho-Stratigraphic and Geotechnical section between CPT-5 – versus CPT-1

Figure 11: Litho-Stratigraphic and Geotechnical section between CPT-5 – versus CPT-1

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Figure 12: 3D Block-Diagram subsurface Geological - Geotechnical modeling

GEOTECHNICAL LABORATORY TESTS In correspondence to every CPTs, one sample of soil has been extracted until the depth of 4-6 meters and sent to the laboratory tests of Calabar University. In brief, Table 9 shows the extracted samples and the respective results of tests of laboratory. Table 10: Scheme representing the extracted samples CALABAR ENGINEERING GEOLOGY INVESTIGATIONS UNDISTURBED SAMPLES BLOCKS EXCAVATION for oedometer test UNCONFINED SPECIMEN FROM GROUND with triaxial moulds Legend: Sampling date

FILTERS AREA:

consolidation tests

Computer Identification

Testing date

11-aug-99 DEPTH -4,00M

PIT n° 1 SAMPLE n° 1

1.1.4mSat

OEDOM: 1 saturated

12-aug-99

11-aug-99 DEPTH -4,00M

PIT n° 1 SAMPLE n° 1

1.1.4mUns

OEDOM: 2 not saturated

13-aug-99

13-aug-99 DEPTH -6,00M

PIT n° 1 SAMPLE n° 1

1.2.6mSat

OEDOM: 3 saturated

17-aug-99

13-aug-99 DEPTH -6,00M

PIT n° 1 SAMPLE n° 2

1.2.6mUns

OEDOM: 4 not saturated

14-aug-99

FILTERS AREA:

13-aug-99 DEPTH -6,00M 11-aug-99 DEPTH -4,00M

CLARIFIERS AREA:

unconfined tests PIT n° 1 SAMPLE n° 1 PIT n° 1 SAMPLE n° 4

Unc1.1.1.6m Specimen n°1

from

13-aug-99

Unc1.1.2.6m Specimen n°2

ground

13-aug-99

Unc1.4.1.4m Specimen n°1

from block

16-aug-99

Unc1.4.2.4m Specimen n°2

with wax

16-aug-99

Unc1.4.3.4m Specimen n°3

in lab.

16-aug-99

consolidation tests

13-aug-99 DEPTH -4,00M

PIT n° 2 SAMPLE n° 3

2.3.4mSat

OEDOM: 1 saturated

21-aug-99

13-aug-99 DEPTH -4,00M

PIT n° 2 SAMPLE n° 3

2.3.4mUns

OEDOM: 2 not saturated

22-aug-99

14-aug-99 DEPTH -6,00M

PIT n° 2 SAMPLE n° 4

2.4.6mSat

OEDOM: 3 saturated

26-aug-99

14-aug-99 DEPTH -6,00M

PIT n° 2 SAMPLE n° 4

2.4.6mUns

OEDOM: 4 not saturated

23-aug-99

CLARIFIERS AREA:

14-aug-99 DEPTH -4,00M 14-aug-99 DEPTH -6,00M

unconfined tests PIT n° 2 SAMPLE n° 2 PIT n° 2 SAMPLE n° 3

Unc2.2.1.4m Specimen n° 1

from

14-aug-99

Unc2.2.2.4m Specimen n° 2

ground

14-aug-99

Unc2.3.1.6m Specimen n° 1

from

14-aug-99

Unc2.3.2.6m Specimen n° 2

ground

14-aug-99

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15 Table 11: Unconfined compression test

The results of unconfined compression test and consolidation test are shown in the tables 10 and 11, as depicted below: Table 12: Consolidation test

The type section of the Coastal Plain Sands according to Allen (1967), is made up of fine grained sands, pebbles moderately sorted with local lenses of fine grained poorly cemented sands and gravels with clay and shale intercalations. The sands are sub angular to well rounded. Sieve analysis and Atterberg limits laboratory tests were carried out on some samples. Sieve analysis was based on ASTM D422-63 standards while Atterberg limits tests (liquid and plastic) were based on ASTM D423-66 and D424-57 standards respectively. Tables 12 locates the soil in the sandy region, but with appreciable amount of fines between 12 % and 47 %. Atterberg Limits on minus 30 (US sieve size) for the soils are also presented in Tables 12 and a plot on the plasticity chart places the soil dominantly in the Inorganic clays and silts with medium plasticity. The soil is thus classified (USC classification) as SC, SM, MH and CH.

Vol. 13, Bund. J Table 13: S.P.T. tests, Sieve Analysis and Atterberg Limits of sample borehole 1

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Table 14: S.P.T. tests, Sieve Analysis and Atterberg Limits of sample borehole 1A

(continued on next page)

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Table 15: S.P.T. tests, Sieve Analysis and Atterberg Limits of sample borehole 2 (details are in the Appendix) Table 16: S.P.T. tests, Sieve Analysis and Atterberg Limits of sample borehole 3 (details are in the Appendix)

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19 Table 17: Consolidation tests sample 1, pit 1 (details are in the Appendix) Table 18: Consolidation tests sample 2, pit 1 (details are in the Appendix) Table 19: Consolidation tests sample 3, pit 2 (details are in the Appendix) Table 20: Consolidation tests sample 4, pit 2 (details are in the Appendix)

Consolidation tests were carried out on both saturated and unsaturated samples based on procedure described in ASTM D 2345 - 70 using the loading sequence 10, 30, 50, 100, 200, 400, 800, 1600, and 3200kPa, and the floating ring type consolidometer. Other tests such as natural moisture content, consistency limits, specific gravity, and bulk density were determined in accordance with relevant ASTM standards.

Figure 13: Estimation of preconsolidation pressure using Casagrande method for the 4m depth saturated sample, Oedometer 1, Sample 1, Pit 1 , located in the filters area

Figure 14: Estimation of preconsolidation pressure using Casagrande method for the 4m depth unsaturated sample, Oedometer 2, Sample 1, Pit 1 , located in the filters area

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Figure 15: Estimation of preconsolidation pressure using Casagrande method for the 6m depth saturated sample, Oedometer 3, Sample 1, Pit 1 , located in filters area

Figure 16: Estimation of preconsolidation pressure using Casagrande method for the 6m depth unsaturated sample, Oedometer 4, Sample 2, Pit 1 , located in filters area

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Figure 17: Estimation of preconsolidation pressure using Casagrande method for the 4m depth saturated sample, Oedometer 1, Sample 3, Pit 2 , located in clarifiers area

Figure 18: Estimation of preconsolidation pressure using Casagrande method for the 4m depth not saturated sample, Oedometer 2, Sample 3, Pit 2 , located in clarifiers area

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Figure 19: Estimation of preconsolidation pressure using Casagrande method for the 6m depth saturated sample, Oedometer 3, Sample 4, Pit 2 , located in clarifiers area

Figure 20: Estimation of preconsolidation pressure using Casagrande method for the 6m depth unsaturated sample, Oedometer 4, Sample 4, Pit 2 , located in clarifiers area

EVALUATION OF VERTICAL SETTLEMENTS Assuming that a layer is considered tough if it has a Es value greater than 10 times the one of the below adjacent layer, in this case study the fourth layer doesn‟t suffer settlements appreciable. Using the theoretical formulation of Poulos and Davis (1974), we calculate the short-period and consolidation settlements:

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Rectangular structure (filters)

In these formulas, q represents the net pressure, L and B are the measures of the structure, Δσx, Δσy and Δσz are the settlements in the three components “vi” is the Poisson coefficient and Ei is the elastic modulus. Circular structure (clarifiers)

where R is the radius of the structure With this method the settlement is calculated in the center of the structure both for the filters and the clarifers (parameters), as shown in tables 14, 15, 16 and 17. The clarifers are subjected to the influence each other and the total settlement is due to the near clarifiers, multiplied to an influence factor: (Westergaard formulation) where r is the distance from the point and z is the deep of foundation

Table 26: Settlements at B1 point in the clarifer B (details are in the appendix) Using the immediate and consolidation settlement calculations and considering the hypothesis of adoption of micropiles foundations of small diameter steel piles (Micro-Tubix Piles) with two holes made on opposite sides of the piles at every 0.5 m intervals along the length of each pile, founded on gravel bed (layer 4), in the clarifiers, the filters and the reagent, area, the total settlement, for clarifiers and filters, results to be congruent to the settlement monitored after the building construction of Water Treatment Plant, by Akwagiobe, Becket and Ilori (A Record of Pile Load Test and Ground Improvement within the Coastal Plain Sands, Southeastern Nigeria, EJGE, 2002), as shown in Figure 21. The limits of these settlements were established and fixed by the Project Engineers at ≈ 3 cm.

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24 Table 27: Summary of Settlements both in the filters and clarifiers

Figure 21: Plant model of location of monitoring measurements

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The settlements of the clarifiers and filters, were monitored over a period of eight months (November, 2000 to June, 2001) by Akwagiobe, Becket and Ilori. The Table 28 (adapted from Akwagiobe, Becket, Ilori - 2002) presents the observed settlement values for the different parts of the structures. The maximum settlement obtained for the filter over this period was 6 mm at location „T‟ while the clarifier records the maximum of all the settlement values over this period at 21 mm at point „C1‟ on clarifier C. Table 28: Monitored settlement values for different parts of the filter and clarifier Structures

DISCUSSION AND CONCLUSIONS On the basis of the results interpretations and considerations of the all Geological-Engineering investigations in situ and the Geotechnical Laboratory Tests, have been obtained the input data, which are the geotechnical parameters, namely, qc (cone resistance in kPa); e0 (initial void ratio); Eeod (compressibility modulus in kPa); Dr (relative density); Φ (friction angle); cu (undrained shear strength in kPa). These parameters gathered from empirical classifications and from laboratory tests have been correlated to realize a 3D subsurface geological geotechnical modeling, for the clayey sand and gravelly sand. This 3D geological geotechnical model, describe the variability spatially and the influence of these parameters on the immediate and consolidation settlements and suggest appropriate support to optimize the design and the Engineering structures of the Water Treatment Plant. In conclusion using this model 3D for the immediate and consolidation settlement calculations and considering the hypothesis of adoption of micro-tubix-piles foundations of small diameter steel piles, founded on gravel bed (layer 4), the total settlement, for clarifiers and filters, results to be congruent to the settlement monitored after the building construction of Water Treatment Plant.

ACKNOWLEDGEMENT The author would like acknowledge the C.I.B.A. Consortium (Consortium - Impregilo - Bakolori - Associates) of Lugano (Switzerland) and Cross River State, Republic of Nigeria for the support given in this research and for the opportunity given us to participate at the solutions of the project, to resolve the dispute inherent the realization of the third lot of the Water Treatment Plant in Calabar.

APPENDIX The details of tests referred to in this paper can be found at http://www.ejge.com/2008/Ppr0895/Appendix.pdf

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REFERENCES 1. Allen, J. R. L. (1965) Late Quaternary Niger Delta and Adjacent Areas: Sedimentary Environmental and Lithofacies. AAPG Bulletin, 49(5): 547-600. 2. Akwagiobe G. A., Becket J.C., Ilori A.O. (2002), “A Record of Pile Load Test and Ground Improvement within the Coastal Plain Sands, Southeastern Nigeria”. EJGE Vol. 7 – 2002. 3. Bell, F. G. (1980) Engineering Geology and Geotechnics, Butterworth & Co. (Publishers) Ltd. 4. Bell, F. G. (1983) Fundamentals of Engineering Geology, Butterworth & Co. (Publishers) Ltd. 5. Bowles, Joseph E. (1978) Engineering properties of soil and their measurement, McGraw-Hill Inc. 6. Bowles, J. E. (1991) Fondazioni McGraw-Hill Inc. 7. BS 1377, Part 1–4 (1990) “Soils for civil engineering purposes”, British Standards Institution, London. UK. 8. BS 1924, Part 5–9 (1990) “Soils for civil engineering purposes”, British Standards Institution, London. UK. 9. Colombo P. (1979) “Elementi di Geotecnica” ed. Zanichelli. 10. Esu E. O., Ilori O. (2003) Deformation Characteristics of Coastal Plain Sands at a Water Treatment Plant Site, Calabar, South-Eastern Nigeria”. EJGE Vol. 7 – 2002. 11. Geological Survey of Nigeria (1957), “Geological Map of Calabar sheet 85”. first edition 1957. 12. Holtz, R. D., and W. D. Kovacs (1965) An Introduction of Geotechnical Engineering. Prentice-Hall, Inc., Englewood Cliffs, New Jersey, P.187. 13. Lambe, T. W., and Whitman, R. V. (1979) Soil Mechanics. S. I. version. John Wiley and Sons, New Yorks, Pp. 157, 287, 323. 14. Mickinlay, D, G. (1992). Soils In Jackson, N. and R. Dhir k.. (eds) Civil Engineering Materials. 4th Edition, Macmillan Education Ltd Hamsphire, Britain p325. 15. Peck. R. B., W. W. E. Hanson, and T. H. Thorburn (1974) Foundation Engineering 2nd Edition, John Wiley and Sons. New York Pp 64, 66. 16. Ramiah B.K. & Chickanagappa L.S. (1990) “Soil Mechanics and Foundation Engineering” ed. A.A. Balkema / Rotterdam). Rodio (1975), Indagini Geognostiche. 17. Roy E. Hunt (1983) Geotechnical Engineering Investigation Manual, McGraw-Hill Inc. 18. Sanglerat G. (1979) The Penetrometer and soil exploration, Elsevier Scientific Publishing Co. Inc.. 19. Short, K. C., and A. J. Stauble (1967) Outline of Geology of Niger Delta, AAPG Bulletin, Vol. 51. 20. Skempton, A.W. and D.H. MacDonald (1956) The allowable settlements of buildings. Proceedings of the Institution of Civil Engineers. Purt 3, 5, Pp.727-784. 21. Terzaghi, K. (1948) Theoretical Soil Mechanics. John Wiley and Sons, New York. 22. Terzaghi, K. and R. B. Peck, (1976) Soil Mechanics in Engineering Practice. 2``nd Edition. John Wiley, New York. 23. Tomlinson, J. (1980) Foundation Design and Construction. 4th Edition. Pitman Advanced Publishers, London, Pp. 133, 138-139.

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