Geotechnical Investigations of Sub-Grade Soils at the Connector Road, New Tiba City, Luxor, Egypt

The presented study dealt with geotechnical investigations on the sub-grade soils along the connector road between the electrical transformer station and the industrial city, New Tiba city, Luxor, to classify these soils and to examine their geotechnical behavior and their proportionality for constructing the road at the study area. One of the most important aims of this work was to determine the problematic sub-grade soils and to recommend the suitable reclamation. To achieve these goals sixty disturbed samples from six mechanical wash drilling boreholes and three undisturbed samples from three open pits were collected. The studied soils were belonged to Quaternary age. Gradation parameters (coefficient of uniformity, Cu and coefficient of concavity, Cc), plasticity, California bearing ratio (CBR), proctor density and free swelling percent of the studied soils were measured. PH-value, dissolved chloride, dissolved sulfate, calcium carbonate, total carbonate, and total dissolved salts were determined. The results pointed that the studied Quaternary soils along the study road were mainly composed of gravels, sands and clayey sands. The studied gravels were classified as poorly graded gravels (GP) according to Unified Soil Classification System (USCS) and as A-1-b according to American Association of State Highway and Transportation Official (AASHTO). The studied sands were classified as well graded sands (SW) according to USCS and as A-1-a according to AASHTO. The results showed also that the sub-grades at boreholes no. 1, 3, 4, 5, and 6 were excellent to good and the sub-grade at boreholes no. 2 was fair to poor. Free swelling percent of the studied clayey sand soils was ranging from 30% to 80% and they were classified as low to medium grade expansive soil. Replacement and/or chemical stabilization (using lime and/or cement kiln dust) of the problematic clayey sands soils were suggested to reduce their swelling and to prevent the possible heave. How to cite this paper: Ismaiel, H.A.H. (2018) Geotechnical Investigations of Sub-Grade Soils at the Connector Road, New Tiba City, Luxor, Egypt. Open Journal of Geology, 8, 1133-1145. https://doi.org/10.4236/ojg.2018.812069 Received: August 7, 2018 Accepted: November 26, 2018 Published: November 29, 2018 Copyright © 2018 by author and Scientific Research Publishing Inc. This work is licensed under the Creative Commons Attribution International License (CC BY 4.0). http://creativecommons.org/licenses/by/4.0/ Open Access


Introduction
To solve a problem of population increase in Egypt, the Egyptian government constructs several of new cities in the western and eastern deserts and Sinai Peninsula like New Qena city, New Sohag city, New Tiba city, etc. The studied area lies at the New Tiba city which is one of these new cities. New Tiba city locates at the East of Luxor city in the eastern desert ( Figure 1). Several roads are constructed at the study area to complete the infrastructures of the New Tiba city.
One of the most important roads at the study area is the connector road which connects between the electrical transformer station and the industrial city. A roadway section consists of a complete pavement system [1]

Previous Works
The study area was geologically investigated by many authors such as [2]- [15], and others. Few engineering and geotechnical investigations were conducted on the studied area like engineering geophysical study to evaluate the geotechnical behavior of the soils at Tiba city [16], investigation of rock deterioration in the Royel Tomb of Seti I, Valley of The Kings, Luxor [17], engineering geophysical study at New Qena city north the study area [18], engineering classification of the soils exposed along Upper Egypt-Red Sea road north of the study area [19], geotechnical evaluation study of Pliocene sedimentary rocks exposed along Qena-Safaga road north of the study area [20], and geotechnical evaluation of the sub-grade soils at the Cemeteries area, New Tiba city [21].

Scopes of the Present Work
The present work is concentrated on the geotechnical behavior of the sub-grade soils of the connector road at new Tiba city to classify these soils and to determine their proportionality for constructing the road at the study area. This study focused also on an exploration of the problematic soils especially the fine grained soils to suggest the favorable treatment.

Geological Setting
The study area is located about 10 km to the east of Luxor city and about 50 km to the south of Qena city. It lies between latitudes 25˚43 − N and 25˚46 − N and longitudes 32˚45 − E and 32˚47 − E ( Figure 3 and Table 1). The area has a wide variety of sediments belonging to the Upper Cretaceous-Lower Tertiary succession    . Geological map of the study area, modified after [22].
as well as the Pliocene-Recent sediments [15]. The surface of the study area is

Materials
Sixty three samples were collected; sixty disturbed samples collected from six mechanical drilling boreholes, from the surface to ten meters depth including one sample each one meter depth, to carry out the grain size analyses and plas-  Figure 5).

Methods
Six wash mechanical drilling boreholes were conducted to collect sixty studied disturbed samples ( Figure 6). Three 0.5 m depth open pits were done to collect three undisturbed samples. Five geotechnical tests including grain size analysis [23] [24], plasticity [25], proctor [26], California bearing ration (CBR) [27] and free swelling percent [28] were carried out on the studied soils. Chemical (X-ray fluorescence, XRF, type of the instrument is JEOL, JSX 3222, Japan) and mineralogical (X-ray diffraction, XRD, PW1710 BASED diffractometer with a generator   representative gravel pebbles were also applied to determine the geological origin and the sources of these gravels. Total dissolved salts, dissolved sulfate, and chloride were measured. The dissolved sulfate content was measured using Spectrophotometer (Cecil C/7400). The dissolved chlorides content was measured using the calibration method using a silver nitrate solution and potassium dichromate guide. Hydrogen ion concentration (PH-value), calcium carbonate, and total carbonate contents were also determined by the calibration method using sulfuric acid with phenolphthalein guide to estimate the chemical aggressiveness of the studied soils. As well as, Petrographical examination of the studied representative pebbles (gravels) using polarized light microscope was conducted to describe the lithology. The representative gravel pebbles were selected according to the difference of the lithology of the hand specimens.   were classified as poorly graded sands (SP) where the gradation parameters of the studied sands including coefficient of uniformity (Cu) were less than 6.

Grain Size Analyses Results
The results pointed to the clayey sands samples were classified as SC according to USCS, the percent of clay was ranging from 17% to 24%. According to American association of state highway and transportation official (AASHTO), SW samples were classified as A1-a group and SP samples classified as A1-b, they described as excellent to good subgrade soils. On the other hand, SC samples were classified as A2-7 group and described as fair to poor subgrade soils.

Plasticity Test Results
The plasticity test results showed that the plasticity index (PI), which equal to the difference between liquid limit (LL) and plasticity limit (PL), of the clayey sands samples was ranging from 15% to 17%, they are medium plastic clayey sands. Liquid limit (LL) and plastic limit (PL) were ranging from 41% to 44% and from 26% to 27%, respectively. The clayey sands samples described as medium plastic (Table 3 & Table 4).

Proctor Test Results
The Modified Proctor Test was carried out to determine the maximum dry density (MDD) (Proctor density) and the optimum water content (OWC) of the studied undisturbed samples. Three selected undisturbed samples at 0.5 m depth were tested according to [26]. The test results are listed in Table 4.

California Bearing Ratio Test Results
The results of California bearing ratio (CBR) test pointed to that CBR-unsoaked   (Table 4 & Table 5). The quality of the sub-grade clayey sands is described as very poor to fair according to [29].

Free Swelling Test Results
Free swelling test results illustrated that the free swelling percent of the studied clayey sands undisturbed samples was ranging from 30% to 80%. The most tested clayey sands samples having free swelling percent more than 50%, they are classified as low to medium expansive soils according to [28] (Table 4 & Table 6).

Petrographical Examination Results
Petrographical examination of the hand specimens and some representative stu-

Conclusions
The study Quaternary gravels were mainly composed of silica (about 68.18%), and calcium (about 13.27%). The poorly graded sands were mainly composed of silica (85.53%) and aluminum (6.90%). The clayey sands were mainly composed of silica (59.22%), aluminum (10.45%), and iron (11.60%). The studied gravels Table 5. Relationship between CBR-values and quality of sub-grade soils after [29].  Table 6. Relationship between the free swelling values and the ability of expansion after [28]. 1, 2, and 3 were classified as poorly graded sands (SP) where the gradation parameters of the studied sands including coefficient of uniformity (Cu) were less than 6. The results pointed to the clayey sands samples were classified as SC according to USCS, the percent of clay particles was ranging from 17% to 24%.
According to American association of state highway and transportation official (AASHTO), SW samples were classified as A1-a group and both SP and GP samples classified as A1-b, they described as excellent to good sub-grade soils.
On the other hand, SC samples were classified as A2-7 group and described as good to fair sub-grade soils.
The plasticity index of the clayey sands which occurred as one lens and two tongues at the studied area was ranging from 15% to 17%. The clayey sands samples described as medium plastic soils. Depend on the PH-value, calcium carbonate, and total carbonate contents, the chemical aggressiveness of the studied gravels, sands, and clayey sands is moderately chemical aggressive for both gravels and sands and highly chemical aggressive for the clayey sands soils.
CBR-soaked (4 day's water soaking) values of the clayey sands soils were ranging from 2% to 7%. They were classified as very poor to fair sub-grade according to [29]. The free swelling percent of the studied clayey sands was ranging from 30% to 80%. Most of the studied clayey sands samples had free swelling percent more

H. A. H. Ismaiel
than 50% corresponding to [28]. They were classified as low to medium expansive soils according to [28]. The sub-grade at boreholes no. 1, 3, 4, 5, and 6 (Gravels and Sands) was good to excellent. The sub-grade at borehole no. 2 (Clayey sands) was poor to fair. The clayey sands are expansive soils and may be lead to a heave of the road at borehole no. 2. Finally, the studied clayey sands samples are problematic sub-grade soils and described as medium plastic, highly chemical aggressive and low to medium expansive soils and classified as poor to fair sub-grade soils. Finally, the present work provide that the Quaternary sediments like the present investigated soils characterized by rapid lateral and vertical changes in the lithology and texture that means each different project area in the Quaternary sediments need to a special geotechnical subsurface exploration program to investigate the Quaternary soils in details and to suggest the suitable soils reclamation and the suitable foundations design.

Suggestions
To avoid the engineering problems due to the problematic clayey sands sub-grade of the road especially at borehole no. 2, one of the following treatments can be applied: 1) Replacement the expansive clayey sands sub-grade with imported well graded gravels or imported mixture of well graded gravels and sands percent (50% gravels plus 50% sands). The thickness of replacement must be at least 50 cm. Compaction of the imported materials in two layers each layer has 25 cm thickness, until they reach to at least 97% of the modified maximum proctor density.
2) Chemical stabilization of the problematic clayey sands soil sub-grade at B2 using cement kiln dust (by-product) or mixture of cement kiln dust with lime.
3) Mechanical stabilization including compaction of the clayey sands soil sub-grade at B2 using Geotextile technique to prevent the lateral displacement of the soils especially in case of rainfall or arrival the water to the sub-grade soils.