Experimental Study of the Bearing Capacity of Helix Pile Foundation

The use helix pile foundations in supporting structures on peat soil has became a challenge for road infrastructure. The helix pile foundation is an alternative for substituting the pile foundation if hard soil is located too far from the surface. Therefore, in this study we examine the bearing capacity of the helix pile foundation on peat soil, including analyzing the effect of the number of helix plates on the bearing capacity of the peat soil. The type of foundation used is a helix pile foundation with a single blade, double blades and triple blades. From the results of the research the bearing capacity of helix double is 35% greater than the bearing capacity of a single helix, the value of triple helix bearing capacity is 25% greater than the double helix and 70% of the single helix. The more number of helix plates used, the greater the bearing capacity of the piles given.

FIELD STUDY OF GROUP EFFECTS ON THE PULLOUT CAPACITY OF ‘DEEP’ HELICAL PILES IN SAND

This paper presents the results of a field load test program used to investigate group effects on the pullout capacity of single-helix ‘deep’ helical piles/anchors in sand. The high tensile capacity and silent installation of helical piles has given them serious consideration as an alternative to conventional deep foundations and anchors for offshore renewable energy structures. New offshore applications may consider the use of groups of helical piles to resist structural loads. Group interaction effects are known to occur in helical piles but there is a scarcity of field data on groups in sands under tensile loading. This study involved the installation and load testing of single-helix 152-mm diameter round shaft piles and pile groups embedded in sand to depths of 12 and 18 helix diameters below the ground surface. The study was designed to explore the effects of close pile spacing, group configuration (i.e. number of piles), and soil strength as interpreted from Cone Penetration Test (CPT) resistance. The results showed group efficiencies ranging from about 0.6 to 1.0 at a horizontal spacing of 2 to 3 times the helix diameter in sands with friction angles of about 39 to 44 degrees. The data from this study may also be useful for calibration and validation of numerical models for further analysis of helical pile group interactions.

Experimental Study on Configuration and Spacing of Screw Pile Group Effect Subjected to Lateral Cyclic Loading

Despite the great development in the manufacture of the helical pile and the development of their use, especially in transmission towers and wind turbines, there is little research on their lateral behavior. In this laboratory study investigate the behavior of screw piles group (2×1) and (1×2) with the spacing to the diameter of helix ratio (S/Dh =1.5, 3, and 4.5) having a diameter (10 mm) and embedded length to diameter ratio (L/D = 40) by using single and double helix embedded in soft clay and extend to stiff clay under a cyclic lateral load of frequency (0.2 Hz). The results showed that increasing the distance between the piles had a great effect on increasing the lateral resistance. the increase of pile spacing in the groups from (1.5 Dh) to (3 and 4.5 Dh) increases the lateral resistance about 34-38% and 50% respectively. Also, from result showed that the group (2×1) gave a lateral resistance more than the group (1×2) about 11% for single helix and about 6% for a double helix, and for the same spacing and configuration the screw pile with double helix gives an increase in lateral resistance about 5-10 % from the single helix.

A digital PCR system based on the thermal cycled chip with multi helix winding capillary

This paper presents a digital PCR system based on a novel thermal cycled chip, which wraps microchannels on a trapezoidal structure made of polydimethylsiloxane (PDMS) in a multi-helix manner for the first time. It is found that compared to the single helix chip commonly used in previous reports, this kind of novel multi-helix chip can make the surface temperature in the renaturation zone more uniform, and even in the case of rapid fluid flow, it can improve the efficiency of the polymerase chain reaction. What’s more, the winding method of multi helix (such as double helix, six helix and eight helix) can obtain better temperature uniformity than the winding of odd helix (such as single helix and three helix). As a proof of concept, the temperature-optimized double-helical chip structure is applied to continuous-flow digital PCR and there is no need to add any surfactant to both the oil phase and reagent. In addition, we successfully analyzed the fluorescence signal of continuous-flow digital PCR by using CMOS camera. Finally, this method is applied for the absolute quantification of the clinical serum sample infected by HBV. The accuracy of the test results has been confirmed by commercial instruments.