Determination of the smallest crack width the cement could possibly penetrate is today based on readings from a filter press or a filter pump. Both these methods give conservative results, which strongly effects the calculated depth of penetration and grouting time. Without knowledge on which fractures that could be grouted with a certain grout, it is hard to predict how large a volume that will be grouted. This is hence a crucial knowledge in order to carry out an optimal grouting procedure.
This project has two main aims defined by what is stated above:
1.Define a technique/methodology on how to define the smallest crack width that could possibly be grouted for a specific grout material. This will be done in a laboratory study performed by using an artificial fracture with a length of 5 m and variable widths. This is a more detailed study on the same topic than previously was performed at KTH. Former research at KTH has shown that the now planned method simulates a real fracture better than the methods using a filter press or a filter pump. Hence this study is an important step in order to develop methods that can decrease the uncertainties in determining the most narrow fracture that the grout could possibly penetrate.
2.The second aim is to verify the spreading model based on the RTGCM method. This is planned to be done in both field tests and on the artificial fracture in the laboratory. In the laboratory the actual grout penetration depth will be measured and compared with the theoretically predicted grouting depth. In the field tests a few clear bedding planes (fractures) will be grouted from a borehole close to a slope. The spreading of the grout will be studied by observe when the grout reaches the slope and a number of observation boreholes along the bedding plane.
The RTGMC project is split in a PhD project and a Sr researcher project.
PhD project activities:
• Development of the long artificial fracture, including design and manufacturing.
• Study of hydraulic and arithmetic width, including tests of the water transmissivity
• Planning of a detailed program for grout penetration testing
• Model tests on the long artificial fracture and calibration of the filter press and the filter pump. The grouting properties bmin and bcritical will be determined for three different grouts and three different grouting pressures.
• Corresponding measurements using filter press, filter pump and for the short artificial fracture
• In total 32 different configurations will be studied
Sr project activities:
• Preliminary calculations regarding grout penetration for a presumed fracture will be the basis for finding an appropriate site for field tests.
• Design and performance of the field-test
• Borehole drilling and in situ transmissivity determination
• New grouting calculations using actual field properties
• Grouting and RTGMC measurements
• Analysis of predicted vs collected results
Almir Draganovic - contact
Univ. lektor Institutionen för geovetenskaper, Geofysik KTH
Ali Nejad Ghafar
Professor Emeritus, Jord och Bergmekanik, KTH
Professor Jord- och Bergmekanik, KTH
1.Develop methodology on how to predict the smallest fracture size that could possibly be grouted with full penetration
2.Verification of the RTGC method for grout penetration