Reliability analysis of drilled piers in expansive soils

1991 ◽  
Vol 28 (6) ◽  
pp. 834-842 ◽  
Author(s):  
Carlos Ferregut ◽  
Miguel Picornell
Keyword(s):  
Probabilistic Models ◽  
Load Transfer ◽  
Expansive Soils ◽  
Free Field ◽  
Expansive Soil ◽  
Maximum Tensile Stress ◽  
Limit States ◽  
Tensile Stresses ◽  
Head Displacement ◽  
Soil Movements

Heavy structures in areas with expansive soils are commonly founded on piers resting beneath the surface active zone. During construction, the piers remain essentially unloaded and are exposed to potentially high tensile stresses that can split the pier unless the pier has been adequately reinforced. In this context, uncertainties arise relative to (i) the parameters governing the load transfer from the soil to the pier, (ii) the potential heave to be expected in a "free field" condition, when the soil movements are not restricted by the pier, and (iii) the estimation of the pier capacity to resist the induced stresses. Probabilistic models to handle and to quantify these uncertain parameters are constructed and then used to compute the probability of exceeding two potential limit states: (i) vertical pier head displacement and (ii) maximum tensile stress in a cross section of the pier. The displacements are used to assess the serviceability performance of the pier, and the maximum tensile stresses are used to estimate the reliability of the pier. Key words: piers, expansive soil, reliability, probability, foundations.

The Australian Approach to Residential Footing Design on Expansive Soils

2013 ◽  
Vol 438-439 ◽  
pp. 593-598
Author(s):  
Jie Li ◽  
An Nan Zhou
Keyword(s):  
Arid Regions ◽  
Current Practice ◽  
Expansive Soils ◽  
Residential Buildings ◽  
Expansive Soil ◽  
Site Classification ◽  
Residential House ◽  
Semi Arid ◽  
Soil Movements

Expansive soils in semi-arid regions are of great concern to design and geotechnical engineers. Damage to residential buildings resulting from expansive soil movements has been widely reported in Australia. This paper describes the current practice in Australia, which includes the site classification, laboratory tests and residential footing design. A case study of a residential house damaged by expansive soils is also presented.

scholarly journals GEOTECHNICAL STRUCTURES: INVESTIGATION OF DRILLED SHAFTS IN HIGHLY EXPANSIVE SOILS

2014 ◽  
Vol 6 (2) ◽  
pp. 69-76 ◽  
Author(s):  
Mohammed Faruqi ◽  
Eliborio Pena ◽  
Jina Balogh
Keyword(s):  
Load Transfer ◽  
Expansive Soils ◽  
Expansive Soil ◽  
Drilled Shafts ◽  
Positive Skin ◽  
Vertical Movements ◽  
Load Carrying ◽  
Potential Failure ◽  
Support Conditions ◽  
Corrosion Of Steel

Construction over extremely expansive soils raises the risk of structural foundation failure and potential failure to the building itself. This is due to shrinkage and swell characteristics of expansive soils. This works presents an extensive case study of a distressed building built on drilled piers and expansive soil, and describes innovative practical ideas that can be used in the renovation of its foundation. The building is located west of San Antonio, Texas, USA. This building has experienced significant settlements and differential building movement resulting in widespread building distress. The following foundation based structural distresses were found in the building: 1) vertical movements of more than 300 mm, 2) bearing surface had completely spalled away and the beams were supported solely by bent and corroded anchor bolts which were not well confined in the surrounding concrete, 3) the beam rotations and lateral movement caused the steel stub columns supporting the floor framing to tilt sideways. This created eccentric support conditions that could result in sudden instability failure of either the beams or columns, and 4) under bathrooms in the northwest corner of the building, significant corrosion of steel framing was observed due to long term exposure to moisture leaking through cracks in the floor slab above. Drilled piers were studied using spot study, soil data obtained from boreholes and laboratory tests based on American standards. It is recommended that 0.5 m diameter piers of lengths 18.3 m with positive skin friction to prevent uplift, and a load carrying capacity of 1737 kN be used to rehabilitate the failing foundation. Also, new shafts are to be designed for a minimum factor of safety 2.5 and the rejection of an unacceptable pier required installation of one or more replacement piers at locations that would facilitate load transfer from the structure above.

scholarly journals The Use of Geogrids in Mitigating Pavement Defects on Roads Built over Expansive Soils

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Richard Shumbusho ◽  
Gurmel S. Ghataora ◽  
Michael P.N. Burrow ◽  
Digne R. Rwabuhungu
Keyword(s):  
Seasonal Changes ◽  
Expansive Soils ◽  
Expansive Soil ◽  
Real Field ◽  
Experimental Program ◽  
Swelling Potential ◽  
Swelling Behaviour ◽  
Wetting And Drying ◽  
Potential Benefits

This study was conducted to investigate the potential benefits of using geogrids in mitigating pavement defects notably roughness and longitudinal cracking on pavements built over expansive soils. The seasonal changes of expansive soils (periodic wetting and drying) cause detrimental effects on the overlying road pavements. Such detrimental behavior of expansive soils was simulated in a controlled laboratory environment through allowing cyclic wetting and drying of an expansive soil underlying a pavement section. The shrink/swell effects of the expansive soil subgrade were examined through monitoring its change in moisture, and measuring deformation of overlying pavement section. The experimental study suggested that a geogrid layer in a reinforced pavement section can reduce surface differential shrinking and swelling deformation resulting from underlying expansive soils by a factor of 2 and 3 respectively in comparison to unreinforced section. Given that an oedometer test which is typically used to predict swelling potential of expansive soils is known to overpredict in-situ soil swell, experimental program also investigated quantitatively the extent to which the oedometer can overestimate swelling behaviour of the real-field scenarios. It was found that oedometer percent swell can overpredict in-situ swelling behaviour of the expansive soil by a factor ranging between 2 and 10 depending upon the period over which the in-situ expansive soil has been in contact with water.

scholarly journals Reliability-Based Safety Evaluation of the BISTOON Historic Masonry Arch Bridge

2020 ◽  
Vol 30 (1) ◽  
pp. 87-110 ◽  
Author(s):  
Majid Pouraminian ◽  
Somayyeh Pourbakhshian ◽  
Ehsan Noroozinejad Farsangi ◽  
Sevil Berenji ◽  
Salman Keyani Borujeni ◽  
...  
Keyword(s):  
Probabilistic Analysis ◽  
Safety Evaluation ◽  
Random Variables ◽  
Load Resistance ◽  
Maximum Tensile Stress ◽  
Safety Index ◽  
Limit States ◽  
Masonry Arch ◽  
Arch Bridge ◽  
Historic Masonry

AbstractThis research examines the probabilistic safety assessment of the historic BISTOON arch bridge. Probabilistic analysis based on the Load-Resistance model was performed. The evaluation of implicit functions of load and resistance was performed by the finite element method, and the Monte-Carlo approach was used for experiment simulation. The sampling method used was Latin Hypercube. Four random variables were considered including modulus of elasticity of brick and infilled materials and the specific mass of brick and infilled materials. The normal distribution was used to express the statistical properties of the random variables. The coefficient of variation was defined as 10%. Linear behavior was assumed for the bridge materials. Three output parameters of maximum bridge displacement, maximum tensile stress, and minimum compressive stress were assigned as structural limit states. A sensitivity analysis for probabilistic analysis was performed using the Spearman ranking method. The results showed that the sensitivity of output parameters to infilled density changes is high. The results also indicated that the system probability of failure is equal to p fsystem =1.55 × 10−3. The bridge safety index value obtained is βt = 2.96, which is lower than the recommended target safety index. The required safety parameters for the bridge have not been met and the bridge is at the risk of failure.

scholarly journals STABILISASI TANAH EKSPANSIF MENGGUNAKAN KAPUR DAN SPENT CATALYST UNTUK TANAH DASAR PERKERASAN

2019 ◽  
Vol 19 (1) ◽  
pp. 21-30
Author(s):  
Arifudin Nur ◽  
Suryo Hapsoro Tri Utomo ◽  
M. Zudhy Irawan
Keyword(s):  
Soil Stabilization ◽  
Expansive Soils ◽  
Expansive Soil ◽  
Petroleum Processing ◽  
Spent Catalyst ◽  
Maximum Increase ◽  
Lime Content ◽  
Road Pavement ◽  
Pozzolanic Material ◽  
Spent Catalysts

Abstract Expansive soils have high swelling and shrinkage potentials, which may cause damage to road structures. Therefore, stabilization is required. One method of stabilization is to use lime and spent catalysts with the aim of increasing carrying capacity and reducing swelling. Spent catalyst is a petroleum processing waste and classified as pozzolanic material. The addition of lime and spent catalysts can increase the CBR value and reduce swelling of soils. The results of this study indicate that the maximum increase in soaked CBR and unsoaked CBR values occurred in soil mixtures with optimum lime content and 12% spent catalyst with 7 days of curing. While the soil mixture with optimum lime content and 12% spent catalyst, with 7 days of curing, is the best mixture that produces soaked CBR value of 49.67%, swelling of 0.15%, and plasticity index value of 11.97%, so the soil meets the requirements to be used as pavement subgrade. Keywords: expansive soil, stabilization, road structure, subgrade, road pavement  Abstrak Tanah ekspansif memiliki potensi pengembangan dan penyusutan yang tinggi, sehingga dapat menyebabkan kerusakan struktur jalan. Oleh sebab itu, perlu dilakukan stabilisasi. Salah satu metode stabilisasi adalah menggunakan kapur dan spent catalyst dengan tujuan meningkatkan kapasitas dukung dan menurunkan swelling. Spent catalyst merupakan limbah pengolahan minyak bumi dan termasuk bahan pozzolan. Penam-bahan kapur dan spent catalyst mampu meningkatkan nilai CBR dan mereduksi swelling. Hasil studi ini menunjukkan bahwa peningkatan maksimum nilai CBR soaked maupun CBR unsoaked terjadi pada campuran tanah dengan kadar kapur optimum dan 12% spent catalyst dengan peraman 7 hari. Sedangkan campuran tanah dengan kadar kapur optimum dan 12% spent catalyst, dengan peraman 7 hari, merupakan campuran terbaik yang menghasilkan nilai CBR soaked sebesar 49,67%, swelling sebesar 0,15%, dan nilai indeks plastisitas sebesar 11,97%, sehingga tanah memenuhi syarat untuk digunakan sebagai tanah dasar perkerasan jalan. Kata-kata kunci: tanah ekspansif, stabilisasi, struktur jalan, tanah dasar, perkerasan jalan

scholarly journals Finite Element Simulation and Multi-Factor Stress Prediction Model for Cement Concrete Pavement Considering Void under Slab

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5294
Author(s):  
Bangyi Liu ◽  
Yang Zhou ◽  
Linhao Gu ◽  
Xiaoming Huang
Keyword(s):  
Finite Element ◽  
Tensile Stress ◽  
Concrete Slab ◽  
Three Dimensional ◽  
Mesh Size ◽  
Maximum Tensile Stress ◽  
Concrete Pavement ◽  
Slab Thickness ◽  
Void Size ◽  
Tensile Stresses

Uneven support as result of voids beneath concrete slabs can lead to high tensile stresses at the corner of the slab and eventually cause many forms of damage, such as cracking or faulting. Three-dimensional (3D) finite element models of the concrete pavement with void are presented. Mesh convergence analysis was used to determine the element type and mesh size in the model. The accuracy of the model is verified by comparing with the calculation results of the code design standards in China. The reliability of the model is verified by field measurement. The analysis shows that the stresses are more affected at the corner of the slab than at the edge. Impact of void size and void depth at the slab corner on the slab stress are similar, which result in the change of the position of the maximum tensile stress. The maximum tensile stresses do not increase with the increase in the void size for relatively small void size. The maximum tensile stress increases rapidly with the enlargement in the void size when the size is ≥0.4 m. The increments of maximum tensile stress can reach 183.7% when the void size is 1.0 m. The increase in slab thickness can effectively reduce maximum tensile stress. A function is established to calculate the maximum tensile stress of the concrete slab. The function takes into account the void size, the slab thickness and the vehicle load. The reliability of the function was verified by comparing the error between the calculated and simulated results.

scholarly journals Experimental Study on Dynamic Resilient Modulus of Lime-Treated Expansive Soil

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Zheng Lu ◽  
Yang Zhao ◽  
Shaohua Xian ◽  
Hailin Yao
Keyword(s):  
Moisture Content ◽  
Environmental Changes ◽  
Resilient Modulus ◽  
Expansive Soils ◽  
Expansive Soil ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
The Stability ◽  
Compaction Degree

Dynamic resilient modulus is the design index of highway subgrade design code in China, which is significantly affected by the traffic loads and environmental changes. In this study, dynamic triaxial tests were conducted to investigate the influence of moisture content, compaction degree, cyclic deviator stress, and confining pressure on lime-treated expansive soil. The suitability of UT-Austin model to lime-treated expansive soils was verified. The results indicate that the dynamic resilient modulus of lime-treated expansive soils increases nonlinearly with the increase of compaction degree, while decreases nonlinearly with the increase of dynamic stress level. The dynamic resilient modulus decreases linearly with the increase of moisture content and increases linearly with the increase of confining pressure. Moreover, the moisture content has a more significant effect on the dynamic resilient modulus of lime-treated expansive soil. Therefore, it is necessary to ensure the stability of soil humidity state and its excellent mechanical properties under long-term cyclic loading for the course of subgrade filling and service. Finally, the calculated results of the UT-Austin model for dynamic resilient modulus show a good agreement with the test results.

scholarly journals Experimental investigation of soil blended with lime and lignosulphonate

2018 ◽  
Vol 7 (2.25) ◽  
pp. 74
Author(s):  
Soundarya M.K ◽  
Bhuvaneshwari S ◽  
Prasanna Kumar.S
Keyword(s):  
Expansive Soils ◽  
Research Work ◽  
Expansive Soil ◽  
Pozzolanic Reaction ◽  
Clay Particles ◽  
Bearing Strength ◽  
Pulp Industry ◽  
Saw Dust ◽  
Change Behavior ◽  
Volume Change Behavior

The deterioration of the structures which are built on the expansive soils is due to its volume change behavior, due to the presence of Mont-morillonite minerals in soil. Hence this soil requires adequate stabilization before commencement of any construction activities. The stabili-zation phenomenon in which addition suitable additives completely alters the behavior of the soil by changing the basic properties and there-by increasing the bearing strength of soil. The choice of the additives depends on the ease and permanence of the stabilizing characteristics achieved for the expansive soil. In this paper, an attempt is done to evaluate the behavior of soil when blended with additives like saw dust ash, lime and lignosulphonate at varying blending ratio. The objective of the research work is to focus on the change in the plasticity charac-teristics by utilizing the industrial waste as additive due to its cementitious value, making it eco-friendly and reduction in cost. Lignosulpho-nate is a by-product of paper pulp industry, generated during the sulphite process. From the literature, the optimum percentage for stabilizing works for lime and lignosulphonate was found to be two to eight percent and one to three percent respectively. Basic Index properties and compaction characteristics test were determined for both virgin and treated soil. The additives decreased the plasticity index, causing ag-glomeration of clay particles involving pozzolanic reaction. 

scholarly journals Use of Nanomaterials in the Stabilization of Expansive Soils into a Road Real-Scale Application

Materials ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3058
Author(s):  
Julia Rosales ◽  
Francisco Agrela ◽  
José Ramón Marcobal ◽  
José Luis Diaz-López ◽  
Gloria M. Cuenca-Moyano ◽  
...  
Keyword(s):  
Soil Stabilization ◽  
Expansive Soils ◽  
Expansive Soil ◽  
Subsequent Development ◽  
Base Layer ◽  
The Road ◽  
Road Section ◽  
Control Section ◽  
Technical Specifications ◽  
Real Scale

Stabilization is a traditional strategy used to improve soils with the main objective of ensuring that this base is compliant with the technical specifications required for the subsequent development of different infrastructures. This study proposes the use of commercial nanomaterials, based on a solution of silicates, to improve the technical characteristics and bearing capacity of the expansive soil. A physical–chemical property study was carried out on the additive nanomaterial. Subsequently, different mixtures of expansive soil, selected soil and artificial gravel with quicklime and commercial nanomaterials were developed to evaluate the improvement obtained by the use of nanomaterials in the technical characteristics of the soil. Compressive strength and the Californian Bearing Ratio index were considerably increased. A full-scale study was carried out in which the nanomaterial product was applied to two different sections of stabilized road compared to a control section. The results obtained showed that the use of nanomaterial led to the possibility of reducing the control section by 30 cm, thus achieving less use of quicklime and a mechanical means for preparing the road section. The use of commercial nanomaterial improved the behavior of the stabilized sub-base layer. Through life cycle assessment, this study has shown that the use of nanomaterials reduces the environmental impact associated with soil stabilization.

Responses of single piles to tunneling-induced soil movements in sandy ground

2007 ◽  
Vol 44 (10) ◽  
pp. 1224-1241 ◽  
Author(s):  
Kuo-Hui Chiang ◽  
Chung-Jung Lee
Keyword(s):  
Load Transfer ◽  
Bending Moment ◽  
Test Results ◽  
Axial Forces ◽  
Depth Ratio ◽  
Sandy Ground ◽  
Single Piles ◽  
Pile Settlement ◽  
Ground Loss ◽  
Soil Movements

The responses of single piles under various working loads to nearby tunneling were investigated using centrifuge model tests. First, the tunneling-induced soil movements and the tunnel stability in saturated sandy ground were examined. Two instrumented piles with penetration depths of 27 m were located either side of, and at various distances from, tunnels embedded at depths with various cover-to-diameter ratios, and used to measure the bending moments and axial forces at various depths for various ground loss ratios during tunneling simulations. The test results show that in the case of shallow tunneling near a long pile the unit skin frictions on the pile from the tunnel axis to an elevation of 1.5 tunnel diameters above the tunnel axis rapidly decrease with increases in the ground loss ratio. A significant degradation of the end bearing capacity results in a large settlement of the pile if the pile tip is near the tunnel. The depth ratio was found to be a significant influence on the bending moment profiles along the piles, but both the depth ratio and the working loads on the pile head determine the axial load profile and the pile settlement. A mechanism for pile load transfer during new tunneling is proposed to enable construction engineers to prevent structure failure in piles and excessive pile settlement.

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