Optical measurement of sand deformation around an uplifting deep anchor using digital image correlation method

This report presents a study on the soil deformation around an uplifting deep circular anchor in sand. A scaled model anchor test setup, including a loading frame, a Plexiglas mould, a camera, and a computer, was developed and a series of scaled model test were performed in order to investigate the mechanical behavior and failure modes of a deep anchor embedded in sand. To find the displacement field the digital image correlation (DIC) method was applied. A set of images were captured while a semi-circular anchor was uplifted against the Plexiglas window, and soil displacement field was calculated by comparing any two consecutive images using DIC method. The study shows that the density of soil has a significant effect on both the deformation characteristics and the failure mechanism of the anchor. While in loose sand the failure zone is a compressed bell shape, in dense sand the failure zone is a truncated cone extending from the anchor edge to the surface of the soil. Furthermore, in dense sand the anchor experiences smaller displacement before reaching to the peak pullout force compared to a larger displacement in loose sand. This report has been done by Pezhman Sainia for the M.Eng degree's research project final report with the supervision of Dr. Jinyuan Liu.

Optical measurement of sand deformation around an uplifting deep anchor using digital image correlation method

This report presents a study on the soil deformation around an uplifting deep circular anchor in sand. A scaled model anchor test setup, including a loading frame, a Plexiglas mould, a camera, and a computer, was developed and a series of scaled model test were performed in order to investigate the mechanical behavior and failure modes of a deep anchor embedded in sand. To find the displacement field the digital image correlation (DIC) method was applied. A set of images were captured while a semi-circular anchor was uplifted against the Plexiglas window, and soil displacement field was calculated by comparing any two consecutive images using DIC method. The study shows that the density of soil has a significant effect on both the deformation characteristics and the failure mechanism of the anchor. While in loose sand the failure zone is a compressed bell shape, in dense sand the failure zone is a truncated cone extending from the anchor edge to the surface of the soil. Furthermore, in dense sand the anchor experiences smaller displacement before reaching to the peak pullout force compared to a larger displacement in loose sand. This report has been done by Pezhman Sainia for the M.Eng degree's research project final report with the supervision of Dr. Jinyuan Liu.

Force State of Country Rock and Supporting Structure in Multi-Arch Tunnel under Central Hole + CRD Method

The reason situ stress is very complicated, and it is still not very clear question. In this paper, the construction process through practical engineering analysis on a variety of construction methods and steps arch tunnel to study the effects of different excavation methods and deep anchor support large section tunnel under guard by theoretical analysis of surrounding rock stress field, strain field and variation of the displacement field, analysis of different rock excavation methods, supporting stress state characteristics, in order to optimize the choice of tunneling method provides a theoretical basis. Under the conditions all kinds of rock reasonable steps to secure construction methods put forward and lay the foundation for long-term safety arch tunnel.

Field Performance of Ground Anchors in Taichung Basin

This research carried out field tests on nine vertical anchors to investigate their behavior in gravel of Taichung Basin. An anchor can be categorized as a deep anchor when the free length Z exceeds 8D (D is the diameter of the anchor). The shape of the heave on the ground surface of a shallow anchor is similar to a normal distribution curve. The extended diameter of the heave was between 170 and 300 cm, which could be divided into two zones, primary and secondary, based on the failure mode of the ground. As the fixed length of a shallow anchor increased, the extended diameter also increased. The ultimate load of an anchor increased with the free length and, to a greater degree, with the fixed length of an anchor: a fixed length of only 3 m (D = 0.12 m) generated an ultimate load of over 1100 kN.

Behavior of pressure-grouted anchors in gravel

This study consisted of field tests conducted on nine vertical and three inclined low-pressure-grouted anchors to investigate their behavior in gravel. An anchor can be categorized as a deep anchor when the overburden depth (free length) Z exceeds 8D (D is the diameter of the anchor). The shape of the heave on the ground surface of a shallow anchor is similar to a normal distribution curve. The extended diameter of the heave was between 170 and 300 cm, which could be divided into two zones, primary and secondary, based on the failure mode of the ground. As the fixed length of a shallow anchor increased, the extended diameter also increased. The ultimate load on an anchor increased with the free length and, to a greater degree, with the fixed length of an anchor: a fixed length of only 3 m generated an ultimate load of over 1100 kN. However, the permissible load, determined from the creep coefficient, is inapplicable for short anchors in gravel. The earth pressure coefficient K of vertical anchors was approximately 29 and for an anchor shaft inclined at 25º it was approximately 17.7.

A Numerical Study on the Uplift Behavior of Under-Reamed Anchors in Silty Sand

Ground anchors are common to be employed in geotechnical engineering. Under a limited space of an urban district or a restricted thick of an anchored stratum, an under-reamed anchor could meet both the requirements of a short length and a high anchorage capacity. To investigate the anchorage mechanism of the anchor, a series of triaxial tests was performed to obtain the parameters demanded for a constitutive model, SHASOVOD (A continuous strain hardening/ softening and volume dilatancy model for cohesionless soil during stressing). A numerical program was then developed to study the uplift behavior of the under-reamed anchor in silty sand. Analyzing results show that, for two under-reamed anchors located in different test sites, the complete load-displacement curves estimated numerically were consisted with those measured from the field test. The total load, friction load and end bearing do not reach their peaks simultaneously. According to the behavior of the end bearing, a critical overburden depth H of 6D was found to classify an under-reamed anchor as a shallow anchor or a deep anchor.