| Title |
Development of Test Method for Evaluating Root Resistance of the Basis and Lap Joint in Membranes for Waterproofing |
| Keywords |
Waterproofing Membrane ; Test Method ; Rhizome ; Penetrating Force ; Basis of Waterproofing Membrane ; Lap Joints of Waterproofing Membrane ; Bamboo Grass ; Lawn Grass |
| Abstract |
A penetrating needle into a membrane was first developed on the basis and lap joints of the observation of bamboo grass tips and lawn grass tips. Then, the penetrating load of the needle was measured for various waterproofing membranes at the needle displacement speed of 1mm/min. These two types of grass were also planted in the containers, inside of which the waterproofing membranes were applied. After the rearing of 1 year， the membranes were inspected. The two results of each membrane type were compared. We were interested in the maximum strength and the strength at 1mm displacement. These values are considered to be useful as indices for the estimation of the waterproofing membranes' root resistance. The resistance of the membranes at lap joints having non adhesives and different bonding strengths was determined as a measure of its vulnerability to root penetration. Results from field tests indicated that bamboo grass tips (rhizome) easily penetrated lap joints of non adhesive membranes. Hence it was evident that waterproofing membrane systems having non adhesive overlapped joints do not provide adequate resistance to root penetration of the membrane. The resistance to root penetration is dependent on the adhesive strength of the lap joint. The specimens with lap joints having lower bonding strengths were readily penetrated by the rhizome. From this knowledge, a test method was developed to assess the expected resistance of membrane lap joints to the penetration of a needle. The needle, in essence, emulated the shape of bamboo grass tips. Thereafter, the test result from field test on the resistance of membrane to the penetration of roots were compared to those obtained from tests using a penetrating needle. Results from the penetrating needle test indicated that the resistance measured at a 10 mm displacement of needle was effective means of evaluating the resistance of membrane lap joints to the penetration of roots. |