Research Article Determination Permeability Coefficient From . - Hindawi
Hindawi Publishing Corporation Advances in Materials Science and Engineering Volume 2014, Article ID 396428, 7 pages http://dx.doi.org/10.1155/2014/396428 Research Article Determination Permeability Coefficient from Piezocone Qiang Wang1 and LiYuan Tong2 1 2 Department of Civil Engineering, Anhui University of Science and Technology, Huainan Anhui 232001, China Institute of Geotechnical Engineering, Southeast University, Nanjing, Jiangsu 210096, China Correspondence should be addressed to Qiang Wang; wangqiang0711@163.com Received 8 January 2014; Accepted 27 March 2014; Published 27 April 2014 Academic Editor: John W. Gillespie Copyright 2014 Q. Wang and L. Tong. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The permeability coefficient of soil profile is one of the problems concerned by engineers, and the determination of permeability coefficient method mainly relies on the laboratory permeability test and field pumping test, but these tests are time-consuming and inefficient, and especially the permeability coefficient of soil under the condition of partial drainage was difficult to determine; in this paper, the modern digital CPTU technology was used. Dimensional permeability πΎπ was defined by using the dimensionless normalized cone tip resistance ππ‘ , friction factor πΉπ , and pore pressure ratio π΅π , these parameters enable plots of π΅π -ππ‘ , πΉπ -ππ‘ , π΅π -πΉπ to be contoured πΎπ and hence for permeability coefficient. The relationship has been applied to Nanjing 4th Yangtze river bridge, and compared with laboratory penetration test. The results indicate that the method can accurately determine the permeability coefficient of soil under partial drainage condition and provide the theoretical basis for engineering application. 1. Introduction With the development of foundation pit engineering to larger and deeper and the surrounding environment is increasingly complex, especially in the city downtown area, some excavations close to the high-rise buildings, some excavations close to the subway tunnel. At the same time, the groundwater treatment around the excavation cannot be avoided, and the environmental problems around the excavation caused by dewatering are becoming more and more serious. How to arrange dewatering to reduce the impact as much as possible is the key issue for many scholars and technicians. In order to reasonably arrange the dewatering well, we must grasp permeability characteristics of each soil accurately. The key parameter of permeability characteristics is the permeability coefficient. The permeability coefficient is the relative strength index of soil. It is a basic parameter and it must be used for seepage calculation; therefore, the accurate determination of soil permeability coefficient is a very important work, and it plays an important role in the success of the excavation. The current methods for determining the permeability coefficient are routine laboratory permeability test, field pumping test, water pressure test, and so forth. Routine laboratory permeability test is divided into constant head permeability test and variable head permeability test. The laboratory permeability test is widely used, mainly because of its easy operation and simple equipment; however, it has some disadvantages: (1) soil disturbance, (2) inaccurate permeability test, especially sand inclusion or interbed, (3) not simulating field boundary conditions, and (4) the heavy workload and high cost. These drawbacks make much difference for the permeability coefficient between field test and laboratory test. Piezocone penetration test (CPTU) is a time-saving, little disturbance, convenient and economic method for permeability coefficient of soil. The permeability coefficient of the soil was able to relatively accurately obtain, especially mixed-layer or thin interbed experts and scholars at home and abroad dedicated to the study method that can accurately determine the permeability coefficient. 2. Methods Since the advent of multifunction, a lot of the relationships between permeability coefficient and multifunctional CPTU parameters have been proposed. The main methods of permeability coefficient of cohesive soil are divided into
2 Advances in Materials Science and Engineering πh qt fs ππ h c π 0 qt u0 u2 Figure 1: Tip local conditions. Cone expansion stress is ππ‘ . two categories: (1) to estimate permeability coefficient based on the soil classification and (2) to estimate permeability coefficient based on the pore pressure dissipation test. The correct tip resistance ππ‘ , pore pressure ratio π΅π and sleeve friction ππ were modified to determine the type of soil [1β3] and (Olsen [4]). The permeability coefficient was estimated from soil classification [5]. And by the pore pressure ratio π΅π [6] and by the side friction ππ to determinate the permeability coefficient of soil, the coefficient of permeability coefficient was directly determined by using the cone tip resistance and side friction [7, 8]. View of the calculation of consolidation coefficient is less than 7.1 10 5 m/s2 , the consolidation coefficient of the cohesive soil can be determined by the pore pressure dissipation in the completely undrained condition, and then the permeability coefficient can be determined by the consolidation coefficient according to the relationship between permeability coefficient and consolidation coefficient. However, the consolidation coefficient between 7.1 10 5 m/s2 and 1.4 10 2 m/s2 was taken for the part of drainage condition, so the pressure dissipation was not used. The partial drainage state boundary range π΅π ππ‘ 1.2 ππ‘ πΉπ 0.3 π΅π /πΉπ 4 was proposed. Based on the partial drainage condition given by Elswroth [9], the permeability coefficient was put forward to determine by using CPTU data. 2.1. Cavity Expansion Theory. For the saturated clay under undrained conditions, cylindrical cavity expansion stress was proposed by using [10] 4 πΊ ππ πV0 ππ’ [1 ln ( )] , 3 ππ’ (1) where πΊ is shear modulus, πΊ πΈ/2(1 π), π is Poissonβs ratio, πΈ is elastic modulus, ππ’ is undrained shear strength, kPa, and πV0 is overburden stress, kPa. Under undrained conditions, the excess pore pressure caused by cavity expansion can be calculated using the average total stress increment Ξππ In the CPTU penetration process, the horizontal stress is assumed to be equal to the cavity expansion stress. For the cohesionless soil π 0, the normalized friction ratio πΉπ and pore pressure were established relationships, and noticed the sleeve friction, ππ ππβ , πβ πβ π’2 , π, π were the soil strength parameters. The friction factor is assumed to be π tan π as shown in Figure 1 ππ (πβ π’2 ) tan π. (3) 2.2. Dimensionless Parameters. CPTU sounding yields profiles of the correct tip cone resistance, ππ‘ , cone shoulder pore pressures, π’2 , and sleeve friction, ππ , with depth. These dimensional metrics may be defined as normalized magnitudes of tip resistance, ππ‘ , pore pressure ratio, π΅π , and friction ratio, πΉπ , as ππ‘ ππ‘ πV0 , πV0 π΅π π’2 π’0 , ππ‘ πV0 πΉπ ππ , ππ‘ πV0 (4) where πV0 is the effective overburden stress, kPa, π’0 is hydrostatic pressure, kPa, and π’2 is cone shoulder pressure, kPa. If the adhesion of the cone sleeve is assumed to be equal to the undrained shear strength, ππ ππ’ , then the magnitudes of nondimensional cone metrics of end-bearing, sleeve friction, and pore pressure ratio may be determined by substituting (1) and (2) into (4) to yield ln (πΊ/ππ’ ) π’2 π’0 ππ‘ πV0 1 ln (πΊ/ππ’ ) (5) ππ‘ (6) 1 4 πΊ (Ξππ 2Ξππ ) ππ’ ln ( ) , 3 3 ππ’ (2) ππ‘ πV0 4π πΊ π’ [1 ln ( )] πV0 3πV0 ππ’ πΉπ ππ 1 tan π (1 π΅π ) ππ‘ πV0 ππ‘ (7) where π’2 is cone shoulder pressure, π’0 is hydrostatic pressure, and ππ‘ is the correct cone tip resistance. π΅π ππ‘ π’2 π’0 ππ‘ πV0 4π πΊ π’ ln ( ) . ππ‘ πV0 πV0 3πV0 ππ’ (8) Ξπ’ π’2 π’0 Ξππ π΅π
Advances in Materials Science and Engineering 3 2r0 qt 2r0 u u0 Elestic zone u u0 Plastic zone U u u0 u0 Udt qn R (a) (b) Figure 2: Geometry of process zone surrounding advancing penetrometer. LIU HE QI XIA CXNA-ZK22 CXNA-ZK23 60.03 5.14 4.54/1.00 1.94/3.60 1.86/7.40 2.86/8.40 62.62 5.11 1 0 3.31/2.20 1 1 1 2 4.29/9.80 6.49/12.00 2 3 33.06/38.60 45.16/50.70 33.39/38.90 7 3 46.99/52.50 54.49/60.03 57.11/62.62 Figure 3: The soil profile of north anchorage of the Yangtze river 4th bridge A0 Clay, A1 silty clay, A2 silt, B3 silty clay with fine sand interbed, G3 bedrock.
4 Advances in Materials Science and Engineering Hole 4 ZK22 ZK23 ZK24 ZK25 Hole 5 Hole 2 Medline ZK21 ZK30 ZK31 ZK27 ZK28 Hole 6 ZK32 Hole 1 Hole 3 ZK26 Technological drilling General drilling ZK29 CPTu drilling Figure 4: Layout diagram of CPTu holes in Yangtze River four bridge north anchorage. fs (kPa) qt (MPa) Depth (m) 0 0 5 10 15 20 0 0 50 100 u2 (kPa) 150 200 0 5 5 5 10 10 10 15 15 15 20 20 20 25 25 25 30 30 30 35 35 35 40 40 40 0 200 400 600 800 Water table Figure 5: Results of CPTu. It is assumed that the penetration of a standard cone has a stable speed (i.e., 20 mm/s). According to the fluid continuity theorem and the Darcy law, the water volume is equal to the cone penetration volume in unit time, as shown in (9) and π’π is the hydrostatic pressure where π πβ it is assumed that the permeability coefficient has a small variation in the penetration process. At the same time, when πβ and π0 /πβ 0, the pore pressure is hydrostatic pressure π’0 , namely, (10) calculation diagram as shown in Figure 2. Consider πΎπ€ ππ πΎ π π (1 0 ) ππ 0 π€ (1 0 ) π’2 π’π 4ππΎβ π0 πβ 4πΎβ πβ πΎπ€ ππ πΎ π’2 π’0 ππ 0 π€ . 4ππΎβ π0 4πΎβ (9) (10) Take into consideration π’ π’0 ππ‘ πV0 π’2 π’0 , π΅π ππ‘ 2 ππ‘ πV0 πV0 πV0 (11) and assumption that π΅π ππ‘ 1 . πΎπ (12) Obtain πΎβ ππ0 πΎπ€ πΎπ , 4 πV0 (13) where π is penetration rate of m/s; π0 is cone radius m; πΎπ is the dimensionless permeability index; πΎβ is permeability coefficient, m/s.
Advances in Materials Science and Engineering 5 1000 1000 Fr 0.02 Fr Qt 2.0 Bq Qt 6.0 100 Qt Qt 100 Fr Qt 0.3 Bq Qt 0.2 10 10 Fr Qt 0.2 Bq Qt 1.0 1 0.2 0.0 0.2 0.4 Bq 0.6 0.8 Fr Qt 0.7 1 1E 3 1.0 0.01 0.1 Fr (a) (b) 0.1 Bq/Fr 4.0 Fr Bq/Fr 0.4 0.01 1E 3 0.2 Bq/Fr 8.0 0.0 0.2 0.4 Bq 0.6 0.8 1.0 (c) Figure 6: Contoured plots of π΅π -ππ‘ , πΉπ -ππ‘ , and π΅π -πΉπ . Substitute π΅π 1/ππ‘ πΎπ into (7) πΉ 1 πΎπ ( π 1 π΅π ) , π΅π tan π πΎπ 1 , ππ‘ (1 1/ππ‘ πΉπ / tan π) 3. Engineering Examples (14) (15) where π΅π is the pore pressure ratio, ππ‘ is the normalized tip resistance, πΉπ is resistance ratio, πΎπ is the dimensionless permeability index, and πΎβ is the permeability coefficient, m/s. Equation (14) showed that the friction ratio πΉπ and pore pressure ratio π΅π can calculate the dimensionless permeability index πΎπ . Equation (15) shows that πΎπ can be calculated by the frictional ratio πΉπ and the normalized tip resistance ππ‘ . , the soil permeability According to πβ ππ0 πΎπ€ πΎπ /4 πV0 coefficient can be calculated in partially drained conditions by using the obtained πΎπ values. 3.1. Engineering Overview. South and North Anchorage of the 4th Nanjing Yangtze River Bridge are located in the Yangtze River levee on both sides of south and North, belonging to the lower reaches of the Yangtze River alluvial floodplain. The site of north anchor of the 4th Nanjing Yangtze River Bridg is located in Nanjing fine mag Technology Co. Ltd. factory area, the ground elevation is about 5.5 6.1 m. The northern boundary of south anchor is apart from dyke and river more than 60 meters and 200 meters respectively. The north anchorage ground elevation is about 4.5 5.2 m, the site and the surrounding for forest, the southern boundary of north anchor is apart from the dyke and river about 120 m and 120 m respectively. The Quaternary loose sediment thickness is more than 60 m in north anchor. 3.2. Results of CPTU Test. From June 17, 2007, to June 23, 2007, the CPTU tests (six holes) were carried out in north anchor of Nanjing 4th Yangtze River Bridge. The soil profile of north anchorage of the Yangtze river 4th bridge is shown in Figure 3.
6 Advances in Materials Science and Engineering Table 1: Estimated soil permeability (π) based on normalized CPT soil behavior type (SBTn) by Robertson [2] (modified from Lunne et al., [11]). SBTn zone 1 2 3 4 5 6 7 8 9 SBTn Sensitive fine grained Organic soils clay Clay Silt mixture Sand mixture Sand Dense sand gravelly sand Very dense/stiff soil Very stiff fine-grained soil Range of k (m/s) 3 10 10 to 3 10 8 1 10 10 to 1 10 8 1 10 9 to 1 10 9 3 10 9 to 1 10 7 1 10 7 to 1 10 5 1 10 5 to 1 10 3 1 10 3 to 1 1 10 8 to 3 10 5 1 10 9 to 3 10 7 πΌπ NA πΌπ 3.60 2.95 πΌπ 3.60 2.60 πΌπ 2.95 2.05 πΌπ 2.60 1.31 πΌπ 2.05 πΌπ 1.31 NA NA Overconsolidated and/or cemented. Figure 7. As seen from Figure 6, the permeability coefficients from the laboratory test and the CPTU test were consistent and the trend is basically same. The permeability coefficient using the presented method to calculate was in accordance with the scope of permeability coefficient in Table 1 [2]. 15 20 Depth (m) 4. Conclusion 25 30 35 40 10 9 10 8 10 7 10 6 10 5 10 4 10 3 Permeability coefficient (m/s) Laboratory test This method The dimensionless penetration index πΎπ was derived through the normalized tip resistance ππ‘ , frictional ratio πΉπ , and the pore pressure ratio π΅π relationship in partial drainage conditions; based on πΎπ , the permeability coefficient can be calculated. Comparing the results of laboratory test and the CPTU test, we can see the permeability coefficient in the range of 10 4 m/sβ10 7 m/s from the test results of soil under partially drained conditions and more than 10 4 m/s in complete drainage conditions and less than 10 7 m/s in undrained condition the permeability coefficient can be calculated through the pore pressure dissipation test. The engineering application shows that the permeability coefficients obtained from the pumping test and CPTU test are identical. This method can provide the reference for practical foundation pit dewatering. Figure 7: Curve of permeability coefficient changing with depth. Conflict of Interests The hole position is shown in Figure 4. The CPTU test results were as shown in Figure 5. From Figure 6, it can be seen that the measuring points of the sand layer are located in the range of 0 π΅π ππ‘ 0.2, ππ‘ πΉπ 0.2 0.7, π΅π /πΉπ 4, πΉπ 0.2, which belongs to the section of the partial drainage conditions, so it can calculate the soil permeability coefficient according to (12) (15). Based on laboratory tests, the internal friction angle of slit is 30.9 , and the internal friction angle of fine sand is 32.5 and the internal friction angle of silty soil is 31 . The permeability coefficient related to the depth can be calculated by the equation (13). Figure 7 shows the comparison between the calculated results and the laboratory test ones, shown in The authors declare that there is no conflict of interests regarding the publication of this paper. Acknowledgments The work described in this paper was supported by the Outstanding Youth Fund of the Education Department of Anhui Province (Project no. 2011SQRL045), Master/Doctor Fund of the Anhui University of Science and Technology, Young Scholar Fund of the Anhui University of Science and Technology, and the National Natural Science Foundation of China (Project no. 51208005).
Advances in Materials Science and Engineering References [1] Douglas, B. J, Olsen, and R. S, βSoil classification using electric cone penetrometer. Cone penetration testing and experience,β in Proceedings of the ASCE National Convention (ASCE β81), pp. 209β227, New York, NY, USA, 1981. [2] P. K. Robertson, βSoil classification using the cone penetration test,β Canadian Geotechnical Journal, vol. 27, no. 1, pp. 151β158, 1990. [3] P. K. Robertson and C. E. Wride, βEvaluating cyclic liquefaction potential using the cone penetration test,β Canadian Geotechnical Journal, vol. 35, no. 3, pp. 442β459, 1998. [4] R. S. Olsen and J. V. Farr, βSite characterization using the cone penetrometer test,β in Use of in Situ Tests in Geotechnical Engineering, pp. 854β868, American Society of Civil Engineers (ASCE), New York, NY, USA, 1986. [5] M. Manassero, βHydraulic conductivity assessment of slurry wall using piezocone test,β Journal of Geotechnical Engineering, vol. 120, no. 10, pp. 1725β1746, 1994. [6] R. S. Olsen, βNormalization and prediction of geotechnical properties using the cone penetrometer test,β Tech. Rep. GL-9429, U.S. Army Corps of Engineers, WES, Vicksburg, Miss, USA, 1994. [7] J. M. Smythe, P. B. Bedient, R. A. Klopp, and C. Y. Chiang, βAn advanced technology for the in situ measurement of heterogeneous aquifers,β in Proceedings of the Conference on New Field Techniques for Quantifying the Physical and Chemical Properties of Heterogeneous Aquifer, pp. 605β628, 1989. [8] C. Y. Chiang, K. R. Loos, and R. A. Klopp, βField determination of geological/chemical properties of an aquifer by cone penetrometry and headspace analysis,β Ground Water, vol. 30, no. 3, pp. 428β436, 1992. [9] D. Elsworth and D. S. Lee, βPermeability determination from on-the-fly piezocone sounding,β Journal of Geotechnical and Geoenvironmental Engineering, vol. 131, no. 5, pp. 643β653, 2005. [10] R. Hill, The Mathematical Theory of Plasticity, Oxford University Press, Oxford, UK, 1983. [11] T. Lunne, P. K. Robertson, and J. J. M. Powell, Cone Penetration Testing Geotechnical Practicem, Chapman and Hall, London, UK; Spon press Taylor & Francis Group, New York, NY, USA, 1997. 7
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two categories: to estimate permeability coe cient based on the soil classi cation and to estimate permeability coe cient based on the pore pressure dissipation test. e correct tip resistance , pore pressure ratio and sleeve friction were modi ed to determine the type of soil [ ] and (Olsen [ ]). e permeability coe cient was estimated
The constant head permeability test procedure determines the permeability of a material by maintaining a constant head (h) on the sample surface and measuring the time needed for collecting a known amount of water. The permeability can then be calculated using the equation QL k - * 7200 c Ah (1) where kc coefficient of permeability (ft/day .
Amendments to the Louisiana Constitution of 1974 Article I Article II Article III Article IV Article V Article VI Article VII Article VIII Article IX Article X Article XI Article XII Article XIII Article XIV Article I: Declaration of Rights Election Ballot # Author Bill/Act # Amendment Sec. Votes for % For Votes Against %
Constant Head Falling Head Permeability Cell 38-T0184/C11 Constant Head permeability cell, 75 mm internal dia., 3 take-off points. 38-T0185/C12A Falling Head permeability cell, 100 mm internal dia. complete with 75-micron gauze and 2 m of tubing conforming to BS EN ISO 17892-11. 38-T0184/C2 Constant Head permeability cell, 114 mm internal dia.,
Most in situ permeability tests are interpreted by assuming isotropy of permeability (3, 8). The permeability of a soil may be calculated from the results of variable-head permeability tests from the standard expression A k - F T (1) From the results of constant-head tests more commonly used in the United Kingdom,
laboratory test procedures for determination of the coefficient of permeability of soil: 1- The constant head method, for high permeability soils. 2. Falling Head Method, for medium and low permeability soils. Both methods use Darcy's law: V ki and the corresponding flow rate is: q kiA .where : q quantity of fluid in a unit time
between air permeability and porosity values calculated according to three different theoretical models. A specific experimental set of knitted fabrics with defined structural parameters is to be used for this purpose. 2 RESEARCH METODOLOGY 2.1 Air permeability Air permeability AP [m/s] of textile materials
3-8 Gas permeability Gas permeability of NEOFLON FEP film is shown in Figure 13 and Table 9, and is compared with other plastic films in Figure 14. Table 9 Gas Permeability of NEOFLON FEP Film (Test method: ASTM D-1434, JIS Z0208) Gas Gas permeability* NEOFLON FEP PTFE Low densit
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