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In real-life costal engineering problems, the foundations are subjected to complex loads as increase in both deviator stress and major principal stress direction simultaneously. To investigate undrained deformation behavior and pore pressure accumulation of soft clay under different initial major principal stress directions, hollow cylinder apparatus (HCA) tests were carried out. The influence of intermediate principal stress coefficient was also considered. Combined principal stress rotation means that deviator stress and major principal stress direction simultaneously increase during shearing. It can be obtained that the deformation behavior and pore water pressure accumulation of tested samples are significantly influenced by intermediate principal stress coefficient b. Furthermore, the undrained behavior of tested natural soft clay samples is affected by the initial major principal stress direction. Moreover, the variation of stress and strain components is not synchronous with the increase of deviator stress and principal stress direction. The failures of soft clay specimens are controlled by strain other than pore water pressure involved combined principal stress rotation. The non-coaxiality of natural soft clay is influenced by different initial major principal stress direction significantly rather than b values.

It is important to be fully aware of the dynamic characteristics of saturated soft clays under complex loading conditions in practice. In this paper, a series of undrained tests for soft clay consolidated with different initial major principal stress direction ξ were conducted by a hollow cylinder apparatus (HCA). The clay samples were subjected to pure principal stress rotation as the magnitudes of the mean total stress p, intermediate principal stress coefficient b, and deviator stress q were all maintained constant. The influences of intermediate principal stress coefficient and initial major principal stress direction on the variation of strain components, generation of pore water pressure, cyclic degradation and non-coaxiality were investigated. The experimental observations indicated that the strain components of specimen were affected by both intermediate principal stress coefficient and initial major principal stress direction. The generation of the pore water pressure was significantly influenced by intermediate principal stress coefficient. However, the generation of pore water pressure was merely influenced by initial major principal stress direction when b = 0.5. It was also noted that the torsional stress–strain relationships were affected by the number of cycles, and the effect of intermediate principal stress coefficient and initial major principal stress direction on the torsional stress–strain loops were also significant. Stiffness degradation occur under pure principal stress rotation. Anisotropic behavior resulting from the process of inclined consolidation have considerable effects on the strain components and non-coaxial behavior of soft clay.

In order to investigate the cyclic deformation behavior of natural soft marine clay under the general stress condition, which is due to travelling waves involved principal stress rotation, a series of undrained tests were carried out by using GDS hollow cylinder apparatus (HCA). The principal stress axis rotates continuously while holding the deviator stress (difference between the vertical normal stress and horizontal normal stress) at a constant level. The tests results show that, the pore water pressure, stress-strain hysteretic loop, dynamic modulus of the tested samples are significantly dependent on CSR s and confining pressures. Furthermore, pore water pressure generates slightly during the first 30 cycles, and accumulates with the increase of cycles. The tensile axial strain occurs in the initial loading cycles and the development styles are various with different CSR s and confining pressures. With the larger CSR s and confining pressures, higher strain degradation occurs. A new critical value between 0.16 and 0.18 is suggested for CSR under continuous principal stress rotation.

This paper presents a series of monotonically combined lateral loading tests to investigate the bearing capacity of the MSCs (modified suction caissons) in the saturated marine fine sand. The lateral loads were applied under load- and displacement-controlled methods at the loading eccentricity ratios of 1.5, 2.0 and 2.5. Results show that, in the displacement-controlled test, the deflection-softening behavior of load-deflection curves for MSCs was observed, and the softening degree of the load-deflection response increased with the increasing external skirt length or the decreasing loading eccentricity. It was also found that the rotation center of the MSC at failure determined by the load-controlled method is slightly lower than that by the displacement-controlled method. The calculated MSC capacity based on the rotation center position in serviceability limit state is relatively conservative, compared with the calculated capacity based on the rotation center position in the ultimate limit state. In the limit state, the passive earth pressures opposite the loading direction under load- and displacement-controlled methods decrease by 46% and 74% corresponding to peak values, respectively; however, the passive earth pressures in the loading direction at failure only decrease by approximately 3% and 7%, compared with their peak values.

To study the effect and mechanism of carbon fiber reinforced clay, a series of unconfined compression tests for clay reinforced with carbon fiber have been performed under the conditions of controlled water content and dry density. The carbon fiber is mixed into soil with the quality percentage of 0.01, 0.02, 0.03, 0.05, 0.1, 0.15, 0.25, 0.35, and 0.5%, then a certain quality of water was added in the soil to achieve the optimum soil water content. Ten groups of samples were tested by the unconfined compression experiment. The results showed that the incorporation of carbon fiber elements can effectively improve the unconfined compressive strength and brittle failure mode of soil. The soil is strengthened at the beginning and then weakened with the increased incorporation of carbon fiber, the effect is especially significant when the mix percentage becomes 0.1%. The interaction at the interface between carbon fiber surface and soil matrix is analyzed by using scanning electron microscopy (SEM). It...

The spectral representation method (SRM) is widely used when simulating spatially variable ground motions. It has mainly two formulas, i.e., the random amplitudes and the random phases formulas. There exist three methods for decomposing the cross spectral density matrix: Cholesky decomposition, eigen decomposition, and root decomposition. Therefore, there are six forms with respect to the different combinations of the simulation formulas and the decomposition methods. To provide researchers and engineers with the guidance on choosing simulation method, the six forms are systematically investigated from five aspects: the power intensity, response spectra, and stochastic error of auto/cross spectral density, Fourier spectra, and difference indexes for Fourier amplitudes and phases. Finally, we give the following advice: the characteristics of the ground motions simulated by the random amplitudes formula are independent of the decomposition method, while the characteristics of the ground motions simulated by...

To assess the effectiveness of vacuum preloading combined electroosmotic strengthening of ultra-soft soil and study the mechanism of the process, a comprehensive experimental investigation was performed. A laboratory test cell was designed and applied to evaluate the vacuum preloading combined electroosmosis. Several factors were taken into consideration, including the directions of the electroosmotic current and water induced by vacuum preloading and the replenishment of groundwater from the surrounding area. The results indicate that electroosmosis together with vacuum preloading improve the soil strength greatly, with an increase of approximately 60%, and reduce the water content of the soil on the basis of consolidation of vacuum preloading, however, further settlement is not obvious with only 1.7 mm. The reinforcement effect of vacuum preloading combined electroosmosis is better than that of electroosmosis after vacuum preloading. Elemental analysis using X-ray fluorescence proves that the soil strengthening during electroosmotic period in this work is mainly caused by electroosmosis-induced electrochemical reactions, the concentrations of Al2O3 in the VPCEO region increase by 2.2%, 1.5%, and 0.9% at the anode, the midpoint between the electrodes, and the cathode, respectively.

The spectral representation method (SRM) is most widely used in simulating the stochastic field. The proper orthogonal decomposition (POD) based SRM is an important form. This paper investigates the approximate approaches to the POD-based SRM in simulating two typical problems, i.e., the seismic ground motion and wind velocity fields simulations. Then, the accuracy resulting from the power spectral density matrix-based POD method (PSRM) is compared to that of the coherency matrix-based POD method (CPSRM). It is concluded that the CPSRM maintains a much higher accuracy than the PSRM. In the CPSRM, the linear interpolation of eigenvectors and third-order polynomial interpolation of eigenvalues can be accepted to attain high accuracy; the linearly distributed interpolation nodes are effective in the ground motions simulation; however, the exponentially distributed interpolation nodes are effective in the wind velocity simulation.

Slurry dredged soil at coastal area has a high water content, poor permeability, and low surface intensity. Hence, it is infeasible to use vacuum preloading method to treat this type of soil foundation. For the special case of super soft ground, a floating bridge is first constructed on muddy soil and used as a service road and platform for implementing the modified vacuum preloading method. The modified technique of vacuum preloading and its construction process for the super soft soil foundation improvement is then studied. Application of modified vacuum preloading method shows that the technology and its construction process are highly suitable for improving the super soft soil foundation in coastal areas., {"references":["jellman, w. 1952. Consolidation of clayey soils by atmospheric pressure. Proceedings of a conference on soil stabilization, Massachusetts institute of technology, Boston: 258-263.","Liu H. L, Mahfouz, A. H., and Chen Yong-hui., 2004. Ground Treatment of sea embankment by vacuum preloading with PVDs. Southeast University Journal, SEUJ, Nanjing, China, 20(1): 96-101. (EI)","Mahfouz, A.H., Liu Han-long, Gao Yu-feng, and Li Hao, 2004. Soil improvement for Hangzhou express highway – China by Using Vacuum Preloading Method and PVD Application. J. of Petroleum and Mining Engineering, JPME, Suez, Egypt, June 7(1): 115-125.","Mahfouz, A.H. 2005. Study of combined vacuum-surcharge preloading mechanism for ground treatment. PhD Thesis, Hohai University, Nanjing, China.","Mahfouz, A.H., Liu Han-long and Yu Xiang Juan. 2005. Soil improvement for Jing-Zhu expressway in Guangdong province–China by using vacuum preloading method. Proc. of 3rd Int. Conf. on Geotech. Eng. combined with 9th Yearly Meeting of the Indonesian Society for Geotech. Eng. (ISGE) for Disaster Prevention and Rehabilitation. Aug. 3-4, 2005, Semarang, Indonesia, 303-313.","Mahfouz, A. H., Liu Hanlong, Mohammed A Sakr and Samir IShalaby. 2007. New technique of ground improvement by using vacuum preloading method with PVDs. 12th International Colloquium on Structural and Geotechnical Engineering (ICSGE) 10-12 Dec. 2007, Cairo - Egypt.","Mahfouz, A.H., Shen Yang, New. 2014. Technology of Vacuum Preloading for Super Soft Soil Foundation. MPM 12 International conference, 20-22 October 2014, Geo 1.","CAO Yong Lang, Cong Jian, Wu Xiaopeng. 2003 Expressway super soft vacuum preloading of (J). Rock and Soil Mechanics, 24 (5):771-775.","Zhao Weibing, Qian Huan. 1990. Preloading Sand foundation design. Journal of Waterway engineering, (9):5-10.\n[10]\tMahfouz, A.H Liu Han-long and Gao Yu-feng, 2002. Behaviour of soft soils under consolidation with applied surcharge and vacuum preloading. Proc. of Symp. on Soil/Ground Improvement and Geosynthetic Application, 12-13 Dec. 2002, SEAGS, Bangkok, Thailand, 2545, 199-211.\n[11]\tMahfouz, A. H, Liu Hanlong, and Gaoyufeng, 2004. Ground Improvement by Using Vacuum Preloading with Sand Drains. IS-OSAKA 2004 International Symposium on Engineering Practice and Performance of Soft Deposits 2-4 June, Osaka, Japan, 287-292.\n[12]\tGround Handling Manual prepared by the Committee. Ground Handling Manual (Second Edition) (M). Beijing: China Building Industry Press, 2000.\n[13]\tLi Hao,Gao Yu-feng,Liu Han-long,Peng Jie, and Mahfouz, A.H. 2003. Simplified method for subsoil improved by vacuum combined with surcharge preloading, Chinese Geotechnical Engineering Journal, Nanjing, China, 25(1): 58-62, (in Chinese). (EI).\n[14]\tCai Xiaoguang, Liu Han. 2009. Composites reinforced embankment on soft soil drainage water cushion design method (J). Disaster Prevention and Mitigation Engineering, (3): 356-360.\n[15]\tY. Shen, M. Tao, H. L. Liu, Y. F. Gao, Y. Cui. 2012. The performance of super soft foundation under modified vacuum preloading method. Forensic Engineering, American Society of Civil Engineers (ASCE) 2012 pp. 708-715."]}

The driven cast-in-situ concrete thin-wall pipe pile (PCC) is a new technique for soft ground improvement and has been recently approached in China. It has become one of the most cost-effective soft soil improvement methods that can increase the bearing capacity and reduce the settlement of the soil. This paper presents a field application in a highway foundation improvement project. The field study has demonstrated that PCC pile composite foundation is a cost-effective way of improvement. The cast-in-PCC composite foundation piles; design theory, construction technology and monitoring are described. From the test results of cast-in-reinforcement it is clearly easier to control and the PCC technology is economically advantageous. The advantages of the method are proposed to be promoted in expressway construction to have greater social and economic benefits in the world.

Vacuum preloading is a new technique for ground improvement. The vacuum drains out the pore-water, thus creating negative pore-water pressure and increasing the effective stress. The microstructure of soil samples after application of vacuum pressure has examined using scanning electron microscopy, and the orientation of soil aggregates and pores has been determined with GEOIMAGE software. The orientation of aggregates in fine-grained soil is an important factor influencing the anisotropy and engineering properties of the soil. Two quantitative indices to assess the orientation of the aggregates of fine-grained soil, alignment entropy ( ) and frequency distribution function of clay aggregate orientation , are introduced in this paper. The difference between the anisotropy index and is discussed. The image analysis reveals that , , and other fabric data change with the method of consolidation; the isotropic and disordered soil fabric changes into anisotropic and ordered fabric. Therefore a quantitative ana...

PCC energy pile is a new technology for sustainable development of urban areas. Learning and understanding the temperature variation of PCC energy pile are very important to its development and application. In this study, the Brillouin optical frequency domain analysis (BOFDA) technology is firstly used to measure the temperature variation of PCC energy pile from a model test. The aim is to provide an optical fiber sensing method for monitoring the temperature distribution of PCC energy pile. When the temperatures of circulating water are 70°C, 60°C, 50°C, and 40°C, the result shows that the temperatures of PCC energy pile under different conditions are measured well by the optical fiber sensor. It will help to master the temperature distribution and thermomechanical characteristic of PCC energy pile. It can also provide the important scientific and theoretical basis for the design and application of PCC energy pile.

An analytical solution for diffraction of both plane and cylindrical SH waves induced by a horseshoe shaped cavity with an inverted arch is presented in this paper. The geometry of the cavity is assumed to be composed of two circular arcs. By introducing an auxiliary boundary, the whole physical region is divided into two computational regions. The scattered wavefield in the open region and the standing wavefield in the enclosed region are presented by means of the wave function expansion method. Both of the wavefields are given in terms of the wave function series with unknown coefficients. By applying the Graf’s addition formula, two systems of equations for seeking the unknowns are derived by taking advantage of the boundary conditions based on the region-matching strategy. The problem of wave scattering is finally solved after seeking the solutions of the two systems of equations through standard matrix techniques. Then the effects of the excitation frequency, the cavity embedment depth and cavity geometry are discussed. The differences in terms of ground motions under different excitations and the influence of source location under cylindrical waves are also examined.