Geotechnical Resistances of Drilled Shafts in Triassic Basin Sedimentary Rocks

Load tests on drilled shaft foundations with rock sockets in sedimentary formations associated with various Triassic Basins in the Mid-Atlantic region show that some generalizations are possible for estimating geotechnical resistances. Axial load tests on drilled shafts in locations several hundred miles apart produce surprisingly similar results. The common feature is the geology: all of the load-tested rock sockets considered were constructed in sedimentary rock associated with one of the rift basins that developed in response to breaking apart of the supercontinent Pangaea that began during the late Triassic Period (about 220 million years ago) and coincided with opening of the Atlantic Ocean. More specifically, all of the tested rock sockets were in the ‘red bed’ facies of the rift basin sediments consisting of reddish-brown siltstone, sandstone, and shale. Each of the projects described herein and the associated load tests are described and used to illustrate fundamental principles of rock socket design and how load testing can be used as a design tool. The important role of quality construction, in combination with quality assurance through inspection and testing, is emphasized, especially as it relates to the evaluation of base resistance for rock socket design.

Application of CS-CHO-g-PMMA emulsion in paper reinforcement and protection

Paper has a high value of culture, history and scientific research as the cultural carrier of historical inheritance. However, with the passage of time and the change of environment, many paper files are aging and damaged. Therefore, it is of great significance to carry out the protection of paper archives. Chitosan, a natural material, has a good compatibility with paper fibers. In this paper, chitosan (CS) was modified by epoxy cyclohexane (CHO) and methyl methacrylate (MMA) to prepare CS-CHO-g-PMMA emulsion. CS-CHO-g-PMMA was applied to paper protection, and the effects of CS-CHO-g-PMMA on heat aging resistance, reversibility and acid-base resistance were investigated. In order to improve the mechanical strength of paper, CS-CHO-g-PMMA and phosphate ester starch (HPDSP) were blended to determine the optimum ratio. The results showed that the degradation rate of paper sample was slowed down obviously and the coating had certain reversibility. Acid-base resistance experiment showed that CS-CHO-g-PMMA could effectively resisit corrosion of external acid-base to protect the paper. The best combination ratio between CS-CHO-g-PMMA and HPDSP was: m (CS-CHO-g-PMMA): m (HPDSP) = 5:2. Under this compound ratio, the performance indexes of the paper met the requirements, conforming to the “repair as old, keep the original” and other requirements.

Factors Influencing the Prediction of Pile Driveability Using CPT-Based Approaches

This paper investigates the applicability of Cone Penetration Test (CPT)-based axial capacity approaches, used for estimating pile static capacity, to the prediction of pile driveability. An investigation of the influence of various operational parameters in a driveability study is conducted. A variety of axial capacity approaches (IC-05, UWA-05 and Fugro-05) are assessed in unmodified and modified form to appraise their ability to be used in estimating the driveability of open-ended steel piles used to support, for example, offshore jackets or bridge piers. Modifications to the CPT-based design approaches include alterations to the proposed base resistance to account for the resistance mobilized under discrete hammer impacts and the presence of residual stresses, as well as accounting for the effects of static capacity increases over time, namely ageing. Furthermore, a study on the influence of various operational parameters within a wave equation solver is conducted to ascertain the relative impact of uncertain data in this respect. The purpose of the paper is not to suggest a new design procedure for estimating pile driveability, rather to investigate the influence of the various operating parameters in a driveability analysis and how they affect the magnitude of the resulting predictions. The study will be of interest to geotechnical design of piles using CPT data.

Field and theoretical analysis of response of axially loaded grouted drilled shafts in extra-thick fine sand

Research on post-grouted drilled shafts has focused primarily on post-grouted tips. Here, four full-scale shaft load tests were conducted to investigate the behaviors and performance of combined tip-and-side grouted superlong and large-diameter drilled shafts in extra-thick fine sand layers. The enhanced mechanism of the combined grouted drilled shafts is analyzed, and a rational approach for analyzing their load–displacement response is presented. The side and base resistance of the combined grouted drilled shafts exhibited significant strengthening, substantially increasing the bearing capacity and effectively controlling settlement. Under the ultimate load, >60% of the shaft head displacement was caused by shaft compression; a relatively small load proportion was carried by the shaft base. The superlong and large-diameter drilled shaft can be treated as a friction shaft, and the combined tip-and-side grouting cannot change the bearing characteristics. The hyperbolic model describes the relationship between the side resistance and relative shaft–soil displacement and captures the base resistance–displacement response. The proposed approach is verified with a case history, and the bearing behaviors of a large-diameter drilled shaft under an extra-thick fine sand layer are analyzed. These results clarify the bearing characteristics of combined grouted shafts and can help guide the design of post-grouted shafts.