Stability analysis of gravity anchor foundation of layered argillaceous sandstone under dry-wet cycles

To investigate the stability of gravity anchors of suspension bridges,in-situ tests of the vertical bearing capacity of the bedrock,shear resistance of the anchor-rock interface,shear resistance of the bedrock were conducted in a suspension bridge project.Under dry-wet cycles,the deterioration law of the mechanical properties of argillaceous sandstone was identified in laboratory tests:the elastic modulus,cohesion and friction of the argillaceous sandstone deteriorated significantly at first few dry-wet cycles and then declined slowly after 10 cycles,ultimately these three mechanical parameters were reduced to about 1/3,1/3,2/3 of the initial value respectively.Moreover,numerical simulation was used to restore in-situ shear tests and a good agreement was obtained.Base on the results of in-situ and laboratory tests,the stability of the gravity anchor foundation under natural conditions and drywet cycles was calculated and its failure modes were analyzed.The results demonstrated that the dry-wet cycles caused uneven settlement of the anchor foundation,resulting in more serious stress concentration in the substrate.The dry-wet cycles remarkably reduced the stability coefficient of the anchor foundation,whose failure mode shifted from overturning failure under natural conditions to sliding failure.When there was weak interlayer in the rock layer,the anti-sliding stability of the anchor foundation was affected drastically.

Monotonic uplift behavior of anchored pier foundations in soil overlying rock

Rock-embedded foundations with good uplift and bearing capacity are often used in mountains or hilly areas.However,there are soil layers with a certain thickness on the rocks in these mountainous areas,and the utilization of those soil layers is a problem worthy of attention in foundation construction.Considering construction-and cost-related factors,traditional single-form foundations built on such sites often cannot provide sufficient resistance against uplift.Therefore,an anchored pier foundation composed of anchors and belled piers,specifically constructed for such conditions,can be invaluable in practice.This paper introduces an experimental and analytical study to investigate the uplift capacity and the uplift mobilization coefficients(UMCs)of the anchored pier foundation.In this study,three in-situ monotonic pullout tests were carried out to analyze the load–displacement characteristics,axial force distribution,load transfer mechanism,and failure mechanism.A hyperbolic model is used to fit the load–displacement curves and to reveal the asynchrony of the ultimate limit states(ULSs)of the anchor group and the belled pier.Based on the results,the uplift capacity can be calculated by the UMCs and the anchor group and pier uplift capacities.Finally,combined with the estimation of the deformation modulus of the soil and rock,the verification calculation of the uplift capacity and UMC was carried out on the test results from different anchored pier foundations.