Structural Damage of Subway Tunnel Buried Shallowly in Silt Layer under Soil Mound Loading

Based on the structural damage of the shield tunnel caused by a soil mound on the ground surface in a section of subway in Tianjin, China, the deformation and the cracking process of the segment under soil mound loading were simulated. The variations of segment, bolt, and rebar stresses with the height of the mound were analyzed. The results show that, for the stagger-jointed assembled shield tunnel that crosses the marine sedimentary silt with a burial depth of 10 m, as the mound loading increases, the damage is concentrated in the vault and hance. When the mound loading is 16.0 kPa, the segment is damaged; the crack depth and bolt axial force of the vault increase rapidly when the mound loading reaches 38.6 kPa. The analysis results are basically consistent with monitoring data. Based on the above analysis, the control standard of mound loading should be 38.6 kPa. The results of this study can provide data reference for control and structural protection of soil mound loading for similar subway tunnels.

QUALITY ASSESSMENT OF SOIL RIDGE FORMATION WHEN SOWING TILLED CROPS

A hillock drill was desighned, an application of which makes cost-effectively in one pass to perform sowing cultivation, sowing the seeds, form a soil mound above sown seeds, compact the soil mound from three sides and, finally, form a soil ridge of required dimensions and density in it. The article was justified the attack angles of flat disk of the working unit and the spherical roller-discs of roller-ridger of hillock drill. It was revealed, that the process of soil ridges forming of required dimensions and density at seeding tilled-crops are affected by structural and operational parameters of working units with flat discs and the roller-ridges, as well as the physical and mechanical properties of the soil.

Dynamic Consolidation Test Study on Silt and Silt Soil

A dynamic consolidation model of double layered foundation of saturated soil and unsaturated soil is proposed. Mechanism of dynamic compaction treating on double layered foundation is studied by the model. On the base of the mechanism a new technology called soil-mound dynamic consolidation can be applied to treat the ground of saturated silt and silty clay with high groundwater level. The water-pore pressure test, static cone penetration test, settlement plate test are applied to evaluate that of the new technology with different construction parameters. The treatment effect is more remarkable than that of plastic drain-dynamic consolidation.

Geotechnical Aspects of the N1 Tower, Prasat Sour Prat, Angkor Thom, Cambodia

This paper presents a case study of foundation of an inclined independent masonry tower in Angkor. One of the Prasat Sour Prat towers had been dismantled before reconstruction for conservation. The foundation was inclined as the same as the upper structure of the tower and spreading outwards. The inclination was considered caused by foundation failure with some differential settlements of the ground. During dismantling, the soil layers exposed on the trenched section were found rather horizontal than the inclined state that had been expected. Laterite blocks of step slope stones was found to have slid down along the soil mound of the foundation. The mechanism might have been caused by weakening of soil strength by wetting ground. Without dismantling, the real mechanism of the inclination was never known as well as the corresponding counter measures.