An Automatic Kunzelstab Penetration Test

Transcription

1 An Automatic Kunzelstab Penetration Test Yongyuth Sirisriphet 1, Kitidech Santichaianant 2 1 Graduated student: Faculty of Industrial Education in and Technology. King Mongkut's University of Technology Thonburi,Bangkok,Thailand, yy @hotmail.com 2 Lecturer: Faculty of Industrial Education in and Technology. King Mongkut's University of Technology Thonburi,Bangkok,Thailand, kitidech.san@kmutt.ac.th ABSTRACT This research was to build, develop and improve the Automatic Kunzelstab Penetration Test (AKPT) to be more efficiency than the original Kunzelstab Penetration Test (KPT) and lower testing and labor costs than the Standard Penetration Test (SPT). The new system AKPT, with compact platform used stainless steel as a material to construct the penetration rod and its joint system suitable for the very stiff and high bearing capacity soil in Khonkaen province or northeastern zone of Thailand where the typical embedded pile depth is about 7 9 m. The pull out system of AKPT also was developed to be certain of proper recovery. An electronic counter system was also used to reduce human error for counting of blow dropping. The AKPT was conceptually designed to operate by only two workers for both operation and transportation. Five construction sites in Khonkaen province were selected to perform AKPT, KPT and SPT tests for result comparison under five crew teams of testing. The obtained result showed that the AKPT had more efficiency than original system (KPT) considering from the convenience and testing speed and there were confirmations by geotechnical engineering experts that AKPT seemed to show the lower operating cost than typical SPT. Furthermore, the fair correlation between the blow counts of AKPT and SPT was satisfied and possible to benefit the new experience of soil exploration in Khonkaen province area in the future. Keywords: Kunzelstab, Standard Penetration Test, N-value, Automatics 1. INTRODUCTION The data and soil investigation of northeastern zone of Thailand had a few and not be referable for shallow foundation design. At the present time used for there were standard penetration test a mostly but, it has high rather for operate worker, costs and danger in process. In other words this zone need data of foundation in deep about 3-9 m. for pile works so take an interested to study the Kunzelstab Penetration Test (KPT). This research was to build, develop, improve and design concept to the automatic Kunzelstab Penetration Test (AKPT) which more efficiency than original system (KPT) and can operate to 5-9 m. in deep and developed the materials to suitable for the very stiff soil of this zone due to the residence project had expand very much and fast at the present time so had demand data of foundation design to suitable for foundation works of their project. The new system AKPT will help to save cost, reduce risk in process, reduce worker, and reduce usability the standard penetration test; SPT by cause above mentioned. But still remain concept of KPT system by used 10 kg. in weight of hammer, 50 cm. in length of drop hammer and length of rod s settlement is very 20 cm. 2. THEORY OF KUNZELSTAB PENETRATION TEST The Kunzelstab penetration test (KPT) was an in-situ sounding test of soil layer by penetration rod and counting number of blows to approximately determine the strength and thickness of soil layer and showed primary results for physical property of soil layer. The KPT is used widely in Thailand, especially by Electricity Generating Authority of Thailand (EGAT) who used this method to primary investigate soil properties for foundation of electricity post since it is easy to operate with light weight setup and suitable for working in steep terrain or in remote area. This method can be done very fast and save cost more than other methods of soil investigation and also assist to show existing of thin soil layer change. Figure 1. Operation of Kunzelstab Penetration Test. The KPT is a method to test the bearing capacity of soil by penetration of cone tip without effect of surface friction of penetration rod because it has diameter of cone head bigger than the penetration rod, in other words, the cone penetration head has a cone shape 25 mm. in diameter and has 60 degree at tip of cone head, penetration rod has 20 mm. in diameter. The setup detail is shown in Figure 1. The weight of drop hammer is 10 kg. with set drop height of hammer at 50 cm. The penetration rod is 1 m. in length. Counting of blows at very 20 cm. in length of rod s settlement (blows/20cm.) are recorded. The KPT is typically operated in every types of soil, such as gravel, sandy gravel, sand, silty sand, sandy silt and clayey silt. Typical setup is shown in Figure 2. The interpretation of relationship between

2 blows count and bearing capacity are shown in Figure 3. for foundation design in sand and clay. Figure 2. Setup of Kunzelstab Penetration Test. Refer: GERD, 2000 Figure 3. Graph showed interpretation of relationship between blows count and strength of soil for sand and clay. (Refer: GERD, 2000) 3. TESTING AREA Areas used to verify reliability are five construction sites spread over the area of Khonkaen province and selected to perform AKPT, KPT and SPT tests. Five crew teams were circulated to randomly perform those three types of test. Five sites were selected to ensure the good sampling group of testing. Figure 4. Locations of five construction sites for this study in Khonkaen province. Five construction sites were as follows: Site RMUTI UNIVERSITY Site Pacha Samoson Site Roanadi Site Mariwan Site Khok Sri 4. RESEARCH METHODOLOGY 4.1 Design for automatic Kunzelstab Penetration Test (AKPT) Design concept of AKPT Initial design concept of the system for operating the AKPT was how to reduce worker s labor force during operation but still remain concept of convenience in installation and transportation of KPT. The final design drawn by SketchUp TM is shown in Figure 5. Therefore, a small gasoline engine, a dropping hammer, rod holder systems and the steel wire system to tow hammer were installed as shown in Figure 6a. to run automatically. To operate on stiff soil layer with a large number of counting, an electronic counter was attached to reduce human error due to counting as shown in Figure 6b. The structure of steel frame with wide base also played an important role to ensure less vibration while operation.

3 Figure 5. Design of AKPT. Figure 7. Setup of AKPT body by custom cut and welding. Figure 6(a). Setup of AKPT with a small gasoline engine and automatic hammer dropping system. Figure 8(a.) Penetration rod and enhance the joint made by stainless steel. Materials Figure 6(b). An electronic counter. Steel angle bar and tube were used to build main body frame custom cut and welding as shown in Figure 7. Stainless steel was selected as a material to construct the penetration rod, cone head and connection system since steel rod may not be strong enough to penetrate through stiff soil layer as shown in Figure 8a. and 8b. The pull out system also was modified from a truck lifter jack to recover the embedded rods and cone head (Figure 9). Overall weight and size of system were kept as low or small as possible similar to the concept of convenience obtained from original KPT. Figure 10. shows the transportation of AKPT with light truck by two workers. Figure 8(b.) The cone head made by stainless steel.

4 Figure 9. The pull out system modified from a truck lifter jack to recover the rods and cone head. show in Figure 11.) The questions ask about reliability or performance of Mechanics of the system Labor-saving system(gasoline engine and lifted mechanism) Automatic counting system Efficiency of penetration (compared to KPT) Overall physical reliability Number of testing for a day Recovery technique and system Figure 10. The convenience in transportation of AKPT by two workers. 4.2 Testing and operation in field After repeatedly test run in assembly shop for each function of the AKPT to ensure all the systems worked properly, the AKPT was tested in field and adjusted to confirm all functions working properly during driving the rod and head in the soil layer. Transportations and operations for field tests were evaluated to verify mechanic reliability of evaluation the AKPT, geotechnical engineering experts were invited to evaluate efficiency reliability and performance before going to do the real operating test in provided construction sites. Comparison in the labor-saving issues between AKPT and KPT were studied by recording times in second for every meter along the penetration depth. The times for five sites were averaged to show the power consumption of man and engine testing methods. After that, five construction sites in Khonkaen province were contacted to do real testing to perform AKPT, KPT and SPT tests for comparison under five terms of testing crews. Operating cost of AKPT were monitored to compare which SPT method. Analysis of blow count data obtained from sites was validated to show the correlation between of AKPT and SPT linear regression analysis for cohesive and granular soils. 4.3 Evaluation of AKPT by geotechnical engineering experts Four geotechnical engineering experts were invited to evaluate efficiency, reliability and performance of AKPT by questionnaire of 5 choices for rating scale. Questionnaire of five choices for rating scale was prepared for geotechnical engineering experts for overall performance, efficiency and reliability of the AKPT (as Figure 11. The questionnaire 5 choices for rating scale. Figure 12. The original Kunzelstab Penetration Test (KPT) operated manually in construction sites.

5 Figure 13. Automatic Kunzelstab Penetration Test (AKPT) operated in construction sites. Number of blows recorded with time spending for every 20 cm. of penetration through the depth of soil tested by AKPT and KPT from five construction sites. Two worker were limited for each test. Cumulative of spending time (seconds) for whole 1.00m. was averaged from all sites and calculated (for example 0.20,0.40,0.60,0.80 and 1 m., respectively) to plot on Figure 16. Efficiency of AKPT in terms of labor saving was obviously higher than KPT. The result shows that every meter of soil layer the KPT operating time was more than AKPT. In other words the AKPT has tendency operate more consistency with stiffness variation of soil layer, even deeper than 7 m. Figure 14. The Standard Penetration Test (SPT) operated in construction sites. 5. RESEARCH RESULT Figure 12 to 14 show the testing and operation in field for all types of test. The evaluation results of AKPT were obtained from four geotechnical engineering experts who were four university faculties with two Ph.D. graduation degrees and two associated professors. The overall average score showed values 4.73 from 5 which is excellent as well as each question of questionnaire had value over than 4.5 of 5 which is excellent. The results is shown in Figure 15. Figure 16. Efficiency between AKPT and KPT. Average operating cost of AKPT from five construction sites was monitored calculate and compared the operating cost of SPT as shown in table 1. Which showed the AKPT was needed. Approximately AKPT was able to finish 4 tests a day comparing to 2 tests of SPT. Table 1. Comparison the operating cost of AKPT and SPT for a borehole (in Thai Bath). Figure 15. Evaluation results. 6. CONCLUDSION (AKPT) had efficiency higher than original Kunzelstab penetration test (KPT) in terms of labor saving, and productivity showed graph in figure16. (AKPT) had good reliability and performance as evaluated from experts. (AKPT)shows the linear regression relationship of counts (N-values) of AKPT and SPT in terms of clay and sand as shown in

6 equation 1 and 2, respectively. These equations will be able to be applied for foundation design in the future for Khonkaen province. For Clay; SPT = x (AKPT) (1) (R Square = 0.809) For Sand; SPT = x (AKPT ) (2) (R Square = 0.882) Figure 17(b). N-values Relation of AKPT and SPT (5 construction sites) for sand. (AKPT) had operating cost lower than SPT method about three the same as in approximately as shown in table1. Can diminish usability of SPT in the same site. Figure 17(a). N-values Relation of AKPT and SPT (5 construction sites) for clay Figure 17. Overall image to operate of automatic Kunzelstab Penetration Test (AKPT). 7. REFERENCES Geotechnical Engineering Research and Development(GERD). 2000; The Report Strength of Soil Layer in Footing Area.Kasetsart University, Bangkok.17 p. Satraphorn Kuvigidgraru, 2001;Soil Investigation; Boring, Sampling and Field Tests. Kasetsart University. Bangkok. p Boonthep Nanakerungsan. 1999; Foundation Engineering and Tunnelling.Changmai University,Thailand,43 p. Wiroht Chaiyatumb, 2003; Foundation Engineering : Khonkaen University. Thailand, units 1 3. Tanayt Verasiri ; The Experience to Repair Sink and Up Lift Building :Bankok.Thailand, pp "A Study Comparison of Value Between Improved Kunzelstab Penetration Test (N-IKPT) and Standard Penetration Test (N-SPT) in Khonkaen Province Area" very 20 cm you mean every 20 cm? The questionnaire and evaluation could you make translation into English?

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