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The significance of studying soil behaviour in a constant shear stress path to understand rain-induced slope failures and debris flows has long been recognized. Studies with constant shear tests have, however, been limited, and some past results from undisturbed soils appear to show stress path--dependent volume change behaviour. The present study systematically investigates the behaviour of recompacted residual soils in a constant shear stress path using a comprehensive experimental program. It is shown that the results of this test program and previously published data can be interpreted using the concepts of critic a I-state soil mechanics. Key words: constant shear, laboratory test, rain-induced failure, stress path, recompacted soil, pore pressure. Il est reconnu depuis longtemps que l'etude du comportement du sol suivant un cheminement des contraintes de cisaillement constant est importante lors de ruptures de pentes causees par la pluie ainsi que lors d'ecoulements de debris. Les etudes ayant utilise des essais de cisaillement constants sont limites, et certains resultats provenant d'essais anterieurs sur des sols non remanies semblent demontrer que les variations de volume sont dependantes du cheminement des contraintes. La presente etude evalue systematiquement le comportement de sols residuels recompactes suivant un cheminement des contraintes de cisaillement constant a l'aide d'un programme experimental complet. L'etude a demontre que les resultats du programme d'essais el les resultats deja publics peuvent etre interprets en utilisant les concepts de la mecanique des sols a l'etat critique. Mots-cles : cisaillement constant, essai en laboratoire. rupture causee par la pluie, cheminement des contraintes, sol recompacte, press ion interstitielle. [Traduit par la Redaction], Introduction Most slope failures are attributable to an increase in pore pressures following periods of intense rainfall. Rain-induced slope failures in steep natural terrains occur at shallow depths and frequently [...]

The current method of steel bar soil nail construction is both labor intensive as well as expensive and many engineers are considering the use of new soil nail materials. In the present pilot test, an innovative soil nail is constructed by light weight high strength glass fiber-reinforced plastic (GFRP) pipe with the Tube a' Manchette grouting technique. It is found that this new soil nail system can be handled easily on sites with difficult access. Extensive laboratory as well as field tests were carried out on the GFRP pipe nails and the grouted soil mass and numerical modeling of a field test was performed. The installation of the GFRP pipe, laboratory, and field test results that were carried out in Hong Kong and Korea are discussed in this paper. DOI: 10.1061/(ASCE)0899-1561(2009)21:3(93) CE Database subject headings: Soil nailing; Fiber reinforced polymers; Hong Kong; Korea; Material properties.

Soil nailing is commonly used for stabilizing cut slopes and retaining structures. The technique is, however, seldom used in stabilizing old loose fill slopes that were not constructed to the current standards. There is a concern that soil-nailed loose fill slopes may not render safety during heavy rainstorms. Little work has been carried out to investigate the behavior of soil-nailed loose fill slopes. This paper presents a comprehensive field test on a loose fill slope that was constructed by end tipping without any compaction--in the same way old fill slopes were formed. The slope was 4.75 m high, 9 m wide, and 33 deg to the horizontal. Two rows of five grouted nails were installed at a grid of 1.5 m X 1.5 m at an inclination of 20 deg from the horizontal. A surface grillage was used to connect the six nails in the middle of the grid. Performance of the nailed slope was monitored with various instruments for about six months until the slope was tested to fail by surcharging and wetting. The overall results show that soil nailing with a surface grillage is a potentially effective way to enhance the stability of old fill slopes. DOI: 10.1061/(ASCE)1090-0241(2008)134:3(277) CE Database subject headings: Field tests; Slope stability; Fills; Rainfall.

Abstract: Landslide 1 is located on the right bank of the downstream side of the dam for Hongjiadu Hydropower Station in Guizhou Province, China. In view of its close proximity [...]

A soil reinforcement system using the combination of glass-fiber-reinforced polymer (GFRP) pipe and pressure grouting has been developed by a Korean company. The system is being adopted as slope stabilization measures in Hong Kong. Individual GFRP pipes were designed and installed as soil nails with the exception that two-stage pressure grouting was applied instead of gravity grouting. A full-scale field evaluation on constructability and in situ performance of the system was performed in Hong Kong. The performance of the constructed nails was evaluated by pullout tests. The construction procedure, site adaptations of the Korean product made in Hong Kong, field test procedure, and performance of the constructed soil nails are reported in this paper. DOI: 10.1061/(ASCE)0887-3828(2007)21:1(26) CE Database subject headings: Glass fiber; Fiber reinforced polymers; Soil nailing; Soil stabilization; Pull-out resistance; Hong Kong; Field investigations.

Full-scale field tests were performed to study the behavior of two steel H-piles jacked into dense sandy soils. The maximum embedded length of the test piles was over 40 m and the maximum jacking force used was in excess of 7,000 kN. The test piles were heavily instrumented with strain gauges along their shafts to measure the load transfer mechanisms during jacking and the subsequent period of static load tests. Piezometers were installed in the vicinity of the piles to monitor the pore pressure responses at different depths. The time effect and the effect of installation of adjacent piles were also investigated in this study. The test results indicated that, although both piles were founded on stiff sandy strata, most of the pile capacity was carried by shaft resistance rather than base resistance. This observation implies that the design concept that piles in dense sandy soils have very large base capacity and small shaft resistance is likely to be inappropriate for jacked piles. It was also found that the variation in pore pressures induced by pile jacking was closely associated with the progress of pile penetration; the pore pressure measured by each piezometer reached a maximum when the pile tip arrived at the piezometer level. A nearby pile jacking was able to produce large tensile stresses dominating in the major portion of an installed pile; both the magnitude and distribution of the induced stresses were related to the penetration depth of the installing pile. DOI: 10.1061/(ASCE)1090-0241(2006)132:1(24) CE Database subject headings: Field tests; Interactions; Piles; Pore pressures; Sand.

This paper presents the findings of a digital image analysis based study of clay fills, compacted with dynamic compaction for a building foundation in northeast Beijing, People's Republic of China. Three levels of compaction energy were used at three compaction pits, respectively. Ground settlements and soil density increased with the number of dynamic impact blows. Microstructures of dry clay fill samples from the pits were examined with a scanning electronic microscope (SEM). Their microstrucural parameters were further measured and analyzed quantitatively using digital image analysis. The clay SEM images are automatically converted into ternary images representing particles, pores, and contact zones for effective and efficient calculation of the clay microstructural parameters. The effect of dynamic compaction on the clay microstructural properties at different blow numbers and compaction energy levels is examined. Analysis revealed that the changes of the soil microstructural properties have a good correlation with the observed ground settlements at the three pits. The ground settlements are due to the size and shape changes and reorientation of the grain particles and pores of the clay fills. DOI: 10.1061/(ASCE) 1090-0241(2005)131:11(1411) CE Database subject headings: Soil compaction; Digital techniques; Imaging techniques; Clays; Soil stabilization; Fills.

Results of field monitoring of moisture content and matric suction at the crest and berm of a large cut slope in completely decomposed granite in Hong Kong are reported. Field moisture content and matric suction clearly show that the volumetric water content increases as a result of rainfall infiltration and decreases as a result of evaporation. Correspondingly, the matric suction decreases due to rainfall infiltration and increases due to evaporation. Soil--water characteristic curves at different depths at the crest and near the term of the cut slope are determined from the field data. Unlike soil--water characteristic curves determined in the laboratory by testing small specimens, the field measured soil--water characteristic curves show negligible hysteresis. Engineering implications of the field soil--water characteristic curves are discussed. DOI: 10.1061/(ASCE)1090-0241(2005)131:9(1176) CE Database subject headings: Monitoring; Field investigations: Soil water; Moisture content; Hysteresis.

In this paper, a homogeneous type of kinetic rate laws of local internal variables and its corresponding macroscopic behaviors, are explored within the framework of 'normality structures' by Rice. Rice's kinetic rate laws of local internal variables, with each rate being stress dependent only via its conjugate thermodynamic force, are corner stones of the normality structure. It is revealed in this paper that nonlinear phenomenological equations and Onsager reciprocal relations emerge naturally if each rate is a homogeneous function of degree q in its conjugate force. Furthermore, the nonlinear phenomenological coefficient matrix is identical to the Hessian matrix of the flow potential function in conjugate forces only scaled by q. It is further shown that the refined version of Griffith criterion proposed by Rice, (G - 2[lambda])a [greater than or equal to] 0, can be derived from the normality structure with the homogeneous rate laws. Finally, some issues related to damage evolution laws have been discussed based on the remarkable properties. [DOI: 10.1115/1.1867991]

Based on genetic algorithm and genetic programming, a new evolutionary algorithm is developed to evolve mathematical models for predicting the behavior of complex systems. The input variables of the models are the property parameters of the systems, which include the geometry, the deformation, the strength parameters, etc. On the other hand, the output variables are the system responses, such as displacement, stress, factor of safety, etc. To improve the efficiency of the evolution process, a two-stepped approach is adopted; the two steps are the structure evolution and parameter optimization steps. In the structure evolution step, a family of model structures is generated by genetic programming. Each model structure is a polynomial function of the input variables. An interpreter is then used to construct the mathematical expression for the model through simplification, regularization, and rationalization. Furthermore, necessary internal model parameters are added to the model structures automatically. For each model structure, a genetic algorithm is then used to search for the best values of the internal model parameters in the parameter optimization step. The two steps are repeated until the best model is evolved. The slope stability problem is used to demonstrate that the present method can efficiently generate mathematical models for predicting the behavior of complex engineering systems. CE Database subject headings: Algorithms; Slope stability; Stability analysis.

Using Schwarz's alternating method and Muskhelishvili's complex variable function techniques, this paper presents an iterative algorithm method for the effective and accurate calculation of the stresses in an elastic solid of infinite extent containing multiple elliptic holes and subject to external loading at the infinity. The elliptic holes can have different dimensions and locate at any points while their axis orientations must be orthogonal. The proposed iterative algorithm method is based on the approximation of the resultant force vector on each elliptic hole boundary as a series of complex variable. As a result, exact closed-form analytical stress solutions can then be obtained for the solid with a single elliptic hole whose boundary is subject to the reverse resultant force vector in the forms of complex series. The numerical results presented in the paper show that the iterative solution converges quickly and stably. The proposed convergent criterion ensures the satisfaction of the required accuracy of the stress results. The stress concentration at elliptic holes can then be evaluated with high accuracy. CE Database subject headings: Elasticity; Holes; Stress analysis; Stress concentration; Computation.