Deep Soft Soil Research Articles

The September 19th, 2017 Puebla, Mexico earthquake

This report presents the observations and findings following the 2017 Puebla earthquake that occurred inMexico on September 19th, 2017. The reconnaissance mission was a collaboration between the New ZealandSociety of Earthquake Engineering (NZSEE), the Universidad Autónoma Metropolitana (UAM) Azcapotzalco,the American Concrete Institute (ACI) Disaster Reconnaissance team, and the Colegio de Ingenieros Civilesde Mexico (CICM). During the earthquake, 77 buildings suffered partial or total collapse and more than8,000 buildings experienced damage ranging from slight damage to significant structural damage necessitatingdemolition. As observed in previous earthquakes, the unique soil conditions of Mexico City resulted inextensive damage to the city’s infrastructure, primarily due to local site effects. The earthquake causedrelatively more damage to buildings built on transition and soft soil zones (i.e. between hard and deep softsoils) than those on hard soils.The NZSEE and UAM team focussed on areas with widespread and extensive damage. They also assessedthe performance of repaired and retrofitted buildings after the 1985 Michoacán earthquake. It was found thatthe lessons learnt from the 1985 Michoacán earthquake led to some risk mitigation measures which benefitedseveral buildings in the 2017 earthquake. Retrofitted buildings were found to have performed very well withlittle or no damage when compared to other buildings.

Dynamic responses of bridge substructures subjected to high-speed trains

The substructures of high-speed rail (HSR) structures are typically rigid, as they are designed to meet stringent longitudinal displacement limits specified in most HSR design standards. For site conditions such as deep valleys and soft soils, tall columns or low foundation stiffness can lead to a flexible substructure system. Flexible substructures are preferred for bridges in seismic areas because their lower horizontal frequencies yield smaller seismic forces. This cost-effective design strategy is recognised in the California HSR design criteria manual, which specifies larger relative longitudinal displacement limits. In this work, the influences of substructure flexibility on relative displacements were investigated through dynamic analyses of 36 different numerical models representing a 20-span viaduct supported by substructures with first horizontal frequencies of 0.566–3.706 Hz. Four key parameters were investigated: column height, span length, bearing plan layout and ratio of depth to span length. Train models from BS EN 1991-2:2003 were used as dynamic moving loads. The results of this study show that the chances of dynamic responses larger than design limits do exist as the stiffness of substructures departs from being rigid, where resonance effects on substructures are the main contributor to response amplification.

Study on Supporting Structure Performance of Deep Soft Soil Foundation Pit near Sea under Waves, Tides, Vibration, and Unbalanced Loads

In addition to the vibration loads caused by offshore structure construction, the offshore foundation pit can also be affected by additional hydraulic loads such as waves, tides, and typhoons, hindering our understanding of the mechanical performance of the foundation pit supporting structure. In order to illuminate this mechanical performance under waves, tides, hammering, and unbalanced loads, this paper analyzed the supporting structure with theoretical and numerical simulations. The results were verified with field monitoring data. Moreover, the influences of loads, including construction vibration loads and unbalanced loads, on structure and soil were discussed. By applying these results to the engineering design, this research could provide a reference for studying mechanical properties of relevant supporting structures and the construction of offshore foundation pits.

A review of CPT based axial pile design in the Netherlands

Because of the deltaic nature of the Netherlands, deep soft soil deposits are widespread. Due to the population density exploitation of underground space is vital for commercial developments and transport networks. Piles are used as primary support elements in deep excavations, cut and cover tunnels, quay walls, flood defences and to provide uplift resistance to the base of tunnels and basements. This paper examines empirical correlations linking the Cone Penetration Test (CPT) end resistance qc and the resistance of deep foundations in sand. It is found that correlations between qc and pile end resistance are independent of pile diameter. However, the impact of installation method, residual load, plugging and sand creep should be considered. In the case of shaft resistance, constant correlation factors between qc and average shaft resistance are possible for non-displacement piles. For the case of displacement piles, correlations that include the effects of friction fatigue and pile plugging during installation are recommended.

Engineering Characteristics and Reinforcement Program of Inclined Pre-stressed Concrete Pipe Piles

When it comes to the deep soft soil foundation, improper construction, preloading, and excavation may result in the inclination of the pre-stressed concrete pipe (PCP) piles. Lack of understanding on deformation characteristics may lead to inaccurate reinforcement plan, thereby causing new engineering accidents. This study analyzes an engineering accident induced by the pile inclination, based on which the finite element method model is built. Deformation characteristics of the foundation incorporating inclined PCP piles are investigated, and the reinforcement program involving placement of the pile with opposite inclination is proposed and compared with the conventional reinforcement program using vertical piles. Findings of this study are two-folds: 1) A critical inclination angle affecting the vertical settlement exists, below which the pile inclination has limited effects upon the vertical load bearing capacity of the foundation. 2) The vertical subsidence, the lateral displacement and the bending moment of the reinforcement program based on the reversely inclined pile are all decreased, which helps bear the overburden load and improve stability. In the process of engineering accident treatment, the bearing capacity of PCP piles with small inclination angles can be first reduced according to their inclination angles, followed by judgement that whether these PCP piles meet the requirements on bearing capacity. The PCP piles with large inclination angles must be strengthened, and the reverse inclined PCP piles are recommended.

Study on geotechnical characteristics of marine soil at Hong Kong–Zhuhai–Macao tunnel

The Hong Kong–Zhuhai–Macao Bridge (HZMB) immersed tunnel is part of the HZMB, connecting three vibrant cities and crossing the Lingding Sea in South China. It is at the west channel of the Pearl River Estuary and the Tonggu West Channel. The stratum in this area includes deep soft soil with large differences in soil distribution. Based on geotechnical investigation data on marine soil at the HZMB tunnel, the spatial distribution of physical and mechanical properties of deposit soils was statistically analyzed. A field investigation revealed that deposit soils could be subdivided into four strata: Holocene marine deposit stratum, late Upper Pleistocene continental, mid Upper Pleistocene marine alluvial deposit, and early Upper Pleistocene alluvial deposit stratum. Field and laboratory test results indicate that Holocene marine deposit soils had a high water content (42.5% < < 81.2%), large void ratio (1.21 < < 2.43), flow-plastic state ( > 1), high compressibility ( < 5 MPa), low shear strength (2.5 kPa < < 28.5 kPa), and low bearing capacity (58.9 < < 120 kPa); therefore, they could not be used as a natural foundation. The late, mid, and early Upper Pleistocene continental deposit strata had low water content (1.5% < < 40.5%), high bearing capacity ( > 120kPa), low void ratio (0.41 < < 1.24), and low flow-plastic to liquid state ( < 0.95), Additionally, the results of regression analysis showed that the compression ratio was positively correlated with natural water content. Finding from field and laboratory tests provide a basis for immersed tunnel design and construction.

Behavior of Piles Subjected to Surcharge Loading in Deep Soft Soils: Field Tests

A series of field tests were conducted to examine the behavior of pile foundation subjected to adjacent surcharge loading in deep soft soils. The emphasis was on the pile deflection, bending moment, soil horizontal displacement and lateral earth pressure acting on the piles under different surcharge loading conditions. It was found that among the surcharge loading distance, intensity and width, the surcharge loading distance was the most significant factor affecting the adjacent piles in deep soft soils. The springback process of piles subjected to adjacent surcharge loading after unloading was a slow process changing with time. The mean lateral earth pressure on the pile facing the surcharge loading is slightly larger than that opposite to the surcharge loading. The pile bending moment and mean lateral earth pressure acting on the pile decrease with time due to the consolidation process of soft soil. 3D finite element model in ABAQUS is established to study the influence of consolidation process of soft soil on piles subject to adjacent surcharge loading.

Effect analysis on long-short pile combined with reinforcement in passive zone in deep soft soil excavation

The article introduces long-short pile combined with reinforcement in passive zone support structure about some project in detail and analyzes mechanism of the support briefly. The influence of long-short pile and reinforcement in passive zone on deformation of support pile, overall stability of excavation, moment of support pile is analyzed by using finite element method. The results show: compared to no reinforcement, the maximum horizontal displacement of support pile is significantly reduced after reinforcement in passive zone, and overall stability safety factor of excavation has a more substantial increase; After setting a certain amount of reinforcement mass, there has a little effect on maximum horizontal displacement of support pile by using short pile, long-short pile and long pile, but it is minimal by using short pile; The setting of long pile is beneficial to improve the overall stability safety factor of excavation, but whether the passive zone reinforces or not has a greater impact on the stability of excavation; When the parameters of reinforcement mass reach a certain range, the parameters of reinforcement mass has little effect on the maximum horizontal displacement of support pile, but it has a certain role in improving the overall stability safety factor of excavation; The height of reinforcement mass has a great influence on the moment of support pile, but the form and width of reinforcement mass have little effect on the moment of support pile.

TIME EFFECT OF PILE-SOIL INTERACTION AND ITS ELASTIC-VISCOPLASTIC CONSTITUTIVE MODEL

Pile-soil interaction is considered to be one of the most important problems in the study of the mechanical behaviour of pile foundation. In this paper, the lateral friction resistance and pile-soil relative displacement of bridge piles in deep soft soils are monitored for an extended period by using concrete strain gauges that are embedded in the test pile. Field test results show that both the pile lateral frictional resistance and pile-soil relative displacement increase along with time, while the pile-soil interaction demonstrates a time effect. Therefore, an elastic-viscoplastic constitutive model must be established to better simulate the time-dependent mechanical behaviour of the pile-soil contact. Based on the Goodman model, we developed an elastic-viscoplastic interface constitutive model of the pile-soil interface into the FRIC subroutine through ABAQUS software, which is one of the most commonly used finite element analysis softwares in the world, to simulate a well-recorded pile test in deep soft soils. The calculated pile lateral frictional resistance and pile-soil relative displacement are close to the measured values, and the ability of the interface model to describe the changes in the shear stress-strain of the pile-soil interface along with time is validated.

Design Earthquake Response Spectrum Affected by Shallow Soil Deposit

Site response analyses were performed to investigate the earthquake response of structures with shallow soil depth conditions in Korea. The analysis parameters included the properties of soft soil deposits at 487 sites, input earthquake accelerations, and peak ground‐acceleration levels. The response spectra resulting from numerical analyses were compared with the design response spectra (DRS) specified in the 2015 International Building Code. The results showed that the earthquake motion of shallow soft soil was significantly different from that of deep soft soil, which was the basis of the IBC DRS. The responses of the structures were amplified when their dynamic periods were close to those of the site. In the case of sites with dynamic periods less than 0.4 s, the spectral accelerations of short‐period structures were greater than those of the DRS corresponding to the site class specified in IBC 2015. On the basis of these results, a new form of DRS and soil factors are proposed.

Analysis of temperature field of embankment-CFG piles composite soft soil foundation system in cold regions

For the major projects built on the soft soil area in cold regions, the effective treatment of deep soft soil layer and the stable bearing capacity of foundation are of great importance. In this paper, the finite element model of embankment-CFG piles composite soft soil foundation for D3K629-D3K629+950 of Harbin-Dalian railway is established based on ABAQUS. The depth and regional distribution of freezing and thawing and distribution law of temperature field of CFG piles are studied. The results show that the horizontal position of 0-degree line is higher and the protective effect of embankment on the foundation is obvious when the embankment is higher. The embankment almost has no effect on the CFG piles near embankment foot. For the middle pile at the center of the embankment, the protection effect of the embankment is remarkable.

Improved Calculation Method of Super-Long Pile in Deep Soft Soil Area

Improved Calculation Method of Super-Long Pile in Deep Soft Soil Area

Technology Dealing with the Soft Soil Foundation

Soft foundation is one of the important factors affecting the quality of construction in the building construction, so in order to better improve the quality of construction, we must take corresponding measures to deal effectively with this problem, mainly discusses the profound advances in treatment of soft soil subgrade, this paper probes into the combination of the characteristics of the silt along the beach area of the soft foundation treatment technology progress. Aiming at the current development process of municipal beach road construction problems, based on the analysis of deep soft soil subgrade treatment methods, introduces the recent progress in the exploration of China’s tidal silt characteristics in rock and soil engineering, combined reinforcement technology research methods, the combination of the developed new technology of deep soft foundation treatment hope can be applied to practical engineering.

The reinforcement effects of deep soft soil foundation with high degree of saturation under dynamic compaction

The dynamic compaction method is effective to reinforce soft soil foundation with a low degree of saturation. However, deep soft soil foundation with high degree of saturation has some different characteristics. It has been widely considered that dynamic compaction method is unsuitable to improve the characters of deep soft soil foundation with high degree of saturation. In this article, we will show that the dynamic compaction method with vacuum well-point dewatering is effective to deep soft soil foundation with high degree of saturation reinforcement. In situ and laboratorial experiments are used to assess the reinforcement effect of the deep soft soil foundation with high degree of saturation. Our results show that the dynamic compaction method causes long dissipation time of pore water pressure, and the dynamic compaction method with vacuum well-point dewatering makes construction time of a project 25% shorter. The effective depth of deep soft soil foundation with high degree of saturation reinforcement using the two experimental methods can reach to 8.0 m. In comparison with the total settlement and layered settlement of the dynamic compaction method with vacuum well-point dewatering, the dynamic compaction method settlement is relatively smaller. For soils with depth of 4 m, the reinforcement effect of dynamic compaction method with vacuum well-point dewatering is obviously superior to dynamic compaction method. Based on these results, we suggest construction procedures for different reinforcement depth of soils and construction time.

Modified Chicken Claw (&lt;i&gt;Cakar Ayam Modifikasi&lt;/i&gt;) System - A New Concept in Green Pavement Technology over Soft and Swampy Ground

Some parts of Indonesia region, especially near the coast, have soft subgrade and a part of them is swampy with relatively deep soft soil layer. To utilize and develop such areas absolutely need an adequate road network, while the existing road on such areas needs high maintenance cost. Conventional solutions with embankment made of better soil properties through preloading process, or with the technology of slab on pile system, is expensive and not environmentally friendly. This paper discusses the basic principles, methods of analysis and design, implementations, and practical applications of the Modified Chicken Claw (Cakar Ayam Modifikasi) system, which in addition to technically meets the requirements, is also relatively much cheaper, easier and faster to construct, and more environmentally friendly. This is a totally new concept of pavement system originally developed in Indonesia, which has been widely applied as road construction over soft and swampy grounds with satisfactory long-term performance. The system consists of a relatively thin (10~15 cm) reinforced concrete slab, pipes (chicken claws) inserted into the soft ground at about 2.5 m distances as slab stiffener, and underlying soft soil layer. Compared to previous similar versions, the Modified Chicken Claw system has many advantages including (a) a much more accurate method of analysis and design so as to obtain optimal design, (b) much smaller dimension and chicken claw weight, (c) vertical concrete fin as underlying soil barrier for more pavement stability and durability, (d) the present of thin asphalt layer to significantly reduce the effect of cyclic thermal loading and act as wearing course, (e) combination with a light fill material to minimize the consolidation settlement, and (f) a much shorter construction time with a relatively cheaper cost, since heavy equipment are not necessary.

The Design of an Iconic 40-Storey Steel Composite Office Tower in Indonesia with a High Seismic Performance Level

An iconic 40-storey steel composite office building with 6 basement levels is open for activity in end of 2017 in Jakarta, the capital city of Indonesia. The tower is located in one of the most active seismic zone in the world and also stands on a very deep soft soil layers of alluvial deposit.Steel composite structure was introduced in this building consisting of special steel moment frames, concrete-filled tubes for the perimeter columns, and the concrete core wall in the middle. Three floor levels of its basement use double deck lift car-parking system.This paper discusses the reasons behind the selection of the structural system and the use of advanced structural analyses and design methods. In addition the paper highlights how the Performance-Based Design considering the Risk-targeted Maximum Considered Earthquake (MCER) was carried out to satisfy the client requirement in reaching a seismic performance between Immediate Occupancy (IO) and Life Safety (LS) level.

Comparative Analysis of Load Responses and Deformation for Crust Composite Foundation and Pile-supported Embankment

Ground improvement using artificial crust composite foundation, consisting of stabilization of soft clay and composite foundation, is an effective technique for the treatment of deep soft soil layers under infrastructure embankments. In this study, the load responses and settlement performance of this improvement technique were investigated using two centrifuge model tests to compare the variations of the vertical deformation, pore water pressure, axial force of the piles and tensile stress at the bottom of the artificial crust in the crust composite foundation with those in pile-supported embankment. The results of centrifuge model tests showed that the load responses and settlement performance of artificial crust composite foundation was different from the pile-supported embankment, which displayed mainly that the final middle settlement of crust composite foundation can be reduced by about 15% compared with those of pile-supported embankment with the same length of pile and construction cost. The deformation of the crust with the characteristics of the plate was found based on the change of the tensile stress. Additionally, the excess pore water pressure in the crust composite foundation was lower owing to the stress diffusion effect of the crust during the loading period and the dissipation rate of excess pore water pressure was slower due to lower permeability of the crust at the same loading period. Eventually, the axial force of the middle piles was reduced. At the same time, the boundary stress was functioned with the crust, the axial force of the side piles was improved. The comparison of measured and calculated results was carried out using the stress reduction ratio, the result shows that the bearing capacity of the subsoil in the crust composite was improved.

Soil and ribbed concrete slab interface modeling using large shear box and 3D FEM

Cast in situ and grouted concrete helical piles with 150-200 mm diameter half cylindrical ribs have become an economical and effective choice in Shanghai, China for uplift piles in deep soft soils. Though this type of pile has been successful used in practice, the reinforcing mechanism and the contribution of the ribs to the total resistance is not clear, and there is no clear guideline for the design of such piles. To study the inclusion of ribs to the contribution of shear resistance, the shear behaviour between silty sand and concrete slabs with parallel ribs at different spacing and angles were tested in a large direct shear box (600 mm × 400 mm × 200 mm). The front panels of the shear box are detachable to observe the soil deformation after the test. The tests were modelled with threedimensional finite element method in ABAQUS. It was found that, passive zones can be developed ahead of the ribs to form undulated failure surfaces. The shear resistance and failure mode are affected by the ratio of rib spacing to rib diameter. Based on the shape and continuity of the failure zones at the interface, the failure modes at the interface can be classified as punching, local or general shear failure respectively. With the inclusion of the ribs, the pull out resistance can increase up to 17%. The optimum rib spacing to rib diameter ratio was found to be around 7 based on the observed experimental results and the numerical modelling.

Effects of Pit Excavation on an Existing Subway Station and Preventive Measures

AbstractAs traffic lifelines of modern cities, subways are being rapidly developed in China. With this development, an increasing number of subway interchange stations will be built at deep soft soil areas. Because of the absence of data on the effects of pit construction on existing subway stations, no theory is available to predict deformation of a subway station caused by adjacent pit construction. The proposed Line 10 subway station intersects with the operating Line 4 subway station at Hailun Road, Shanghai, China, where the underlying stratum is composed of several different sandy-silt layers and two confined aquifers. The double-layered confined water meets at the south end well of the proposed subway station. With such complicated hydrogeological conditions, the development of technology that can control the effects of groundwater and guarantee the safe operation of Line 4 during pit construction is essential. In this article, the effects of dewatering and pit excavation on the Line 4 subway stati...

Creep behaviors and constitutive model for high density polyethylene geogrid and its application to reinforced soil retaining wall on soft soil foundation

The reinforced soil retaining wall has been applied extensively with its numerous advantages. However, the performance of geogrids reinforced soil retaining wall was affected by creep behavior of geogrids and soft soil foundation as well as stress relaxation of geogrids. In this paper, the creep behavior and stress relaxation of high density polyethylene geogrids have been investigated in a laboratory. Four different sustained load levels of 20%, 40%, 50% and 60% of ultimate tensile strength were employed as load levels for creep tests. A constitutive model, which was capable of simulating creep behaviors and stress relaxation of geogrids, was established based on experimental data and verified. Numerical modeling using finite element method has also been used to assess the impact of creep behavior and stress relaxation of geogrids on the long-term performance of reinforced soil retaining wall on the deep soft soil foundation. The results show that the constitutive model for creep behavior and stress relaxation of geogrids was in good qualitative agreement with experimental data under different load levels. To ensure the stability of the retaining wall, the working stress of geogrids should be less than 40% of ultimate tensile strength, and the high strength geogrids should be adopted in the middle of the wall or the spacing of geogrid reinforced layers should be reduced. The deep soft soil foundation which is treated by piles can ignore the creep behavior of soft soil.