3d Geotechnical Model of the Soil Susceptible to Liquefaction, In the Central Area of Caimanera, Guantánamo

Models are widely used in all sciences to simplify the most complex problems in reality, allow a representation of the behavior of a system and acquire great relevance in Geological Engineering.The conceptual geological model is very useful for projects developed in the field. Geotechnical models have evolved in parallel to computer-assisted techniques, from 2D to 3D models. The correct modeling of the physical-mechanical properties contributes to obtaining a representation of the characteristics of the geological object.The low availability of soils in the city of Caimanera, province of Guantánamo, appropriate for construction, has forced the use of swamp areas for urban development, through the use of low-thickness fill materials. The execution of constructions on swamp areas and low plasticity soils contributes to the increased risk of liquefaction.The 3D model obtained allowed the approximate spatial distribution of the variables (liquid limit, natural humidity, number of blows of the standard penetration test, percentage of fine soil and plasticity index) that affect the susceptibility of the soils in the area. Caimanera power station.The results of the 3D model indicate that the soils represented by compressible clays, silty clay, calcareous shale and organic silt have a high susceptibility to liquefaction; and that the compressible clays located in the University Venue have the highest susceptibility to liquefaction, taking into account the relatively low fines content (14%).


Introduction
Models are widely used in all sciences to simplify the most complex problems in reality, allow a representation of the consists in the identification of the lithological, geomorphological and structural characteristics of the object of study. These allow us to infer the characteristics of the medium through which the groundwater would eventually circulate and the predisposition or susceptibility of the medium to the occurrence of geological processes generating geotechnical hazards can be determined, whose prediction methods always imply the lithology variable [3].
MGGs allow the engineer to understand the conditions existing in a certain place, in addition to identifying the main geotechnical problems and making the estimation of soil properties more objective.
The correct modeling of the physical-mechanical properties contributes to obtaining a representation of the characteristics of the geological object. The geometry of the basic information unit is used as a virtual limit for the estimation of the property of interest [4][5][6]. With this application it is possible to reduce considerably the incompatibilities between the quantitative interpretation, conceived based on a geotechnical parameter and the reality of the physical environment. In Cuba, studies of this type are aimed at making models that allow the visualization of soil behavior, especially in areas of vulnerability or risk to geological phenomena.
This case study is located in the city of Caimanera, Guantánamo province, where the active Bartlett-Caimán earthquake is located.
The low availability of appropriate soils for construction has forced the use of swamp areas for urban development, through the use of infill materials with low thicknesses. The surface geology of urban areas greatly influences the level of seismic shocks, there being a strong relationship between the geotechnical properties of soils and their seismic susceptibility. According to Youd & Perkis, unconsolidated materials are usually responsible for important changes in the amplitude of seismic shocks and for induced effects such as liquefaction [7]. The aforementioned parameters have been used, to a greater or lesser extent, in the liquefaction studies in Cuba developed by Fernández and Bandera [8,9]. These works have been oriented to the delimitation of areas vulnerable to liquefaction, without considering the 3D spatial behavior of each one. Taking this need as a starting point, this work plans to perform 3D modeling of the geotechnical parameters that allow characterizing the soils susceptible to liquefaction. The insufficient knowledge of the 3D spatial distribution of the geotechnical parameters of the soil susceptible to liquefaction arises as a research problem. Therefore, the objective of the work is to develop a 3D geotechnical model of the soils susceptible to liquefaction in the central area of Caimanera, Guantánamo province.

Physico-geographical and geological features of the study region
Caimanera is one of the 10 municipalities that make up the current province of Guantánamo, it is located 17 km of the same, limiting to the north with him and with the Manuel Tamez municipality, to the east with the municipality of San Antonio del sur, to the south with the Caribbean Sea and to the west with the municipality of Niceto Pérez. Being located in the coastal strip of southern Cuba, it is part of the so-called Cuban semi-desert. It presents alluvial soils of clays on limestones and sandstones. The coastline is surrounded by a swampy area and mangroves that have

Regional and local geology
The Caimanera municipality is located in the delta of the Guantánamo river, it is represented by the formations that appear in Figure 2.
Shrimp Formation: It is made up of polymictic conglomerates, with sub-rounded and rounded edges, and coarse-grained polymetric sandstones. The matrix of the conglomerate is sandy and polymictic in composition. These coarse lithologies transition to medium grain sandstones, but maintain their composition. can pass laterally to limestone. The limestones have a massive appearance, they are laminated and, on occasions, weak, with a predominance of brown and cream colors; They consist of crypto to microcrystalline calcite, containing clay material and iron oxides and hydroxides. In some cases, they include benthic forms, indicative of shallow waters of the sublitoral zone; at other times they only contain planktonic forms indicating deep environments.
The latter is mainly seen towards the easternmost part of the territory. Likewise, in the limestone grains of plagioclase, quartz, metal, chlorite and effusive rocks can be seen.
The terrigenous sequences are made up of fine and coarsegrained sandstones, which transition to calcareous sandstones due to the increase in carbonate material. This is represented by fragments of limestone, organisms and by a contact type cement, calcite, generally recrystallized. The terrigenous material is very varied, characterized by basic, medium and acid effusive rocks, intrusive rocks, clay rocks and grains of plagioclase of different composition, clinopyroxenes, quartz and grains of metal. The organisms present are fragments of algae, planktonic and benthic foraminifera, rarely siliceous, and some of them formed by phosphate minerals are observed in isolation. The cement of these rocks is calcite, undefined cryptocrystalline material and zeolites [10].

Regional geomorphology
The province is made up of two large natural regions: the Guantánamo Valley, with flat relief and an extensive Bay of Stock Exchange, classified as the third largest in the world. It presents important rivers that make up the third hydrographic basin prioritized at the national level, called Guantánamo-Guaso, where 80% of the territory's population is concentrated. The study area presents a fairly flat relief, with heights or remnants of mountains, reaching heights of 25 meters above sea level (s.n.m.), in some places they reach up to 40m. Its smooth and wavy relief is formed by swampy sea plains and some pre-mountainous areas. The area occupied by the head town and its surroundings is extremely low, with values up to 1 meter above sea level [10].

Hydrogeological characteristics
The structure of the aquifer complex to which the area belongs  depth (towards the bay) to 3m in isolated cases, which indicates that there is little variation as stated [11].

Figure 3:
Depth diagram of the water table in the Caimanera municipality, Guantánamo province [8].
Generally, due to the hydraulic characteristics of this aquifer complex, groundwater is predominant. So, you are in the presence of saturated and semi-saturated rocks.

Engineering-geological characteristics of the region
Within the limits of the territory studied, two layers are

Seismicity
The seismic phenomena registered in the territory indicate differences in the values of longitudinal and transverse wave velocities. The denser the soil, the faster the propagation of the seismic waves will be. The multiplication of propagation speed and density results in seismic stiffness, which varies depending on the type of soil. In gravels there are high values of seismic rigidity, however, in clay soils the values are small, which means that the movement of the soil in these cases will be greater.

Seismicity-Liquefaction
Caimanera is located in a seismically active area, several earthquakes have taken place in the territory. The Haiti earthquake of January 12, 2010 generated great negative perceptions in the population. Then on Saturday, March 20, at 2:38a.m., an event occurred in Baconao of Magnitude 5.6 that generated intensities of VI degrees in Santiago de Cuba, Guantánamo and Caimanera. In the study area, since 1987, site effects have been reported that have generated the differential settlements of the Soviets GPS IV Grand Panel buildings, even one of them was demolished and the other was reduced to 2 levels [9].

Methodology Used in the Research
The methodology applied in the research for modeling in the urban sector of the Caimanera municipality, Guantánamo province, can be seen in Figure 4.

Bibliography search and analysis
At this stage, a bibliographic search is carried out by reviewing a series of scientific articles, diploma works, master's thesis, geological engineering reports of engineering works located in the archives of the National Company for Applied Research (ENIA) in Santiago de Cuba. In addition to reviewing internet articles, books and all kinds of documents on the subject to be developed. The research design was elaborated defining the problem and the methodology to be used to solve it. In a second moment, the methodologies used for the modeling derived from the revised information were analyzed, determining the distribution of the soils with physical-mechanical properties that make them liquefiable, responding to the research objective and constituting a rigor tool, fundamentally applicable to the solution of geotechnical phenomena in the municipality.  c.

General concepts on the liquefaction phenomenon
In most cases where liquefactions have been observed, the water table was at a shallow depth (0-3m) below 9m,

liquefaction susceptibility is very low
There is a threshold of minimum earthquake intensity for liquefaction phenomena to occur. In highly susceptible soils, this intensity threshold is VI on the Modified Mercali scale, or magnitudes greater than 5.5 [8].
Geological criteria: The soils of fluvial and wind deposits, when saturated, have a high probability of being susceptible to liquefaction.
Criteria based on soil state: Loose soils are more susceptible to liquefaction than dense soils and, for a given density, soils under high effective confining stresses are more susceptible than soils under low effective confining stresses [8].

Geotechnical parameter limits used in liquefaction analysis
for fine-grained soils to liquefy, certain granulometric conditions proposed by Wang in 1979 must be met. These are: a.
e. Shape of rounded particles.
Seed and Idriss consider that a soil can liquefy if the weight percentage of particles <0.005mm is less than 15%, LL <35, W / Ll> 0.9 [13]. This criterion was known as the Chinese criterion [8]. wide at its bottom. The mold is placed on a base and subjected to controlled blows. The liquid limit is the humidity of the sample when giving 25 blows the channel is closed to about 12mm. As this condition is difficult to achieve, the humidity is determined by interpolation, from two samples, in which the 12mm closure must be achieved with more and less strokes than 25.

Volume 2 -Issue 5 Copyrights @ Deynier Montero G, et al. Adv in Rob & Mech Engin
199 Liquefaction of soils: it is the process of loss of resistance of certain types of soils, which are saturated in water and when subjected to the shock of an earthquake flow as a liquid due to an increase in pressure.

Inverse method of a distance power
The

Central zone
In this zone, soils filled with SC clay sands were identified, not

Obtaining the 3D model of the Geotechnical Parameters
The professional Gemcom Gems V6.4 software was the basic tool that allowed this type of modeling, it is based on the Microsoft Access database manager: 1. Database processing.
a. Creation and import of databases in Gemcom.

2.
Development of the digital terrain model.

3.
Estimation of the geotechnical parameters used.

Database Processing at Gemcom
The information provided by the databases comes from samples of drilling wells for geotechnical studies. The database was built using a series of tables or relational files, linked through some

Volume 2 -Issue 5 Copyrights @ Deynier Montero G, et al. Adv in Rob & Mech Engin
200 key fields. From the data in ASCII format, a drillhole type workspace was created, where the field (HOLEID) was specified, which served as a link between the different tables. Additionally, the HEADER, SURVEY, ASSAY and LITHOLOGY tables were created, in which the fields to be used in the database were defined. For each field, a type (real, integer, text) was assigned, the default value and the number of decimals were modified ( Figure 6). To import the database, an import profile was first designed for each table. In each table, the fields were listed in the order established within the ASCII file.
In the GEMCOM project, a directory was created with the name Imports, which contains the data from the different tables.
Geotechnical data were imported into these tables, thus forming the database within the Gemcom Software (Figure 7).   NECKLACE, spatial location x, y, z of the well.

Results
The visualization of the wells was based on a color scheme with which the geotechnical properties were coded. To do this,     Table 1. The parameters used in the estimation of the variables are shown in Table 2.  *Rotation: A -Azimuth, D -Dip, R -Rake. According to SGemS 3.0 software For the validation of the results achieved in the model, the mean of the samples was compared to that obtained by the estimates (Table 3), providing a level of precision of the data above 95%, where the largest error is found in the percentage of fine (% F) with a 2.91 difference.

Discussion
The Caimanera municipality is characterized by a liquefaction susceptibility, before high intensity earthquakes, in high, medium and low, according to the forecast map presented by Fernández ( Figure 11) [8]. The central zone, according to this study, is  Table 4). The high plasticity clay type soils (CH), clayey sand (SC), silty sand (SM) and low plasticity clay (CL) present in the Caimanera municipality present conditions that make the liquefaction of the soils favorable from earthquakes of great magnitude (6.5 and more) [8].
Taking into account what the researchers proposed and after interpreting the information available, it can be stated that liquefiable soils are types CL, Cl / Ml, SM and SC, which meet the conditions for seismic waves are amplified and liquefaction of soils occurs [13,14].  Figure 11: Diagram of the location of the central zone, according to the liquefaction susceptibility forecast map [8].

203
The fine content is one of the parameters that define the soil classification; it allows to discriminate between a coarse-grained or fine-grained soil. From the 3D model of the behavior of this parameter, it was possible to define that the University Venue is the area of greatest susceptibility to liquefying taking into account the relatively low fines contents (14%) (Figure 12). The soils with a low liquid limit (<35%) are poorly distributed (Figure 13), mainly in the entry dwellings, Bandec Branch and Servicentro at levels 5, 14, 15 in the southern part of the study sector; suggesting a high susceptibility to liquefaction. According to the criteria of Wang and Brandes, soils with Ll below 32% and low fines content may be susceptible to liquefaction in the event of earthquakes [14,15].        The model shows layers with low N values of SPT but given the high depth at which they are found and the weight of the overlying layers, they are considered of low potential due to the liquefaction phenomenon. The classifications obtained from the geotechnical models of the central region, regarding the susceptibility to liquefaction do not coincide with the results obtained by Fernández, shown in Figure 11, an example of which is evidenced in the University Venue where according to the model obtained in the present investigation is characterized by high susceptibility [8]. The discrepancy between these results may be motivated by the use of 2D maps vs. 3D models, the latter considering the vertical distribution of the layers. For a better illustration of the results produced by the models, Table 5 was prepared, in which the susceptibility to liquefaction of the soils of the study sector is classified considering each geotechnical parameter. Figure 18 shows the distribution of soils where highly susceptible soils stand out with the highest percentage.

1.
The soils of the central zone of Caimanera are mainly composed of silty sand, silty clays, clay sand fill and organic silt.

2.
The 3D model obtained allowed obtaining the approximate spatial distribution of the (liquid limit, natural humidity, number of blows of the standard penetration test, percentage of fine soil and plasticity index) that affect the susceptibility of the soils of the central area of Caimanera.

3.
The soils of the central region represented by compressible clays, silty clay, calcareous shale and organic silt have a high susceptibility to liquefaction.

4.
It was possible to delimit that the compressible clays located in the University Venue present the highest susceptibility to liquefaction, taking into account the relatively low fines contents (14%).