A.Zh.Zhussupbekov Department of Civil Engineering and Engineering Mechanics, Columbia University, New York, USA

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1 UDK 69.0 A.Zh.Zhussupbekov Department of Civil Engineering and Engineering Mechanics, Columbia University, New York, USA Research of displacement pile and continuous flight auger technologies on construction sites of Kazakhstan Abstract:The results of DDS (drilling displacement system) and CFA (continuous flight auger) boring piles research are presented in this paper. Static load tests (SLT) of DDS and CFA to definition of bearing capacity and settlement-load dependence was performed. Research of adjacent soil compaction due to of high value of concrete pressure during CFA pile installation is also presents, as well as results of compression tests of surrounding soil after DDS pile installation. INTRODUCTION Modern geoengineering face with engineers and designers modern requirements, therefore traditional technologies were replaced by resent economically, ecologically and energy-efficient technologies, including pile foundation. Pile foundation is a widespread type of foundations on construction sites of Kazakhstan. Expediency of pile foundation is explained by high value of bearing capacity of high-rise buildings. At the same time settled design Standards is not corresponding with new emerged technologies, because of absence any recommendation for new pile design. Disadvantages of out of date technologies led to refuse from traditional piles technologies (traditional boring and driving diesel-hammer piles) and use new more economical and reliable technologies like DDS and CFA. This paper presents research of new boring pile technology namely DDS or FDP (full displacement pile) technology and CFA. Today these technologies have high practical value on construction sites of Kazakhstan and apply during last 0 years. While CFA and DDS pile installation is commonly using German and Italian boring rigs established by BAUER and SOILMEC companies. The general advantages of these technologies (comparing with traditional boring pile technology) are: fast installation of pile, essential economical efficiency, low noise during installation, absence of vibration, high value of bearing capacity. In spite of that DDS technology is not recommended to use near existed buildings and constructions due to of influences of DDS technology on nearby existed foundations and during CFA pile installation extra expenses of concrete due to of high pressure has a place. The big difference between experimental bearing capacity obtained by SLT and designed obtained by Kazakhstan Standard authenticate incomplete usage of these technologies resources.

2 2 FETURES OF DDS AND CFA PILE TECHNOLOGIES Installation of DDS pile consist of four steps, the steps of the DDS technology are: placing the boring machine to the boring place; boring the pile hole to the design level; filling the concrete under the pressure of 300 kpa; installation of steel anchor into the pile body. The pile hole forming via two stages: during the moving of boring element down the bullet teeth loose the soil and stabilizer displaces surrounding soil. During the moving of boring element up the secondary compaction of hole has a place, Sultanov et al. (200). DDS technology allows installing the pile till 0,6m of diameter and 30m of length. During DDS pile design it is required to take into account following parameters: diameter of pile, torque moment, indentation forces, density (strengthen, compaction of soil and power of concrete pump). A CFA pile is a type of drilled foundation in which the pile is drilled to the final depth in one continuous process using a continuous flight auger. The use of the continuous flight auger rig avoids many of the problems of drilling and concreting piles experienced when using conventional power augers. The new CFA equipment can perform piles in most type of soils (including sand, gravel, silt, clay, chalk and weak weathered rock) with diameters up to 200 mm and lengths down to meters. So, with proper planning and design, performing equipment and skilled personnel, high production rates and high quality product can be achieved, Klosinski & Rychlewski (2003). Installation of CFA pile consist of following steps: placing the boring machine to the boring place; boring the pile hole to the design level; removing the screw with simultaneous concrete filling under the high pressure and replace the boring machine, installation of steel anchor into the pile body with preparation of pile head. In modern CFA technology the systematic employment of devices auto-recording the drilling data represent a real breakthrough considering that in the past the CFA method was not accurate, and relied on the operator s ability: now such devices guarantee the control and recording of the data during the whole construction process. The recorded working data are usually drilling/withdrawal speed, rotation speed, depth, concrete pressure and delivery rate per increment of auger lift during casting. 3 STATIC LOAD TEST OF DDS AND CFA PILES Totally it was performed 4 static tests of DDS and 5 CFA piles of different diameters and length. There are 7 tested DDS piles of 40 mm diameter and 8 m length, 2 piles of 500 mm diameters and 2.5 m lengthnd one pile of 600 mm diameter and 2 m length. Field static load tests were carried out for CFA and traditional piles with diameter of 600 mm and 630 mm and length of 0, 20, and 28 m. The first count out right after putting the loading, then consequently 4 counts out with the interval 5 minutes, 2 counts out with the interval 30 minutes and further in every hour till the conditional stabilization of deformation. For the criterion of conditional stabilization of deformation was taken the speed of

3 settlement of boring piles on the given stage of loading that did not exceed 0.mm during the last hour of observation, SNiP RK COMPARISON OF EXPERIMENTAL AND DESIGN BEARING CAPACITY OF PILES To analysis of bearing capacities obtained by SLT the calculation of designed bearing capacity by Kazakhstan Standards was performed, SNiP PK Experimental and designed values of bearing capacities are presented in Tab. () and (2). As you see there is big difference between experimental that is real and designed that is predicted values of bearing capacities, Sultanov et al. (200). Table. DDS comparison of bearing capacity Description of piles Bearing capacity, кn Experimental F u Designed F d Coefficient k= F u /F d , ,39 3 Pile DDS ,50 L=7m ,60 d=40 5 mm , , ,42 8 Pile DDS L=7m d=600mm ,28 9 Pile DDS ,73 0 L=2m ,80 d=500mm ,69 It is necessary to take into account that CFA piles of 22, 24 and 28m of length are not achieved recommended by Kazakhstan standard settlement criteria (24mm), that is to say real coefficient k which show non-correspondence design bearing capacity to the experimental is greatly understated. The comparison diagram of SLT and designed bearing capacity is presented in Figure. All the linear function points are arrange

4 higher of diagonal, it means that all experimental values of bearing capacity are higher of designed. Figure. SLT and designed bearing capacity 5 LABORATORY TESTING OF SURROUNDING SOIL OF DDS The main goal of laboratory test performance is research dependence between elastic modulus, angle of internal friction and cohesion and diameter of pile. The shalby tubes of soil specimens were taken before and after DDS pile installation. The samples were taken on the aforementioned construction sites. The laboratory tests were performed according to Kazakhstan Standard GOST In this case we interested by coefficient of soil work condition around the DDS pile. These coefficients are recommends by Kazakhstan Standard for different types of pile. For example for driving pile this coefficient equal, for boring 0,7, and the biggest value of coefficient,3 for pile DIT (discharge impact technology). DIT technology means reprocessing of fine concrete body by high-voltage charges. This technology usually used in saturated soil. And in the end of installation pile`s diameter doubly increase depending on hidro-geological condition of site. And so this coefficient depends on compaction condition of adjacent soil. In case of traditional bored pile no compaction therefore coefficient equal 0,7, in case of DIT pile, due to of double expansion of pile this coefficient equal,3. From aforementioned the necessity of ascertaining and chancing this coefficient for DDS pile is become obvious. Moreover in case of DDS pile only surrounding soil undergoes to compaction, under the pile no compaction is occur and so we interested by coefficient of soil work condition around of pile. The obtained results were subjected to statistic analysis, the purpose of which is revelation of random departure (random value of interested variable). The reason of this might be disturbed structure of soil during the tacking or inaccurate measurement of testing equipment. It was taken many soil specimens around of different diameters piles and different geological elements. After reprocessing of obtained data by statistic analysis several results of elastic modulus were rejected from following analysis. It is necessary take account elastic

5 modulus, angle of internal friction and cohesion increase due to compaction during design DDS pile. 6 ECONOMICAL EFFICIENCY OF DDS PILES In order to show economical effect by using coefficient of surrounding soil work it were designed DDS piles by standard and by proposed method. It was compared real piles bearing capacities of real sites mentioned before. Table (3) shows results of designed bearing capacity of DDS pile (by standard) and recommending (by proposed method). For example for construction site 500 kpa soil resistance is required by project. Standard pile resistance a little bit bigger and equal 545kN providing that computed pile length is equal 5m. Recommending bearing capacity of pile is also meet to required soil resistance and equal 556kN, but length of pile in this case reduced to 2m. Same situation with construction site 2 where designed 2m versus recommending,2m. Total expanse per one DDS pile installation reduced on 20-40%. Table 3. Designed and recommended length Designed bearing capacity of DDS / corresponding length of DDS Construction site (d=40mm) Construction site 2 (d=500mm) Designed Recommending Designed Recommending 545kN / 5m 556kN / 2m 272kN / 2m 274kN /,2m 7 ECONOMICAL EFICIENCY OF CFA PILE Installation of CFA pile has economical efficiency in case of productivity of piles per day and total expenses. It is confirm the actual productivity of piles per day. Comparing CFA technology and Casing pile with performing (productivity) of piles per day, CFA technology is 3 times more than traditional Casing pile in difficult soil grounds in Astana. Performing of bored piles per day and labours are presented in comparing Tab. (4).

6 Table 4. Performing of bored piles per day with length 20 m, length of reinforcing cage 20 m and required labours CFA technology Profession of labour Qua ntit y Pile s per day Bored pile installed with casing Professi on of labour Qua ntity Piles per day Drilling rig - operator Drilling rig - operator Concrete pumpoperator 9 Vibratin g- operator 3 Unskilled worker 2 Unskille d worker 3 Total labours 4 Total labours 5 8 CONCLUSIONS. By results of SLT experimental bearing capacity on average in.5 times exceeds Standard bearing capacity for DDS and in.6 for CFA piles. The nomograms and linear functions to correct Standard bearing capacity were developed and might be used during design in similar soil condition. 2. The reason of big difference between DDS experimental and designed bearing capacity is strengthening of surround soil due to of technological compaction. This lead to increase of soil parameters such as angle of internal friction, cohesion, Young modulus and so on. By the results of laboratory testing the nomograms to correct angle of internal friction, cohesion, and Young modulus were developed. It is possible to use these nomograms during design DDS pile of 400, 500 and 600mm of diameter in similar soil condition. 3. By the numerical modelling the comparison between traditional and DDS pile bearing capacity was performed. The coefficient of surround soil work was defined and equal.28 on average. The differences between experimental and designed bearing capacity decrease from.5 to.4 by using this coefficient. 4. Developed bearing capacity definition method allows reducing total expanse per one DDS pile installation on 20-40%. 5. The actual volume of concrete expense of CFA in.4 times higher than volume of borehole, therefore for designing CFA pile it needs to consider volume changing of pile by appearance in borehole additional pressure respectively

7 over-expenditure of the concrete depending soil conditions and length of piles. 6. FEM modeling approved necessity of pile expansion considering during CFA piles design. According to FEM analysis bearing capacity of tested CFA piles produced generally by shaft resistance, at the average 76-77%. 7. CFA pile more productivity than traditional casing pile. It is possible to install 6 CFA piles per working day versus 3 casing piles. Economical efficiency reflected by labour expense - 4 labours for CFA pile installation versus 5 for casing pile. REFERENCES Sultanov, G., Zhusupbekov, A., Lukpanov, R, Enkebaev, S., (200). Comparison analysis of DDS and traditional boring pile works by FEM analysis results. Proc. L.N.Gumilyev Eurasian National University. Astana, Kazakhstan, Klosinski, B. & Rychlewski, P. (2003). Analysis of bearing capacity and settlement of CFA piles. Deep foundations on bored and auger piles, Van Impe (ed.). Rotterdam, Alibekova, N., Bukenbayeva D., (2008). About the engineering-geological conditions of Astana, Proc. 6th Asian Young Geotechnical Engineers Conf. Bangalore, India, SNiP RK Pile foundation. SNiP RK Soil basement and foundations. Sultanov, G., Zhusupbekov, A., Lukpanov, R, Enkebaev, S., (200). Laboratory testing of elastic modulus of soil around of displacement pile. Proc. L.N.Gumilyev Eurasian National University. Astana, Kazakhstan, GOST Laboratory methods of strengthen and deformation characteristic definition.