Research Proposal AnExperimental investigation on shaft resistance cast in situ bored piles insound rock S.Suloshini140608JSupervisor: Dr. L.I.N.
de Silva 12thJanuary,2018 Department of Civil EngineeringFaculty of EngineeringUNIVERSITY OF MORATUWA-SRILANKA Table of Contents Introduction. 1 Problem Statement 1 Significance of the research. 2 Scope of the study. 2 Aims and Objectives of the research. 2 Hypothesis (if any) 3 Review of the literature. 3 Proposed Methodology. 3 Time schedule/work plan.
4 Budget/estimated cost built up. 4 References. 5 Introduction Nowadays in the construction industry the pile foundationsocketed into the rock plays a key role in the high rise buildings due to thehigh bearing capacity and minimum settlement. The bearing capacity of the rocksocketed piles contains two basic components, base resistance and shaftresistance or skin friction. Shaft resistance is more significant whencalculating the bearing capacity of the pile because shaft resistance isinduced earlier than the base resistance for a very small movement. And thebase resistance needs the pile base free from debris. It is difficult toachieve this condition in the practical situation. Therefore shaft resistanceis considered as an important part in designing the pile foundation.
Firstshaft resistance of the pile should be estimated to evaluate the bearingcapacity of the pile foundation. This research focus on the experimental investigation on shaft resistance of cast insitu bored piles in sound rock.Manyresearch have been carried out in this area and from those studies it is foundthat the shaft resistance of the rock socketed pile is governed by the severalparameters like mechanical properties of the surrounding rock, RQD value of thesurrounded rock, pile diameter, roughness of the rock – concrete interface,discontinuities of the rock, the radial force induced by the load and the rocktype. The shaft resistance should be evaluated correctly for the safety of thestructure. The under estimation of the shaft resistance is not economical butit is conservative. Therefore the designers must pay attention on this.Problem Statement The investigation of the shaft resistance of the pile – rockinterface is a very complex problem because many factors should be consideredand the lack of knowledge in shaft resistance. The knowledge of shaftresistance is necessary for the designing of the structure safely andeconomically.
Empirical methods are used in calculation process of shaftresistance. Those empirical methods may not be reliable for some cases. From the literature survey it is noticed that severalstudies have been carried out on the shaft resistance of the cast in situ boredpiles socketed in sound rock all over the world. Even though there is no properinvestigation for the shaft resistance of rock socketed piles. The main problemof the design engineers is the value of the shaft resistance of the underlyingrock. This study is to evaluate the shaft resistance of the rock socketed pilesfor different types of rock.
Significance of the research Pile foundation is used in the heavy loaded structures likebridges, high rise building complex. The piles are socketed into the sock toincrease bearing capacity. The bearing capacity of the pile foundation can beincreased by introducing the rock socketed piles. The applied load istransferred to the bed rock in the rock socketed piles. The bearing capacity ofthe rock socketed pile foundation depends on the shear strength of the rock-concrete interface.
The shaft resistance is mainly governed by the roughness ofthe concrete- rock interface.Forthe safety of the structure the shaft resistance should be estimated correctly.In the normal practice the shaft resistance is calculated using empiricalmethods.
It is not economical. In the Engineering practice all the design andconstruction works should be done to optimize the cost. Mostly the geotechnicalengineers need the shaft resistance between the piles – rock interface in theirdesign process.Theshaft resistance varies with the type of rock type. Most of the methods whichare available to calculate the shaft resistance are empirical. So it may not becorrect for other types.
The significance of this study is to provide moreunderstanding about the shaft resistance. From this study the ultimate shaftresistance of the rock socketed can be evaluated which is helpful in the designprocess of the pile.Scope of the study The scope of this study is to develop a fundamentalknowledge on shaft resistance of the rock – concrete interface. This is a fullylaboratory experimental study. All the tests will be conducted in thelaboratory. The shaft resistance is calculated using the rock sample.Aims and Objectives of theresearch The aim of this study is to investigate the shaft resistanceof cast in situ bored piles in sound rock through laboratory experiment.Hypothesis (if any) Review of the literature Many researchers have carried out their researches on the shaft resistanceof the bored piles in rock.
Most of the researches have been conducted to findthe parameters which are affecting the shaft resistance or shear strength ofthe intermediate surface between concrete and rock. From those studies it isconcluded that the factors affecting the shaft resistance are strength of rockmaterial, rock mass, RQD, roughness of pile-rock interface, diameter of thepile, fracturing of the rock etc. The studies have been done according todifferent theories like cavity expansion theory, fractal theory etc. The shaftresistance correlations are different to country to country and they haveproposed different equation. Many empirical relationships have been proposed tocalculate the shaft resistance.
Proposed Methodology Literature survey would be carried out to identify thefindings on this topic up to now. The methods which the researchers werefollowed, factors affecting the shaft resistance, problems in finding the shaftresistance, the existing methods to estimate the shaft resistance of the rocksocketed piles will be studied.The intact rock samples would be collected from the fieldand brought to the laboratory. The rock sample will be cut in an angle usingthe rock cutter.
The concrete will be placed on the top of the sample to getthe concrete – rock interface. Then the sample will be tested in the triaxialapparatus. The shear strength of the concrete – rock interface will becalculated.The above mentioned procedure will be proceeded by changingthe rock type. The results obtained from the test will be analyzed.
Time schedule/work plan Work breakdown November December January Febrary March April May June July Literature review Collecting samples Laboratory Experiment Analyzing results Budget/estimated cost built up References
