Mitigation the Geohazard of Carbonate Karst Features in Construction Sites by Applying of Combined Techniques in (Kinta Valley) Perak - Peninsular Malaysia

Abstract

This research study focuses on the combination of geological, geophysical, aerial photographs and satellite images techniques as identification techniques to assess, mitigate and monitor the potential geo-hazard of various classes of carbonate karst features extend in the surface and subsurface of construction sites. These techniques have coupled with the engineering surface and subsurface remediation techniques and performed across five(5) selected construction sites distributed over a region of carbonate karst environment in north and south of Ipoh city (Kinta valley), Perak state, Peninsular Malaysia. The carbonate karst bedrock in the area represents one of the most complicated ground conditions, its riddle with various solution features, which might be detrimental to any overlaying structures in its vicinity. These karst features such as sinkholes, caves, voids, cavities, channel pipes, depressions, conduits, internal drainages system, solution-widened joints, intensely fractured zones and faults. Thus, creating problems can directly or indirectly affecting the foundation of structures when overlapping carbonate karst environment sites. The substantial damage resulting from carbonate dissolution features such as sinkholes was resulting through the construction works could cause massive losses all over the region. It will be directly or indirectly affect the construction structures. Indirectly have the potential to cause catastrophic damages in the near future or perhaps many years after the project has ended. It can precipitate cracking in the building and halt the construction project totally. In addition, it will maximize the cost of the project overall. Other problems also may cause in the area such as the settlement of the houses or the buildings. In addition, the negative consequences that could precipitate years after the project has completed will result in massive losses that lead to enormous financial costs, to both the developers and the lands. Several subsurface karst features were recognizing in these construction sites, during the utilization of high-resolution geophysical site characterization, by applying of Two-dimensional (2D) Winner's Electrical Resistivity Tomography (ERT) technique, to capture the images of the subsurface in order to pinpoint evidence for near-surface karst features. Resistivity traverses have conducted along the survey area at each construction site. The orientation, extension, and the degree of inclination of those traverses have shown in the location map. The resistivity data from the multi-electrode measurements from several profiles have collected and corrected. Then the correct resistivity data was interpreting by using the (res2dinv software) and plotted in the tomography sections. This study also proved that high-resolution Electrical Resistivity Tomography (ERT) can effectively be employed to reflect the bedrocks. It is also completely suitable for differentiating surficial soil, clay, weathered rocks, compact or intact rocks, and air-filled karst voids or cavities, and intensely fractured rocks. The interpretation of geophysical techniques can help civil engineers to identify the irregularity in subsurface karst topography of marbleized limestone bedrocks in Perak, the degree of karst level, and identify what causes these karst features. Five construction sites have chosen from numerous construction sites that are studying. The geological model is clarifying via the geophysical data, consists of a basal marbleized limestone unit and constitutes the bedrock of the study area. This bedrock unit appears to have been dissected or intervened by solution-widened joints and fractures, enclosed by overburdened layers consisting of sand, containing lenses of stiff, non-stiff moisturized clay and covered by soil mixed with friable sand and rock fragments in certain places. Intervened by sinkholes and cavities in-filled with clay or sandy clay and sand; it is interpreted as created due to karst process. In addition, the difference in the depth of bedrocks varies from one site to another; in site# 1, it varied from 17m to > 28.0m. In site# 2, the depth varies from 20m to > 28. 459 site# 3, the depth varies from 6.0m to > 28.0m. In site # 4, the depth varies from 1.5m to 22.0m, and in site# 5, the depth varies from 3.0m to > 28.0 m. The interpretation of the inverse model section in construction site #1 indicated that the area has been affected by an irregular tabular channel that contain stiff, non-stiff moisturized clay, and sandy clay over karstified marbleized limestone. The interpretation of the inverse model section in construction site #2 indicated that the area has been affected by a thick covering of alluvium deposits containing several sinkholes and lenses, filled with both stiff and non-stiff clay that is highly moisturized, rendering the area hazardous over karstified marbleized limestone. The interpretation of the inverse model section in construction site #3 indicated that the area has been affected by many channel pipes, with soil cover collapse sinkholes containing both stiff and sandy clay, and sand over karstified marbleized limestone and cavities. The interpretation of the inverse model section in construction site #4 is indicative of the fact that the area has affected by various fractures in bedrocks that contain both stiff sandy clay and sand. The interpretation of the inverse model section in construction site #5 indicated that the area has been exaggerated by a massive sinkhole, thus containing stiff and non-stiff clay that is saturated with water, rendering the area hazardous to any projects. In accordance with the engineering classification of karst ground conditions by Waltham A.C., Fookes P.G. (2005), the karst in these construction sites is extreme karst. Through studying the karst regions in Malaysia found that the strength of the karstification process is different from one site to another in the same region. A geo-technical table for engineering classification of karst ground conditions which presented by Yassin, R., R & Haji, Tap, S. (2012) which describe the subsurface features that come upon in engineering works on the carbonate karst environments, after applying of the geotechnical survey. This table applies in Malaysia peninsular and includes five (5) classes, start from Youthful karst (KaI) and ending with extremely complex karst (KaV). The geotechnical survey identifies that the thin red cover that contains the different sizes of granite rocks and minerals with thickness is mostly about (5.0cm-12.0cm). This thin red cover found over a layer of lateritic clay with different thickness from site to another between (1.0m-1.25m), (2.0m-5.0m) and with the maximum thickness (6.0m-9.0m) are mostly returns to the period of a global flood (Noah's Flood) (3300-3100) BCE. The appearance of this thin red cover and the layer of lateritic clay are due to runoff heavy rains that have deeply eroded and washed both the highest granite ranges around the Kinta valley and then carried away by the new rivers and canyons that formed due to the erosion. A thin layer of carboniferous organic material with different thickness of (3.0cm-5.0cm), (8.0cm-10.0cm) have seen beneath the lateritic clay. There are several causes for the occurrence of sinkhole collapse in the Kinta Valley; the primary reason among them is the irregular distribution of unconsolidated material on the bedrocks surface. The secondary reason is the running of heavy rainwater on the ground surface. The third reason is the heavy acidic rainfall in this region. The fourth reason is the earthquakes and the subsidence movement. The fifth reason is the heavy loads of buildings or foundations. The sixth reason is the human influence. The seventh reason is the vibration from traffic. The eight reasons are the weather patterns. The ninth reason is the groundwater movement. The tenth reason is the water quality. The eleventh reason is Air high pollution. All these reasons after the development of the sinkholes and other karst feature rapidly in this tropical area of Peninsular Malaysia. Early planning of engineering subsurface remediation techniques are needs to mitigate or minimize the potential of geo-hazard of karst features and its deposits in these construction sites over carbonate karst environmental bedrock. The initial consideration is to utilize the reverse graded filter technique to fill the huge sinkhole in construction. Skin friction piles have driven into the layers that contain non-stiff materials (soil, clay, silt, sand). Drive off long piles down to the sound bedrock due to the difference in the depth of bedrock from one side to the other. Furthermore, it requires a new process of grouting method in the study areas of those sites such as chemical grouting techniques. Besides, they need to control of surface and subsurface water drainages. All of these plans must put into operation in these construction sites when the work is going to start at these respective sites. One of the steps of environmental management in oil and gas exploration uses bentonite drilling mud and the rock gutting from the drilling operation after the water and other liquids have removed to refill the depressions and sinkholes in karst regions. This study also discusses many considerations about the important elements that play major roles in the development of karst phenomena and the dissolution process in (Kinta Valley). Mining and human activities, air and water high pollution, and heavy rain developed the karst features rapidly in this tropical area of Peninsular Malaysia.