Internal Friction Angle Values Research Articles

Engineering properties of pozzolanic cement-stabilised organic soil

In this study, the engineering properties of organic soil (OS) stabilised with pozzolanic cement (PC) were investigated. In tests, 10%, 15% and 20% proportions of PC were added to organic soil. Consistency limits, Proctor, unconfined compressive strength (UCS), triaxial (UU), swelling and compressibility tests were performed for OS stabilised with PC. The addition of PC to OS increased the minimum dry density (MDD) and optimum moisture content (OMC) values. The UCS values for OS stabilised with PC increased up to the 56 th day and then there was a reduction in unconfined compressive strength after the 56 th day. The internal friction angle value increased by 26% and the cohesion intercept value increased by 86% for OS stabilised with PC. With the increase in cement content in OS stabilised with PC, the UCS, internal friction angle and cohesion intercept values increased. Swelling of OS stabilised with PC rapidly reduced up to the 10th day and this reduction slowed after the 10th day. The compressibility of OS stabilised with PC increased until the 10 th day and this increase slowed after the 10th day. With the increase in cement content in OS stabilised with PC, swelling and compressibility values reduced. As a result of the study, it appears that pozzolanic cement is an effective stabiliser for organic soil.

Geotechnical and slope stability analysis in the landslide-prone area: A case study in Sawla – Laska road sector, Southern Ethiopia

Examining the factors underlying landslides and assessing the stability of slopes is crucial for reducing the negative impact of landslides on the environment and the lifespan of infrastructure. This study assessed certain slope portions along the Sawla to Laska Road to determine the factors contributing to landslides and identify the mechanisms and conditions that lead to slope failure. Slope stability analysis was conducted using the limit equilibrium method, and a range of laboratory tests were conducted following ASTM standards. The analysis has shown that the three slope portions, specifically sections 1, 2, and 3, had distinct shear strength characteristics, as shown by variations in their cohesion and internal friction angle values. The average values for cohesion were 19.24, 10.41, and 12.9, respectively, while the internal friction angle values ranged from 11.32 to 17.8 for slope section three, 18.96 to 21.12 for slope section two, and 30.08 to 37.26 for slope section one. The limit equilibrium method was utilized to compute the safety factor of slopes. Five methods were employed to evaluate the safety factor: the ordinary method, Bishop method, Janbu method, Spencer method, and Morgenstern-Price method while considering three groundwater conditions (GWT at great depth, GWT at half of the slope, and GWT on the surface). Only slope section one exhibited a slightly stable safety factor that exceeded one under dry conditions. The slope-mass rating analysis showed that rock slopes one and two were deemed stable under class II, rock slopes three and four were partially stable under class III, and rock slope five was unstable under class IV. A slope mass range of 78 to 79 indicates excellent to very good rock mass quality and high stability potential for RSs1. In contrast, RSs5 shows a wide SMR range from 7 to 57, indicating a spectrum of very poor to fair to good quality rock mass and an associated range of stability from extremely low to moderate. RSs2 and RSs3 fall within the SMR range of 71.1–72 and 49.9–55.9, respectively, indicating good to fair rock mass quality with varying degrees of stability potential. Last, RSs4, with an SMR range of 39.6–45.1, shows poor rock mass quality and substantial stability concerns. RSs1 has a UCS of 28.68 MPa, indicating a "Medium strong" classification, and it belongs to the lithology type of "Trachyte." RSs2 showcases a higher UCS value of 32.25 MPa, similarly classified as "Medium strong," and is also identified as "Trachyte." RSs3, with a UCS of 28.83 MPa, falls under the "Medium strong" classification and is categorized as "Basalt." In contrast, RSs4 demonstrates a lower UCS of 18.41 MPa, leading to a "Weak" classification associated with the lithology type "Basalt." Lastly, RSs5 presents a UCS of 25.77 MPa, classified as "Medium strong," and shares the lithology type of "Basalt." The study identified that the landslide types in the study area were rockfall, earth flow, and soil/rock slides. The factors contributing to landslides in the study area were slope steepness, weathering, groundwater, and rainfall.

Comparative analysis of the expansion rate and soil erodibility factor of some gullies in Nnewi and Nnobi, Southeastern Nigeria

The research focused on assessing the expansion rate and soil erodibility factor (K) of specific gullies located in Nnewi and Nnobi, Southeastern Nigeria. Fifteen representative gullies were studied extensively. The Grain size distribution analysis revealed that the soils are composed of gravel (5.77–17.67% and 7.01–13.65%), sand (79.90–91.01% and 82.47–88.67%), and fines (2.36–4.05% and 3.78–5.02%) for Nnewi and Nnobi respectively. The cohesion and internal friction angle values range from 1–5 to 2–5 kPa and from 29–38° to 30–34° for Nnewi and Nnobi respectively, which suggests that the soils have low shear strength and are susceptible to shear failure. The plasticity index (PI) of the fines showed that they are nonplastic to low plastic soils and highly liquefiable with values ranging from 0–10 to 0–9% for Nnewi and Nnobi respectively. Slope stability analysis gave factor of safety (FoS) values in the range of 0.50–0.76 and 0.82–0.95 for saturated condition and 0.73–0.98 and 0.87–1.04 for unsaturated condition for both Nnewi and Nnobi respectively indicating that the slopes are generally unstable to critically stable. The erosion expansion rate analysis for a fifteen-year period (2005–2020) revealed an average longitudinal expansion rate of 36.05 m/yr and 10.76 m/yr for Nnewi and Nnobi gullies respectively. The soil erodibility factor (K) are 8.57 × 10−2 and 1.62 × 10−4 for Nnewi and Nnobi respectively indicating that the soils in Nnewi have higher erodibility potentials than those of Nnobi. Conclusively, the Nnewi area is more prone to erosion than the Nnobi area.

Laboratory Geotechnical Investigations on Five Silty Soils Sampled along the Banks of the Lubumbashi River/Haut-Katanga/DR Congo

An adequate design of port structures along waterways requires a good knowledge of the geotechnical properties of the surrounding soils. This study aims to characterize the geotechnical laboratory properties of alluvial soils along the Lubumbashi river (section between the Tshombe and Tshondo bridges, approximately 3 km long) in the city of Lubumbashi, province of Haut Katanga in DR Congo. To meet this objective, five sampling zones were selected from which samples were taken with a hand auger and various geotechnical laboratory tests were performed. Identification tests reveal that the tested soils have low to moderate plasticity and are in the range of sandy silt to silty sand with a low fraction of clay particles, essentially inactive. Oedometric compression tests reveal that the soils in place are (moderately) compressible. The consolidated undrained (CU) triaxial compression and direct shear tests indicate effective values of internal friction angle and negligible drained cohesion that, are consistent for this kind of soil. In the end, the compressibility and strength parameters of the five tested soils are correlated with their plasticity index, showing a decrease in the shear strength and an increase in the compressibility when the plasticity index increase.

ULTIMATE BEARING CAPACITY OF RING FOOTINGS ON SAND

The ultimate bearing capacity of ring footings for different conditions such as internal to external diameter ratio and angle of internal friction for sand is determined using the finite element program ELPLA Professional Edition, Version 9.0. A semi-empirical relation for determining the bearing capacity of ring footings that developed by other researchers is also described and used in compared. The value of ultimate bearing capacity is found to decrease significantly with an increase in (r =di/de), where di and de are the internal and external diameter of the ring, respectively. For larger values of internal friction angle of soil (), the magnitude of ultimate bearing capacity is seen to be higher than smaller values. The obtained results are compared with those available in the literature.

Geotechnical Evaluation of Loess Modifications as the Sustainable Compacted Soil Liner Material in Solid Waste Landfill.

This paper studied the anti-seepage ability of the modified loess by using attapulgite, which is abundant in local areas. The possibility of using the modified loess as the sustainable compacted soil liner material in a solid waste landfill was also considered in this research. The materials were then evaluated using Nuclear Magnetic Resonance (NMR), Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), and an Impermeability Mechanism (IM). The experimental results showed that the permeability coefficient of the attapulgite-modified loess decreases significantly with increasing attapulgite content. However, it becomes less significant when the attapulgite level approaches 10%. Both cases can meet the landfill impermeability requirements, based on the attapulgite content remaining at 10%, adding 15% lime or 5% cement, respectively. The triaxial consolidation and drainage experiment was carried out to investigate the shear strength of the materials under three different working circumstances. The stress–strain curves of each specimen were produced, as were the cohesion and internal friction angle values. This research lays the groundwork for using attapulgite-modified loess as a landfill lining material. It establishes a solid platform for future studies on attapulgite adsorption and purifying performance in landfills.

Internal friction angle model of particles

Currently, pressure from industry to streamline processes by creating their simulation models, and thus to gradual digitization is increasing. The essence of representative simulation models of bulk materials is to understand the principles and laws of the real behavior of particles. The aim of this study is therefore to find and quantify the possibilities and principles of how particles can change their position relative to other particles. The possibilities of particle displacements were expressed using their specific trajectories and work ratios, or internal friction angle values. This created a new comprehensive model of the internal friction angle of particles independent of particle size. It enables the interpretation of the determined values of the angles of internal friction of particles and its application in the field of simulations of mass and process models. The model can be used to determine the basic composition of particles in volume and the dominant ways of their mutual displacements.

The comparative analysis of methods for determining the mechanical performance of macrofragmental soils

Many researchers, including Marachi, Frost, Varadarajan, Mojtaba, Gupta, Kuznetsov and others, have investigated the mechanical properties of coarse clastic soils. In this work, two methods were considered to determine the strength and deformation characteristics of coarse clastic soil.The first method is based on the determination of normative values for the mechanical properties of coarse clastic soils based on their physical characteristics (developed by the Far Eastern Research Institute for Structural Design and Technology (FERISDT)), and the second method is based on consolidated-drained (CD) tests in a triaxial compression device at five different values of hydrostatic pressure. According to the results of the study carried out in accordance with the two methods, a significant difference in the values of specific cohesion and deformation modulus of the coarse clastic soil was obtained.The values of specific adhesion obtained by FERISDT method are nearly two times lower than those obtained by triaxial tests. While the specific cohesion has been largely influenced by aggregate percentage, the values of in-ternal friction angle and the modulus of deformation changed only slightly.

In Situ Needle Penetration Test and Its Application in a Sericite Schist Railway Tunnel, Southwest of China

AbstractThe sericite schist is a typical metamorphic soft rock. Large deformation of surrounding rock often occurs in the construction of a tunnel in this stratum. Due to the broken rock mass structure and poor mechanical strength in Baishitou tunnel project of Dalin line of Southwest railway, it is impossible to prepare standard samples for a traditional rock mechanical test. Therefore, we chose penetrometer (SH-70) for an in situ test. Firstly, we monitored the deformation of typical sections and analyzed the characteristics of large deformation of soft rock in the tunnel. Secondly, we tested the needle penetration index of fresh excavation face and side wall. Then, we estimated some mechanical parameters of sericite schist by a needle penetrometer and Hoek-brown criterion and discussed the acquisition of mechanical parameters of soft rock. The results show the following: (1) the characteristics of extrusion rock tunnel are summarized as large deformation, fast deformation rate, and obvious construction disturbance. (2) The reference value of penetration index of sericite schist (the vertical joint direction) is 3.90~7.77 N/mm, and the parallel joint direction is 1.27~2.99 N/mm. (3) The uniaxial compressive strength estimated by a penetrometer is 0.78~8.53 MPa, and the strength of the surrounding rock is negatively correlated with the amount of deformation. Therefore, it can be considered that the insufficient strength of surrounding rock is the fundamental reason for large deformation. (4) The reference value of cohesion of sericite schist estimated by a penetrometer is 0.203 MPa, and the reference value of internal friction angle is 18.224°. Compared with the common estimation methods, the penetrometer is more convenient and economical, which can provide a new idea for obtaining the mechanical parameters of sericite schist soft rock tunnel.

PENGARUH LEBAR PONDASI TERHADAP KEDALAMAN MUKA AIR TANAH DI BAWAH DASAR PONDASI DALAM MENENTUKAN BESARNYA DAYA DUKUNG ULTIMIT DAN DAYA DUKUNG AMAN PONDASI MENERUS PADA TANAH LUNAK DENGAN METODE TERZAGHI PADA KONDISI KERUNTUHAN GESER LOKAL

The foundation is the lowest part of the building that continues the load force into the soil or rocks in the soil. Longitudinal foundations are foundations that support elongated walls and rows of closely spaced columns so that if you use a footed foundation, the sides coincide. The design of the foundation must meet the requirements of the safety factor with a value of more than equal to three and the settlement of the foundation is within the tolerance limit. Long-term stability of the foundation must pay attention to the location of the base of the foundation in order to reduce the risk of swelling and shrinkage of the soil, erosion of the foundation surface, scouring on the foundation walls and other soil disturbances.
 The method used in this study is the terzaghi method because the soil layer is homogeneous and the internal friction angle is < 29o. The ultimate bearing capacity of Terzaghi is used to calculate the bearing capacity of granular soils and soils that have internal friction angle values (Ø) and cohesion (c).
 The depth of the groundwater table from the base of the foundation greatly affects the ultimate bearing capacity and the safe bearing capacity of the foundation. The further away the groundwater table is from the base of the foundation, the greater the value of the ultimate bearing capacity of the foundation (qu) causing the higher value of the foundation's safe bearing capacity (qs).
 This study analyzes local shear failure with the highest ultimate bearing capacity of 173.36 t/m2 and the largest safe bearing capacity of 59.56 t/m2 occurs when the depth of the groundwater table is greater than the width of the foundation, while the lowest ultimate bearing capacity is 170.72 t/m2. m2 and the lowest safe bearing capacity of 58.68 t/m2 occurs when the water level is at the base of the foundation.

Triaxial creep tests of glacitectonically disturbed stiff clay – structural, strength, and slope stability aspects

Abstract This study concerns the creep impact on strength parameters of the selected very cohesive soils (PI = 30–70%). The analysis refers to Neogene clays characterized by a complex structure, resulting directly from a complicated load history in the geological time scale and identified glacitectonic deformations. In the process of samples’ preparation for strength tests as well as during the interpretation of the post-failure state, particular attention was paid to the soil structure. The imaging methods (X-ray densitometry and computer microtomography) enabled the comparison of the soil structure and the selection of samples with similar characteristics. The completed program of strength tests consisted of two series of tests in the triaxial stress state, differentiated by the occurrence of the initial creep stage, preceding the typical strength test scheme under undrained conditions. This study allowed to obtain a quantitative assessment of the influence of the creep process on the strength parameters of tested soils. Constant stress lower than 60% of the shear stress deviator leads to the deceleration creep course (m parameter 0.64–0.89). As a result, higher values of internal friction angle (20% increase comparing to triaxial tests without creep stage) and cohesion reduction are obtained from triaxial creep tests. Creep parameter m is found to be a valuable indicator for differentiation of landslide activity trend. The tests proved low values of axial strains (1–5%) at failure, which was associated with lithogenesis. By the implementation of obtained strength parameters into the 3D finite element model of the slope, the potential influence of the creep process on the stability of an exemplary cross section of the Warsaw slope could be determined.

Experimental study on shear strength parameters of municipal solid waste employing a large direct shear apparatus

ABSTRACT In this study, in order to conduct shear tests on solid waste samples encompassing waste materials of all/actual sizes (unlike many previous studies), a large direct shear device (with the capacity of 100 × 100 × 110 cm3 test samples) is designed, built, and put into practice. Disturbed (and remoulded) municipal solid waste (MSW) samples of 10 years old, taken from local landfill, are tested with shear stresses being applied under strain-controlled conditions. Two sets of tests in the form of four consolidated-drained (CD) or slow and four consolidated-undrained (CU) or quick direct shear tests are performed. The results clearly indicate that MSW, in this specific landfill, mainly show a frictional behaviour with friction angles of 31.4 (for CD/slow tests) and 38.6 (for CU/quick tests) degrees, and the cohesion values of almost zero for both sets of tests. Higher value of internal friction angle obtained from the undrained tests is attributed to the changes occurring in sample structure, texture, and composition after being completely saturated with water. These values are within the range of shear strength parameters of MSW reported in the literature. In addition, shear stress-displacement responses of all MSW samples show normally consolidated with high compressibility characteristics and strain hardening behaviour.

Classification and effect of compaction on soil shear strength by direct shear test on peat soil of Tapanuli Utara Regency, North Sumatera Province

Planning for development on peat soil requires an understanding of the behavior of peat soil because of the large potential damage that can occur to buildings on peat. The points of this study were to determine the index properties, to classify the peat soil classifications, and to determine the effect of compaction on internal friction angles and cohesion values. The water content of Pohan Tonga peat soil was 729.33% and the specific gravity was 1.302. Based on ASTM D442-84, the sample of peat soil was classified as medium ash peat because it had ash content of 8.260%, and was classified as moderately acidic because of its pH value of 5.5. From Standard Proctor test, the optimum moisture content obtained was 98% and maximum dry unit weight was 0.419 gr/cm3. The effect of compaction increased the dry unit weight value of the undisturbed sample from 0.126 g/cm3 to 0.454 gr/cm3 of 108% sample. The highest value of internal friction angle in peat was obtained from 108% sample, namely 5.391° with a cohesion of 0.024 MPa compared to undisturbed sample which had internal friction angle of 0.375° with a cohesion of 0.019 MPa.

GIS-Based Landslide Susceptibility Map Verification by its Geotechnical and Geological Characteristics

The famous 2006 Laplae rainfall-triggered landslide has caused hundreds of million Baht lost. The objective of this paper is to evaluate and to compare present geotechnical and geological conditions between the landslide area and landslide-free area to verify a landslide susceptibility map. Detailed field surveys acquired 14 samples: undisturbed, disturbed soils as well as rocks. Sensitivity and back-analysis were also performed. 35.44% of landslides occurred in meta-shale - greywacke-interbedding Formation, and another 64.56% happened in meta-greywacke - basaltic andesite Formation. The dominant slope of the landslide is in 300-400 slope, with aspects toward South direction, and in a range of <1,000 meters from geological structures. Landslide area is distinguished from the non-landslide area by its various grades of materials, lower quartz content, higher clay content, finer composition of parental rocks and soils, higher average ratio of smectite versus quartz, lower compressive strength, lower shear strength, lower angle of internal friction, lower cohesion value, more poorly graded, higher soil moisture, higher liquid limit and plasticity index, and factor of safety is generally less than 1. The result of the sensitivity analysis indicated that in a failure condition, the cohesion and angle of internal friction angle values are equal to 2.51 kPa and 13.700, respectively. However, the results of laboratory tests showed that the cohesion and angle of internal friction values are equal to 8.59 kPa and 14.20. These results verified the landslide susceptibility map that the high landslide susceptibility area has the engineering characteristics of the landslide-prone area, while the low susceptible one has the characteristics of the non-landslide area.

Improvement of shear strength characteristics of İzmir Bay’s dredged soil

In the last decades, Izmir Bay is negatively affected both environmentally and commercially due to the alluvial deposits carried by Gediz River and other rivers around. To find a solution to this problem, “Izmir Bay and Port Rehabilitation Project” was conducted. After the dredging process, approximately 22 million m3 of dredged soil was unearthed in and around the bay. The dredged soil comprises organic matter; thus, it has a problematic internal structure which has many uncertainties. Therefore, the engineering properties must be comprehensively clarified. In this study, the geotechnical properties of the dredged soil with different organic matter contents (0, 4, 7, and 11% OM) were investigated, and the shear strength behavior was examined with the direct shear test. First, shear strength characteristics of natural dredged material were defined and then, it was aimed to improve the shear strength properties with lime (L), silica fume (S), and thermal power plant fly ash (T). To define the internal structure of dredged soils with different organic matter contents, SEM, FTIR, and XRD analyses were conducted. The specific gravities ranged from 2.52 to 2.76, and the liquid limits ranged between 32.6 and 39.5. The plastic limit values are between 26.4 and 31.0. The plasticity of the dredged soil showed a proportional increase as the percentage of organic matter increased. The internal friction angles of dredged materials were ranged between 34 and 40°. Stabilization process positively affected the internal friction angle with all additive materials. Although lime-added samples have higher internal friction angle values for 20% additive content, silica fume and thermal power plant fly ash–added samples have higher internal friction angle values for 10% additive content.

Wellbore stability analysis to determine the safe mud weight window for sandstone layers

The wellbore stability of a vertical well through the sandstone reservoir layers of the Asmari oil-bearing formation in south-west Iran is investigated. The safe drilling-fluid density range for maintaining wellbore stability is determined and simulated using FLAC3D software and a finite volume model established with drilled strata geomechanical features. The initiation of plastic condition is used to determine the safe mud weight window (SMWW) in specific sandstone layers. The effects of rock strength parameters, major stresses around the wellbore and pore pressure on the SMWW are investigated for this wellbore. Sensitivity analysis reveals that a reduction in cohesion and internal friction angle values leads to a significant narrowing of the SMWW. On the other hand, the reduction of pore pressure and the ratio between maximum and minimum horizontal stresses causes the SMWW to widen significantly. The ability to readily quantify changes in SMWW indicates that the developed model is suitable as a well planning and monitoring tool.

Investigation of Soil Active Wedge Angle with Linear Matric Suction Distribution Below the Footing

In this paper, a theoretical approach is established to determine the active wedge angle of unsaturated soils, based on the limit equilibrium method, while matric suction varies linearly with respect to depth. In the previous researches, constant suction distribution profile within the soil has been pointed out, however, generally linear and nonlinear suction profiles develop above the ground water table. The range of suction value covers transition zone and residual zone of unsaturation. Sensitivity of the proposed model, with respect to different parameters, shows that the value of active wedge angle is more dependent on the internal friction angle, in comparison to other properties. Therefore, instead of a complex relation, simple equation can be used. The results show that the active wedge angle for unsaturated soils is equal to $$\frac{\pi }{6} + \frac{7}{8}\phi$$. Comparisons between the presented model and experimental data show that, for some values of internal friction angle, the active wedge angle in unsaturated state is close to saturated state.

Effects of clay properties in the landslides genesis in flysch massif: Case study of Aïn Draham, North Western Tunisia

Heavy rainfall in Aïn Draham province in the North-Western of Tunisia lead to the formation of some landslides which could poses danger to lives and properties. The geological outcrops of the region mainly consist of Numidian flysch rocks. In this study, field based 15 undisturbed samples were taken, from 11 boreholes drilled in 4 landslide points, to understand the real behaviour of soils when landslides occur. For this purpose, the geotechnical characterization of all samples was carried out. The grain size distribution shows that the clay and silt fractions prevail. The clay fraction ranges between 4% and 64% with an average of 40.4%, the silt fraction ranging from 19% to 71% averaging 39.8% and the sand fraction was between 6% and 44% with an average of 19.8%. The Casagrande plasticity chart indicates that 33.3% of samples were in the high plasticity group (CH group) and 66.6% having a medium to low plasticity. The water content varies between 12% and 31%. The direct shear strength test shows that the cohesions values range from 41 KPa to 77 KPa and the internal friction angle values range widely from 12° to 27°. A statistical approach was taken to determine the most important factors responsible for the decrease of the cohesion and friction angle which are in charge of slope failure. For this, a correlation matrix of all soil properties was done. The coefficients of correlation show that the clay fraction is the most correlated parameter to the cohesion with an index of −0.872. Unfortunately, the internal friction angle is very low correlated to all geotechnical parameters. The clay fraction, as the most correlated to the cohesion, and the water content, which depends on rainfall (landslide triggering factor), were considered as two independent parameters for the establishment of a multiple linear and non-linear regression models of the cohesion. The multiple linear model showed that the cohesion decrease with the increase of water content and especially the increase of clay fraction with coefficients of −0.083 and −0.441, respectively. The non linear model showed that the cohesion decrease exponentially and linearly with the increase of the clay fraction and water content, respectively. The statistical study of the effect of geotechnical parameters on the landslide triggering, shows that the clay formations and also the increases of soils clay fraction by alteration phenomena is the crucial factor in landslides genesis. During rainfall the increase of the water content of clayey soils decreases the shear strength of soils more and more.

Effect of cement injection on sandy soil slope stability, case study: slope in Petang district, Badung regency

Slope is a part of soil topography formed due to elevation difference from two soil surface. Landslides is frequently occur in natural slope, it is because shear force is greater than shear strength in the soil. There are some factor that influence slope stability such as: rain dissipation, vibration from earthquake, construction and crack in the soil. Slope instability can cause risk in human activity or even threaten human lives. Every years in rainy season, landslides always occur in Indonesia. In 2016, there was some landslide occurred in Bali. One of the most damaging is landslide in Petang district, Badung regency. This landslide caused main road closed entirely. In order to overcome and prevent landslide, a lot of method have been practiced and still looking for more sophisticated method for forecasting slope stability. One of the method to strengthen soil stability is filling the soil pores with some certain material. Cement is one of the material that can be used to fill the soil pores because when it is in liquid form, it can infiltrate into soil pores and fill the gap between soil particles. And after it dry, it can formed a bond with soil particle so that soil become stronger and the slope as well. In this study, it will use experimental method, slope model in laboratory to simulate a real slope behavior in the field. The first model is the slope without any addition of cement. This model will be become a benchmark for the other models. The second model is a slope with improved soil that injects the slope with cement. Injection of cement is done with varying interval distance of injection point is 5 cm and 10 cm. Each slope model will be given a load until the slope collapses. The slope model will also be analyzed with slope stability program. The test results on the improved slope models will be compared with unimproved slope. In the initial test will consist of 3 model. First model is soil without improvement or cement injection, second model is soil with cement injection interval 5 cm and third model is soil with cement injection interval 10 cm. The result is the shear strength (ϕ value) the soil is increase from 32.02° to 47.57°. The increase value of internal friction angle (ϕ) shows that an increase in shear strength of the cement improved soil. While, the value of cohesion (c) is zero indicating there is no cohesion in the soil. This is common for sand soil or sandy soil. The calculation of safety factor with GeoStructural Analysis obtained an increase of safety factor from 0.78 if the soil without cement injection to 1.07 and 1.17 if the soil is injected with cement at a distance of 10 cm and 5 cm.

A Correction Term in the Terzaghi Equation for Subsoil Bearing Capacity Analysis

This paper proposes to introduce an additional term in the Terzaghi trinomial equation for more accurate evaluation of strip and circular footing bearing capacity for any ratios of soil cohesion over soil specific weight. Some effects connected up with footing shape and circular footing solution for high values of internal friction angle are discussed.