Authors: Sowmik Islam
Certificate: View Certificate
Bangladesh\'s first access-controlled expressway is the Dhaka-Khulna (N-8) Expressway. The project consists of 8 lane road of 55 km length, 54 culverts, 20 underpasses, 2 interchanges, 4 major bridges, 25 minor bridges, and 5 flyovers. Teghoria Interchange of this project is structured with 19 Reinforced Earth Wall, out of which a crack appeared in a wall that has 146 meters length and 7 meters height. Detailed inspection and analysis were followed by repair and rectification work. The aim of this paper was to find out the likely causes of this crack, discuss detailed retrofitting methodology and bring forth some recommendation. This crack may form due to weak workmanship during compaction and installation of tendons of reinforced earth, environmental load, heavy-loaded vehicle travel above the RE wall etc. The specialist team of the consultants of the project and experts from development partner inspected the problem and worked out how to repair the cracked area. The development partner developed repair methodology and executed the crack repair work as well as the treatment plan under strict supervision of consultants. Surface preparation, preparation of precast veneer & epoxy-based mortar, placement and finishing work make up the treatment process.
Dhaka-Khulna (N-8) expressway Improvement Project is the first ever access controlled expressway of Bangladesh. This Highway from Jatrabari Intersection to Mawa and Patchchar to Bhanga connects the south western parts of Bangladesh with Dhaka through the long-cherished Padma Multipurpose Bridge. The project is led by Roads & Highways Department and implemented by Bangladesh Army. This road is a Part of National Highway N8 and the Annual Average Daily Traffic (AADT) of the road exceeded 30000 at many locations. The road comprises of 08 lanes including service roads at both sides. The project includes 05 flyovers, 20 underpasses, 02 interchanges, 04 railway over bridges, 4 major bridges, 25 minor bridges and 54 culverts also. One Major structure of this project is Teghoria Interchange. In this Interchange, there are more than 19 nos RE Wall, Total RE Wall Length 1332m, and Maximum length of RE Wall 170m. A crack appeared in a RE wall located at Chainage 4+805 to 4+810, which is included at Ch. 4+805 to 4+951 and total length is 146m, Hight-7.00m.
Based on the methodology sent by the Development Partner, the repairing/ rectifying work was conducted after detailed inspection and analysis.
The data has been gathered thorough physical survey and experiments which gained by quantitative methodology. With the Descriptive and experimental result the research could make the conclusion. The study presents a practical approach based on scientific research and technology development for repairing of cracks in nicol blocks.
IV. GOALS AND OBJECTIVES
The main goal of the research was to establish a method to repair the cracks in nicol block.
The objectives are following:
V. DESCRIPTION OF TEGHORIA INTERCHANGE
This interchange connects Jatrabari to Mawa Express Highway and Babu Bazar Link Road together. This a Trumpet type of Interchange. The trumpet interchange allows for interchange of secondary two-way streets to a multi-lane roadway with minimal traffic mix. It takes the place of a T-intersection which is often used when a roadway ends at the intersection of another roadway.
A. Statement of Problem
Longitudinal Cracks were found on the surface of some modular blocks of reinforcement earth wall at Tegoria Interchange Bridge abutment-3.
B. Joint Inspection
The site inspection was done jointly by technical advisers, international team leader, deputy team leader, senior material engineer, Senior Bridge engineer, client's executive to analyse the problem in depth and work out how to repair the cracked area.
C. Reason for Crack
D. Treatment Method
The development partner (China Harbour Engineering Company) submitted the treatment method for these problems. The total work is finished by this treatment method given below:
a. Surface Preparation
b. Precast Veneer
c. Mixing epoxy based mortar (Sikadur?R -31IN):
Mixing epoxy-based mortar under the product date sheet Sikadur?R -31IN.
Protruded epoxy-based mortar shall be cleaned.
If depth of the damage is more than 40-50mm, the detail procedures of repairing are as follows:
f. Surface Preparation
g. Precast Veneer
h. Mixing epoxy based mortar (Sikadur?R -31IN)
2. Horizontal gaps between adjacent layers of blocks: Settlement of RE walls are likely to achieve an equilibrium by 4 months continuous monitoring at Ramp B (close to abutment 3 of Teghoria Interchange Bridge) and Ramp D (close to abutment 0 of Link Road Flyover).
If the gap only 20-25mm, the detail procedures of repairing are as follows:
a. Surface preparation
Cleaning sundries from the gaps between adjacent layers.
b. Mixing epoxy based mortar (Sikadur?R -31IN):
Mixing epoxy based mortar under the product date sheet Sikadur?R -31IN.
Filling the gap with epoxy-based mortar and matching the hexagonal shape at surface by precision trowelling.
Protruded epoxy-based mortar shall be cleaned.
If the gap is large say 40-50mm, the detail procedures of repairing are as follows
e. Surface Preparation
f. Veneer Preparation
g. Mixing epoxy based mortar (Sikadur?R - 31IN)
1) Strict adherence to precise workmanship must be maintained while compacting reinforced earth or installing tendons. 2) Overloading on the roadway must be restricted by any means to avoid unexpected stress on RE Wall. 3) Concrete blocks used on RE wall must be of required compressive strength to survive external impact. 4) The Service Road used next to the RE wall should be kept safe. 5) Construction of safe guide walls next to the RE wall so that the Heavy vehicle dose not hit. 6) No big Trees can be Planted along the RE wall. 7) Care should be taken to ensure that the drainage/Rain water does not seep inside the wall.
Copyright © 2022 Sowmik Islam. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.