Engineering geological map of the riverfront in the old city of Mosul

The local and central governments focused on the right side of Mosul for urban development, especially after the destruction that occurred during its liberation. The view of the study area on the river and the green spaces on the other side of the river drew the attention of the Municipality of Mosul to develop it into a tourist attraction that reflects the cultural aspect of this ancient city. 26 exploratory boreholes were drilled in the study area, with depths ranging from 10 to 20 meters, and their geotechnical specifications were determined. In this study, the Pearson correlation coefficient was used to identify the parameters that have the greatest influence on the geotechnical specifications of the layers and to classify the engineering classes. Interpolation was used in Arc GIS to compare the distribution of geotechnical properties in the three layers at depths of (3, 6, and 9 m) and to calculate the average values of geotechnical properties from a depth of (1.5 - 9 m). The specifications were classified into five classes using a classification of the different characteristics. Geotechnical maps of the study area were created to show the distribution of engineering properties and their classification into isotropic zones, allowing each application zone to be provided with the appropriate building type. The results revealed that the northwestern part of the area is best suited for towering structures, while the rest of the neighborhoods were considered less suitable.


Introduction
Mosul is the capital of Nineveh Governorate, the second-largest governorate in Iraq (Figure 1).Since the Assyrian Civilization BC, it has had a prosperous civilizational history, and the city has gone through various cultural successions as a city with basic components of life.The Tigris River runs through Mosul, dividing it into the right and left sides.The right side holds a distinct civilizational and cultural position since it contains the old city, which Mosul's first inhabitants inhabited over time.The old city of Mosul's riverfront is on a plateau in a rectangular shape bordered by two bridges, the Nineveh and 5th bridges.In the past, the area was residential with commercial buildings.The city has gone through many stages of construction and destruction throughout its long history, including seven eras of construction and nine eras of destruction, the most recent of which was the major destruction that occurred during the operations to liberate the city from terrorism (Figure 2).Several accumulations of construction and demolition over the eras built on top of each other resulted in an impact on the geotechnical specifications of the ground of the city.This is evidenced by the problems caused by subsidence and sinkholes in the old city.Following the destruction that the city was subjected to during the liberation operations in 2018, the areas on the right side were destroyed catastrophically, with up to 20,000 buildings damaged or destroyed, according to preliminary assessments in the UN-Habitat 2016 report [1].Figures (2 and 3) show that a high percentage of these destroyed structures were residential and many historic and iconic structures, most of which were located on the western bank of the Tigris River.Several tours of Mosul revealed that there are many ruins as a result of the demolition of residential homes as a result of the liberation operations that the city witnessed at the hands of terrorism [2].In terms of destruction, the city was divided into several sectors, and the study area falls within a largely destroyed one (Figure 4).As a result, it was necessary to rebuild the riverfront of the city in a way that reflected its heritage [3].Although wars cause disasters, they can also provide opportunities for sustainable development by advancing the reality of those cities and communities through reconstruction [4].Based on previous similar experiences of cities that were exposed to wars and natural disasters, such as the devastation that occurred in Germany after the World War.According to the method that was adopted in building East Germany and West Germany, which included many projects, including the Kaiser Wilhelm Memorial Church -Berlin 1957-1963, Reichstag, New German Parliament 1999, and Dresden Central Station, urban planning was studied for the reconstruction of Mosul [4].fully destroyed with less (3) partial destruction.
Indonesia is a country through which the Pacific Ring of Fire passes, which leads to many natural disasters, whether in the past or the future, such as landslides, tsunamis, and earthquakes [5].Like many others, the Indonesian city of Milii was rebuilt after disasters and wars and converted into a tourist destination.The rebuilding process includes two approaches: the comprehensive process of rehabilitation and reconstruction following the Aceh disaster, and design solutions from the preparation stage to the rebuilding stage.Mila City, in northeast Algeria, was devastated by a devastating earthquake with a magnitude of Mw = 5.The foundations and designs of existing buildings were studied, as well as the causes of their collapse, and more modern designs with earthquake-resistant foundations were proposed.In addition to supporting the foundations present in the ancient buildings [6].
Proper riverfront development adds beauty to the urban city and connects people to water.However, as a result of overpopulation and uncontrolled urbanization, rivers have become highly polluted, dangerous places to drown, and have lost contact with cities and people [7].In addition to riverfront economic characteristics such as employment and income levels, are critical factors in determining the success of revitalization efforts in these areas.It demonstrates that cities with high employment and income levels are more likely to attract investment and develop their riverfronts, resulting in successful revitalization outcomes [8].
In a city like Mosul, where a river runs through it, paying attention to the riverfront during the reconstruction process is critical.It is difficult to imagine developed cities without a suitable riverfront, especially given that the area opposite it is a green tourist area from which the riverfront can be seen from a long distance.Because the city's riverfront had been severely damaged (Figure 3), the Mosul Municipality proposed constructing a modern-style riverfront similar to the old style.The municipality drilled several exploration boreholes in the area to study the soil characteristics to plan the possibility of establishing facilities and propose a site plan for the area.The study aims to assist the Mosul Municipality in reconstructing the riverfront by analyzing data obtained through exploratory borehole drilling and determining the distribution of building and service locations.The area was studied vertically and laterally and was divided into three zones vertically, the first with depths of 3m, 6m, and 9m.A rate of 1.5 to 9m was also taken, and the area was divided into several zones based on building tolerance according to building standards.

Geological setting
From a tectonic perspective, Mosul City was affected by several faults, which influenced the geotechnical specifications of the rocks as well as urban distribution [2].Fatha Formation (Middle Miocene) consists of cycles of green marl or marly clay, gypsum or anhydrite, silt, and limestone with alternating marl or marly clay.In the Mosul area, the thickness of this formation ranges from 170-190 meters and gradually decreases towards the northeast [9].The geological influence of the right side is characterized by the presence of the Fatha Formation, which consists of swellable marl, dissolvable gypsum, and limestone successions (Figure 5).The flood plain and river terraces, or Quaternary Deposits, cover the majority of the area on the right side, near the river [9].

Methodology
Data were obtained from the Mosul Municipality Directorate, where approximately 26 exploratory wells were drilled and physical and engineering tests were conducted.Physical tests included measuring the liquid limit, plasticity index, density, swelling, and solubility, and the percentage of sulfur trioxide was measured.The engineering tests included grain size analysis, bearing capacity BC, and Standard Penetration Test SPT.In this study, the SPSS software was used to create a correlation coefficient between the data to study the extent of the relationship and correlation between them.The Arc GIS software was also used to plot the data into three layers (3, 6, 9 m) by performing interpolation and then classifying the area based on the relationship between the data by performing reclassification through the Arc GIS program.

Results and discussion
By analyzing the data statistically using the Pearson Correlation, it was found that there are almost good relationships between the different characteristics (Table 1).The relationship between the size distribution of clay with gravel was a good inverse relationship, and the relationship of gravel with bearing capacity and SPT was also good and inverse, so increasing the size distribution of clay indicates good engineering properties.The density-solubility relationship was strong, as was the percentage of sulfur trioxide.This relationship makes logical sense because the density of gypsum rocks is higher than the density of marl and limestone.This relationship was good and positive because gypsum rocks are the most soluble rocks in the region and contain the most sulfur in their chemical composition.
The soil in the site, which is mostly marl rocks belonging to the Fatha Formation, was classified as low liquid limit clayey soil CL and low liquid limit organic soil OL, except for a small part at a depth of nine meters, which was classified as low liquid limit silty soil ML and OL (Figure 6).Figures (7,8,9, and 10) of the distribution of soil particle sizes show that the size of clay is almost uniformly distributed vertically in most of the study area, whereas the lateral change is more noticeable, with the highest percentage of clay at the northern end near the bridge, reaching more than (35%), gradually decreasing towards the south to reach about (27%), and then increasing again to reach (about 30%).Almost the same thing happens with silt size, and we notice that the silt size has the highest percentage of grain size, reaching (40-47%).On the contrary, the rate of difference in size distribution is related to the size of sand and gravel, and the percentage of particle size ranges from (9-19%) to (5-16%), respectively.Figure (11) depicts SPT values, which are generally high at a depth of 9 m, whereas decrease in the central area of the study area at a depth of 6 m, and their values are also low in most of the central and southern areas at a depth of 3 m, but increase in the northern part.The soil was described using SPT values from [11] and applied using the Arc GIS.The northern part appeared to be moderately compact clay at a depth of 3 meters, while the northern and southern parts at a depth of 6 meters were compact to stiff clay, silt and lose sand, moderately compact sand and gravel, followed by moderately compact clay, and the middle area is soft clay type, but at a depth of 9 m, it is mostly moderately compact clay (Figure 12).When the values of bearing capacity are interpolated, the distribution of values appears differently at the three depths.At a depth of 3 m, the values are low, ranging from (1.5-9.7 tons/m 2 ), but at a depth of 6 m, they rise to (13.4 tons/m 2 ).At a depth of 9 m, they reach (26.9 tons/m 2 ) in some southern areas, and in general, the values are higher than (8.2 tons/m 2 ) in the rest of the area except the central part (Figure 13).It is clear from the foregoing that the soil in the area is somewhat non-swelling (Figure 14) [12,13].Furthermore, the granular classification of the soil revealed that the areas at a depth of 3 m are in the northern part of moderately compact clay and that the bearing capacity values are higher than the rest of the area, in addition to the depth of the areas of weakness that appear due to the presence of cavities in these areas (Figure 15).As a result, buildings of low height can be built at this depth, while the remaining areas should be green spaces or open spaces.With a depth of 6 m, the percentage of bearing capacity for this area increases, supporting the idea of building on it.While some areas in the south of

Conclusions
The area opposite the riverfront is an open tourist area that extends far into the forests of Mosul.The riverfront is located on a high plateau called the Mosul Plateau, so it is visible from afar.The ancient city was built in this area, close to the river to its highest area, and some geotechnical problems appeared in it due to the city being built on the ruins of older buildings on several levels.The reconstruction of the area and the construction of the riverfront in a building style similar to the city's heritage, but using modern and sustainable methods, required conducting detailed geotechnical investigations.The results revealed that the area's characteristics are not identical and that there is a significant difference, so the types of foundations in each area, as well as the type of building in terms of number of floors and land use, were determined.As a result, it is recommended that this study be used in riverfront urban planning.

2 Figure 1 :
Figure 1: Location map of the study area.Several accumulations of construction and demolition over the eras built on top of each other resulted in an impact on the geotechnical specifications of the ground of the city.This is evidenced by the problems caused by subsidence and sinkholes in the old city.Following the destruction that the city was subjected to during the liberation operations in 2018, the areas on the right side were destroyed catastrophically, with up to 20,000 buildings damaged or destroyed, according to preliminary assessments in the UN-Habitat 2016 report[1].Figures (2 and 3) show that a high percentage of these destroyed structures were residential and many historic and iconic structures, most of which were located on the western bank of the Tigris River.Several tours of Mosul revealed that there are many ruins as a result of the demolition of residential homes as a result of the liberation operations that the city witnessed at the hands of terrorism[2].

Figure 2 :
Figure 2: Part of the riverfront near the 5 th Bridge before and after destruction.

Figure 3 :
Figure 3: Riverfront has been photo from the area of study a. before destroyed b. after destroyed.

Figure 4 :
Figure 4: A map representing the three destruction sectors (1) complete and intense destruction (2)fully destroyed with less (3) partial destruction.

Figure 5 .
Figure 5. Stratigraphic section of Fatha Formation and geological map of Mosul City [10].

Figure 6 .
Figure 6.Soil classification of the study area according to the depth 3,6 and 9m.

Fig 7 .
Fig 7. Distribution of clay grain size soil in the study area by the interpolation in ArcGIS using the IDW method in boreholes to depths of 3, 6, and 9 m.

Figure 8 .
Figure 8. Distribution of silt grain size soil in the study area by the interpolation in ArcGIS using the IDW method in boreholes to depths of 3, 6, and 9 m.

Figure 9 .
Figure 9. Distribution of sand grain size soil in the study area by the interpolation in ArcGIS using the IDW method in boreholes to depths of 3, 6, and 9 m.

Figure 10 .
Figure 10.Distribution of gravel grain size soil in the study area by the interpolation in ArcGIS using the IDW method in boreholes to depths of 3, 6, and 9 m.

Figure 11 .
Figure 11.Distribution of SPT (N) of soil in the study area by the interpolation in ArcGIS using the IDW method in boreholes to depths of 3, 6, and 9 m.

Figure 12 .
Figure 12.Distribution of stiffness of soil in the study area by the interpolation in ArcGIS using the IDW method in boreholes to depths of 3, 6, and 9 m.
have a high BC value at a depth of 9 m, the presence of cavitation areas at depths close to 9 m indicates that the area requires cavitation treatment.

Figure 13 .
Figure 13.Distribution of bearing capacity of soil in the study area by the interpolation in ArcGIS using the IDW method in boreholes to depths of 3, 6, and 9 m.

Figure 14 .
Figure 14.Distribution of swelling potential of soil in the study area by the interpolation in ArcGIS using the IDW method in boreholes to depths of 3, 6, and 9 m.

Figure 15 .
Figure 15.Distribution of cavities in the study area.

Table 1 .
Pearson Correlation among different engineering characteristics.