Uncertainties of Piles Load Transfer Parameters

doi:10.16183/j.cnki.jsjtu.2008.11.025

Abstract

Abstract:

The load-transfer method (t-z method) is easy to calculate and can be used in design practice. The most important thing of using the t-z method is the determination of the load-transfer parameters. The uncertainties of the two parameters in the hyperbolic load-transfer function of pile foundation were investigated. Data of seven static load tests with strain gauges, twelve static load tests without strain gauges together with 75 load tests at a single site in Shanghai were collected. Statistical analyses were conducted for both measured and back-calculated parameters for different soil layers. It was found that the uncertainties of the back-calculated values are close to those of the measured ones. The parameters a and b are negatively correlated. Compared with basic soil properties such as unit weight and shear strength parameters, the COVs of the load transfer parameters are greater. According to the Kolmogorov-Smirnov (K-S) test at a significance level of 5%, the normal distribution for both parameters can not be rejected.

Key words: load transfer function, back analysis, statistical analysis

CLC Number:

TU473

SUN Bo, ZHANG Lu-lu, WANG Jian-hua. Uncertainties of Piles Load Transfer Parameters[J]. Journal of Shanghai Jiao Tong University, 2008, 42(11): 1866-1870.

Figures/Tables 9

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Fig. 1

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Fig. 2

Tab. 7

References 8

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工程	桩号	类型	桩长/m	截面尺寸/mm
上海电车修配厂	1-2 #	钻孔灌注桩	25.8	?600
上海宝钢总厂码头	2-1 #	钢管桩	60.0	?1 200
?	2-2 #	预制桩	37.0	600×600
上海宝钢无缝扩建	3-T 2	预制桩	61.0	?550
上海宝钢总厂一期	4-S3	预制桩	33.1	?550
?	4-S6	预制桩	60.8	500×500
上海宝钢总厂二期	5-S4	预制桩	44.2	450×450

土层	桩号	a			b
土层	桩号	实测值	均值	变异系数/%	实测值	均值	变异系数/%
粉质粘土	1-2 #	0.131	0.330	85.2	0.040	0.038	9.4
?	?	0.528	?	?	0.035	?	?
?	2-2 #	0.809	0.333	124.2	0.019	0.026	24.4
?	?	0.117	?	?	0.031	?	?
?	?	0.072	?	?	0.029	?	?
?	3-T2	0.342	0.354	74.8	0.018	0.020	45.8
?	?	0.095	?	?	0.030	?	?
?	?	0.624	?	?	0.012	?	?
淤泥质	3-T2	0.311	0.311	0	0.017	0.014	30.3
?	?	0.311	?	?	0.011	?	?
粉质粘土	1-2 #	0.089	0.125	40.7	0.010	0.023	79.9
?	?	0.161	?	?	0.036	?	?
?	4-S3	0.121	0.156	31.4	0.023	0.024	5.9
?	?	0.190	?	?	0.025	?	?
?	4-S6	0.078	-	-	0.018	-	-
?	5-S4	0.072	-	-	0.036	-	-
淤泥质粘土	2-1 #	0.294	-	-	0.014	-	-
?	2 -2 #	0.159	0.133	27.6	0.007	0.008	17.7
?	?	0.107	?	?	0.009	?	?
?	3-T2	0.316	0.734	74.9	0.015	0.010	81.9
?	?	0.529	?	?	0.004	?	?
?	?	1.356	?	?	0.8×10^-4	?	?
砂质粉土	2-1 #	0.490	0.392	35.4	0.3×10^-4	0.002	138.6
?	?	0.294	?	?	0.003	?	?
?	3-T2	0.183	-	-	0.009	-	-
?	4-S6	0.411	-	-	0.004	-	-
?	5-S4	0.126	-	-	0.009	-	-

土层	样本数量	a			b			ρ_a,b
土层	样本数量	均值	标准差	变异系数/%	均值	标准差	变异系数/%	ρ_a,b
粉质粘土	8	0.340	0.283	83.3	0.027	0.009	35.4	-0.605
淤泥质粉质粘土	8	0.167	0.098	58.7	0.022	0.010	46.0	-0.361
淤泥质粘土	6	0.460	0.463	100.5	0.008	0.006	70.5	-0.722
砂质粉土	5	0.301	0.152	50.6	0.005	0.004	80.6	-0.231

工程	桩号	类型	桩长/m	截面尺寸/mm
上海宝钢总厂一期	S1	预制桩	31.0	?400
?	S2	预制桩	32.9	?550
?	S4	预制桩	57.7	?550
?	S5	预制桩	57.1	?550
上海宝钢总厂二期	S2	预制桩	44.9	?550
?	S3	预制桩	40.8	?550
?	S5	预制桩	44.2	450×450
浙江省人民医院	3 #	钻孔灌注桩	34.0	?800
上海复兴西路203工程	10 #	钻孔灌注桩	44.9	?650
上海外高桥电厂	T1	预制桩	70.3	?800
?	T3	钢管桩	77.2	?762
?	T4	钢管桩	72.8	?609

土层	样本数量	a			b			ρ_{a, b}
土层	样本数量	均值	标准差	变异系数/%	均值	标准差	变异系数/%	ρ_{a, b}
粉质粘土	17	0.317	0.140	44.3	0.024	0.011	47.0	-0.834
淤泥质粉质粘土	16	0.325	0.171	52.7	0.028	0.010	35.9	-0.816
淤泥质粘土	10	0.290	0.148	51.2	0.022	0.010	44.9	-0.520
粉质粘土夹粉砂	9	0.436	0.103	23.6	0.016	0.005	34.0	-0.393