Evaluation Of Grouting Research Articles

Incorporating Silica Sol as a Binder to Improve Long-Term Stability of Blocky Coal

Long-term stability evaluation of grouting materials is critical to the safe operation of geological engineering. Taking blocky No. 8 coalseam of Huaibei coalfield as engineering background, taking coal fragmentation distribution and grouting quantity as the control variables, uniaxial compression tests were conducted every 1 or 2 months to study long-term mechanical behavior of silica sol grout. Results indicated that (a) long-term strength stability of samples could not be achieved in the case that silica sol was mixed into coal samples including big fragments (5–10 mm); (b) in the case that silica sol was mixed into coal sample without big fragments (5–10 mm), 200 days was the least maintenance time that the strength need to turn stable; (c) in the case that silica sol was mixed into the coal samples with small fragments (< 2 mm), long-term stiffness of samples could be achieved. In other words, coal fragmentation had a negative correlation with the long-term consolidated stability of silica sol grouting. Generally, grouting quantity had a linear positive correlation with strength, peak strain, brittleness coefficient, and had an exponential function increasing relation with pre-peak strain energy density. But grouting quantity was of no influence on secant modulus. There existed a lower limit of grouting quantity and long-term stability of silica sol grouting strength couldn’t be achieved when grouting quantity was below the limit. The research results can guide grouting design and long-term stability evaluation of grouting.

Evaluation of Grouting for Hydraulic Barriers in Rock

In January 1964, Engineering Geology made its debut as the bulletin of the Association of Engineering Geologists. The inaugural issue consisted of a collection of five papers on grouting, which were presented at the 6th Annual AEG Meeting in San Francisco, California, in October 1963 (Campbell and Daly, 1964; Fabregue, 1964; Grant, 1964a; Karol, 1964; and O'Neil and Lyons, 1964. The authors of those papers shared their experience on various projects employing grouting as a means to create a hydraulic barrier in the subsurface. Nearly a half century later, grouting continues to play a prominent role in the profession. The present authors continue the tradition of sharing experience by discussing methods for evaluating the adequacy and progress of grouting and items to consider in evaluating the performance of grouting for hydraulic barriers in rock. Methods to evaluate the adequacy and progress of a grouting program include analysis of drilling data (water losses and water levels), water pressure testing results (closure trends), grouting records, and piezometer data; drilling, imaging, and testing verification holes; seepage monitoring; excavation; and performance testing. Items to consider in evaluating the performance of grouting include grouting objectives, grout materials and mixes, grouting methods and procedures, hole geometry and spacing, hole sequencing and staging, and field quality control.

Evaluation of grouting in tunnel lining using impact-echo

The shield tunneling method is commonly used for tunnel excavation. After the excavation, curved reinforced concrete members are used to support the surrounding ground/rock and seal the tunnel. Grouting is performed to provide adhesion between the concrete members and the ground. The assessment of the grouting quality by pull-out tests and core sampling is destructive, time-consuming and expensive. In the present case, impact-echo was applied as a means of non-destructive and time-effective evaluation. Excitation was conducted by an impact hammer on the surface of several concrete plates and the reflection was acquired by a low frequency accelerometer. Combined use of time domain characteristics, spectral content and wavelet transform reveal the effectiveness of grouting and indicate that impact echo is valuable for quick and reliable assessment of grouting in such cases.

Evaluation of grout behind the lining of shield tunnels using ground-penetrating radar in the Shanghai Metro Line, China

For shield tunnelling construction in soft soil areas, the coverage uniformity and quality of consolidation of the injected grout mortar behind the prefabricated tunnel segment is the main concern for tunnel safety and ground settlement. In this paper, ground-penetrating radar (GPR) was applied to evaluate the grout behind the tunnel lining segments in Shanghai, China. The dielectric permittivity of the grout material in Shanghai Metro tunnelling construction was measured in the laboratory. Combining physical modelling results with finite different time domain numerical modelling results, we suggest that the antenna with frequency 200 MHz is well suited to penetrate the reinforced steel bar network of the tunnel lining segment and testing grout patterns behind the segment. The electromagnetic velocity of the grout behind the segment of the tunnel is 0.1 m ns−1 by the analysis of field common-middle point data. A wave-translated method was put forward to process the GPR images. Furthermore, combining the information acquired by GPR with experience data, a GPR non-destructive test standard for the grout mortar evaluation in Shanghai Metro tunnel construction was brought forward. The grout behind the tunnel lining segment is classified into three types: uncompensated grout mortar with a thickness less than 10 cm, normal grout mortar with a thickness between 10 cm and 30 cm and overcompensated grout mortar, which is more than 30 cm thick. The classified method is easily put into practice.