Miniature Cone Penetration Test Research Articles

Correlation of CPT measurements and relative density of LEAP-2017 and LEAP-2020 centrifuge models

Miniature cone penetration tests (CPTs) were conducted during the LEAP 2017 and LEAP 2020 centrifuge experiments to characterize and quantify the soil deposit properties. A total of 43 CPTs were obtained for deposits with varying relative densities. All experiments were performed using Ottawa F-65 Sand and used the same CPT tool model. A comprehensive study was undertaken to assess the quality and consistency of the CPT data. Outlier and regression analyses were used to develop an empirical relation to evaluate the relative density of Ottawa sand (centrifuge) deposits from measurements of the CPT tip resistance. This relation provides an estimate of the mean relative density profile, and associated standard deviation to quantify uncertainty. The relation accounts for the overburden pressure influence and the potential effects of container width (when the used container is narrow). The experimental results were found to have a good consistency with a regression R2 equal to 0.85.

Performance of a cyclic miniature cone penetration test in dry granular soil: experimental approaches

Shaft friction degradation in geotechnical problems occurs alongside large uncertainties. Under cyclic loadings, offshore foundations can episodically suffer the loss of stiffness and strength. In such cases, initial in situ soil state is lost as soil is disturbed during cyclic loading. In this sense, it is important to develop a testing procedure to assess the lateral friction degradation. Considering that a cone is a miniature driven pile, the use of this testing technique allows monitoring the degradation of sleeve friction during cyclic loading. This paper aims to improve the knowledge on the feasibility of using cone testing for the recognition of lateral friction degradation of a dry granular soil. Cyclic miniature cone penetration tests were performed in a calibration chamber considering a range of loading conditions. The effect of cyclic displacement amplitude and the confining pressure were investigated. Lateral friction, fs, degrades while repeating the load cycling, resulting in loss of lateral strength due to soil–cone interface friction degradation. After about ten load cycles, degradation tended to stabilise for all tests.

Experimental Investigation of sample preparation and grouting technology on microbially reinforced tailings

The nonuniformity of samples in reinforcement treatment is a bottleneck that restricts the development of microbial geotechnical technologies, which severely affects the reinforcement effect of microbially reinforced tailings and other fine-grained geotechnical materials. This study presents a mixing method that represents an innovative sample preparation and grouting technology for reinforcing tailings using microbially induced calcite precipitation (MICP) based on the characteristics of tailings discharged in the form of mud and accumulated layer-by-layer. A large number of mechanical experiments and microanalyses were conducted to compare the effects of various methods on tailings reinforcement, including the methods of adding bacterial solution (i.e., the traditional grouting method and the proposed mixing method) and the treatment methods of cementing solution (i.e., the grouting method and soaking). The results of the shear test showed that the strength of the samples generated by the mixing method increased compared with the original tailings samples and samples generated using the traditional grouting method. Moreover, miniature cone penetration test results showed that the samples made using the mixing method had better uniformity, which could be attributed to the fine particles (silt and clay particles) of tailings that strongly adsorb bacteria and the low permeability of the fine particle tailings, which is not conducive to the spread of bacteria. In the tailings samples, the traditional grouting method only makes the bacteria gather at the region where the bacterial solution initially makes contact. However, the mixing method evenly distributed the bacteria among the tailings particles, which significantly improved the reinforcement effect of bacteria, as the reinforcement reaction occurred throughout each region of the samples. Therefore, the mixing method can be used for reinforcement research and in the application of MICP to tailings or other fine-grained geotechnical materials.

Effect of Overconsolidation on K in Centrifuge Models Using CPT and Tactile Pressure Sensor

Abstract Assessing the state of stress in soil in the free field, as defined by the vertical and lateral earth pressures, is important in some geotechnical problems such as the design of underground structures and estimation of soil liquefaction potential. Unlike the vertical earth pressure, several factors can influence the lateral earth pressure, particularly overconsolidation. This is typically accounted for by relating the coefficient of lateral earth pressure at rest, K0, with the estimated overconsolidation ratio (OCR). The corresponding relations available in the literature are related to the K0 occurring for a given OCR during unloading, and do not take into account the unloading–reloading effect that may be present in centrifuge tests. In this paper, the relationship between the coefficient of lateral earth pressure at rest, K0, and overconsolidation ratio, OCR, is investigated for the whole loading–unloading–reloading condition. Four centrifuge model experiments were conducted on Ottawa F#55 sand. Two of the models were tested using a tactile pressure sensor to measure K0 and the other two models were tested using a miniature cone penetration test (CPT) system. The paper concludes with recommendations for centrifuge operation when testing overconsolidated sand in the centrifuge.

Penetration Rate Effects on Cone Resistance: Insights From Calibration Chamber and Field Testing

Cone penetration in mixed or intermediate soils (soils containing mixtures of sand, silt and clay) is neither fully drained nor fully undrained at the standard cone penetration rate of 20 mm/s. Considerable research, mainly relying on centrifuge tests, has been undertaken to quantify the effects of penetration rate (and thus partial drainage) on cone resistance. In this paper, the effects of penetration rate on cone resistance in saturated clayey soils were investigated by performing field tests and miniature cone penetration tests in a calibration chamber. The field tests were performed at sites especially selected to span the range of drainage conditions from fully drained to fully undrained. The calibration chamber tests, using both conical and flat-tip penetrometers, were performed at different penetration rates in two specimens prepared by mixing kaolin clay and sand with different mixing ratios and one-dimensionally consolidateding the mixtures. A correlation between cone resistance and drainage conditions is established based on the cone penetration test results. The transitions from no drainage to partial drainage and from partial drainage to full drainage are defined as a function of penetration rate normalized with respect to the penetrometer diameter and the coefficient of consolidation.

해상풍력 모노포드 버켓기초의 지지력 거동 - 원심모형실험 및 수치해석

해상풍력 기초로 사용되는 모노포드 석션 버켓기초의 지지력 거동에 대하여 원심모형실험과 수치해석을 통하여 연구하였다. 대상 구조물은 서해안 지역을 대상으로 검토된 해상풍력타워 기초로, 실트질 모래층에 설치하는 것으로 설계되었다. 원심모형실험에 사용된 모형지반은 대상 지반과 유사한 물성을 갖도록 조성하였다. 실험 가속 상태에서 소형 콘 관입시험과 벤더 엘리먼트를 사용한 전단파속도 측정을 통하여 물성을 평가하고 모사 대상 지반과의 유사성을 검증하였다. 원심모형실험으로 해상풍력 기초에 작용하는 하중을 재하하고 거동을 계측할 수 있도록 실험 시스템을 구축하였고, 모노포드 석션 버켓기초의 하중-회전각 관계를 통해서 지지력 거동을 평가하였다. 최적의 실험 조건을 선정 및 검증하기 위하여 수치해석을 수행하였으며, 모델의 자중, 모델과 경계면의 거리 및 지반 탄성계수의 변화에 따른 지지력 거동의 차이를 검토하였다. In order to evaluate the bearing capacity behaviour of a monopod suction bucket foundation for an offshore wind tower at the western sea of Korea, a centrifuge load test and numerical analyses were performed. The monopod bucket foundation was designed to be installed in a silty sand layer. The model soil was prepared to simulate a target site by using soil samples having similar properties and controlling relative density. In-flight miniature cone penetration test and bender element array were used to confirm that the model soil had represented the target site conditions. The load - rotation curve of the centrifuge load test was analysed. A series of numerical analyses were performed to validate the experimental conditions. Self-weight of the model, distance to the boundary and elastic modulus of the soil layer were varied to study their effects on the load - rotation curves.

Scale Effects and Field Applications for Continuous Intrusion Miniature Cone Penetrometer

콘관입시험은 현장조사 시험법으로 사용 빈도가 증가되고 있다. 그러나 콘관입시험은 콘크기와 용량 등에 따라 적용 가능한 현장조건이 제한되는 단점이 있다. 소형콘의 감소된 단면적은 시스템 용량을 증대시켜 적용성을 향상시킬 수 있으며, 코일식 롯드를 이용한 연속관입 시스템은 신속하고 경제적인 지반조사를 가능하게 한다. 본 연구에서는 국내 여러 현장에서 연속관입형 소형콘관입시험 시스템의 성능을 표준 콘관입시험 시스템과의 비교시험을 통하여 평가하였다. 소형콘관입시험 장비는 기존의 표준콘관입시험 장비와 비교하여 지반정수 도출 및 지반분류에 동일한 성능을 발휘하는 것을 확인하였으며, 장비의 기동성 및 적용대상 토질 확대 등의 장점을 나타내는 것으로 평가되었다. 크기효과 검증을 위한 현장시험 결과 기존 시험 방법에 비해 콘저항력의 경우는 약 10% 과대평가하는 것으로 나타났다. 차량 형태의 조사장비는 표층이 연약하거나 진입이 어려운 경우에는 조사의 한계가 있으므로, 궤도장치에 탑재된 연속관입형 소형콘관입시험 시스템으로 개선하여 적용성을 확대시켰다. 따라서 개선된 연속관입형 소형콘관입시험 시스템은 연약지반 심도탐지 및 흙분류시 경제적이고 신뢰성 높은 지반조사 방법으로 활용할 수 있다. Cone penetration tests (CPTs) have been increasingly used for site characterizations. However, the site investigations using CPTs are often limited due to soil conditions depending on the cone size and capacity of the CPT system. The small sectional area of a miniature cone improves the applicability of the CPT system due to the increased capacity of the CPT system. A continuous intrusion system using a coiled rod allows fast and cost effective site investigation. In this study, the performance of the continuous intrusion miniature cone penetration test (CIMCPT) system has been evaluated by comparison tests with the standard CPT system at several construction sites in Korea. The results show that the CIMCPT system has a same performance with the CPT system and has advantages on the mobility and applicability. According to field verification tests for scale effect evaluation, the cone tip resistance evaluated by CIMCPT overestimates by 10% comparing to standard CPTs. A crawler mounted with the CIMCPT system has been implemented to improve accessibility to soft ground, and has shown improvement over the truck type CIMCPT system. Therefore, the improved CIMCPT system can be utilized as a cost effective and highly reliable soil investigation methodology to detect the depth of soft ground and to evaluate soil classification.

Development and Calibration of an Electronic Miniature Cone Penetrometer for Design of Small Piles in Silty Clays

Abstract For the design of shallowly embedded small size pile under lateral load, a new kind of electronic miniature cone penetrometer is developed. And a novel mini calibration chamber is also designed to form homogeneous soil specimens for miniature cone penetration test (MCPT) in laboratory. A series of MCPTs and pile loading tests in silty clay are carried out. For silty clay, penetration curve has no correlation with cone angles within the tested range of 19° to 32°. The initial segment of penetration curve is linear for silty clay. However, the cone tip resistance tends to be stable when the cone is penetrated to a certain depth. It is implied that the critical depth effect occurs for MCPT of silty clay. For silty clay, the critical depth effect is caused by different soil failure mechanisms under different confining pressures. The lateral bearing capacity and stiffness of small size pile are all directly related to the ultimate cone tip resistance of soil. It is concluded that the miniature cone penetrometer is an effective apparatus for the design of small size shallowly embedded pile.

Evaluation of trench backfills at highway cross-drains

A highway cross-drain is an important element in a highway drainage system. This structure, however, has been related to the ride quality deterioration caused by pavement surface dips above this structure. In-situ probing techniques, such as the cone penetration test (CPT), miniature cone penetration test (Mini-cone) and dynamic cone penetrometer (DCP), were used to diagnose the causes of the dip problem. The field evaluations indicated that when a pavement surface dip occurred, the trench backfill underneath was softer than the adjacent subgrade soil. Because of its simplicity and potential as a quality control tool during the backfill process, the DCP test was given special attention. The field case histories and full-scale laboratory tests confirmed that DCP results can provide a reasonable estimation of the stiffness (modulus) of different trench backfills and subgrade soils. A possible way to prevent a pavement dip from occurring at a cross drain is to make a backfill stiffer than adjacent subgrade soils. The compaction results from the full-scale laboratory tests indicated that sand is not always successfully used for highway cross-drains due to its poor gradation and difficulty in compaction. Other materials, such as crushed limestone and recycled asphalt pavement (RAP), are good alternates because of their good workability and high stiffness when compacted.

Development of a Continuous Intrusion Miniature Cone Penetration Test System for Subsurface Explorations

This paper describes the development of a continuous intrusion miniature cone penetration test system (CIMCPT) for shallow to semi-deep subsurface investigations. A novel feature of this new in situ testing system is the chain driven caterpillar-type continuous push device powered by a hydraulic motor to advance the cone penetrometer, which greatly increases productivity and serviceability. The system is housed in an environmentally controlled van body that is mounted on a one-ton, four-wheel drive, all-terrain vehicle. A new state-of-the-art data acquisition system using interface modules and a global positioning system, for real-time monitoring, acquiring, storing, and displaying data in real time on a computer screen in graphic form was developed and implemented. The miniature cone penetrometer has a projected cone area of 2 cm2 and a friction sleeve surface area equal to 40 cm2. It gives finer detailed soil profiles compared to the standard 10 cm2 cross-sectional area reference cone penetrometer. In situ calibration of the CIMCPT system with the standard 10 cm2 cone penetrometer indicated that the average tip resistance of the CIMCPT was 11 percent higher than that of the standard cone penetrometer. The average CIMCPT sleeve friction was 11 percent lower than that of the standard cone penetrometer.

Implementation of Miniature Cone Penetrometer in Roadway Design and Construction

A continuous-intrusion miniature cone penetration test (CIMCPT) system was developed, calibrated, and implemented by the Louisiana Transportation Research Center. The cone-penetration technology is fast, reliable, and cost-effective, especially when compared with the traditional site-characterization methods such as borings and laboratory and field tests. The implementation phase of the CIMCPT system in roadway design and construction in Louisiana is presented. The CIMCPT was used to evaluate the structural capacity of pavement shoulders to support diverted traffic during the I-10 rehabilitation near Rayne, to redesign and construct a stone base-course layer for State Route LA-182 in Franklin, and to evaluate the failure surface of the I-20/Missouri Pacific Railroad overpass embankment near Tallulah. The CIMCPT system was successfully implemented by the Louisiana Department of Transportation and Development (LA DOTD). Implementation of the CIMCPT technology in roadway design and construction has saved LADOTD money and time compared with traditional subsurface exploration techniques.

Miniature Cone Penetration Tests in Soft and Stiff Clays

Abstract An electric continuous intrusion miniature cone penetration test system was recently developed for roadway design and construction control of embankments. The system continuously advances a 2 cm2 electric miniature cone penetrometer by uncoiling a stainless steel push rod. Field and laboratory testing programs were conducted on overconsolidated, normally consolidated, and compacted Louisiana clays. The field testing program consisted of cone penetration tests using both 2 and 15 cm2 electric cone penetrometers in conjunction with soil sampling, while laboratory tests included physical properties and strength characteristics of the investigated soils. Analyses of cone penetration tests were conducted to assess the repeatability and reliability, as well as confirming that the electric miniature friction cone output is in compliance with output of the 15 cm2 cone.

Centrifuge cone penetration tests in sand

When performing centrifuge tests, it is necessary to carry out in-flight tests such as the cone penetration test (CPT). Recently, miniature CPTs have formed one collaboration entitled 'European Pro ...

Continuous Intrusion Miniature Cone Penetration Test System for Transportation Applications

The electronic cone penetrometer is an important investigation tool of choice for in situ site characterization. Application of this proven concept of the cone penetration test (CPT) to transportation applications is described. A miniature cone penetrometer with a projected cone area of 2 cm2 has been developed and implemented in a continuous intrusion miniature CPT system (CIMCPT). This device may be used for rapid, accurate, and economical characterization of sites as well as to determine engineering soil parameters needed in the design of pavements, embankments, and earth structures. The miniature CPT (MCPT) gives finer details than the standard 10-cm2 cross-sectional area reference cone penetrometer, which makes it attractive for subgrade characterization, quality control assessment, compaction control of embankments, and assessment of ground improvement effectiveness for transportation infrastructure. In situ calibration of the CIMCPT system was conducted at a highway embankment site in Baton Rouge, Louisiana. MCPT penetration profiles were compared with those obtained with the standard cone penetrometer at the same site. The tip resistance of the MCPT was 10 percent higher than that of the reference CPT. The sleeve friction and friction ratio of the reference CPT were higher than that of the MCPT by 12 and 23 percent, respectively. Calibration was also performed to determine empirical cone factors required for estimating undrained shear strength from MCPT data.

Evaluation of Resilient Modulus of Subgrade Soil by Cone Penetration Test

Pavement design based on the resilient modulus of subgrade soil has been adopted by many transportation agencies following the recommendations of the AASHTO guide for design of pavement structures. Laboratory and field nondestructive tests are generally used to evaluate the resilient modulus of subgrade soil. These methods have shortcomings and limitations and are considered laborious, time-consuming, and expensive. The difficulties associated with the existing methods signify the need for a popular in situ technology for evaluating the resilient modulus of subgrade soil. Among other methods, the cone penetration test (CPT) is fast, simple, and economical and provides repeatable and reliable results. The results of a pilot investigation to assess the possibility of predicting the resilient modulus of subgrade soil from the CPT soundings are presented here. Field and laboratory testing programs were carried out on two types of cohesive soils at the Louisiana Transportation Research Center/Pavement Research Facility. Field tests consisted of CPT soundings using the 15-cm2 friction cone penetrometer and the 2-cm2 miniature friction cone penetrometer. Laboratory tests included the resilient modulus and physical properties of the investigated soils. The results of the miniature CPT were evaluated and compared with the soundings of the 15-cm2 cone at the same site. Both laboratory and field tests were analyzed. Based on statistical analyses, a model was proposed to estimate the resilient modulus from the CPT data and basic soil properties. Predicted values of the resilient modulus are consistent with laboratory measurements.

Calibration of a Miniature Cone Penetrometer for Highway Applications

The electronic cone penetrometer is an important in situ investigation tool of choice for site characterization. Application of this proven concept of the cone penetration test (CPT) to highway design and construction control by miniaturization is described. A miniature cone penetrometer with a projected cone area of 2 cm2 has been developed and implemented in a continuous intrusion miniature cone penetration test system (CIMCPT). This device may be used for rapid, accurate, and economical characterization of sites and to determine engineering soil parameters needed in the design of pavements, embankments, and earth structures. The miniature cone penetration test (MCPT) gives finer details than the standard 10-cm2 cross-sectional area reference cone penetrometer. This makes the MCPT attractive for subgrade characterization, quality-control assessment, compaction control of embankments, and assessment of ground improvement effectiveness for transportation infrastructure. In situ calibration of the CIMCPT system was conducted at a highway embankment site in Baton Rouge, Louisiana. MCPT penetration profiles were compared with those obtained by using the standard cone penetrometer at the same site. The tip resistance of the MCPT was 10 percent higher than that of the reference CPT. The sleeve friction and friction ratio of the reference CPT were higher than that of the MCPT by 12 and 23 percent, respectively. Calibration was also performed to determine empirical cone factors required for estimating undrained shear strength from MCPT data.