1、 24 12 Vol.24 No.12 2005 6 C hi nese Jo urna l of Roc k Mec ha nics a nd E ng in eeri n g June 2005 2004 06 01 2004 11 02 (1965 ) E-mail Q-s 1 2 (1. 710048 2. 450053) Q-s Q-s Q-s Q-s Q-s Q-s TU 473 A 1000 6915(2005)12 2129 07 ERRORS STUDY ON Q-s CURVE OF PILE SIMULATED BY HIGH STRAIN DYNAMIC TESTIN
2、G METHOD ZHAO Hai-sheng 1 2 (1. Xi an University of Technology Xi an 710048 China 2. He nan Provincial Academy of Building Research Zhengzhou 450053 China) Abstract Based on the test results of pressed piles by static load test and high strain dynamic test in an engineering test as well as the analy
3、sis of mechanical behaviors of pile shaft material and developing behaviors of soil resistance and the load transfer behavior an analysis of errors of Q-s curve simulated by high strain dynamic testing method is made. The settlement of pile calculated by high strain dynamic testing method is higher
4、than that of pile tested by load test when load is smaller and it is bigger than the result of load test when load is higher. These errors are relative with the mathematical model about pile shaft concrete and soil resistance in high strain testing. Concrete is thought as elastic body in high strain
5、 testing but actually it is nonlinear this brings about some errors in Q-s curve of pile simulated by high strain dynamic testing method. The model of static soil resistance in high strain testing which is thought as elasto plastic model is not the same as the actual developing behaviors of soil res
6、istance and the settlement of pile in high strain testing is smaller than that in static loading test these are major factors which bring about errors in Q-s curve of pile simulated by high strain dynamic testing method. These factors should be considered when the Q-s curve is simulated by high stra
7、in dynamic testing method. Key words soil mechanics high strain dynamic testing method Q-s simulation curve of pile error behavior of load-deformation of concrete development of soil resistance 2130 2005 1 ( ) Q s Q-s Q s Q-s 1 8 Q-s Q-s Q-s Q-s Q-s 2 Q-s L x dx 1 Q x qU d d = (1) U ) (s f q = ) (s
8、f s Q 0 Q x x Q = x x x qU Q Q 0 0 d ( 2) = L L x qU Q Q 0 0 d ( 3) 1 Fig.1 Balance of force in pile shaft x EA Q s x d d = ( 4) s p = L x x EA Q s 0 p d ( 5) L Q s b s 0 b 00 0 b p 0 d d 1 s x x qU EA L EA Q s s s Lx + = + = (6) ( ) (6) Q-s (6) Q-s Q-s E c 2 c E = ( 7) dx sx L Q 0Q Q + dQ qUdx x 24
9、 12 . Q-s 2131 ( 2) s quake s u q s s s u q u s s u 2 Fig.2 Basic model of soil static resistance 3 3.1 22 3 20 m(12 m 8 m ) 400 mm 400 mm( ) C40 T1 ( 3) 4 3 Fig.3 Soil profile and location of strain test point for test pile 3.2 3 9 PDA 1.0 m 60 kN 1.2 2.0 m 3 5 4 4 T1 Fig.4 High strain testing curv
10、es of the test pile No.1 2 3 200 kN 4 50 mm 9 10 3.3 3 Q-s 5 1 3 CAPWAP 5 Q-s 5 Q-s Fig.5 Q-s curves of test piles 1 Table 1 Bearing capacity of test piles by load test and high strain testing /kN /kN T1 3 585 3 600 T2 3 384 3 300 T3 3 260 3 300 s us q 0 m 5 m 10 m 15 m 20 m 25 m F/ kN t / ms o 2132
11、 2005 1 3 5 Q-s Q-s Q-s 4 4.1 T1 6 / 10 6 6 Fig.6 Stress-strain curves of pile shaft ) 5 835 . 0 ( exp 2 . 444 9 = ( 8) 481 32 = (9) 0.9985 0.986 8 4.2 Q-s = 2 450 kg/m 3 c = 3 950 m/s E = 38 226 MPa 226 38 = (10) 6 6 Q-s 7 Fig.7 Relations between elastic modulus and load in pile shaft ( ) E Q 7 7 (
12、Q 1 200 kN ) (Q 1 200 kN) Q-s 1.110 3 1.4 24 12 . Q-s 2133 a m F( ) 9 ma F = (11) ( 9) 4.3 8 T1 6 T1 9 / 10 6 8 Fig.8 Axial strain in pile shaft 9 Fig.9 Axial force distribution in pile shaft 8 i s i s L i 2 / ) ( 1 i i i i L s s + = ( 12) T1 b q s q s 10 11 10 11 10 Fig.10 Relation between resistance and displacement of pile toe 11 Fig.11 Relation curves between skin resistance and displacement of shaft 2134 2005 4.4 10 11 CAPWAP ( ) 10 11 Q-s Q-s ( ) ( ) 10 11 Q-s Q
