Accuracy and precision of the CSLT measurement system: An experiment to defect diagnoses in bored piles

A new measurement system called Crosshole Sonic Logging Tomography (CSLT) provides information on the size, shape, and orientation of defects in a bored pile. The CSLT measurement system has not (yet) been accredited in Hong Kong for foundation testing. Bored piles in Hong Kong are generally wide and deep. Existing measurement accuracy studies do not consider this large type of bored piles. The objective of this research is to quantify the measurement accuracy and precision of the CSLT method for large diameter bored piles (the most common pile type for public housing projects in Hong Kong). A test pile was constructed with known defects and perform experiments with a CSLT measurement system to quantify its accuracy and precision. CSLT is found to be accurate in detecting shape, size, and location of large defects but small defects close to the tube are difficult to detect. Generally speaking, CSLT has satisfactory accuracy and precision for practical use. The use of CSLT can be considered as a feasible method in defect diagnosis of bore piles in Hong Kong.

Potential and prospects of photocatalytic disinfection: using sustainable solarenergy- driven photocatalysts

A new measurement system called Crosshole Sonic Logging Tomography (CSLT) provides information on the size, shape, and orientation of defects in a bored pile. The CSLT measurement system has not (yet) been accredited in Hong Kong for foundation testing. Bored piles in Hong Kong are generally wide and deep. Existing measurement accuracy studies do not consider this large type of bored piles. The objective of this research is to quantify the measurement accuracy and precision of the CSLT method for large diameter bored piles (the most common pile type for public housing projects in Hong Kong). A test pile was constructed with known defects and perform experiments with a CSLT measurement system to quantify its accuracy and precision. CSLT is found to be accurate in detecting shape, size, and location of large defects but small defects close to the tube are difficult to detect. Generally speaking, CSLT has satisfactory accuracy and precision for practical use. The use of CSLT can be considered as a feasible method in defect diagnosis of bore piles in Hong Kong.

Load Transfer On Bored Pile Foundation Instrumented With Fiber Optic And Concrete Quality Analysis

The problem in the construction method of the bored pile is the contamination of mud or the other contaminant that can cause the modulus of elasticity of concrete to decrease. This research determines the modulus of concrete on a bored pile foundation instrumented with fiber-optic (FO) with a manual calculation based on strain data during loading test, validated with the results of research in the laboratory and numerical analysis. Fiber optic was used to measure the strain along with the pile during the loading test. The bored pile foundation is divided into 12 segments with the same strain characteristics, and then the modulus value is calculated. The result is the modulus value of each segment is different, and the value of the modulus changes along with the increase in strain; the modulus will decrease as the strain increases. This differs from the theory that the modulus has a fixed value approximated by empirical equations. Made a cylindrical concrete sample on both sides, which installed a FO to record the strain during the loading test. The result is true that the modulus is not constant but decreases as the strain increases. It is shown in the result of analysis to fiber-optic measurement data. Created a model in Plaxis2D for validation, and the results are not much different from the manual calculation.

Study on Deep and Large Foundation Pit of a National First-Class Key Tomb Protection Project

For the support engineering of the deep and large foundation pit (DLFP) due to tomb protection, there are still no clear standards. The construction of DLFP will introduce large-range transverse and longitudinal disturbance on the stratum; therefore, it should be reinforced. In this paper, the reinforcement of the deep and large foundation pit of a national first-class key tomb protection project is studied. By comparing the existing supporting scheme and the stress conditions of the reinforced tomb, the combination reinforcement scheme by bored pile and pile slab retaining wall is found to be safe and feasible. Furthermore, according to the simulated bending moment, displacement, and axial force of the tomb by numerical analysis, an economic and reasonable mixed anchor support scheme is selected. In order to ensure the stability of the tomb during the supporting process of the foundation pit, a maximum value of 10 mm for the overall settlement of the tomb can be treated as the control benchmark based on the support and anchorage schemes in each specification and the in-site measured settlement values of the tomb. The determined support, anchorage schemes, and the control benchmark can provide certain technique guidance and research significance for the protection of similar ancient buildings in the future.