Competency Demonstration Report Career Episodes CE1 Narrative A (a) Introduction CE1.1 When I was working as civil engineer in regional office of central engineering consultancy bureau (CECB) in Kurunegala district of Wayamba province in year 2007, I was assigned as resident engineer for the construction of pile foundation for maternity ward complex at Teaching hospital, Kurunegala. CE1.2 This site was located in the Teaching hospital in Kurunegala city. CE1.3 I have been working in Central Engineering Consultancy Bureau since year 2005. CE1.4 I was working as resident engineer for this project (b)Background CE1.5 This project was the stage one construction of eight storied maternity ward complex in teaching hospital, Kurunegala which was planned to be constructed soon to cater the requirement of the area .This hospital is located at geographically important point of the country. Therefore there was a long felt need to expand the facilities of the hospital to provide better services to the patients of the area. This hospital is at the heart of the city and most of the buildings were of single storied buildings dates back to colonial era .Hence it was a great challenge to expand the service as it needed to increase capacity of the wards, theatres etc. As a result of it, my organisation had prepared master plan for the future developments of the hospital and the sequence of development to be carried out. CE1.7
Therefore eight storied state of the art maternity ward was planned to be constructed in a marshy land at the hospital premises. Once this building was completed three single storied buildings could be removed to provide space for new developments according to the master plan. CE1.8 Hence ministry of the healthcare and nutrients had phased the construction of maternity ward complex to ease the financial burden to the ministry. So it was decided to construct pile foundation for the building as stage one. Further being a government organisation, CECB had been selected as consultant and procurement procedure was followed according to ICTAD(Institute of Construction, Training and Development) guidelines in Sri Lanka. But dismay to the ministry of healthcare, all bidders had quoted threefold the price of engineers estimate. At that time there was a huge demand for the piling contractors in capital of Sri Lanka and that was the reason for such a big bid prices. CE1.9 Therefore ministry of healthcare and nutrients had decided to award this contract CECB as design and built basis to price of engineers estimate hoping that project would be delivered in time while maintaining the quality.But it was a great challenge as CECB did not have piling machines. So Deputy General Manager,CECB had given
me a task to
discuss with all piling contractors for hiring piling machinery for this project. However it was not possible to hire pilling machines within the allocated budget during that period. So I informed to my Deputy General Manager of the situation and also I informed him that if the number of piles can be reduced, cost could be brought down. Then he had discussed this matter with design engineers to reduce the number of piles. Then he proposed to have raft foundation at one half the building where soil was comparatively good. But then there was a problem of having differential settlement due to raft foundation and the pile foundation. So this option was also abandoned and design engineer had decided to decrease number of piles introducing larger diameter group piles(750 mm,900 mm,1000 mm) piles instead of smaller diameter group piles (300 mm,450 mm). As a result number of piles were reduced to 154 from 340.And I was able to hire a piling contractor within allocated budget. CE1.11
Ministry of healthcare and nutrients had given their consent to go ahead with the new design having identified the dire requirements of new maternity ward complex as well as to develop General Hospital, Kurunegala into full-fledged hospital in the country. CE1.14 Organization structure Chairman
Additional General Manager
Deputy General Manager Project Manager
Civil Engineer Technical Staff
CE1.15 As a project engineer, followings were my list of duties I. II.
Site planning Preparing of work program using MS Project
III.
Supervision percussion boring
IV.
Concreting of piles
V. VI. VII. VIII. IX. X. XI. XII. XIII.
Monitoring of pile tests Designing of a shoring system Supervision of construction work Calculate quantities for payments for sub contractors Deal with client Giving instructions and guiding sub contractors Monitoring the progress and keeping records of boring of piles Document management Coordination with design engineers and the regional office of my organisation
(c)Personal workplace activities CE1.16 I went to site to commence construction activities with my Deputy General Manager and I was asked to request staff necessary to complete this project in time. Then I requested to have three technical officers for technical staff. After that I had meeting with the Director of the hospital and other concerned parties to inform them about the construction and I was requested to take measures to make minimum disturbances to the patients as site is very close to wards of the hospital. Therefore I immediately started the erecting of twenty feet high protective fence covered using Galvanized Iron as a sound barrier, dust barrier and for security purpose. Then I constructed office facilities, accommodation for workers including sanitary facilities. I always paid maximum attention for the safety within the site by installing putting several power outputs by shortening length of wires to equipments and machinery. Especially in
country like ours, workers very reluctant to use safety boots, helmets and other safety measures so I had to take bold decision to remove workers who were not adhered to the safety requirements. Also I conducted site meeting in the morning with all site staff and workers and monthly progress review meeting was conducted at every month with participation of all parties including client, client representative, sub-contractors and design engineers. CE1.17 After site clearing, initial setting out was carried out according to the master plan and I found that some part of the foundation was lied on old generator room and the control room of power supply to the hospital. This was a major obstacle at the beginning of the project so I immediately informed to my project manager. This was a big issue but decision was taken to relocate the power room and old generator. So I completed the setting out for the all locations using total station and coordinates were taken for all points. I always checked the position of the pile point before staring boring as maximum of 75 mm eccentricity was allowed by the design engineer. I had to complete the foundation for the ward with 154 piles, comprised of 74 numbers of 750 mm diameter piles, 50 numbers of 900 mm diameter piles and 1000mm diameter piles, with pile caps and ground beams. The piling contractor used percussion type piling machines and had mobilised five piling machines. In this percussion type machines, cutting tool is hanged on the tri pod and one end of the steel cable attached to the cutting tool and other end is on the motor. During operation cutting tool is dropped at the location where boring is to be carried out. Normally tri pod is located at any point using crane and some workers has to adjust the legs of the tri pod so as to cutting tool is at centre of the point and this tedious procedure. Most of the area of the site was of week soils, mobile crane used frequently get stuck in the mud while it was in the operation for shifting piling machines to other locations. From percussion type piling machines, generation of vibration is very high usually it cannot be deployed in built-up areas. But in this site percussion type machines could be used as this site 2.0 meter below the surrounded area although buildings were at close proximity to sites. Also, all of buildings were single storied. CE1.18 From bore-hole log sheets and contour of the bed rock, it can be understood that bed rock could be found at the depth ranging from 9.0 meter to 15 meter. Also bore holes data, I noticed that sandy soil was encountered in the depth ranges from 3 meter to 8 meter and ground water level was at the depth of 1.5 meter. Hence for soil boring
Bentonite slurry was used to prevent collapse of soil into the bore by exerting pressure against the pore water pressure. Therefore I had to monitor the density of the bentonite as well as the viscosity of the slurry. Density of the Bentonite slurry was tested using mud balance and the viscosity was checked using cone penetration test. So I gave instruction to contractor to do these tests frequently to prevent collapse of pile. CE1.20 Structural design engineer had given instruction to socket the piles on rock minimum length of diameter of the particular pile. But I had great difficulty in get this socket length as contractor was not willing to do this as cutting tool was worn very fast during rock socket. So I always maintained a log sheet and marked the penetration rate for the pile boring. When the soil boring was completed, rate of penetration was changed. Then rock boring was continued until penetration rate is 3.0 mm per hour. Also I referred the borehole data close to particular point and contour of the rock to have knowledge of the level at which rock could be found. At the same time, I collected the rock samples at every half an hour to identify the rock quality and samples were sent to site office to display with the depth at which it was collected for future reference. CE1.21 Sometimes piling contractor tried me bamboozled by hitting the cutting tool slowly to show me that rate of penetration is below the 3.00 mm hour and I had hot arguments with contractor’s personals during rock boring. So I assigned one technical officer full time at the piling machine when rock socket was started and I gave them all facilities during rock socket such as foods, drinks to prevent them being exhausted. Sometimes I game them day off analysing case by case. After pile boring was completed, pile bore was thoroughly washed using bentonite slurry to remove all soil and rock particles. Then reinforcement cage was slowly lowered in to the pile bore using a crane. After that tremi pipe (assemblage of tremi pipes of length of 6.0 meter and diameter of 200 mm), through which concrete was poured, was inserted into the pile bore for pouring concrete to the pile. Ready mixed concrete of Grade 30n/mm2 (cube strength) was used. Concrete was taken to site and initially tested for slump. It should be within range of 150 mm to 180.If the slump of concrete was within the range I allowed to start pouring concrete and three test cube were cast for compressive strength testing. Then concrete was filled into the tremi bucket and tremi was repeatedly immersed in and lifted to fill the concrete into the pile. But I had to make sure that tremi was not lifted above the poured concrete level otherwise bentonite and mud would be mixed with the fresh concrete. While the pouring of concrete was done, tremi pipes had to be removed one by
one to facilitate pouring and not to disturb already filled concrete. But I always made sure that balance tremi bars were at inside the previously poured concrete by calculating volume of the poured concrete. For this exercise, close attention was very much needed and quality of the pile depended on my crucial decisions. I had to be genuine when doing this work and if I understood that crane operator had lifted tremi bar more than instructed, I immediately reported in the log sheet for selecting this pile for testing. Normally pile is bored, it can be estimated the concrete volume needed and I ordered concrete with 5% more giving some tolerance. However some instances I had noted that more and more concrete was required. I faced great difficult situation when such situation was happened and one pile had to be under-cast due to that reason. As Ready mixed concrete plant was at 30 kM away from the site ,it was not practical to bring concrete when extra concrete was needed due to pile bulging. Hence as remedial measures to this, I always tried to make ready two or three piles for pouring concrete by staggering the time of pouring concrete by half an hour to one hour depended on pile depth. Then I was able to manage the concrete requirement as I could ask for additional quantity and it could be brought at site before initial setting time of the concrete. I always made available mould for kerbs, cover slabs to use excess concrete. CE1.23 So I had built up good relationship with the ready mixed supplier and even ready supplier’s drivers. Also I always stationed one of my technical officers at concrete batching plant to have better communication channel as well as to get priority for our concrete. CE1.24 Sometimes I noticed that some piles needed less quantity than calculated volume. So I noted those in the log sheet as it could be due collapse of soil or due to pile necking (cross section of pile is reduced).Hence I referred this matter to geotechnical engineer and structural engineer that this was serious issue to be attended. Also I noticed this condition especially at particular area and suspected that was due to sandy soil condition. After inspection of the site, design engineer and geotechnical engineer decided to use steel casing for piles at this particular area due to sandy soil condition. CE1.25 Then affected piles were selected for Pile Integrity Test (PIT)The pile integrity testing (PIT) is performed by applying an impact wave at the pile top using a hand held hammer and measuring the resulting signals on a PIT collector instrument. The PIT collector function is based on the” Low Strain Pile Integrity Testing Methods”. It is called Low
Strain since the impact of the hand held hammer generates small velocity and strain values. The pile top is required to be leveled and free from water, dirt or other debris before test is carried out. The testing technician will clean a portion of the pile top for the attachment of an accelerometer. The pile identification for testing is then keyed into the PIT collector. The accelerometer is attached to the pile top using a suitable bonding wax. Three hammer blows are generally given to the pile top and recorded by the PIT collector. The averaged signal is then displayed on the PIT collector for interpretation on site. When there is a necking in the pile, collected velocity traces shows a tensile response caused by reduction in impedance of the pile. But this reduction of impedance may be due to variation of concrete stiffness. I arranged to have PIT test for randomly selected piles after discussing with project manager. So I selected four number of 750 mm diameter piles, twenty number of 900 mm diameter piles and seven number of 900 mm diameter piles. In PIT reports, some piles were suspicious of having necking due to tensile response of velocity and depth at which it could be possible was given in the report. CE1.26 So I decided to excavate those piles as depth was 4.0 meter below the ground level. After excavation I noticed that there were some reduction in the pile and I asked to design engineer to visit this and advised me on this. He came to site and instructed me to do PDA (Pile Dynamic Analyzer) test for that pile to make sure this pile can take the anticipated load. For this excavation I designed shoring using universal column of 200mm x200mm, which were available at site. I inserted universal columns at interval of 600 mm and tied at the bottom, middle and the top by welding 75mm x75 mm equal angles. Then 25 mm thick timber planks were placed between universal columns. At four corners, horizontal bracings using 75mm x75 mm equal angles were welded for preventing twist of the shoring. CE1.27 On the other hand there old generator room and main power supply control room had to be relocated. So met in charge of power supply and discussed this matter him then he explained the gravity of the situation as power supply could not be disconnected for even
five
minutes
for
ICU(Intensive
Care
unit),CCU(Cardiac
care
Unit)
and
PBU(Premature baby care unit) as none of the unit did not have UPS for emergency situation. So I discussed situation with the director of the hospital and other section heads of the hospital. Then director had agreed to send some patients to nearby hospitals but he said for any emergency all these facilities should be ready. Then I also
understood the situation. So I discussed this with our electrical engineer to get his advice and he proposed to install standby generators for all key units. But he explained me that to connect standby generators power had to disconnected at least for half an hour. Hence I decided to shift whole control panel mounted on a carriage to new location by travelling on a two guided rails. As this method required less than minute of power cut to mount the control panels to carriage, our project manager and director of the hospital was very happy and gave their consent to go ahead with the idea. CE1.28 Hence I had to relocate power control room and the office room, rest room of the electricians to new locations. So I decided to construct a two storied building block for control panel rooms and office room and rest rooms for electricians in ground floor and upper floor respectively. CE1.29 Project manager asked me to do the structural design for this two storied building block. As this new building was to be built adjacent to the new generator room, I had to design four combined footings for eight columns due to restricted edge at one side. Hence I decided to observe soil condition by a trial pit and I found that the soil below 500 mm was very weak soil. Therefore I decided to improve bearing capacity of soil by packing rubble from 2.5 m below ground level to 2.0 m level and from 2.0 m level to 1.2 level sand was filled and compacted. And I was able to improve bearing capacity of 150kN/mm2 at 1200 mm below. This new building was 12 meter wide and 40 meter in length and columns were spaced at 12m and 16 m intervals. Grade 25(fcu=25N/mm2) concrete was used for all structural works. Columns were designed as un-braced short columns and all slab panels were designed as two way slabs from the coefficients given in BS 8110.Wall foundations were designed as spread foundation using rubbles. After completing this building, relocating of control panel was planned to be done. I used the caster wheels from broken trolleys in hospital to build a carriage to travel control panels and rail lines were built using 50 mm x50mm equal angles and fixed on timber logs laid on the ground. After completing this I informed director of the hospital and relevant heads of to be affected units that I was ready to relocate control panels. Then director had informed relevant parties and made available additional ambulance as a contingency plan. After that I selected highly capable team for this work and had a meeting to explain them how to do this work. In this meeting, I asked from the team members to express their idea and I deliberately accepted some ideas although those were of very
minor things to please them. Also I gave them safety boots, helmets, grouses and overalls as safety precautions. And I was able relocate the control panels successfully.
(d) Summary CE1.30 Government decision to develop key hospital in the country to enhance the quality of the health service is commendable. Otherwise patients are congregated into few of the hospital which has more physical facilities as well as trained staff. From this project I was able to develop my ability work with different section of the society and to work as a team to archive target. It also helped me to refresh my undergraduate teaching on geotechnical engineering as well as the structural design. So I was able refresh my memory and knowledge on codes of practises and publications such as BS 8110, BS 8100, “Foundation Design and construction” by M.J.Tomlinson,”Foundation Analysis and design by Joseph E.Bowels”. Further I was able to sharpen my analytical skill from this and I was really appreciated my senior engineers for keenness for the work and my suggestion. Also I was able to widen my knowledge on geotechnical engineering knowledge as civil engineer. During this project period I had the opportunity to witness test like PIT and PDA, which were learnt at the university. Also I understood that construction of piles should be done with close supervision as there are lot of pitfalls where one can go wrong. After completing this project I was more confident on any type of pile foundation construction as well as to work in even very challenging environment.
