Slope Stability in Rainfall Induced Landslided Area In Tirumala Hills By-Geotechnical Investigation

Landslides are the sudden events which results in loss of both human and environmental life. It mainly happens due to the rainfall occurred in soil instable areas. If the rainwater passes into the pores of soil in slope areas then the soil transforms as slurry or muddy and the runoff takes place along with soil. So landslide will occurs accordingly in hill down areas. The soil samples will be collected at five successive selected locations where the slide occurred. The slope stability of the soil in landslide area can be tested and Factor of safety will be calculated. If the factor of safety will be less than 1, then the soil will be susceptible for instability. If the FOS will be greater than 1, then the soil will be stable under saturated conditions. Generally landslides are common in Tirumala hills. This paper explains about the nature of soil and properties of land erupted soil in Tirumala ghat road.


Introduction
Natural disasters will always make troubles because they are so often unpredictable. Frequ en t ly these types of events are occurred by mass wasting, deforestation, m ining, slope failures, mudflows, road and railway works, drainage works. These types of errors lead to dangerous disasters. Mainly, man-made disasters can be controlled easily by taking several precautions or measures. The m ain aim is to save the lives and properties affected by natural disasters especially in hilly areas. Landslides can be controlled by growing vegetation, construction of barriers, reducing deforestation, etc., Generally, The mudflows will takes place during rainy season in slope areas. The mass wasting will also occurs during rains.
Sometimes the wasting of soil leads to rock falls also. On steep hillsides, debris flow begins as shallow landslides that liquefy and accelerate. Sometimes, landslides lead to earthquakes, volcanos. There are several causes for landslides, both natural and human-induced. Landslides are capable of damaging highways and trains, burying fields and crops, falling houses and causing numerous deat h s. Because of soil slope deficiencies, the devastation of buildings and trees will occur. Shear power, particle size distribution, density, permeability, moisture content, plasticity and angle of repose are t h e properties influencing the stability of a slope. Slope stability can be strengthened by stabilising the soil, supplying piles or retaining walls with lateral reinforcements, grouting or asphalt injecting into special positions. The safety factor Atlast can assist in the study of soil slope stability.

Methodology
• Selecting the study area

Study area
The samples were collected in these geographical coordinates in Tirumala Hills.

Sieve Analysis
A Sieve Analysis is a tool or technique used to determine the distribution of particle size of a gran u lar substance to move through a set of os sieves of increasingly smaller mesh size weighing the volume of material stopped as a fraction of the entire mass of each sieve.

Moisture Content
In most industrial and testing facilities, moisture content measurement is a vit al com pon en t of material consistency and is basically a function of quality management. Spectroscopic, chemical, conductivity, and thermo gravimetric analysis are the main approaches. The weight of the soil sample after the sample has been oven dried. Take the weight of t h e sam ple of oven dried dirt. The moisture content is measured using the phrase below.

Specific Gravity Test
That's the ratio between both the density of a matter and the density of a technical in form at ion given. The specific gravity of liquids is almost always measured against water at its densest. It will sink a substance with a relative density greater than 1. In industrial sector, specific gravity is frequently seen as a simple way to obtain information on the concentration of solutions of different materials, such as brines, sugar solutions and acids.

Direct Shear Test
A direct shear test is a field and laboratory test used only by engineering applications to calculate the shear ultimate strength of soil or rock content, or low shear strength discontinuity of soil or rock. This test is known for the ease of design and facilities used and the potential to evaluate un der different conditions of saturation, drainage and consolidation. Results fromtheTesting: According to literature reviews, the unit weight of soil in Tirumala hills is equal to 18.

Factory of Safety
The following equation proposed by Vanacker (2003)is used to calculate the factor of safety.  10. Discussion and future scope • Landslides will be controlled by constructing barriers,retaining walls,growing vegetation over the surface etc., generally landslides happen due to both natural and man-made ways • Naturally occurred landslides cannot be stopped and can be controlled by barriers and vegetation growth • Man-made landslides can be stopped and controlled by afforestation, forest fires control et c. • So, The natural disasters can be controlled in natural ways by growing of vegetation .

Conclusion
Landslides are inevitable. Eventually, the factor of safety for all the samples are greater than 2. So, all the samples proves that the landslides will not happen in Tirumala hills(According to the area where samples collected).