The Effect of Samples Disturbance of Partially Saturated Expansive Clay Soils on the Soil Properties

Abstract

The internal structure of the expansive clay soils is sensitive to the disturbance. When the samples are extracted, the structure of the natural soil is damaged when it is remolded. Therefore, a change in the properties of the expansive soil happens. This matter must be more precisely defined in the design of the foundations of engineering facilities. The objective of this research is to conduct a study of the effect of the disturbance of expansive clay partially saturated soil samples. The obtained results indicate that the behavior of the expansive soil tends to change during the formation of samples. This behavior is based on soil properties, chemical composition and the content of their expansive soil minerals. Soil structure disturbance causes a decrease in soil property variables.

1. Introduction

An expansive clay soil can be defined as soil whose volume changes with changes in its moisture. The volume of the soil increases when it swells as a result of the increase in the thickness of the water membranes around the soil particles, while when it shrinks, the volume of the soil decreases as a result of the decrease in the thickness of the water membranes around those particles [1].

The behavior of expansive soil is affected by several physical, chemical and environmental factors attributed to the expansive nature of the soil, which is represented by the type and amount of clay minerals, the physical and chemical properties of the expansive clay, soil density, water content, evidence of plasticity, temperature and time [1].

The special behavior of this soil and its direct relationship with water, and the risks that this behavior leads to for various engineering facilities, make this soil a field for much research (Figure 1) [2].

Figure 1.

Cracks in the swollen soil of the soil of Umm Rawaq village (Suwayda Governorate – Syria).

Clay minerals greatly affect the volumetric change in expansive soils, as kaolinite, montmorillonite, and Illite are the common clay minerals in expansive soils, and soils containing montmorillonite minerals are swollen in nature [3].

The importance of engineering trial in choosing the distinctive characteristics of expansive soils and the effects of their application and modification in order to ensure the safety and stability of the structure and thus reach the optimal solution for choosing the appropriate type of soil for designing the foundations of engineering facilities [4].

An expansive soil tests have a significant impact on the design of foundations, as they provide sufficient information to determine the characteristics of the expansive soil and its parameters, and to know whether there are technical Remolded that require research and investigation [5, 6].

2. Research justifications

The behavior of expansive soils is a reflection of the capillary property of the soil under the influence of periodic paths of wetting and drying due to natural environmental fluctuations [7]. This behavior is related to the disturbance occurring to the sample when it is transported to the laboratory, which can be classified as follows:

1. Changes in the stress status of the soil.

2. Changes in moisture content and void ratio.

3. Chemical changes.

The change in the stress situation in the soil is related to the water saturation state of the soil, which is either completely saturated with water or partially saturated with water. These saturated states of expansive soil led to thinking that there is a major Remolded in determining the stress state of the soil and the compressibility of expansive soil, especially for large engineering structures such as dams and bridges [8].

The foundations for determining the specifications of the swell rank are based on the results given by intact samples. The Remolded of research is that we are often forced to resort to remolding samples in the laboratory due to our inability to obtain intact samples [9].

In light of this, it is important to recognize indicators of the properties of expansive soils, which are determined by the soil resistance associated with the soil texture, which can be known from Atterberg’s limits, especially the liquidity index (LI) [1]. The extent of the soil’s ability to swell is related to the plasticity index (PI) and the soil structure, which depends mainly on the mineralogical analysis of the studied samples [10].

3. The main objective of the research

The importance of this research is focused on providing a clear vision of the effect of sample disturbance on the properties of the partially saturated expansive clay soils [11], through:

1. Introducing the concept of disturbance of samples of expansive clay soil in conditions of unstable soil from wetting and drying (partially saturated soil) by presenting

   1. The main causes of sample disturbance.

   2. Effects resulting from sample disturbance.

2. Study the effect of disturbance on the behavior and properties of partially saturated expansive clay soils, which includes physical, mechanical and chemical properties

4. Forms of soil tests

Most tests performed in the laboratory are to determine the physical, mechanical and chemical properties of the soil. The most important of these laboratory and field tests, with reference to the standard references and codes based on which the tests can be conducted. We will mainly refer to the standards of the American Society for Testing and Materials (ASTM) (Table 1) [11].

ASTM D-2216	Moisture content (W)
ASTM D-4318	Atterberg Limits
ASTM D-7263	Total unit weight (γ)
ASTM D-854	Specific gravity
ASTM D-422	Sieve analysis
ASTM D-1140	Percent finer sieve 75 micron (sieve # 200)
ASTM D-3080	Direct shear
ASTM D-2435	One-dimensional consolidation
ASTM D-698	Standard Proctor test
ASTM D-5084	Falling Head Soil Permeability Test
Organic fertilizer reference	Organic matter content
ASTM-D 4972	PH value

Table 1.

Laboratory tests according to the American code (ASTM).

5. Samples disturbance

Taking samples is considered one of the most important stages of engineering work, and its importance is no less important than the tests that will be conducted on it. Therefore, it is necessary to exercise accuracy and caution when taking samples and how to fill them so that they are samples representative of the nature of the natural soil. Samples are taken to describe the type of soil and conduct laboratory tests, which are:

1. Classification tests (Atterberg limits).

2. Tests to determine engineering design standards (resistance, compressibility and permeability).

Soil disturbance occurs during excavation, during sampling, during transportation and storage, or during preparation for testing. In general, any soil sample taken from the site and transported to the laboratory will be subject to disturbance. The availability of good engineering standards for design depends on careful testing. The test can be carried out in the laboratory or in the field, but in both cases the most important factor for judging the quality of the final results must be to avoid disturbing the soil samples [12].

6. Main causes of sampling disturbance

They can be classified according to the following table into the various stages of site inspection into [12]:

1. Reasons before taking samples.

2. Reasons during sampling.

3. Reasons after sampling (Table 2).

Reasons before sampling Reasons during sampling Reasons after sampling	Reasons before sampling Reasons during sampling Reasons after sampling	Reasons before sampling Reasons during sampling Reasons after sampling
Reducing or releasing stresses Reducing or releasing stresses. Reducing or releasing stresses	Reducing or releasing stresses Reducing or releasing stresses. Reducing or releasing stresses	Reducing or releasing stresses Reducing or releasing stresses. Reducing or releasing stresses
Swelling Collapse of soil Moisture loss	Swelling Collapse of soil Moisture loss	Swelling Collapse of soil Moisture loss
Pressure displacement effects of sample freezing	Pressure displacement effects of sample freezing	Pressure displacement effects of sample freezing
Displacement cracking or shattering of soil by high temperatures	Displacement cracking or shattering of soil by high temperatures	Displacement cracking or shattering of soil by high temperatures
Foundation stones swell at the cutting edge due to the effects of vibration and shock	Foundation stones swell at the cutting edge due to the effects of vibration and shock	Foundation stones swell at the cutting edge due to the effects of vibration and shock
Collapses, mixing and separation of soil, effects of chemical reactions during pouring	Collapses, mixing and separation of soil, effects of chemical reactions during pouring	Collapses, mixing and separation of soil, effects of chemical reactions during pouring

Table 2.

Main causes of sampling disturbance.

7. Effects resulting from sample disturbance

In addition to the process of digging and taking samples, soil disturbance can affect several factors, as the difference in the method of taking samples directly affects the value of the shear resistance of undrained soil, as high-quality methods for extracting samples such as (JPN & Sherbrook) samples, which give undrained shear strength It costs double the values for samples extracted using the (Shelby & NGI54) method (Figure 2) [13, 14].

Figure 2.

The effect of the sampling method on the relationship curve between (deformation and shear stress) within the direct shear experiment.

8. Criteria for evaluating the quality of samples

The data values of the studied samples are analyzed to estimate the quality of the sample using several criteria, which is called the sample quality presumption (SQD), defined by the scientist Terzaghi et al. [15] in addition to Lunne et al.’s [16], and these criteria are summarized in the following Table 3:

Sample quality standards (SQD)		$\left(\frac{\Delta e}{e_0}=\frac{\Delta V}{V_0}\right)Criteria/Lunne\left(1997\right)$
${\epsilon }_v$	SQD	OCR = 1–2	OCR = 2–4	Rating
<1	A	<0.04	<0.03	Very good
1–2	B	0.04–0.07	0.03–0.05	Good to fair
2–4	S	0.07–0.14	0.05–0.10	Poor
4–8	D	>0.14	>0.14	Very Poor
>8	E	—	—	—

Table 3.

Criteria for evaluating the quality of samples according to Terzaghi et al. [15], Lunne et al.’s [16].

9. Precautions to be taken to preserve samples

9.1 Soil sampling tools

There are many tools that are used in taking soil samples, such as a soil roller, auger, shovel, soil auger, drill, and rings for taking soil samples (Figure 3).

Figure 3.

Taking a soil sample using a shovel.

9.2 How to take soil samples from the field and prepare them for analysis

A field visit is made to the field or study area and some information is recorded about it by looking at it, such as the topography of the land, the condition of the plants there (if any), construction, texture, and the condition of the ground water. Then a sketch drawing of the field is made and the fixed places surrounding the land are placed on this drawing (Roads, mosques and churches) He also signs the points from which samples will be taken. After completing the previous step, he goes down to the field (study area) and takes samples from the specified places using the appropriate tool.

After taking the sample, it is placed in bags bearing the sample data (such as the sample number, sample coordinates, and the depth from which the sample was taken). The sample is then transported to the laboratory and spread out to air dry at the temperature of the laboratory. After that, we keep it in the bags with the data written on it until it is analyzed.

9.3 Laboratory description of the soil

We have mentioned that the soil must be described by mentioning its necessary engineering properties. Therefore, the size of the soil grains constitutes an essential factor in describing non-cohesive soils, while cohesive (silty) soils are described according to their degree of cohesion, as the percentage of clay present in the soil constitutes the controlling element on the soil’s properties and behavior.

One of the difficulties encountered in describing soil is that most soils are a mixture of gravel, sand, silt, and clay, and there are general methods that must be followed when we want to describe a soil in the laboratory.

1. We read the description page provided by the sounding controller and compare its numbers with the numbers of the samples to be described, then we open the boxes carefully and with special care if the samples are intact.

2. We arrange the samples logically according to their numbers so that we separate healthy samples from damaged samples.

3. We remove the wax cover with a sharp cutting tool so that the sample is not exposed to damage or scratches.

4. We must maintain the degree of humidity of the sample as much as possible and not remove wax from sealed samples except at the time of use, and always take only the necessary amount. We also try to prevent changing its chemical composition due to oxidation in the air.

5. We examine the sample without destroying it, and we specifically mention the degree of its cohesion or disintegration [17].

9.4 Sample filling

Immediately upon obtaining the samples, the samples are filled in sealed containers, such as plastic containers or plastic bags, and then placed inside fabric bags, taking care not to crush them when inserting them into the bag. The sample must fill the container as much as possible, and in the event that the sample is a continuous sample Like rock samples, they are kept in boxes with divisions of appropriate diameters so that they hold the samples without compressing them. However, in the case of extracting healthy samples, these samples must be protected in appropriate ways from drying out, changing their size, or slipping in the container.

As for samples taken from cohesive soil and cut into cubes, the samples can be covered well with one or more layers of wax, and each sample is placed separately in an outer cover with the same dimensions of wood or something similar to protect it during transportation.

The sample is usually coated with wax after melting it to maintain its moisture and structure by [17]:

1. Paraffin wax.

2. Labels that are attached or affixed to the sample or the container that contains it.

3. Sequentially numbered stickers.

4. Electric heater to heat the wax.

5. Containers for storing extracted samples.

6. Samples must be documented according to their number in the form of a booklet or a packet of papers.

7. Racks for storing samples.

9.5 Waxing samples

Its purpose is to preserve the moisture of the samples in their natural state and to preserve their structure from damage.

Intact block or cubic samples can be waxed by pouring wax on them, with the advisability of covering them once or twice with a preliminary coating using a brush so that the wax does not enter into their cracks and pores. Then the entire sample can be dipped in molten wax, and the work is repeated until a wax layer of about (2) thickness is obtained. 5 mm), and to protect the sample from shattering, the sample can be wrapped in a linen cloth after covering it with wax, then immerse it again with the cloth in the molten wax (Figure 4) [17].

Figure 4.

Packaging and waxing of samples used in research.

9.6 Storage of samples

Samples are stored in sealed containers and placed on exposed shelves. Healthy samples must be separated from spoiled samples. The destroyed samples are stored in bottles or metal containers of an appropriate size in order to reduce the loss of moisture as much as possible. Cards are placed inside the containers and numbered stickers are affixed to them on the outside of the containers or bottles. Then a list of the samples, their type and numbers is written, mentioning the date the sample was stored if we want to store a large number of samples. Samples for long periods of time. In all cases, the following data must be recorded when sampling [12]:

1. The general location, with its clarification on a sketch plan.

2. General information about the project.

3. Hole number and dimensions.

4. Number of samples and locations of extraction.

5. Date the sample was taken and weather conditions.

6. Sampling method.

7. Approximate area or quantity.

8. Groundwater level, if detected.

9. General description of the soil.

9.7 The importance of sample formation

Sample formation is of utmost importance in geotechnical science because it has a clear impact on laboratory results and its reflection on the design reality later. This is due to our inability to obtain intact samples during drilling (the difficulty of drilling, the nature of the site, the use of water during drilling) and the inability to obtain samples. Sufficient in length, therefore, the sample must be reconstituted to understand the behavior of the soil and determine its variables. The destroyed sample can be utilized by classifying the soil and determining the classified physical specifications (Atterberg limits, granular sieve analysis).

The basic physical specifications (natural humidity, normal volumetric weight, dry volumetric weight) can be determined if there are pieces of the destroyed sample that are similar to the mother soil (do not use water during excavation) and the mechanical specifications (cohesion and friction) cannot be determined, so the sample must be formed according to one of the codes. Then, experiments were conducted on it, including direct shear experiments and compression experiments, in order to determine the mechanical specifications and benefit from them in determining the bearing capacity and subsidence [18].

9.8 Methods used in sample formation

There are several ways to form samples according to the desired purpose of forming the sample to serve the desired scientific purpose, and methods of forming samples according to the American Code (ASTM).

Samples are prepared using the specified optimum moisture content and maximum dry volumetric weight. The sample is formed either by compacting it or knocking it into layers. The amount of soil for each layer is determined and placed in the device. Then the sample is compacted to achieve the required volumetric weight. The soil continues to be added and compacted until the entire sample is compacted. The materials subjected to the test will be completely mixed with a sufficient amount of water to obtain the desired moisture content, and the samples will be left for periods of time according to the classification (ML, CH). According to the instructions and according to the American Code, the minimum waiting time is (18 hours).

• The destroyed sample is formed [19] and requires passing the soil through sieve No. (#4) and drying it in the oven at a temperature of (105°–110°C). The sample similar to the original sample is formed by hammering it into the mold (direct shear box – odometer ring). Within three layers, each layer with (25 strokes), thus we obtained a sample similar to the sample formed according to the regular Proctor experiment.

• The formed sample is formed, which is obtained by the regular Proctor experiment (optimal humidity and maximum dry volumetric weight), where the first and last 3 cm are scraped off from the Proctor mold sample so that the middle part remains, and from it a sample is taken for the direct shear square and a sample for the odometer ring.

Mold specifications for the regular Proctor experiment (D = 10.2 cm, h = 11.6 cm).

Where h: height of the cylinder, D: diameter of the cylinder.

Number of layers: Three layers, with (25) strokes for each layer.

Hammer Weight: (2.5 kg), Screen No.: #4), Drop Height: 12″).

Therefore, all damaged and damaged samples have the same ideal humidity and the same volumetric weight, and they can be taken as a group and one spirit for study, and thus the effect is the same on all samples.

10. Reference studies

There are many previous studies that addressed the subject of studying the effect of disturbance on swollen soil samples partially saturated with water and approached it from different angles.

10.1 Search [A1]

The researcher [20] studied the effect of sample disturbance on the behavior of moderately plastic clay soil. He conducted tests on vandalized samples and compared them with intact samples within the odometer experiment (CAUC-L). The samples were loaded with increasing loads (0.25 – 0.5 – 0.75). – 1 kg/cm²) for (24) hours for each stage, and in order to obtain values that mimic reality, standards such as:

Types of samples: (ratio of sample height to diameter for all samples (h/d = 1.8).

1. An intact sample using a tube with a cutting edge (tube sample 30°) and a diameter of 100 mm.

2. An intact sample using a tube with a cutting edge (tube sample 5°) and a diameter of 100 mm.

3. An intact sample using a block sample tool with a diameter of 50 mm.

4. A vandalized sample (reconstructed) (Mostap sample) with a diameter of 50 mm (Figure 5 and Table 4).

Figure 5.

Distortions caused by a sampling tube for a dried soil sample [20].

Percentage of volumetric deformation for each sample
Intact sample (tube 30°)	εv = 5.9%
Intact sample (tube 5°)	εv = 4%
Intact sample (block)	εv = 4.3%
Disturbance sample	εv = 7.8%

Table 4.

Mechanical properties of moderately plastic clay soil samples [20].

According to the results of the study, the research concluded that the results of sample quality are related to the percentage of volumetric deformation, and the relationship between the variables was that the sample was intact (tube 5°) the best sample (Figure 6).

Figure 6.

Comparison of the various results of the odometer experiment for good quality values [20].

10.2 Search [A2]

Amundsen et al. [21] studied the effect of disturbance of intact samples (block samples) on the behavior of low-plastic clay soil by studying the relationship curve (horizontal deformation – shear stress) within a triaxial experiment And the odometer test (CAUC triaxial and CRS Oedometer tests), as shown in Figure 7, for both intact, low-plasticity swelling soil samples that were taken using a block sample method with dimensions (160 × 160 mm) and other samples that were taken using a diameter tube (75 mm).

Figure 7.

Block samples and tubular samples [21].

According to the results of the study, the research concluded that the shear strength and specifications of block specimens are generally better than tubular specimens, and the decrease in the strength of tubular specimens is due to the destruction of structural bonds in the soil (Figure 8).

Figure 8.

Relationship curve (horizontal deformation – shear stress) [21].

10.3 Search [A3]

Al-Miqdad studied the effect of sample reshaping on mechanical specifications in clay soil by conducting laboratory experiments on intact samples and formed samples, which are similar to the intact sample in terms of moisture and natural volumetric weight, within a direct shearing experiment (fast – undrained) at a cutting speed (0.5 mm/min).), the applied stresses (1.11 – 2.22 – 3.33 kg/cm²) Several sites were chosen for the study (Jdeidet al Wadi – Deir ez-Zor – Sahnaya – Ghabagheb – Dabbagat). The results of the study were as follows [17]:

1. The relative change in soil cohesion between the healthy sample and the Remolded sample ranged between (8–56) %.

2. The relative change in the angle of internal friction of the soil between the intact sample and the Remolded sample ranged between (3–9) %.

10.4 Search [A4]

The researcher [22] studied the effect of the degree of water saturation of the soil on the behavior of a highly plastic clay soil by studying the size and rate of subsidence of the swollen soil before construction in a certain condition of soil moisture, by studying the behavior of intact samples of swollen soil according to different degrees of saturation. Within the odometer and triaxial experiment (CAUC-UL) [23].

The samples used are intact samples using a tube sample, diameter (75 mm), height (40 mm) and depth (1.5 m) (Figure 9 and Tables 5 and 6).

Figure 9.

The relationship between the compressibility index and the degree of water saturation of the soil [22].

Cartilage activity	1.73
The type of metal present	Montmorillonite

Table 5.

Chemical properties of highly plastic clay soil samples [22].

τ (kN/m^2)	Cc	W (%)	Sr (%)
491.4	0.088	1.85	20
485.8	0.157	3.69	40
362.3	0.2917	5.54	60
243.7	0.2181	7.38	80
209.3	0.3238	9.23	100

Table 6.

Mechanical properties of highly plastic clay soil samples [22].

According to the results of the study, the research concluded that there is a linear relationship between the initial compressibility index and the degree of water saturation of the soil. As the degree of water saturation of the soil increases, the compressibility index increases, and this relationship is given in the following form: Cc = 0.0027*Sr. + 0.0559.

10.5 Search [A5]

The researcher [24] studied the change in moisture content with changes in pore pressure in the behavior of swelling soil, where a comparison was made between intact soil samples within the odometer experiment (CAUC-UL) [24].

The samples used are intact samples using a tube sample with a diameter of 6.35 cm and a height of 1.7 cm. Sample depths: from 0.5 m to 1.00 m (Figures 10 and 11 and Tables 7–9).

Figure 10.

Mineral analysis of the soil sample (X-ray diffraction of clay Soko, Ngawi).

Figure 11.

The relationship between the degree of water saturation and the percentage of vertical, horizontal and volumetric swelling of the soil [24].

Relative composition (%)	Composition type
76.1	SiO2
18.59	Al2O3
2.75	Fe2O3
1.80	CaO
0.50	MgO
0.22	Na2O
0.04	K2O

Table 7.

Chemical properties of intact clay soil samples [24].

Relative composition (%)	Type of minerals
76.1	Montmorillonite
16.20	Feldspar
5.3	Alpha Quartz
4.30	Halloysite
0.90	Cristobalite

Table 8.

Relative composition of clay soil minerals [24].

Sr (%)	W (%)	Vertical swelling Sx (%)	Horizontal swelling Sy (%)	Volumetric swelling Sv (%)
24.27	10	0.0	0.0	0.0
42.49	20	3.99	1.62	7.38
56.61	30	7.54	3.34	14.85
67.54	40	1.31	4.99	22.70
75.88	50	1.09	6.73	31.10
82.81	60	18.86	8.44	39.37
91.10	70	20.10	9.83	44.89

Table 9.

Mechanical properties of intact clay soil samples [24].

The research concluded according to the results of the study:

1. Swelling of soil is related to the properties of the soil, its chemical composition, and the content of metals in the soil.

2. The behavior of swelling soil is related to the change in water content in the soil according to a linear relationship.

3. The degree of soil saturation with water is linearly related to the percentage of soil deformation, and swelling stops at a total degree of saturation.

11. Research materials and methods

11.1 Swelling soil

Soil samples were brought from the Damascus countryside governorate and As-Suwayda governorate. The samples were extracted using a simple drilling mechanism to a depth of (60 cm) from the bottom of the soil layer. The samples were brought in sealed plastic bags, and then two samples were studied for each site and the samples were named according to the following Table 10.

Site code	Location	Soil color
A	Umm Rawaq Village – Suwayda	dark brown
B	Deir Al-Hajar village – Al-Ghazlaniyah – Damascus countryside	light brown

Table 10.

Soil sample locations.

11.2 Method of forming samples

The method is based on conducting all experiments on the basic physical, classified, mathematical, mechanical and chemical properties of the soil used in this research [4], taking into account the conditions stated in the American specifications (ASTM). In the second stage, the shear resistance properties of the studied soil were calculated (angle of internal friction, cohesion Soil), [14] within a direct shearing experiment [11] for vandalized soil samples and comparing them with samples formed in the laboratory.

• Testing within a direct shear experiment on a sample (uncompressed – undrained),

• (Unconsolidated Undrained Direct Shear Test)

• The sample inside the direct shear device cell was subjected to shear stress at a constant speed (0.2 mm/min).

• Internal shear box dimensions (6.1 cm × 6.1 cm), shear box height (2.3 cm).

The disturbance sample was formed according to the American specification (ASTM D-3080) [11], which requires passing the soil through sieve No. (4) and drying it in the oven at a temperature of (105–110°C). The sample similar to the original sample is formed by pounding it into the mold. (Direct shearing box) in three layers, where each layer has (25 strokes), and thus we obtained a sample similar to the sample formed according to the regular proctor.

The formed sample was formed according to the American standard (ASTM D-3080), which is obtained using a regular proctor (optimal humidity and maximum dry volumetric weight), where the first and last 3 cm of the proctor mold sample were scraped off so that the middle part remained, and from it a sample was taken for the shear square. Direct.

• Thus, the American standard (ASTM D-3080) completely regulates the method of forming samples, and therefore all spoiled and formed samples have the same ideal humidity and the same volumetric weight, and therefore they can be taken as a group and one spirit for study, and the effect is the same on all samples.

• The degree of water saturation of the soil samples from the direct shear experiment was determined by knowing the specific gravity, optimum moisture, and dry volumetric weight according to the Proctor experiment of the soil sample through the following relationship:

$$S_r=\frac{w^{\ast }{G}_s}{e}=\frac{w^{\ast }{G}_s}{\frac{G_s{}^{\ast }{\gamma }_w}{{\gamma }_d}-1}$$E1

$S_r$: Degree of water saturation (%)

$G_s$: Relative specific gravity

${\gamma }_d$: Dry volumetric weight of soil g/cm³

${\gamma }_w$: The volumetric weight of one unit of water, g/cm³

$w$: Optimum humidity according to Proctor’s systematic experience

$e$: Coefficient of porosity

See Table 11.

ASTM	A	B	Units
Specific gravity of solids, Gs	2.68	2.71	g/cm^3
Optimum moisture content, wi	24.30	20	%
Maximum Dry density, w Optimum	1.42	1.55	g/cm^3
Degree of saturation, Sr	72.85	71.88	%

Table 11.

Results of water saturation values for soil samples within the direct shear experiment.

12. Results and discussion

12.1 Results of physical properties

12.1.1 Gradient

The particle size of each of the studied soils was determined by the granular sieve analysis method for particles with diameters larger than (0.075 mm), according to (ASTM-D422), and by the hydrometer sedimentation method for particles with diameters less than (0.075 mm), according to (ASTM-D1140) (Figure 12).

Figure 12.

Hydrometric analysis curve.

12.1.2 Basic physical properties

See Table 12.

ASTM	Site		Unit
	A	B
Natural moisture content	37.1	23.57	%
Relative specific gravity	2.68	2.71	g/cm^3
Volumetric weight	1.62	1.57	g/cm^3
Dry volumetric weight	1.18	1.27	g/cm^3

Table 12.

Results of basic soil physical properties experiments.

12.1.3 Computational physical properties

See Table 13.

ASTM	Site		Unit
	A	B
Voids ratio	1.27	1.13	%
porosity	0.56	0.53	g/cm^3

Table 13.

Results of computational physical properties experiments.

12.1.4 Atterberg limits results

See Table 14.

ASTM	Site		Unit
	A	B
Liquidity limit	65.92	42.73	%
Plasticity limit	33.33	36.76	%
Liquidity index	0.12	0.48	_
Plasticity index	32.59	5.97	%
Percentage of fineness (passing through sieve #200)	97.54	78.18	%
Gluten content	74.56	33.88	%
Celt content	25.44	47.12	%
Sand content	2.46	19	%

Table 14.

Results of experiments on classified soil physical properties.

12.1.5 Classification of the studied soils

The soils for the studied samples were classified according to the American Standard Soil Classification System (USCS) using the Casagrande plasticity scheme [5] as follows:

1. Highly plastic clay soil (CH), which is the soil (Umm Rwaq village), site (A).

2. Low plasticity (ML) silty soil (Deir Al-Hajar village), site (B) (Figure 13).

Figure 13.

Soil classification scheme according to the plasticity scheme.

12.1.6 Results of the systematic Proctor experiment

The aim of conducting the compaction experiment is to determine the maximum dry density and ideal moisture of the studied samples in order to form the samples according to the American standard (ASTM D-3080) (Figure 14 and Table 15).

Figure 14.

Compaction curves for the soil of the two sites (A–B).

ASTM	Site		Unit
	A	B
Ideal humidity	24.3	20.0	%
Maximum dry density	1.42	1.55	g/cm^3
Saturation humidity	33.4	27.8	%

Table 15.

Results of the systemic Proctor experiment.

12.1.7 Results of chemical experiments

See Table 16.

ASTM	Site		Unit	Comments
	A	B
Organic matter content	24.3	20.0	%	It is greater than (2%) and the soil is rich in organic matter
Determine the pH	1.42	1.55	g/cm^3	The soil is moderately acidic

Table 16.

Results of the chemical properties of the soil used in the research.

Figures 15 and 16 represent the metallic analysis of samples using X-ray diffraction, which was conducted at the General Institution of Geology [19].

Figure 15.

Mineral analysis of soil sample /A/.

Figure 16.

Mineral analysis of soil sample /B/.

The most abundant clay mineral in both sites is quartz, which is a mineral that has a weak relationship with water. The presence of quartz in high proportions in the two types of soil explains the low values of plasticity, especially since quartz is known to prevent sintering of soil particles and thus gives low plasticity [25], as in the soil of the site. (B). The soil samples from site (A) contain swollen clay minerals such as montmorillonite and kaolinite, but in low percentages (Table 17).

Types of metals found in the soil	Sample
Quartz – Phillipsite – Gismodine – Kaolinite-Montmorillonite	A
Calcite – Quartz – Mordenite – Forsterite	B

Table 17.

Types of metals found in the samples used in the research.

12.2 Results of direct shear experiments

The figures show the horizontal deformations recorded for the studied specimens with shear stress plotted in normal coordinates.

• Highly plastic soil (fertilized soil-A) (Figure 17):

• Low plasticity soil (fertilized soil-B) (Figure 18):

• Highly plastic soil (Remolded soil – A) (Figure 19):

• Low plasticity soil (B-Remolded soil) (Figure 20):

Figure 17.

The relationship curve between (horizontal deformation and stress) for vandalized samples (A).

Figure 18.

Relationship curve between (horizontal deformation and stress) for vandalized samples (B).

Figure 19.

Relationship curve between (horizontal deformation and stress) for formed samples – (A).

Figure 20.

Relationship curve between (horizontal deformation – stress) for formed samples – (B).

13. Conclusions

Since determining the behavior of swelling soil depends mainly on the metallurgical analysis of the samples, and by comparing the curves of the relationship between (horizontal deformation – shear stress), it was noted that the effect of the disturbance of the samples on low plasticity soil is greater compared to high plasticity soil, as the results of the metallurgical analysis of the samples using X-rays showed X-ray diffraction The types of metals present in the soil samples used in this research are the dominant minerals montmorillonite and kaolinite in terms of their effect on the swelling behavior of the site’s soil (A (high plasticity soil), which is characterized by its high ability to absorb water [26]. It has the advantage of cohesion, which helps maintain the shape of the damaged or laboratory-formed clay sample, thus reducing the amount of disturbance occurring to the sample.

14. Results

Through the previous curves, the results were analyzed to find the amount of relative change between the following variables:

1. The amount of relative change in soil cohesion for vandalized samples and laboratory formed samples.

2. The amount of relative change in the angle of internal friction of the soil for vandalized samples and laboratory-formed samples.

   • Highly plastic soil (Figure 21):

• Low plasticity soil (Figure 22):

Figure 21.

Coulomb’s straight line for damaged samples with shaped samples (A).

Figure 22.

Coulomb’s line for damaged samples with formed samples (B).

The previous results match what was reached in similar studies, where it was found that the disturbance occurring in the vandalized samples leads to a decrease in the values of both soil cohesion and the internal friction angle of the bulging soil, but the amount of decrease was greater for the low-plasticity soil than for the high-plasticity soil, as shown in the following Table 18:

$\left(\Delta \varphi /\varphi \right)$ (%)	ΔC / C (%)	Remolded sample		Disturbance sample		Site
		$\varphi$ (°)	C (kg/cm^2)	$\varphi$ (°)	C (kg/cm^2)
10.7	75.0	26	0.00	23	0.01	A
62.2	60.0	34	0.44	13	0.12	B

Table 18.

Results of the relative change in the mechanical specifications of the studied soil samples.

After analyzing the results, we reached in the previous paragraphs, we reach the following final conclusions and recommendations in this research:

• The behavior of swelling soils tends to change during the formation of samples, and this behavior depends on the properties of the soil, its chemical composition, and the content of swelling metals in the soil.

• Disturbance of the soil structure causes a decrease in the shear resistance variables of the soil (angle of internal friction, soil cohesion), as the disturbance occurring in the vandalized samples leads to a decrease in the values of both soil cohesion and the angle of internal friction for the swelling soil, but the amount of decrease for low-plasticity soil was greater than for high-plasticity soil. Plasticity.

• The amount of relative change in soil cohesion between the destroyed sample and the formed sample ranged between (ΔC/C = 60–85%).

• The amount of relative change in the angle of internal friction of the soil between the damaged sample and the formed sample ranged between.

• Since laboratory evaluation of soil specifications is carried out by conducting laboratory experiments on intact samples, and due to our inability to obtain intact samples, we are often forced to reshape the samples in the laboratory, and therefore the possibility of obtaining mechanical soil specifications (angle of internal friction, soil cohesion) is achieved. Through samples formed according to the regular proctor according to the American code.