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.
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 (
The study area was geologically investigated by many authors such as [
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.
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 (
Borehole (Egyptian Coordinate System) | East | North |
---|---|---|
B1 | 790,167.046 | 336,805.229 |
B2 | 789,972.716 | 336,840.494 |
B3 | 789,805.070 | 336,890.693 |
B4 | 790,316.516 | 336,839.630 |
B5 | 790,562.020 | 336,883.890 |
B6 | 790,875.408 | 336,812.278 |
as well as the Pliocene-Recent sediments [
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 plasticity tests. As well as, three undisturbed samples, each sample having thirty kilometers weight, collected at 0.5 m depth open pits near borehole no. 2 (clayey sand sample), near borehole no. 3 (poorly graded sand sample), and near borehole no. 5 (poorly graded gravel sample). The undisturbed samples were collected to carry out the chemical and mineralogical analyses as well as free swelling, proctor, and California bearing tests. The studied soils were belonging to the Quaternary age (
Six wash mechanical drilling boreholes were conducted to collect sixty studied disturbed samples (
operating at 40 KV, 30 mA) analysis of the studied clayey sand soil and some 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.
Soil type Oxides (%) | Poorly gravels Near B5 | Poorly sands Near B3 | Clayey sands Near B2 |
---|---|---|---|
Sio2 | 68.18 | 85.53 | 59.22 |
Tio2 | 0.35 | 0.01 | 0.80 |
Al2o3 | 7.02 | 6.90 | 10.45 |
Fe2o3 | 3.67 | 0.44 | 11.60 |
Mno | 0.06 | 0.05 | 0.12 |
Mgo | 1.22 | 0.04 | 2.44 |
Cao | 13.27 | 11.27 | 6.85 |
Na2o | 0.44 | 0.99 | 0.53 |
K2o | 0.73 | 0.90 | 0.80 |
P2o3 | 0.19 | 0.06 | 0.11 |
Cl | 0.67 | 0.22 | 0.12 |
So3 | 1.70 | 0.93 | 1.33 |
LOI | 2.50 | 2.66 | 5.63 |
albite as main components and anhydrite as traces. The results showed also that the clayey sands were composed of quartz, albite as major components and illite, montmorillonite, gypsum, and hematite as minor components. The results showed that the dissolved sulfate content of studied gravels, sands, and clayey sands is 120, 85, and 99 ppm, respectively. The dissolved chloride content is 490, 630, and 550 ppm, respectively.
The results also illustrated that the PH-value of the studied gravels, sands and clayey sands is 8.4., 8.1, and 7.9, respectively. The calcium carbonate content of the studied gravels, sands, and clayey sands is 0.62, 0.50, and 0.29 ppm, respectively. The total carbonate content of the studied gravels, sands, and clayey sands is 1.05, 0.88, and 0.40 ppm, respectively. Depend on the PH-value, calcium carbonate and total carbonate contents; the chemical aggressiveness of the studied gravels, sands, and clayey sands is moderately aggressive for both gravels and sands and highly aggressive for clayey sands soils.
according to USCS specifications. The sands samples at borehole no. 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 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.
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 (
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 [
The results of California bearing ratio (CBR) test pointed to that CBR-unsoaked
Plasticity index (%) | Consistency |
---|---|
<1 | Non plastic |
1 - 7 | Low plastic |
7 - 17 | Medium plastic |
17 - 35 | High plastic |
>35 | Very high plastic |
Parameter Sample | Consistency Limits | Modified Proctor | CBR Un-soaked (%) | CBR 4-days Soaked (%) | Free Swelling (%) | |||
---|---|---|---|---|---|---|---|---|
LL (%) | PL (%) | PI (%) | MDD g/cm3 | OWC (%) | ||||
SC, B2 | 41 | 26 | 15 | 1.82 | 14 | 14 | 7 | 30 - 80 |
SC, B2 | 44 | 27 | 17 | 1.78 | 15 | 10 | 2 | 35 - 75 |
SP, B3 | - | - | - | 1.91 | 12 | 79 | 55 | - |
GP, B5 | - | - | - | 2.05 | 9 | 92 | 67 | - |
values of the investigated clayey sands soils were ranging from 10% to 14%, in contrast CBR-soaked (4 days water soaking) values of these soils were ranging from 2% to 7% (
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 [
Petrographical examination of the hand specimens and some representative studied gravels pebbles under the polarized light microscope, showed that the examined pebbles were composed of igneous rocks (like granite, rhyolite, gabbro, andesite), metamorphic rocks (like gneiss), and sedimentary rocks (like crystalline limestone, organic limestone, flint, and calcareous sandstone).
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
CBR values | Quality of sub-grade soils |
---|---|
0 - 3 | Very poor |
3 - 7 | Poor to fair |
7 - 20 | Fair |
20 - 50 | Good |
>50 | Excellent |
Free swelling values (%) for soils particles passing sieve 40 | Ability of expansion |
---|---|
<30 | Non expansive |
30 - 70 | Low expansive |
70 - 150 | Medium expansive |
150 - 250 | High expansive |
>250 | Extreme expansive |
were composed of quartz, calcite, and albite as major components and of gypsum and kaolinite as minor. The studied sands were composed of quartz, orthoclase, and albite as main components and anhydrite as traces. The clayey sands were composed of quartz, and albite as major components and illite, montmorillonite, gypsum, and hematite as minor components. The gravels pebbles were composed of igneous rocks (like granite, rhyolite, gabbro, andesite), metamorphic rocks (like gneiss), and sedimentary rocks (like crystalline limestone, organic limestone, flint, and calcareous sandstone). The minerals and chemical compositions of the studied soils in addition to the lithology pointed out that the sources of the studied gravels pebbles were the basement complexes along the red sea coast and the Upper Cretaceous-Lower Tertiary succession. A vertical cross section along the study road in X-Y direction was achieved by a correlation between the studied six mechanical drilling boreholes data. This vertical cross section showed that the studied area along the axis of the connector road is composed of four intercalated Quaternary layers of sediments. The succession included lenses and tongues of the clayey sands, surface clayey sands lens is at borehole no. 2. Additionally, there are two subsurface tongues of clayey sands at boreholes no. 1 (2 m depth), and at boreholes no. 5 and 6 (5 m depth). There is underground water observed until the drill depth end (10 m).
The gravel samples were classified as poorly graded gravels (GP) according to unified soil classification system (USCS) where the gradation parameters of the studied gravels including coefficient of uniformity (Cu) were less than 4. Sand samples especially at boreholes no. 4, 5, and 6 were classified as well graded sands (SW) according to USCS specifications. The sands samples at borehole no. 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 [
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.
The author is grateful for the contractor of the project, for valuable cooperation.
The author declares no conflicts of interest regarding the publication of 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